From bcbcfe3a8fcbd80a8bd96c2552de909a6ada0b18 Mon Sep 17 00:00:00 2001
From: Dan Calacci <dan@dcalacci.net>
Date: Fri, 22 Jul 2016 14:17:45 -0400
Subject: [PATCH 01/10] alerts aren't super annoying anymore

---
 demo/index.html | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/demo/index.html b/demo/index.html
index 0154b27..764f98e 100644
--- a/demo/index.html
+++ b/demo/index.html
@@ -23,7 +23,9 @@
 }
 
 #info {
-    font-size: 22px;
+  font-size: 22px;
+  overflow: scroll;
+  max-height: 300px;
 }
 
 #wrapper {

From 1aeff0b48adf6f1a23cd9fc7ada57bc8c01ca854 Mon Sep 17 00:00:00 2001
From: Dan Calacci <dan@dcalacci.net>
Date: Fri, 22 Jul 2016 14:36:17 -0400
Subject: [PATCH 02/10] updated sibilant version

---
 package.json | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/package.json b/package.json
index 46c26f1..9df5425 100644
--- a/package.json
+++ b/package.json
@@ -18,6 +18,6 @@
     "microevent": "^1.0.0"
   },
   "devDependencies": {
-    "alerts": "^0.1.3"
+    "alerts": "^0.1.4"
   }
 }

From 2360024958e4a95b1500720add05e8e52faf1e76 Mon Sep 17 00:00:00 2001
From: Dan Calacci <dan@dcalacci.net>
Date: Fri, 22 Jul 2016 14:36:55 -0400
Subject: [PATCH 03/10] OOPS

---
 package.json | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/package.json b/package.json
index 9df5425..953e672 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "sibilant-webaudio",
-  "version": "0.1.1",
+  "version": "0.1.2",
   "description": "detect speaking events from webRTC audio",
   "main": "sibilant.js",
   "scripts": {
@@ -18,6 +18,6 @@
     "microevent": "^1.0.0"
   },
   "devDependencies": {
-    "alerts": "^0.1.4"
+    "alerts": "^0.1.3"
   }
 }

From 6d01fc9746b50c69acabddc49c3da649f3703858 Mon Sep 17 00:00:00 2001
From: Dan Calacci <dan@dcalacci.net>
Date: Mon, 6 Mar 2017 17:09:05 -0500
Subject: [PATCH 04/10] also sends out volume data

---
 package.json | 2 +-
 sibilant.js  | 5 ++++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/package.json b/package.json
index 953e672..b5a1618 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "sibilant-webaudio",
-  "version": "0.1.2",
+  "version": "0.1.3",
   "description": "detect speaking events from webRTC audio",
   "main": "sibilant.js",
   "scripts": {
diff --git a/sibilant.js b/sibilant.js
index 8303f46..a7ba70d 100644
--- a/sibilant.js
+++ b/sibilant.js
@@ -24,6 +24,7 @@ function speakingDetectionNode (audioContext, analyser, threshold, emitter) {
   var speakingTimes = []
   var quietHistory = [] // only contains continuous 'quiet' times
   var currentVolume = -Infinity
+  var volumes = []
 
   var hasStoppedSpeaking = function () {
     return (_.max(quietHistory) - _.min(quietHistory) > 500)
@@ -34,6 +35,7 @@ function speakingDetectionNode (audioContext, analyser, threshold, emitter) {
     analyser.getFloatFrequencyData(fftBins)
     var maxVolume = _.max(_.filter(fftBins, function (v) { return v < 0 }))
     currentVolume = maxVolume
+    volumes.push(currentVolume)
     emitter.trigger('volumeChange', currentVolume)
     // speaking, add the date to the stack, clear quiet record
     if (currentVolume > threshold) {
@@ -42,7 +44,8 @@ function speakingDetectionNode (audioContext, analyser, threshold, emitter) {
       quietHistory = []
     } else if (speakingTimes.length > 0) {
       if (hasStoppedSpeaking()) {
-        emitter.trigger('stoppedSpeaking', {'start': _.min(speakingTimes), 'end': _.max(speakingTimes)})
+        emitter.trigger('stoppedSpeaking', {'start': _.min(speakingTimes), 'end': _.max(speakingTimes), 'volumes': volumes})
+        volumes = []
         speakingTimes = []
       } else {
         quietHistory.push(new Date())

From dae97082078d73eb0fb984966491b386a5ff2400 Mon Sep 17 00:00:00 2001
From: Dan Calacci <dan@dcalacci.net>
Date: Mon, 6 Mar 2017 19:52:18 -0500
Subject: [PATCH 05/10] volumes in correct format...

---
 sibilant.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sibilant.js b/sibilant.js
index a7ba70d..5c517e6 100644
--- a/sibilant.js
+++ b/sibilant.js
@@ -35,7 +35,8 @@ function speakingDetectionNode (audioContext, analyser, threshold, emitter) {
     analyser.getFloatFrequencyData(fftBins)
     var maxVolume = _.max(_.filter(fftBins, function (v) { return v < 0 }))
     currentVolume = maxVolume
-    volumes.push(currentVolume)
+    volumes.push({timestamp: Date.now(),
+                  vol: currentVolume})
     emitter.trigger('volumeChange', currentVolume)
     // speaking, add the date to the stack, clear quiet record
     if (currentVolume > threshold) {

From 9ac805df03d5a8e164de1b87c958e504ab4a43af Mon Sep 17 00:00:00 2001
From: Dan Calacci <dan@dcalacci.net>
Date: Mon, 6 Mar 2017 19:52:46 -0500
Subject: [PATCH 06/10] updated version

---
 package.json | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/package.json b/package.json
index b5a1618..a4643c7 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "sibilant-webaudio",
-  "version": "0.1.3",
+  "version": "0.1.4",
   "description": "detect speaking events from webRTC audio",
   "main": "sibilant.js",
   "scripts": {

From 2bf481616b90260e171c8a2def7da23b5c2899c4 Mon Sep 17 00:00:00 2001
From: Dan Calacci <dan@dcalacci.net>
Date: Thu, 13 Sep 2018 15:57:30 -0400
Subject: [PATCH 07/10] slightly better band pass

---
 demo/demo.bundle.js | 34196 ++++++++++++++++++++++--------------------
 demo/demo.js        |    83 +-
 demo/index.html     |     3 +-
 package.json        |     4 +-
 sibilant.js         |   182 +-
 5 files changed, 17895 insertions(+), 16573 deletions(-)

diff --git a/demo/demo.bundle.js b/demo/demo.bundle.js
index 45a2bb7..6bbb7cb 100644
--- a/demo/demo.bundle.js
+++ b/demo/demo.bundle.js
@@ -1,38 +1,63 @@
-(function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);var f=new Error("Cannot find module '"+o+"'");throw f.code="MODULE_NOT_FOUND",f}var l=n[o]={exports:{}};t[o][0].call(l.exports,function(e){var n=t[o][1][e];return s(n?n:e)},l,l.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s})({1:[function(require,module,exports){
-const Sibilant = require('sibilant-webaudio')
-const alert = require('alerts')
-const getUserMedia = require('getusermedia')
-const attachmediastream = require('attachmediastream')
-const $ = require('jquery')
-
-getUserMedia(function (err, stream) {
-  if (err) {
-    console.log('couldnt get user media!', err)
-    alert('Sibilant couldnt get your user media. give it access to audio and try again!')
-    throw err
-  } else {
-    console.log('got a stream!')
-
-    attachmediastream(stream, document.querySelector('#vid video'))
-    document.querySelector('#vid video').muted = true
-    var speakingEvents = new Sibilant(stream, {passThrough: false})
-    speakingEvents.bind('speaking', function () {
-      document.querySelector('#vid video').style.border = '10px solid #27ae60'
-      console.log('speaking!')
-    })
-
-    speakingEvents.bind('stoppedSpeaking', function (data) {
-      console.log('speaking event recorded!', data.start)
-      var start = new Date(data.start)
-      var end = new Date(data.end)
-      var duration = end - start
-      $('#info').prepend('You spoke for ' + duration + ' ms! <br>')
-      document.querySelector('#vid video').style.border = '10px solid #555'
-    })
-  }
-})
+(function(){function r(e,n,t){function o(i,f){if(!n[i]){if(!e[i]){var c="function"==typeof require&&require;if(!f&&c)return c(i,!0);if(u)return u(i,!0);var a=new Error("Cannot find module '"+i+"'");throw a.code="MODULE_NOT_FOUND",a}var p=n[i]={exports:{}};e[i][0].call(p.exports,function(r){var n=e[i][1][r];return o(n||r)},p,p.exports,r,e,n,t)}return n[i].exports}for(var u="function"==typeof require&&require,i=0;i<t.length;i++)o(t[i]);return o}return r})()({1:[function(require,module,exports){
+const Sibilant = require("../")
+const alert = require('alerts');
+const getUserMedia = require('getusermedia');
+const attachmediastream = require('attachmediastream');
+const $ = require('jquery');
+
+
+navigator.getUserMedia (
+    // constraints
+    {
+        video: true,
+        audio: true
+    },
+
+    // successCallback
+    function(stream) {
+      // var video = document.querySelector('video');
+      // video.src = window.URL.createObjectURL(localMediaStream);
+      // video.onloadedmetadata = function(e) {
+      //     // Do something with the video here.
+      // };
+      attachmediastream(stream, document.querySelector('#vid video'));
+      document.querySelector('#vid video').muted = true;
+      var speakingEvents = new Sibilant(stream, {passThrough: false});
+
+      console.log("whoa!", speakingEvents.volumes);
+
+      document.querySelector('#button').addEventListener('click', function() {
+        console.log("boooop")
+        speakingEvents.resumeContext().then(() => {
+          console.log('Playback resumed successfully');
+        });
+      });
+        speakingEvents.bind('speaking', function () {
+            document.querySelector('#vid video').style.border = '10px solid #27ae60';
+            console.log('speaking!');
+        });
+
+        speakingEvents.bind('stoppedSpeaking', function (data) {
+            console.log('speaking event recorded!', data.start);
+            var start = new Date(data.start);
+            var end = new Date(data.end);
+            var duration = end - start;
+            $('#info').prepend('You spoke for ' + duration + ' ms! <br>');
+            document.querySelector('#vid video').style.border = '10px solid #555';
+        });
+    },
+
+    // errorCallback
+    function(err) {
+        if(err === 'PERMISSION_DENIED') {
+            alert('Sibilant couldnt get your user media. give it access to audio and try again!', err);
+            console.log("error", err);
+            // Explain why you need permission and how to update the permission setting
+        }
+    }
+);
 
-},{"alerts":2,"attachmediastream":3,"getusermedia":4,"jquery":5,"sibilant-webaudio":9}],2:[function(require,module,exports){
+},{"../":18,"alerts":2,"attachmediastream":3,"getusermedia":4,"jquery":5}],2:[function(require,module,exports){
 var initialized;
 var container = document.createElement('div');
 
@@ -164,7 +189,7 @@ module.exports = function (stream, el, options) {
     return element;
 };
 
-},{"webrtc-adapter":10}],4:[function(require,module,exports){
+},{"webrtc-adapter":7}],4:[function(require,module,exports){
 // getUserMedia helper by @HenrikJoreteg used for navigator.getUserMedia shim
 var adapter = require('webrtc-adapter');
 
@@ -241,20 +266,19 @@ module.exports = function (constraints, cb) {
     });
 };
 
-},{"webrtc-adapter":10}],5:[function(require,module,exports){
-/*eslint-disable no-unused-vars*/
+},{"webrtc-adapter":7}],5:[function(require,module,exports){
 /*!
- * jQuery JavaScript Library v3.1.0
+ * jQuery JavaScript Library v3.3.1
  * https://jquery.com/
  *
  * Includes Sizzle.js
  * https://sizzlejs.com/
  *
- * Copyright jQuery Foundation and other contributors
+ * Copyright JS Foundation and other contributors
  * Released under the MIT license
  * https://jquery.org/license
  *
- * Date: 2016-07-07T21:44Z
+ * Date: 2018-01-20T17:24Z
  */
 ( function( global, factory ) {
 
@@ -316,24 +340,65 @@ var ObjectFunctionString = fnToString.call( Object );
 
 var support = {};
 
+var isFunction = function isFunction( obj ) {
+
+      // Support: Chrome <=57, Firefox <=52
+      // In some browsers, typeof returns "function" for HTML <object> elements
+      // (i.e., `typeof document.createElement( "object" ) === "function"`).
+      // We don't want to classify *any* DOM node as a function.
+      return typeof obj === "function" && typeof obj.nodeType !== "number";
+  };
+
+
+var isWindow = function isWindow( obj ) {
+		return obj != null && obj === obj.window;
+	};
+
+
+
 
+	var preservedScriptAttributes = {
+		type: true,
+		src: true,
+		noModule: true
+	};
 
-	function DOMEval( code, doc ) {
+	function DOMEval( code, doc, node ) {
 		doc = doc || document;
 
-		var script = doc.createElement( "script" );
+		var i,
+			script = doc.createElement( "script" );
 
 		script.text = code;
+		if ( node ) {
+			for ( i in preservedScriptAttributes ) {
+				if ( node[ i ] ) {
+					script[ i ] = node[ i ];
+				}
+			}
+		}
 		doc.head.appendChild( script ).parentNode.removeChild( script );
 	}
+
+
+function toType( obj ) {
+	if ( obj == null ) {
+		return obj + "";
+	}
+
+	// Support: Android <=2.3 only (functionish RegExp)
+	return typeof obj === "object" || typeof obj === "function" ?
+		class2type[ toString.call( obj ) ] || "object" :
+		typeof obj;
+}
 /* global Symbol */
-// Defining this global in .eslintrc would create a danger of using the global
+// Defining this global in .eslintrc.json would create a danger of using the global
 // unguarded in another place, it seems safer to define global only for this module
 
 
 
 var
-	version = "3.1.0",
+	version = "3.3.1",
 
 	// Define a local copy of jQuery
 	jQuery = function( selector, context ) {
@@ -345,16 +410,7 @@ var
 
 	// Support: Android <=4.0 only
 	// Make sure we trim BOM and NBSP
-	rtrim = /^[\s\uFEFF\xA0]+|[\s\uFEFF\xA0]+$/g,
-
-	// Matches dashed string for camelizing
-	rmsPrefix = /^-ms-/,
-	rdashAlpha = /-([a-z])/g,
-
-	// Used by jQuery.camelCase as callback to replace()
-	fcamelCase = function( all, letter ) {
-		return letter.toUpperCase();
-	};
+	rtrim = /^[\s\uFEFF\xA0]+|[\s\uFEFF\xA0]+$/g;
 
 jQuery.fn = jQuery.prototype = {
 
@@ -373,13 +429,14 @@ jQuery.fn = jQuery.prototype = {
 	// Get the Nth element in the matched element set OR
 	// Get the whole matched element set as a clean array
 	get: function( num ) {
-		return num != null ?
 
-			// Return just the one element from the set
-			( num < 0 ? this[ num + this.length ] : this[ num ] ) :
+		// Return all the elements in a clean array
+		if ( num == null ) {
+			return slice.call( this );
+		}
 
-			// Return all the elements in a clean array
-			slice.call( this );
+		// Return just the one element from the set
+		return num < 0 ? this[ num + this.length ] : this[ num ];
 	},
 
 	// Take an array of elements and push it onto the stack
@@ -453,7 +510,7 @@ jQuery.extend = jQuery.fn.extend = function() {
 	}
 
 	// Handle case when target is a string or something (possible in deep copy)
-	if ( typeof target !== "object" && !jQuery.isFunction( target ) ) {
+	if ( typeof target !== "object" && !isFunction( target ) ) {
 		target = {};
 	}
 
@@ -480,11 +537,11 @@ jQuery.extend = jQuery.fn.extend = function() {
 
 				// Recurse if we're merging plain objects or arrays
 				if ( deep && copy && ( jQuery.isPlainObject( copy ) ||
-					( copyIsArray = jQuery.isArray( copy ) ) ) ) {
+					( copyIsArray = Array.isArray( copy ) ) ) ) {
 
 					if ( copyIsArray ) {
 						copyIsArray = false;
-						clone = src && jQuery.isArray( src ) ? src : [];
+						clone = src && Array.isArray( src ) ? src : [];
 
 					} else {
 						clone = src && jQuery.isPlainObject( src ) ? src : {};
@@ -519,30 +576,6 @@ jQuery.extend( {
 
 	noop: function() {},
 
-	isFunction: function( obj ) {
-		return jQuery.type( obj ) === "function";
-	},
-
-	isArray: Array.isArray,
-
-	isWindow: function( obj ) {
-		return obj != null && obj === obj.window;
-	},
-
-	isNumeric: function( obj ) {
-
-		// As of jQuery 3.0, isNumeric is limited to
-		// strings and numbers (primitives or objects)
-		// that can be coerced to finite numbers (gh-2662)
-		var type = jQuery.type( obj );
-		return ( type === "number" || type === "string" ) &&
-
-			// parseFloat NaNs numeric-cast false positives ("")
-			// ...but misinterprets leading-number strings, particularly hex literals ("0x...")
-			// subtraction forces infinities to NaN
-			!isNaN( obj - parseFloat( obj ) );
-	},
-
 	isPlainObject: function( obj ) {
 		var proto, Ctor;
 
@@ -576,33 +609,11 @@ jQuery.extend( {
 		return true;
 	},
 
-	type: function( obj ) {
-		if ( obj == null ) {
-			return obj + "";
-		}
-
-		// Support: Android <=2.3 only (functionish RegExp)
-		return typeof obj === "object" || typeof obj === "function" ?
-			class2type[ toString.call( obj ) ] || "object" :
-			typeof obj;
-	},
-
 	// Evaluates a script in a global context
 	globalEval: function( code ) {
 		DOMEval( code );
 	},
 
-	// Convert dashed to camelCase; used by the css and data modules
-	// Support: IE <=9 - 11, Edge 12 - 13
-	// Microsoft forgot to hump their vendor prefix (#9572)
-	camelCase: function( string ) {
-		return string.replace( rmsPrefix, "ms-" ).replace( rdashAlpha, fcamelCase );
-	},
-
-	nodeName: function( elem, name ) {
-		return elem.nodeName && elem.nodeName.toLowerCase() === name.toLowerCase();
-	},
-
 	each: function( obj, callback ) {
 		var length, i = 0;
 
@@ -723,37 +734,6 @@ jQuery.extend( {
 	// A global GUID counter for objects
 	guid: 1,
 
-	// Bind a function to a context, optionally partially applying any
-	// arguments.
-	proxy: function( fn, context ) {
-		var tmp, args, proxy;
-
-		if ( typeof context === "string" ) {
-			tmp = fn[ context ];
-			context = fn;
-			fn = tmp;
-		}
-
-		// Quick check to determine if target is callable, in the spec
-		// this throws a TypeError, but we will just return undefined.
-		if ( !jQuery.isFunction( fn ) ) {
-			return undefined;
-		}
-
-		// Simulated bind
-		args = slice.call( arguments, 2 );
-		proxy = function() {
-			return fn.apply( context || this, args.concat( slice.call( arguments ) ) );
-		};
-
-		// Set the guid of unique handler to the same of original handler, so it can be removed
-		proxy.guid = fn.guid = fn.guid || jQuery.guid++;
-
-		return proxy;
-	},
-
-	now: Date.now,
-
 	// jQuery.support is not used in Core but other projects attach their
 	// properties to it so it needs to exist.
 	support: support
@@ -776,9 +756,9 @@ function isArrayLike( obj ) {
 	// hasOwn isn't used here due to false negatives
 	// regarding Nodelist length in IE
 	var length = !!obj && "length" in obj && obj.length,
-		type = jQuery.type( obj );
+		type = toType( obj );
 
-	if ( type === "function" || jQuery.isWindow( obj ) ) {
+	if ( isFunction( obj ) || isWindow( obj ) ) {
 		return false;
 	}
 
@@ -787,14 +767,14 @@ function isArrayLike( obj ) {
 }
 var Sizzle =
 /*!
- * Sizzle CSS Selector Engine v2.3.0
+ * Sizzle CSS Selector Engine v2.3.3
  * https://sizzlejs.com/
  *
  * Copyright jQuery Foundation and other contributors
  * Released under the MIT license
  * http://jquery.org/license
  *
- * Date: 2016-01-04
+ * Date: 2016-08-08
  */
 (function( window ) {
 
@@ -940,7 +920,7 @@ var i,
 
 	// CSS string/identifier serialization
 	// https://drafts.csswg.org/cssom/#common-serializing-idioms
-	rcssescape = /([\0-\x1f\x7f]|^-?\d)|^-$|[^\x80-\uFFFF\w-]/g,
+	rcssescape = /([\0-\x1f\x7f]|^-?\d)|^-$|[^\0-\x1f\x7f-\uFFFF\w-]/g,
 	fcssescape = function( ch, asCodePoint ) {
 		if ( asCodePoint ) {
 
@@ -967,7 +947,7 @@ var i,
 
 	disabledAncestor = addCombinator(
 		function( elem ) {
-			return elem.disabled === true;
+			return elem.disabled === true && ("form" in elem || "label" in elem);
 		},
 		{ dir: "parentNode", next: "legend" }
 	);
@@ -1253,26 +1233,54 @@ function createButtonPseudo( type ) {
  * @param {Boolean} disabled true for :disabled; false for :enabled
  */
 function createDisabledPseudo( disabled ) {
-	// Known :disabled false positives:
-	// IE: *[disabled]:not(button, input, select, textarea, optgroup, option, menuitem, fieldset)
-	// not IE: fieldset[disabled] > legend:nth-of-type(n+2) :can-disable
+
+	// Known :disabled false positives: fieldset[disabled] > legend:nth-of-type(n+2) :can-disable
 	return function( elem ) {
 
-		// Check form elements and option elements for explicit disabling
-		return "label" in elem && elem.disabled === disabled ||
-			"form" in elem && elem.disabled === disabled ||
+		// Only certain elements can match :enabled or :disabled
+		// https://html.spec.whatwg.org/multipage/scripting.html#selector-enabled
+		// https://html.spec.whatwg.org/multipage/scripting.html#selector-disabled
+		if ( "form" in elem ) {
+
+			// Check for inherited disabledness on relevant non-disabled elements:
+			// * listed form-associated elements in a disabled fieldset
+			//   https://html.spec.whatwg.org/multipage/forms.html#category-listed
+			//   https://html.spec.whatwg.org/multipage/forms.html#concept-fe-disabled
+			// * option elements in a disabled optgroup
+			//   https://html.spec.whatwg.org/multipage/forms.html#concept-option-disabled
+			// All such elements have a "form" property.
+			if ( elem.parentNode && elem.disabled === false ) {
+
+				// Option elements defer to a parent optgroup if present
+				if ( "label" in elem ) {
+					if ( "label" in elem.parentNode ) {
+						return elem.parentNode.disabled === disabled;
+					} else {
+						return elem.disabled === disabled;
+					}
+				}
 
-			// Check non-disabled form elements for fieldset[disabled] ancestors
-			"form" in elem && elem.disabled === false && (
-				// Support: IE6-11+
-				// Ancestry is covered for us
-				elem.isDisabled === disabled ||
+				// Support: IE 6 - 11
+				// Use the isDisabled shortcut property to check for disabled fieldset ancestors
+				return elem.isDisabled === disabled ||
 
-				// Otherwise, assume any non-<option> under fieldset[disabled] is disabled
-				/* jshint -W018 */
-				elem.isDisabled !== !disabled &&
-					("label" in elem || !disabledAncestor( elem )) !== disabled
-			);
+					// Where there is no isDisabled, check manually
+					/* jshint -W018 */
+					elem.isDisabled !== !disabled &&
+						disabledAncestor( elem ) === disabled;
+			}
+
+			return elem.disabled === disabled;
+
+		// Try to winnow out elements that can't be disabled before trusting the disabled property.
+		// Some victims get caught in our net (label, legend, menu, track), but it shouldn't
+		// even exist on them, let alone have a boolean value.
+		} else if ( "label" in elem ) {
+			return elem.disabled === disabled;
+		}
+
+		// Remaining elements are neither :enabled nor :disabled
+		return false;
 	};
 }
 
@@ -1388,25 +1396,21 @@ setDocument = Sizzle.setDocument = function( node ) {
 		return !document.getElementsByName || !document.getElementsByName( expando ).length;
 	});
 
-	// ID find and filter
+	// ID filter and find
 	if ( support.getById ) {
-		Expr.find["ID"] = function( id, context ) {
-			if ( typeof context.getElementById !== "undefined" && documentIsHTML ) {
-				var m = context.getElementById( id );
-				return m ? [ m ] : [];
-			}
-		};
 		Expr.filter["ID"] = function( id ) {
 			var attrId = id.replace( runescape, funescape );
 			return function( elem ) {
 				return elem.getAttribute("id") === attrId;
 			};
 		};
+		Expr.find["ID"] = function( id, context ) {
+			if ( typeof context.getElementById !== "undefined" && documentIsHTML ) {
+				var elem = context.getElementById( id );
+				return elem ? [ elem ] : [];
+			}
+		};
 	} else {
-		// Support: IE6/7
-		// getElementById is not reliable as a find shortcut
-		delete Expr.find["ID"];
-
 		Expr.filter["ID"] =  function( id ) {
 			var attrId = id.replace( runescape, funescape );
 			return function( elem ) {
@@ -1415,6 +1419,36 @@ setDocument = Sizzle.setDocument = function( node ) {
 				return node && node.value === attrId;
 			};
 		};
+
+		// Support: IE 6 - 7 only
+		// getElementById is not reliable as a find shortcut
+		Expr.find["ID"] = function( id, context ) {
+			if ( typeof context.getElementById !== "undefined" && documentIsHTML ) {
+				var node, i, elems,
+					elem = context.getElementById( id );
+
+				if ( elem ) {
+
+					// Verify the id attribute
+					node = elem.getAttributeNode("id");
+					if ( node && node.value === id ) {
+						return [ elem ];
+					}
+
+					// Fall back on getElementsByName
+					elems = context.getElementsByName( id );
+					i = 0;
+					while ( (elem = elems[i++]) ) {
+						node = elem.getAttributeNode("id");
+						if ( node && node.value === id ) {
+							return [ elem ];
+						}
+					}
+				}
+
+				return [];
+			}
+		};
 	}
 
 	// Tag
@@ -2455,6 +2489,7 @@ function addCombinator( matcher, combinator, base ) {
 					return matcher( elem, context, xml );
 				}
 			}
+			return false;
 		} :
 
 		// Check against all ancestor/preceding elements
@@ -2499,6 +2534,7 @@ function addCombinator( matcher, combinator, base ) {
 					}
 				}
 			}
+			return false;
 		};
 }
 
@@ -2861,8 +2897,7 @@ select = Sizzle.select = function( selector, context, results, seed ) {
 		// Reduce context if the leading compound selector is an ID
 		tokens = match[0] = match[0].slice( 0 );
 		if ( tokens.length > 2 && (token = tokens[0]).type === "ID" &&
-				support.getById && context.nodeType === 9 && documentIsHTML &&
-				Expr.relative[ tokens[1].type ] ) {
+				context.nodeType === 9 && documentIsHTML && Expr.relative[ tokens[1].type ] ) {
 
 			context = ( Expr.find["ID"]( token.matches[0].replace(runescape, funescape), context ) || [] )[0];
 			if ( !context ) {
@@ -3032,39 +3067,41 @@ var siblings = function( n, elem ) {
 
 var rneedsContext = jQuery.expr.match.needsContext;
 
-var rsingleTag = ( /^<([a-z][^\/\0>:\x20\t\r\n\f]*)[\x20\t\r\n\f]*\/?>(?:<\/\1>|)$/i );
 
 
+function nodeName( elem, name ) {
+
+  return elem.nodeName && elem.nodeName.toLowerCase() === name.toLowerCase();
+
+};
+var rsingleTag = ( /^<([a-z][^\/\0>:\x20\t\r\n\f]*)[\x20\t\r\n\f]*\/?>(?:<\/\1>|)$/i );
+
 
-var risSimple = /^.[^:#\[\.,]*$/;
 
 // Implement the identical functionality for filter and not
 function winnow( elements, qualifier, not ) {
-	if ( jQuery.isFunction( qualifier ) ) {
+	if ( isFunction( qualifier ) ) {
 		return jQuery.grep( elements, function( elem, i ) {
 			return !!qualifier.call( elem, i, elem ) !== not;
 		} );
-
 	}
 
+	// Single element
 	if ( qualifier.nodeType ) {
 		return jQuery.grep( elements, function( elem ) {
 			return ( elem === qualifier ) !== not;
 		} );
-
 	}
 
-	if ( typeof qualifier === "string" ) {
-		if ( risSimple.test( qualifier ) ) {
-			return jQuery.filter( qualifier, elements, not );
-		}
-
-		qualifier = jQuery.filter( qualifier, elements );
+	// Arraylike of elements (jQuery, arguments, Array)
+	if ( typeof qualifier !== "string" ) {
+		return jQuery.grep( elements, function( elem ) {
+			return ( indexOf.call( qualifier, elem ) > -1 ) !== not;
+		} );
 	}
 
-	return jQuery.grep( elements, function( elem ) {
-		return ( indexOf.call( qualifier, elem ) > -1 ) !== not && elem.nodeType === 1;
-	} );
+	// Filtered directly for both simple and complex selectors
+	return jQuery.filter( qualifier, elements, not );
 }
 
 jQuery.filter = function( expr, elems, not ) {
@@ -3074,11 +3111,13 @@ jQuery.filter = function( expr, elems, not ) {
 		expr = ":not(" + expr + ")";
 	}
 
-	return elems.length === 1 && elem.nodeType === 1 ?
-		jQuery.find.matchesSelector( elem, expr ) ? [ elem ] : [] :
-		jQuery.find.matches( expr, jQuery.grep( elems, function( elem ) {
-			return elem.nodeType === 1;
-		} ) );
+	if ( elems.length === 1 && elem.nodeType === 1 ) {
+		return jQuery.find.matchesSelector( elem, expr ) ? [ elem ] : [];
+	}
+
+	return jQuery.find.matches( expr, jQuery.grep( elems, function( elem ) {
+		return elem.nodeType === 1;
+	} ) );
 };
 
 jQuery.fn.extend( {
@@ -3183,7 +3222,7 @@ var rootjQuery,
 						for ( match in context ) {
 
 							// Properties of context are called as methods if possible
-							if ( jQuery.isFunction( this[ match ] ) ) {
+							if ( isFunction( this[ match ] ) ) {
 								this[ match ]( context[ match ] );
 
 							// ...and otherwise set as attributes
@@ -3226,7 +3265,7 @@ var rootjQuery,
 
 		// HANDLE: $(function)
 		// Shortcut for document ready
-		} else if ( jQuery.isFunction( selector ) ) {
+		} else if ( isFunction( selector ) ) {
 			return root.ready !== undefined ?
 				root.ready( selector ) :
 
@@ -3376,7 +3415,18 @@ jQuery.each( {
 		return siblings( elem.firstChild );
 	},
 	contents: function( elem ) {
-		return elem.contentDocument || jQuery.merge( [], elem.childNodes );
+        if ( nodeName( elem, "iframe" ) ) {
+            return elem.contentDocument;
+        }
+
+        // Support: IE 9 - 11 only, iOS 7 only, Android Browser <=4.3 only
+        // Treat the template element as a regular one in browsers that
+        // don't support it.
+        if ( nodeName( elem, "template" ) ) {
+            elem = elem.content || elem;
+        }
+
+        return jQuery.merge( [], elem.childNodes );
 	}
 }, function( name, fn ) {
 	jQuery.fn[ name ] = function( until, selector ) {
@@ -3406,14 +3456,14 @@ jQuery.each( {
 		return this.pushStack( matched );
 	};
 } );
-var rnotwhite = ( /\S+/g );
+var rnothtmlwhite = ( /[^\x20\t\r\n\f]+/g );
 
 
 
 // Convert String-formatted options into Object-formatted ones
 function createOptions( options ) {
 	var object = {};
-	jQuery.each( options.match( rnotwhite ) || [], function( _, flag ) {
+	jQuery.each( options.match( rnothtmlwhite ) || [], function( _, flag ) {
 		object[ flag ] = true;
 	} );
 	return object;
@@ -3474,7 +3524,7 @@ jQuery.Callbacks = function( options ) {
 		fire = function() {
 
 			// Enforce single-firing
-			locked = options.once;
+			locked = locked || options.once;
 
 			// Execute callbacks for all pending executions,
 			// respecting firingIndex overrides and runtime changes
@@ -3530,11 +3580,11 @@ jQuery.Callbacks = function( options ) {
 
 					( function add( args ) {
 						jQuery.each( args, function( _, arg ) {
-							if ( jQuery.isFunction( arg ) ) {
+							if ( isFunction( arg ) ) {
 								if ( !options.unique || !self.has( arg ) ) {
 									list.push( arg );
 								}
-							} else if ( arg && arg.length && jQuery.type( arg ) !== "string" ) {
+							} else if ( arg && arg.length && toType( arg ) !== "string" ) {
 
 								// Inspect recursively
 								add( arg );
@@ -3643,25 +3693,26 @@ function Thrower( ex ) {
 	throw ex;
 }
 
-function adoptValue( value, resolve, reject ) {
+function adoptValue( value, resolve, reject, noValue ) {
 	var method;
 
 	try {
 
 		// Check for promise aspect first to privilege synchronous behavior
-		if ( value && jQuery.isFunction( ( method = value.promise ) ) ) {
+		if ( value && isFunction( ( method = value.promise ) ) ) {
 			method.call( value ).done( resolve ).fail( reject );
 
 		// Other thenables
-		} else if ( value && jQuery.isFunction( ( method = value.then ) ) ) {
+		} else if ( value && isFunction( ( method = value.then ) ) ) {
 			method.call( value, resolve, reject );
 
 		// Other non-thenables
 		} else {
 
-			// Support: Android 4.0 only
-			// Strict mode functions invoked without .call/.apply get global-object context
-			resolve.call( undefined, value );
+			// Control `resolve` arguments by letting Array#slice cast boolean `noValue` to integer:
+			// * false: [ value ].slice( 0 ) => resolve( value )
+			// * true: [ value ].slice( 1 ) => resolve()
+			resolve.apply( undefined, [ value ].slice( noValue ) );
 		}
 
 	// For Promises/A+, convert exceptions into rejections
@@ -3671,7 +3722,7 @@ function adoptValue( value, resolve, reject ) {
 
 		// Support: Android 4.0 only
 		// Strict mode functions invoked without .call/.apply get global-object context
-		reject.call( undefined, value );
+		reject.apply( undefined, [ value ] );
 	}
 }
 
@@ -3710,14 +3761,14 @@ jQuery.extend( {
 						jQuery.each( tuples, function( i, tuple ) {
 
 							// Map tuples (progress, done, fail) to arguments (done, fail, progress)
-							var fn = jQuery.isFunction( fns[ tuple[ 4 ] ] ) && fns[ tuple[ 4 ] ];
+							var fn = isFunction( fns[ tuple[ 4 ] ] ) && fns[ tuple[ 4 ] ];
 
 							// deferred.progress(function() { bind to newDefer or newDefer.notify })
 							// deferred.done(function() { bind to newDefer or newDefer.resolve })
 							// deferred.fail(function() { bind to newDefer or newDefer.reject })
 							deferred[ tuple[ 1 ] ]( function() {
 								var returned = fn && fn.apply( this, arguments );
-								if ( returned && jQuery.isFunction( returned.promise ) ) {
+								if ( returned && isFunction( returned.promise ) ) {
 									returned.promise()
 										.progress( newDefer.notify )
 										.done( newDefer.resolve )
@@ -3771,7 +3822,7 @@ jQuery.extend( {
 										returned.then;
 
 									// Handle a returned thenable
-									if ( jQuery.isFunction( then ) ) {
+									if ( isFunction( then ) ) {
 
 										// Special processors (notify) just wait for resolution
 										if ( special ) {
@@ -3867,7 +3918,7 @@ jQuery.extend( {
 							resolve(
 								0,
 								newDefer,
-								jQuery.isFunction( onProgress ) ?
+								isFunction( onProgress ) ?
 									onProgress :
 									Identity,
 								newDefer.notifyWith
@@ -3879,7 +3930,7 @@ jQuery.extend( {
 							resolve(
 								0,
 								newDefer,
-								jQuery.isFunction( onFulfilled ) ?
+								isFunction( onFulfilled ) ?
 									onFulfilled :
 									Identity
 							)
@@ -3890,7 +3941,7 @@ jQuery.extend( {
 							resolve(
 								0,
 								newDefer,
-								jQuery.isFunction( onRejected ) ?
+								isFunction( onRejected ) ?
 									onRejected :
 									Thrower
 							)
@@ -3930,8 +3981,15 @@ jQuery.extend( {
 					// fulfilled_callbacks.disable
 					tuples[ 3 - i ][ 2 ].disable,
 
+					// rejected_handlers.disable
+					// fulfilled_handlers.disable
+					tuples[ 3 - i ][ 3 ].disable,
+
 					// progress_callbacks.lock
-					tuples[ 0 ][ 2 ].lock
+					tuples[ 0 ][ 2 ].lock,
+
+					// progress_handlers.lock
+					tuples[ 0 ][ 3 ].lock
 				);
 			}
 
@@ -3996,11 +4054,12 @@ jQuery.extend( {
 
 		// Single- and empty arguments are adopted like Promise.resolve
 		if ( remaining <= 1 ) {
-			adoptValue( singleValue, master.done( updateFunc( i ) ).resolve, master.reject );
+			adoptValue( singleValue, master.done( updateFunc( i ) ).resolve, master.reject,
+				!remaining );
 
 			// Use .then() to unwrap secondary thenables (cf. gh-3000)
 			if ( master.state() === "pending" ||
-				jQuery.isFunction( resolveValues[ i ] && resolveValues[ i ].then ) ) {
+				isFunction( resolveValues[ i ] && resolveValues[ i ].then ) ) {
 
 				return master.then();
 			}
@@ -4068,15 +4127,6 @@ jQuery.extend( {
 	// the ready event fires. See #6781
 	readyWait: 1,
 
-	// Hold (or release) the ready event
-	holdReady: function( hold ) {
-		if ( hold ) {
-			jQuery.readyWait++;
-		} else {
-			jQuery.ready( true );
-		}
-	},
-
 	// Handle when the DOM is ready
 	ready: function( wait ) {
 
@@ -4137,7 +4187,7 @@ var access = function( elems, fn, key, value, chainable, emptyGet, raw ) {
 		bulk = key == null;
 
 	// Sets many values
-	if ( jQuery.type( key ) === "object" ) {
+	if ( toType( key ) === "object" ) {
 		chainable = true;
 		for ( i in key ) {
 			access( elems, fn, i, key[ i ], true, emptyGet, raw );
@@ -4147,7 +4197,7 @@ var access = function( elems, fn, key, value, chainable, emptyGet, raw ) {
 	} else if ( value !== undefined ) {
 		chainable = true;
 
-		if ( !jQuery.isFunction( value ) ) {
+		if ( !isFunction( value ) ) {
 			raw = true;
 		}
 
@@ -4178,14 +4228,34 @@ var access = function( elems, fn, key, value, chainable, emptyGet, raw ) {
 		}
 	}
 
-	return chainable ?
-		elems :
+	if ( chainable ) {
+		return elems;
+	}
+
+	// Gets
+	if ( bulk ) {
+		return fn.call( elems );
+	}
 
-		// Gets
-		bulk ?
-			fn.call( elems ) :
-			len ? fn( elems[ 0 ], key ) : emptyGet;
+	return len ? fn( elems[ 0 ], key ) : emptyGet;
 };
+
+
+// Matches dashed string for camelizing
+var rmsPrefix = /^-ms-/,
+	rdashAlpha = /-([a-z])/g;
+
+// Used by camelCase as callback to replace()
+function fcamelCase( all, letter ) {
+	return letter.toUpperCase();
+}
+
+// Convert dashed to camelCase; used by the css and data modules
+// Support: IE <=9 - 11, Edge 12 - 15
+// Microsoft forgot to hump their vendor prefix (#9572)
+function camelCase( string ) {
+	return string.replace( rmsPrefix, "ms-" ).replace( rdashAlpha, fcamelCase );
+}
 var acceptData = function( owner ) {
 
 	// Accepts only:
@@ -4248,14 +4318,14 @@ Data.prototype = {
 		// Handle: [ owner, key, value ] args
 		// Always use camelCase key (gh-2257)
 		if ( typeof data === "string" ) {
-			cache[ jQuery.camelCase( data ) ] = value;
+			cache[ camelCase( data ) ] = value;
 
 		// Handle: [ owner, { properties } ] args
 		} else {
 
 			// Copy the properties one-by-one to the cache object
 			for ( prop in data ) {
-				cache[ jQuery.camelCase( prop ) ] = data[ prop ];
+				cache[ camelCase( prop ) ] = data[ prop ];
 			}
 		}
 		return cache;
@@ -4265,7 +4335,7 @@ Data.prototype = {
 			this.cache( owner ) :
 
 			// Always use camelCase key (gh-2257)
-			owner[ this.expando ] && owner[ this.expando ][ jQuery.camelCase( key ) ];
+			owner[ this.expando ] && owner[ this.expando ][ camelCase( key ) ];
 	},
 	access: function( owner, key, value ) {
 
@@ -4309,19 +4379,19 @@ Data.prototype = {
 		if ( key !== undefined ) {
 
 			// Support array or space separated string of keys
-			if ( jQuery.isArray( key ) ) {
+			if ( Array.isArray( key ) ) {
 
 				// If key is an array of keys...
 				// We always set camelCase keys, so remove that.
-				key = key.map( jQuery.camelCase );
+				key = key.map( camelCase );
 			} else {
-				key = jQuery.camelCase( key );
+				key = camelCase( key );
 
 				// If a key with the spaces exists, use it.
 				// Otherwise, create an array by matching non-whitespace
 				key = key in cache ?
 					[ key ] :
-					( key.match( rnotwhite ) || [] );
+					( key.match( rnothtmlwhite ) || [] );
 			}
 
 			i = key.length;
@@ -4369,6 +4439,31 @@ var dataUser = new Data();
 var rbrace = /^(?:\{[\w\W]*\}|\[[\w\W]*\])$/,
 	rmultiDash = /[A-Z]/g;
 
+function getData( data ) {
+	if ( data === "true" ) {
+		return true;
+	}
+
+	if ( data === "false" ) {
+		return false;
+	}
+
+	if ( data === "null" ) {
+		return null;
+	}
+
+	// Only convert to a number if it doesn't change the string
+	if ( data === +data + "" ) {
+		return +data;
+	}
+
+	if ( rbrace.test( data ) ) {
+		return JSON.parse( data );
+	}
+
+	return data;
+}
+
 function dataAttr( elem, key, data ) {
 	var name;
 
@@ -4380,14 +4475,7 @@ function dataAttr( elem, key, data ) {
 
 		if ( typeof data === "string" ) {
 			try {
-				data = data === "true" ? true :
-					data === "false" ? false :
-					data === "null" ? null :
-
-					// Only convert to a number if it doesn't change the string
-					+data + "" === data ? +data :
-					rbrace.test( data ) ? JSON.parse( data ) :
-					data;
+				data = getData( data );
 			} catch ( e ) {}
 
 			// Make sure we set the data so it isn't changed later
@@ -4443,7 +4531,7 @@ jQuery.fn.extend( {
 						if ( attrs[ i ] ) {
 							name = attrs[ i ].name;
 							if ( name.indexOf( "data-" ) === 0 ) {
-								name = jQuery.camelCase( name.slice( 5 ) );
+								name = camelCase( name.slice( 5 ) );
 								dataAttr( elem, name, data[ name ] );
 							}
 						}
@@ -4517,7 +4605,7 @@ jQuery.extend( {
 
 			// Speed up dequeue by getting out quickly if this is just a lookup
 			if ( data ) {
-				if ( !queue || jQuery.isArray( data ) ) {
+				if ( !queue || Array.isArray( data ) ) {
 					queue = dataPriv.access( elem, type, jQuery.makeArray( data ) );
 				} else {
 					queue.push( data );
@@ -4690,8 +4778,7 @@ var swap = function( elem, options, callback, args ) {
 
 
 function adjustCSS( elem, prop, valueParts, tween ) {
-	var adjusted,
-		scale = 1,
+	var adjusted, scale,
 		maxIterations = 20,
 		currentValue = tween ?
 			function() {
@@ -4709,30 +4796,33 @@ function adjustCSS( elem, prop, valueParts, tween ) {
 
 	if ( initialInUnit && initialInUnit[ 3 ] !== unit ) {
 
+		// Support: Firefox <=54
+		// Halve the iteration target value to prevent interference from CSS upper bounds (gh-2144)
+		initial = initial / 2;
+
 		// Trust units reported by jQuery.css
 		unit = unit || initialInUnit[ 3 ];
 
-		// Make sure we update the tween properties later on
-		valueParts = valueParts || [];
-
 		// Iteratively approximate from a nonzero starting point
 		initialInUnit = +initial || 1;
 
-		do {
-
-			// If previous iteration zeroed out, double until we get *something*.
-			// Use string for doubling so we don't accidentally see scale as unchanged below
-			scale = scale || ".5";
+		while ( maxIterations-- ) {
 
-			// Adjust and apply
-			initialInUnit = initialInUnit / scale;
+			// Evaluate and update our best guess (doubling guesses that zero out).
+			// Finish if the scale equals or crosses 1 (making the old*new product non-positive).
 			jQuery.style( elem, prop, initialInUnit + unit );
+			if ( ( 1 - scale ) * ( 1 - ( scale = currentValue() / initial || 0.5 ) ) <= 0 ) {
+				maxIterations = 0;
+			}
+			initialInUnit = initialInUnit / scale;
 
-		// Update scale, tolerating zero or NaN from tween.cur()
-		// Break the loop if scale is unchanged or perfect, or if we've just had enough.
-		} while (
-			scale !== ( scale = currentValue() / initial ) && scale !== 1 && --maxIterations
-		);
+		}
+
+		initialInUnit = initialInUnit * 2;
+		jQuery.style( elem, prop, initialInUnit + unit );
+
+		// Make sure we update the tween properties later on
+		valueParts = valueParts || [];
 	}
 
 	if ( valueParts ) {
@@ -4764,7 +4854,7 @@ function getDefaultDisplay( elem ) {
 		return display;
 	}
 
-	temp = doc.body.appendChild( doc.createElement( nodeName ) ),
+	temp = doc.body.appendChild( doc.createElement( nodeName ) );
 	display = jQuery.css( temp, "display" );
 
 	temp.parentNode.removeChild( temp );
@@ -4850,7 +4940,7 @@ var rcheckableType = ( /^(?:checkbox|radio)$/i );
 
 var rtagName = ( /<([a-z][^\/\0>\x20\t\r\n\f]+)/i );
 
-var rscriptType = ( /^$|\/(?:java|ecma)script/i );
+var rscriptType = ( /^$|^module$|\/(?:java|ecma)script/i );
 
 
 
@@ -4882,15 +4972,23 @@ function getAll( context, tag ) {
 
 	// Support: IE <=9 - 11 only
 	// Use typeof to avoid zero-argument method invocation on host objects (#15151)
-	var ret = typeof context.getElementsByTagName !== "undefined" ?
-			context.getElementsByTagName( tag || "*" ) :
-			typeof context.querySelectorAll !== "undefined" ?
-				context.querySelectorAll( tag || "*" ) :
-			[];
-
-	return tag === undefined || tag && jQuery.nodeName( context, tag ) ?
-		jQuery.merge( [ context ], ret ) :
-		ret;
+	var ret;
+
+	if ( typeof context.getElementsByTagName !== "undefined" ) {
+		ret = context.getElementsByTagName( tag || "*" );
+
+	} else if ( typeof context.querySelectorAll !== "undefined" ) {
+		ret = context.querySelectorAll( tag || "*" );
+
+	} else {
+		ret = [];
+	}
+
+	if ( tag === undefined || tag && nodeName( context, tag ) ) {
+		return jQuery.merge( [ context ], ret );
+	}
+
+	return ret;
 }
 
 
@@ -4924,7 +5022,7 @@ function buildFragment( elems, context, scripts, selection, ignored ) {
 		if ( elem || elem === 0 ) {
 
 			// Add nodes directly
-			if ( jQuery.type( elem ) === "object" ) {
+			if ( toType( elem ) === "object" ) {
 
 				// Support: Android <=4.0 only, PhantomJS 1 only
 				// push.apply(_, arraylike) throws on ancient WebKit
@@ -5164,7 +5262,7 @@ jQuery.event = {
 		}
 
 		// Handle multiple events separated by a space
-		types = ( types || "" ).match( rnotwhite ) || [ "" ];
+		types = ( types || "" ).match( rnothtmlwhite ) || [ "" ];
 		t = types.length;
 		while ( t-- ) {
 			tmp = rtypenamespace.exec( types[ t ] ) || [];
@@ -5246,7 +5344,7 @@ jQuery.event = {
 		}
 
 		// Once for each type.namespace in types; type may be omitted
-		types = ( types || "" ).match( rnotwhite ) || [ "" ];
+		types = ( types || "" ).match( rnothtmlwhite ) || [ "" ];
 		t = types.length;
 		while ( t-- ) {
 			tmp = rtypenamespace.exec( types[ t ] ) || [];
@@ -5372,51 +5470,58 @@ jQuery.event = {
 	},
 
 	handlers: function( event, handlers ) {
-		var i, matches, sel, handleObj,
+		var i, handleObj, sel, matchedHandlers, matchedSelectors,
 			handlerQueue = [],
 			delegateCount = handlers.delegateCount,
 			cur = event.target;
 
-		// Support: IE <=9
 		// Find delegate handlers
-		// Black-hole SVG <use> instance trees (#13180)
-		//
-		// Support: Firefox <=42
-		// Avoid non-left-click in FF but don't block IE radio events (#3861, gh-2343)
-		if ( delegateCount && cur.nodeType &&
-			( event.type !== "click" || isNaN( event.button ) || event.button < 1 ) ) {
+		if ( delegateCount &&
+
+			// Support: IE <=9
+			// Black-hole SVG <use> instance trees (trac-13180)
+			cur.nodeType &&
+
+			// Support: Firefox <=42
+			// Suppress spec-violating clicks indicating a non-primary pointer button (trac-3861)
+			// https://www.w3.org/TR/DOM-Level-3-Events/#event-type-click
+			// Support: IE 11 only
+			// ...but not arrow key "clicks" of radio inputs, which can have `button` -1 (gh-2343)
+			!( event.type === "click" && event.button >= 1 ) ) {
 
 			for ( ; cur !== this; cur = cur.parentNode || this ) {
 
 				// Don't check non-elements (#13208)
 				// Don't process clicks on disabled elements (#6911, #8165, #11382, #11764)
-				if ( cur.nodeType === 1 && ( cur.disabled !== true || event.type !== "click" ) ) {
-					matches = [];
+				if ( cur.nodeType === 1 && !( event.type === "click" && cur.disabled === true ) ) {
+					matchedHandlers = [];
+					matchedSelectors = {};
 					for ( i = 0; i < delegateCount; i++ ) {
 						handleObj = handlers[ i ];
 
 						// Don't conflict with Object.prototype properties (#13203)
 						sel = handleObj.selector + " ";
 
-						if ( matches[ sel ] === undefined ) {
-							matches[ sel ] = handleObj.needsContext ?
+						if ( matchedSelectors[ sel ] === undefined ) {
+							matchedSelectors[ sel ] = handleObj.needsContext ?
 								jQuery( sel, this ).index( cur ) > -1 :
 								jQuery.find( sel, this, null, [ cur ] ).length;
 						}
-						if ( matches[ sel ] ) {
-							matches.push( handleObj );
+						if ( matchedSelectors[ sel ] ) {
+							matchedHandlers.push( handleObj );
 						}
 					}
-					if ( matches.length ) {
-						handlerQueue.push( { elem: cur, handlers: matches } );
+					if ( matchedHandlers.length ) {
+						handlerQueue.push( { elem: cur, handlers: matchedHandlers } );
 					}
 				}
 			}
 		}
 
 		// Add the remaining (directly-bound) handlers
+		cur = this;
 		if ( delegateCount < handlers.length ) {
-			handlerQueue.push( { elem: this, handlers: handlers.slice( delegateCount ) } );
+			handlerQueue.push( { elem: cur, handlers: handlers.slice( delegateCount ) } );
 		}
 
 		return handlerQueue;
@@ -5427,7 +5532,7 @@ jQuery.event = {
 			enumerable: true,
 			configurable: true,
 
-			get: jQuery.isFunction( hook ) ?
+			get: isFunction( hook ) ?
 				function() {
 					if ( this.originalEvent ) {
 							return hook( this.originalEvent );
@@ -5486,7 +5591,7 @@ jQuery.event = {
 
 			// For checkbox, fire native event so checked state will be right
 			trigger: function() {
-				if ( this.type === "checkbox" && this.click && jQuery.nodeName( this, "input" ) ) {
+				if ( this.type === "checkbox" && this.click && nodeName( this, "input" ) ) {
 					this.click();
 					return false;
 				}
@@ -5494,7 +5599,7 @@ jQuery.event = {
 
 			// For cross-browser consistency, don't fire native .click() on links
 			_default: function( event ) {
-				return jQuery.nodeName( event.target, "a" );
+				return nodeName( event.target, "a" );
 			}
 		},
 
@@ -5562,7 +5667,7 @@ jQuery.Event = function( src, props ) {
 	}
 
 	// Create a timestamp if incoming event doesn't have one
-	this.timeStamp = src && src.timeStamp || jQuery.now();
+	this.timeStamp = src && src.timeStamp || Date.now();
 
 	// Mark it as fixed
 	this[ jQuery.expando ] = true;
@@ -5650,7 +5755,19 @@ jQuery.each( {
 
 		// Add which for click: 1 === left; 2 === middle; 3 === right
 		if ( !event.which && button !== undefined && rmouseEvent.test( event.type ) ) {
-			return ( button & 1 ? 1 : ( button & 2 ? 3 : ( button & 4 ? 2 : 0 ) ) );
+			if ( button & 1 ) {
+				return 1;
+			}
+
+			if ( button & 2 ) {
+				return 3;
+			}
+
+			if ( button & 4 ) {
+				return 2;
+			}
+
+			return 0;
 		}
 
 		return event.which;
@@ -5749,21 +5866,21 @@ var
 
 	/* eslint-enable */
 
-	// Support: IE <=10 - 11, Edge 12 - 13
+	// Support: IE <=10 - 11, Edge 12 - 13 only
 	// In IE/Edge using regex groups here causes severe slowdowns.
 	// See https://connect.microsoft.com/IE/feedback/details/1736512/
 	rnoInnerhtml = /<script|<style|<link/i,
 
 	// checked="checked" or checked
 	rchecked = /checked\s*(?:[^=]|=\s*.checked.)/i,
-	rscriptTypeMasked = /^true\/(.*)/,
 	rcleanScript = /^\s*<!(?:\[CDATA\[|--)|(?:\]\]|--)>\s*$/g;
 
+// Prefer a tbody over its parent table for containing new rows
 function manipulationTarget( elem, content ) {
-	if ( jQuery.nodeName( elem, "table" ) &&
-		jQuery.nodeName( content.nodeType !== 11 ? content : content.firstChild, "tr" ) ) {
+	if ( nodeName( elem, "table" ) &&
+		nodeName( content.nodeType !== 11 ? content : content.firstChild, "tr" ) ) {
 
-		return elem.getElementsByTagName( "tbody" )[ 0 ] || elem;
+		return jQuery( elem ).children( "tbody" )[ 0 ] || elem;
 	}
 
 	return elem;
@@ -5775,10 +5892,8 @@ function disableScript( elem ) {
 	return elem;
 }
 function restoreScript( elem ) {
-	var match = rscriptTypeMasked.exec( elem.type );
-
-	if ( match ) {
-		elem.type = match[ 1 ];
+	if ( ( elem.type || "" ).slice( 0, 5 ) === "true/" ) {
+		elem.type = elem.type.slice( 5 );
 	} else {
 		elem.removeAttribute( "type" );
 	}
@@ -5844,15 +5959,15 @@ function domManip( collection, args, callback, ignored ) {
 		l = collection.length,
 		iNoClone = l - 1,
 		value = args[ 0 ],
-		isFunction = jQuery.isFunction( value );
+		valueIsFunction = isFunction( value );
 
 	// We can't cloneNode fragments that contain checked, in WebKit
-	if ( isFunction ||
+	if ( valueIsFunction ||
 			( l > 1 && typeof value === "string" &&
 				!support.checkClone && rchecked.test( value ) ) ) {
 		return collection.each( function( index ) {
 			var self = collection.eq( index );
-			if ( isFunction ) {
+			if ( valueIsFunction ) {
 				args[ 0 ] = value.call( this, index, self.html() );
 			}
 			domManip( self, args, callback, ignored );
@@ -5906,14 +6021,14 @@ function domManip( collection, args, callback, ignored ) {
 						!dataPriv.access( node, "globalEval" ) &&
 						jQuery.contains( doc, node ) ) {
 
-						if ( node.src ) {
+						if ( node.src && ( node.type || "" ).toLowerCase()  !== "module" ) {
 
 							// Optional AJAX dependency, but won't run scripts if not present
 							if ( jQuery._evalUrl ) {
 								jQuery._evalUrl( node.src );
 							}
 						} else {
-							DOMEval( node.textContent.replace( rcleanScript, "" ), doc );
+							DOMEval( node.textContent.replace( rcleanScript, "" ), doc, node );
 						}
 					}
 				}
@@ -6193,8 +6308,6 @@ jQuery.each( {
 		return this.pushStack( ret );
 	};
 } );
-var rmargin = ( /^margin/ );
-
 var rnumnonpx = new RegExp( "^(" + pnum + ")(?!px)[a-z%]+$", "i" );
 
 var getStyles = function( elem ) {
@@ -6211,6 +6324,8 @@ var getStyles = function( elem ) {
 		return view.getComputedStyle( elem );
 	};
 
+var rboxStyle = new RegExp( cssExpand.join( "|" ), "i" );
+
 
 
 ( function() {
@@ -6224,25 +6339,33 @@ var getStyles = function( elem ) {
 			return;
 		}
 
+		container.style.cssText = "position:absolute;left:-11111px;width:60px;" +
+			"margin-top:1px;padding:0;border:0";
 		div.style.cssText =
-			"box-sizing:border-box;" +
-			"position:relative;display:block;" +
+			"position:relative;display:block;box-sizing:border-box;overflow:scroll;" +
 			"margin:auto;border:1px;padding:1px;" +
-			"top:1%;width:50%";
-		div.innerHTML = "";
-		documentElement.appendChild( container );
+			"width:60%;top:1%";
+		documentElement.appendChild( container ).appendChild( div );
 
 		var divStyle = window.getComputedStyle( div );
 		pixelPositionVal = divStyle.top !== "1%";
 
 		// Support: Android 4.0 - 4.3 only, Firefox <=3 - 44
-		reliableMarginLeftVal = divStyle.marginLeft === "2px";
-		boxSizingReliableVal = divStyle.width === "4px";
+		reliableMarginLeftVal = roundPixelMeasures( divStyle.marginLeft ) === 12;
 
-		// Support: Android 4.0 - 4.3 only
+		// Support: Android 4.0 - 4.3 only, Safari <=9.1 - 10.1, iOS <=7.0 - 9.3
 		// Some styles come back with percentage values, even though they shouldn't
-		div.style.marginRight = "50%";
-		pixelMarginRightVal = divStyle.marginRight === "4px";
+		div.style.right = "60%";
+		pixelBoxStylesVal = roundPixelMeasures( divStyle.right ) === 36;
+
+		// Support: IE 9 - 11 only
+		// Detect misreporting of content dimensions for box-sizing:border-box elements
+		boxSizingReliableVal = roundPixelMeasures( divStyle.width ) === 36;
+
+		// Support: IE 9 only
+		// Detect overflow:scroll screwiness (gh-3699)
+		div.style.position = "absolute";
+		scrollboxSizeVal = div.offsetWidth === 36 || "absolute";
 
 		documentElement.removeChild( container );
 
@@ -6251,7 +6374,12 @@ var getStyles = function( elem ) {
 		div = null;
 	}
 
-	var pixelPositionVal, boxSizingReliableVal, pixelMarginRightVal, reliableMarginLeftVal,
+	function roundPixelMeasures( measure ) {
+		return Math.round( parseFloat( measure ) );
+	}
+
+	var pixelPositionVal, boxSizingReliableVal, scrollboxSizeVal, pixelBoxStylesVal,
+		reliableMarginLeftVal,
 		container = document.createElement( "div" ),
 		div = document.createElement( "div" );
 
@@ -6266,26 +6394,26 @@ var getStyles = function( elem ) {
 	div.cloneNode( true ).style.backgroundClip = "";
 	support.clearCloneStyle = div.style.backgroundClip === "content-box";
 
-	container.style.cssText = "border:0;width:8px;height:0;top:0;left:-9999px;" +
-		"padding:0;margin-top:1px;position:absolute";
-	container.appendChild( div );
-
 	jQuery.extend( support, {
-		pixelPosition: function() {
-			computeStyleTests();
-			return pixelPositionVal;
-		},
 		boxSizingReliable: function() {
 			computeStyleTests();
 			return boxSizingReliableVal;
 		},
-		pixelMarginRight: function() {
+		pixelBoxStyles: function() {
+			computeStyleTests();
+			return pixelBoxStylesVal;
+		},
+		pixelPosition: function() {
 			computeStyleTests();
-			return pixelMarginRightVal;
+			return pixelPositionVal;
 		},
 		reliableMarginLeft: function() {
 			computeStyleTests();
 			return reliableMarginLeftVal;
+		},
+		scrollboxSize: function() {
+			computeStyleTests();
+			return scrollboxSizeVal;
 		}
 	} );
 } )();
@@ -6293,12 +6421,18 @@ var getStyles = function( elem ) {
 
 function curCSS( elem, name, computed ) {
 	var width, minWidth, maxWidth, ret,
+
+		// Support: Firefox 51+
+		// Retrieving style before computed somehow
+		// fixes an issue with getting wrong values
+		// on detached elements
 		style = elem.style;
 
 	computed = computed || getStyles( elem );
 
-	// Support: IE <=9 only
-	// getPropertyValue is only needed for .css('filter') (#12537)
+	// getPropertyValue is needed for:
+	//   .css('filter') (IE 9 only, #12537)
+	//   .css('--customProperty) (#3144)
 	if ( computed ) {
 		ret = computed.getPropertyValue( name ) || computed[ name ];
 
@@ -6311,7 +6445,7 @@ function curCSS( elem, name, computed ) {
 		// but width seems to be reliably pixels.
 		// This is against the CSSOM draft spec:
 		// https://drafts.csswg.org/cssom/#resolved-values
-		if ( !support.pixelMarginRight() && rnumnonpx.test( ret ) && rmargin.test( name ) ) {
+		if ( !support.pixelBoxStyles() && rnumnonpx.test( ret ) && rboxStyle.test( name ) ) {
 
 			// Remember the original values
 			width = style.width;
@@ -6364,6 +6498,7 @@ var
 	// except "table", "table-cell", or "table-caption"
 	// See here for display values: https://developer.mozilla.org/en-US/docs/CSS/display
 	rdisplayswap = /^(none|table(?!-c[ea]).+)/,
+	rcustomProp = /^--/,
 	cssShow = { position: "absolute", visibility: "hidden", display: "block" },
 	cssNormalTransform = {
 		letterSpacing: "0",
@@ -6393,6 +6528,16 @@ function vendorPropName( name ) {
 	}
 }
 
+// Return a property mapped along what jQuery.cssProps suggests or to
+// a vendor prefixed property.
+function finalPropName( name ) {
+	var ret = jQuery.cssProps[ name ];
+	if ( !ret ) {
+		ret = jQuery.cssProps[ name ] = vendorPropName( name ) || name;
+	}
+	return ret;
+}
+
 function setPositiveNumber( elem, value, subtract ) {
 
 	// Any relative (+/-) values have already been
@@ -6405,98 +6550,120 @@ function setPositiveNumber( elem, value, subtract ) {
 		value;
 }
 
-function augmentWidthOrHeight( elem, name, extra, isBorderBox, styles ) {
-	var i = extra === ( isBorderBox ? "border" : "content" ) ?
-
-		// If we already have the right measurement, avoid augmentation
-		4 :
-
-		// Otherwise initialize for horizontal or vertical properties
-		name === "width" ? 1 : 0,
+function boxModelAdjustment( elem, dimension, box, isBorderBox, styles, computedVal ) {
+	var i = dimension === "width" ? 1 : 0,
+		extra = 0,
+		delta = 0;
 
-		val = 0;
+	// Adjustment may not be necessary
+	if ( box === ( isBorderBox ? "border" : "content" ) ) {
+		return 0;
+	}
 
 	for ( ; i < 4; i += 2 ) {
 
-		// Both box models exclude margin, so add it if we want it
-		if ( extra === "margin" ) {
-			val += jQuery.css( elem, extra + cssExpand[ i ], true, styles );
+		// Both box models exclude margin
+		if ( box === "margin" ) {
+			delta += jQuery.css( elem, box + cssExpand[ i ], true, styles );
 		}
 
-		if ( isBorderBox ) {
+		// If we get here with a content-box, we're seeking "padding" or "border" or "margin"
+		if ( !isBorderBox ) {
 
-			// border-box includes padding, so remove it if we want content
-			if ( extra === "content" ) {
-				val -= jQuery.css( elem, "padding" + cssExpand[ i ], true, styles );
-			}
+			// Add padding
+			delta += jQuery.css( elem, "padding" + cssExpand[ i ], true, styles );
+
+			// For "border" or "margin", add border
+			if ( box !== "padding" ) {
+				delta += jQuery.css( elem, "border" + cssExpand[ i ] + "Width", true, styles );
 
-			// At this point, extra isn't border nor margin, so remove border
-			if ( extra !== "margin" ) {
-				val -= jQuery.css( elem, "border" + cssExpand[ i ] + "Width", true, styles );
+			// But still keep track of it otherwise
+			} else {
+				extra += jQuery.css( elem, "border" + cssExpand[ i ] + "Width", true, styles );
 			}
+
+		// If we get here with a border-box (content + padding + border), we're seeking "content" or
+		// "padding" or "margin"
 		} else {
 
-			// At this point, extra isn't content, so add padding
-			val += jQuery.css( elem, "padding" + cssExpand[ i ], true, styles );
+			// For "content", subtract padding
+			if ( box === "content" ) {
+				delta -= jQuery.css( elem, "padding" + cssExpand[ i ], true, styles );
+			}
 
-			// At this point, extra isn't content nor padding, so add border
-			if ( extra !== "padding" ) {
-				val += jQuery.css( elem, "border" + cssExpand[ i ] + "Width", true, styles );
+			// For "content" or "padding", subtract border
+			if ( box !== "margin" ) {
+				delta -= jQuery.css( elem, "border" + cssExpand[ i ] + "Width", true, styles );
 			}
 		}
 	}
 
-	return val;
+	// Account for positive content-box scroll gutter when requested by providing computedVal
+	if ( !isBorderBox && computedVal >= 0 ) {
+
+		// offsetWidth/offsetHeight is a rounded sum of content, padding, scroll gutter, and border
+		// Assuming integer scroll gutter, subtract the rest and round down
+		delta += Math.max( 0, Math.ceil(
+			elem[ "offset" + dimension[ 0 ].toUpperCase() + dimension.slice( 1 ) ] -
+			computedVal -
+			delta -
+			extra -
+			0.5
+		) );
+	}
+
+	return delta;
 }
 
-function getWidthOrHeight( elem, name, extra ) {
+function getWidthOrHeight( elem, dimension, extra ) {
 
-	// Start with offset property, which is equivalent to the border-box value
-	var val,
-		valueIsBorderBox = true,
-		styles = getStyles( elem ),
-		isBorderBox = jQuery.css( elem, "boxSizing", false, styles ) === "border-box";
+	// Start with computed style
+	var styles = getStyles( elem ),
+		val = curCSS( elem, dimension, styles ),
+		isBorderBox = jQuery.css( elem, "boxSizing", false, styles ) === "border-box",
+		valueIsBorderBox = isBorderBox;
 
-	// Support: IE <=11 only
-	// Running getBoundingClientRect on a disconnected node
-	// in IE throws an error.
-	if ( elem.getClientRects().length ) {
-		val = elem.getBoundingClientRect()[ name ];
+	// Support: Firefox <=54
+	// Return a confounding non-pixel value or feign ignorance, as appropriate.
+	if ( rnumnonpx.test( val ) ) {
+		if ( !extra ) {
+			return val;
+		}
+		val = "auto";
 	}
 
-	// Some non-html elements return undefined for offsetWidth, so check for null/undefined
-	// svg - https://bugzilla.mozilla.org/show_bug.cgi?id=649285
-	// MathML - https://bugzilla.mozilla.org/show_bug.cgi?id=491668
-	if ( val <= 0 || val == null ) {
+	// Check for style in case a browser which returns unreliable values
+	// for getComputedStyle silently falls back to the reliable elem.style
+	valueIsBorderBox = valueIsBorderBox &&
+		( support.boxSizingReliable() || val === elem.style[ dimension ] );
 
-		// Fall back to computed then uncomputed css if necessary
-		val = curCSS( elem, name, styles );
-		if ( val < 0 || val == null ) {
-			val = elem.style[ name ];
-		}
-
-		// Computed unit is not pixels. Stop here and return.
-		if ( rnumnonpx.test( val ) ) {
-			return val;
-		}
+	// Fall back to offsetWidth/offsetHeight when value is "auto"
+	// This happens for inline elements with no explicit setting (gh-3571)
+	// Support: Android <=4.1 - 4.3 only
+	// Also use offsetWidth/offsetHeight for misreported inline dimensions (gh-3602)
+	if ( val === "auto" ||
+		!parseFloat( val ) && jQuery.css( elem, "display", false, styles ) === "inline" ) {
 
-		// Check for style in case a browser which returns unreliable values
-		// for getComputedStyle silently falls back to the reliable elem.style
-		valueIsBorderBox = isBorderBox &&
-			( support.boxSizingReliable() || val === elem.style[ name ] );
+		val = elem[ "offset" + dimension[ 0 ].toUpperCase() + dimension.slice( 1 ) ];
 
-		// Normalize "", auto, and prepare for extra
-		val = parseFloat( val ) || 0;
+		// offsetWidth/offsetHeight provide border-box values
+		valueIsBorderBox = true;
 	}
 
-	// Use the active box-sizing model to add/subtract irrelevant styles
+	// Normalize "" and auto
+	val = parseFloat( val ) || 0;
+
+	// Adjust for the element's box model
 	return ( val +
-		augmentWidthOrHeight(
+		boxModelAdjustment(
 			elem,
-			name,
+			dimension,
 			extra || ( isBorderBox ? "border" : "content" ),
 			valueIsBorderBox,
-			styles
+			styles,
+
+			// Provide the current computed size to request scroll gutter calculation (gh-3589)
+			val
 		)
 	) + "px";
 }
@@ -6537,9 +6704,7 @@ jQuery.extend( {
 
 	// Add in properties whose names you wish to fix before
 	// setting or getting the value
-	cssProps: {
-		"float": "cssFloat"
-	},
+	cssProps: {},
 
 	// Get and set the style property on a DOM Node
 	style: function( elem, name, value, extra ) {
@@ -6551,11 +6716,16 @@ jQuery.extend( {
 
 		// Make sure that we're working with the right name
 		var ret, type, hooks,
-			origName = jQuery.camelCase( name ),
+			origName = camelCase( name ),
+			isCustomProp = rcustomProp.test( name ),
 			style = elem.style;
 
-		name = jQuery.cssProps[ origName ] ||
-			( jQuery.cssProps[ origName ] = vendorPropName( origName ) || origName );
+		// Make sure that we're working with the right name. We don't
+		// want to query the value if it is a CSS custom property
+		// since they are user-defined.
+		if ( !isCustomProp ) {
+			name = finalPropName( origName );
+		}
 
 		// Gets hook for the prefixed version, then unprefixed version
 		hooks = jQuery.cssHooks[ name ] || jQuery.cssHooks[ origName ];
@@ -6591,7 +6761,11 @@ jQuery.extend( {
 			if ( !hooks || !( "set" in hooks ) ||
 				( value = hooks.set( elem, value, extra ) ) !== undefined ) {
 
-				style[ name ] = value;
+				if ( isCustomProp ) {
+					style.setProperty( name, value );
+				} else {
+					style[ name ] = value;
+				}
 			}
 
 		} else {
@@ -6610,11 +6784,15 @@ jQuery.extend( {
 
 	css: function( elem, name, extra, styles ) {
 		var val, num, hooks,
-			origName = jQuery.camelCase( name );
+			origName = camelCase( name ),
+			isCustomProp = rcustomProp.test( name );
 
-		// Make sure that we're working with the right name
-		name = jQuery.cssProps[ origName ] ||
-			( jQuery.cssProps[ origName ] = vendorPropName( origName ) || origName );
+		// Make sure that we're working with the right name. We don't
+		// want to modify the value if it is a CSS custom property
+		// since they are user-defined.
+		if ( !isCustomProp ) {
+			name = finalPropName( origName );
+		}
 
 		// Try prefixed name followed by the unprefixed name
 		hooks = jQuery.cssHooks[ name ] || jQuery.cssHooks[ origName ];
@@ -6639,12 +6817,13 @@ jQuery.extend( {
 			num = parseFloat( val );
 			return extra === true || isFinite( num ) ? num || 0 : val;
 		}
+
 		return val;
 	}
 } );
 
-jQuery.each( [ "height", "width" ], function( i, name ) {
-	jQuery.cssHooks[ name ] = {
+jQuery.each( [ "height", "width" ], function( i, dimension ) {
+	jQuery.cssHooks[ dimension ] = {
 		get: function( elem, computed, extra ) {
 			if ( computed ) {
 
@@ -6660,29 +6839,41 @@ jQuery.each( [ "height", "width" ], function( i, name ) {
 					// in IE throws an error.
 					( !elem.getClientRects().length || !elem.getBoundingClientRect().width ) ?
 						swap( elem, cssShow, function() {
-							return getWidthOrHeight( elem, name, extra );
+							return getWidthOrHeight( elem, dimension, extra );
 						} ) :
-						getWidthOrHeight( elem, name, extra );
+						getWidthOrHeight( elem, dimension, extra );
 			}
 		},
 
 		set: function( elem, value, extra ) {
 			var matches,
-				styles = extra && getStyles( elem ),
-				subtract = extra && augmentWidthOrHeight(
+				styles = getStyles( elem ),
+				isBorderBox = jQuery.css( elem, "boxSizing", false, styles ) === "border-box",
+				subtract = extra && boxModelAdjustment(
 					elem,
-					name,
+					dimension,
 					extra,
-					jQuery.css( elem, "boxSizing", false, styles ) === "border-box",
+					isBorderBox,
 					styles
 				);
 
+			// Account for unreliable border-box dimensions by comparing offset* to computed and
+			// faking a content-box to get border and padding (gh-3699)
+			if ( isBorderBox && support.scrollboxSize() === styles.position ) {
+				subtract -= Math.ceil(
+					elem[ "offset" + dimension[ 0 ].toUpperCase() + dimension.slice( 1 ) ] -
+					parseFloat( styles[ dimension ] ) -
+					boxModelAdjustment( elem, dimension, "border", false, styles ) -
+					0.5
+				);
+			}
+
 			// Convert to pixels if value adjustment is needed
 			if ( subtract && ( matches = rcssNum.exec( value ) ) &&
 				( matches[ 3 ] || "px" ) !== "px" ) {
 
-				elem.style[ name ] = value;
-				value = jQuery.css( elem, name );
+				elem.style[ dimension ] = value;
+				value = jQuery.css( elem, dimension );
 			}
 
 			return setPositiveNumber( elem, value, subtract );
@@ -6726,7 +6917,7 @@ jQuery.each( {
 		}
 	};
 
-	if ( !rmargin.test( prefix ) ) {
+	if ( prefix !== "margin" ) {
 		jQuery.cssHooks[ prefix + suffix ].set = setPositiveNumber;
 	}
 } );
@@ -6738,7 +6929,7 @@ jQuery.fn.extend( {
 				map = {},
 				i = 0;
 
-			if ( jQuery.isArray( name ) ) {
+			if ( Array.isArray( name ) ) {
 				styles = getStyles( elem );
 				len = name.length;
 
@@ -6876,13 +7067,18 @@ jQuery.fx.step = {};
 
 
 var
-	fxNow, timerId,
+	fxNow, inProgress,
 	rfxtypes = /^(?:toggle|show|hide)$/,
 	rrun = /queueHooks$/;
 
-function raf() {
-	if ( timerId ) {
-		window.requestAnimationFrame( raf );
+function schedule() {
+	if ( inProgress ) {
+		if ( document.hidden === false && window.requestAnimationFrame ) {
+			window.requestAnimationFrame( schedule );
+		} else {
+			window.setTimeout( schedule, jQuery.fx.interval );
+		}
+
 		jQuery.fx.tick();
 	}
 }
@@ -6892,7 +7088,7 @@ function createFxNow() {
 	window.setTimeout( function() {
 		fxNow = undefined;
 	} );
-	return ( fxNow = jQuery.now() );
+	return ( fxNow = Date.now() );
 }
 
 // Generate parameters to create a standard animation
@@ -6996,9 +7192,10 @@ function defaultPrefilter( elem, props, opts ) {
 	// Restrict "overflow" and "display" styles during box animations
 	if ( isBox && elem.nodeType === 1 ) {
 
-		// Support: IE <=9 - 11, Edge 12 - 13
+		// Support: IE <=9 - 11, Edge 12 - 15
 		// Record all 3 overflow attributes because IE does not infer the shorthand
-		// from identically-valued overflowX and overflowY
+		// from identically-valued overflowX and overflowY and Edge just mirrors
+		// the overflowX value there.
 		opts.overflow = [ style.overflow, style.overflowX, style.overflowY ];
 
 		// Identify a display type, preferring old show/hide data over the CSS cascade
@@ -7106,10 +7303,10 @@ function propFilter( props, specialEasing ) {
 
 	// camelCase, specialEasing and expand cssHook pass
 	for ( index in props ) {
-		name = jQuery.camelCase( index );
+		name = camelCase( index );
 		easing = specialEasing[ name ];
 		value = props[ index ];
-		if ( jQuery.isArray( value ) ) {
+		if ( Array.isArray( value ) ) {
 			easing = value[ 1 ];
 			value = props[ index ] = value[ 0 ];
 		}
@@ -7168,12 +7365,19 @@ function Animation( elem, properties, options ) {
 
 			deferred.notifyWith( elem, [ animation, percent, remaining ] );
 
+			// If there's more to do, yield
 			if ( percent < 1 && length ) {
 				return remaining;
-			} else {
-				deferred.resolveWith( elem, [ animation ] );
-				return false;
 			}
+
+			// If this was an empty animation, synthesize a final progress notification
+			if ( !length ) {
+				deferred.notifyWith( elem, [ animation, 1, 0 ] );
+			}
+
+			// Resolve the animation and report its conclusion
+			deferred.resolveWith( elem, [ animation ] );
+			return false;
 		},
 		animation = deferred.promise( {
 			elem: elem,
@@ -7224,9 +7428,9 @@ function Animation( elem, properties, options ) {
 	for ( ; index < length; index++ ) {
 		result = Animation.prefilters[ index ].call( animation, elem, props, animation.opts );
 		if ( result ) {
-			if ( jQuery.isFunction( result.stop ) ) {
+			if ( isFunction( result.stop ) ) {
 				jQuery._queueHooks( animation.elem, animation.opts.queue ).stop =
-					jQuery.proxy( result.stop, result );
+					result.stop.bind( result );
 			}
 			return result;
 		}
@@ -7234,10 +7438,17 @@ function Animation( elem, properties, options ) {
 
 	jQuery.map( props, createTween, animation );
 
-	if ( jQuery.isFunction( animation.opts.start ) ) {
+	if ( isFunction( animation.opts.start ) ) {
 		animation.opts.start.call( elem, animation );
 	}
 
+	// Attach callbacks from options
+	animation
+		.progress( animation.opts.progress )
+		.done( animation.opts.done, animation.opts.complete )
+		.fail( animation.opts.fail )
+		.always( animation.opts.always );
+
 	jQuery.fx.timer(
 		jQuery.extend( tick, {
 			elem: elem,
@@ -7246,11 +7457,7 @@ function Animation( elem, properties, options ) {
 		} )
 	);
 
-	// attach callbacks from options
-	return animation.progress( animation.opts.progress )
-		.done( animation.opts.done, animation.opts.complete )
-		.fail( animation.opts.fail )
-		.always( animation.opts.always );
+	return animation;
 }
 
 jQuery.Animation = jQuery.extend( Animation, {
@@ -7264,11 +7471,11 @@ jQuery.Animation = jQuery.extend( Animation, {
 	},
 
 	tweener: function( props, callback ) {
-		if ( jQuery.isFunction( props ) ) {
+		if ( isFunction( props ) ) {
 			callback = props;
 			props = [ "*" ];
 		} else {
-			props = props.match( rnotwhite );
+			props = props.match( rnothtmlwhite );
 		}
 
 		var prop,
@@ -7296,19 +7503,24 @@ jQuery.Animation = jQuery.extend( Animation, {
 jQuery.speed = function( speed, easing, fn ) {
 	var opt = speed && typeof speed === "object" ? jQuery.extend( {}, speed ) : {
 		complete: fn || !fn && easing ||
-			jQuery.isFunction( speed ) && speed,
+			isFunction( speed ) && speed,
 		duration: speed,
-		easing: fn && easing || easing && !jQuery.isFunction( easing ) && easing
+		easing: fn && easing || easing && !isFunction( easing ) && easing
 	};
 
-	// Go to the end state if fx are off or if document is hidden
-	if ( jQuery.fx.off || document.hidden ) {
+	// Go to the end state if fx are off
+	if ( jQuery.fx.off ) {
 		opt.duration = 0;
 
 	} else {
-		opt.duration = typeof opt.duration === "number" ?
-			opt.duration : opt.duration in jQuery.fx.speeds ?
-				jQuery.fx.speeds[ opt.duration ] : jQuery.fx.speeds._default;
+		if ( typeof opt.duration !== "number" ) {
+			if ( opt.duration in jQuery.fx.speeds ) {
+				opt.duration = jQuery.fx.speeds[ opt.duration ];
+
+			} else {
+				opt.duration = jQuery.fx.speeds._default;
+			}
+		}
 	}
 
 	// Normalize opt.queue - true/undefined/null -> "fx"
@@ -7320,7 +7532,7 @@ jQuery.speed = function( speed, easing, fn ) {
 	opt.old = opt.complete;
 
 	opt.complete = function() {
-		if ( jQuery.isFunction( opt.old ) ) {
+		if ( isFunction( opt.old ) ) {
 			opt.old.call( this );
 		}
 
@@ -7484,12 +7696,12 @@ jQuery.fx.tick = function() {
 		i = 0,
 		timers = jQuery.timers;
 
-	fxNow = jQuery.now();
+	fxNow = Date.now();
 
 	for ( ; i < timers.length; i++ ) {
 		timer = timers[ i ];
 
-		// Checks the timer has not already been removed
+		// Run the timer and safely remove it when done (allowing for external removal)
 		if ( !timer() && timers[ i ] === timer ) {
 			timers.splice( i--, 1 );
 		}
@@ -7503,30 +7715,21 @@ jQuery.fx.tick = function() {
 
 jQuery.fx.timer = function( timer ) {
 	jQuery.timers.push( timer );
-	if ( timer() ) {
-		jQuery.fx.start();
-	} else {
-		jQuery.timers.pop();
-	}
+	jQuery.fx.start();
 };
 
 jQuery.fx.interval = 13;
 jQuery.fx.start = function() {
-	if ( !timerId ) {
-		timerId = window.requestAnimationFrame ?
-			window.requestAnimationFrame( raf ) :
-			window.setInterval( jQuery.fx.tick, jQuery.fx.interval );
+	if ( inProgress ) {
+		return;
 	}
+
+	inProgress = true;
+	schedule();
 };
 
 jQuery.fx.stop = function() {
-	if ( window.cancelAnimationFrame ) {
-		window.cancelAnimationFrame( timerId );
-	} else {
-		window.clearInterval( timerId );
-	}
-
-	timerId = null;
+	inProgress = null;
 };
 
 jQuery.fx.speeds = {
@@ -7643,7 +7846,7 @@ jQuery.extend( {
 		type: {
 			set: function( elem, value ) {
 				if ( !support.radioValue && value === "radio" &&
-					jQuery.nodeName( elem, "input" ) ) {
+					nodeName( elem, "input" ) ) {
 					var val = elem.value;
 					elem.setAttribute( "type", value );
 					if ( val ) {
@@ -7658,7 +7861,10 @@ jQuery.extend( {
 	removeAttr: function( elem, value ) {
 		var name,
 			i = 0,
-			attrNames = value && value.match( rnotwhite );
+
+			// Attribute names can contain non-HTML whitespace characters
+			// https://html.spec.whatwg.org/multipage/syntax.html#attributes-2
+			attrNames = value && value.match( rnothtmlwhite );
 
 		if ( attrNames && elem.nodeType === 1 ) {
 			while ( ( name = attrNames[ i++ ] ) ) {
@@ -7765,12 +7971,19 @@ jQuery.extend( {
 				// Use proper attribute retrieval(#12072)
 				var tabindex = jQuery.find.attr( elem, "tabindex" );
 
-				return tabindex ?
-					parseInt( tabindex, 10 ) :
+				if ( tabindex ) {
+					return parseInt( tabindex, 10 );
+				}
+
+				if (
 					rfocusable.test( elem.nodeName ) ||
-						rclickable.test( elem.nodeName ) && elem.href ?
-							0 :
-							-1;
+					rclickable.test( elem.nodeName ) &&
+					elem.href
+				) {
+					return 0;
+				}
+
+				return -1;
 			}
 		}
 	},
@@ -7787,9 +8000,14 @@ jQuery.extend( {
 // on the option
 // The getter ensures a default option is selected
 // when in an optgroup
+// eslint rule "no-unused-expressions" is disabled for this code
+// since it considers such accessions noop
 if ( !support.optSelected ) {
 	jQuery.propHooks.selected = {
 		get: function( elem ) {
+
+			/* eslint no-unused-expressions: "off" */
+
 			var parent = elem.parentNode;
 			if ( parent && parent.parentNode ) {
 				parent.parentNode.selectedIndex;
@@ -7797,6 +8015,9 @@ if ( !support.optSelected ) {
 			return null;
 		},
 		set: function( elem ) {
+
+			/* eslint no-unused-expressions: "off" */
+
 			var parent = elem.parentNode;
 			if ( parent ) {
 				parent.selectedIndex;
@@ -7827,30 +8048,45 @@ jQuery.each( [
 
 
 
-var rclass = /[\t\r\n\f]/g;
+	// Strip and collapse whitespace according to HTML spec
+	// https://infra.spec.whatwg.org/#strip-and-collapse-ascii-whitespace
+	function stripAndCollapse( value ) {
+		var tokens = value.match( rnothtmlwhite ) || [];
+		return tokens.join( " " );
+	}
+
 
 function getClass( elem ) {
 	return elem.getAttribute && elem.getAttribute( "class" ) || "";
 }
 
+function classesToArray( value ) {
+	if ( Array.isArray( value ) ) {
+		return value;
+	}
+	if ( typeof value === "string" ) {
+		return value.match( rnothtmlwhite ) || [];
+	}
+	return [];
+}
+
 jQuery.fn.extend( {
 	addClass: function( value ) {
 		var classes, elem, cur, curValue, clazz, j, finalValue,
 			i = 0;
 
-		if ( jQuery.isFunction( value ) ) {
+		if ( isFunction( value ) ) {
 			return this.each( function( j ) {
 				jQuery( this ).addClass( value.call( this, j, getClass( this ) ) );
 			} );
 		}
 
-		if ( typeof value === "string" && value ) {
-			classes = value.match( rnotwhite ) || [];
+		classes = classesToArray( value );
 
+		if ( classes.length ) {
 			while ( ( elem = this[ i++ ] ) ) {
 				curValue = getClass( elem );
-				cur = elem.nodeType === 1 &&
-					( " " + curValue + " " ).replace( rclass, " " );
+				cur = elem.nodeType === 1 && ( " " + stripAndCollapse( curValue ) + " " );
 
 				if ( cur ) {
 					j = 0;
@@ -7861,7 +8097,7 @@ jQuery.fn.extend( {
 					}
 
 					// Only assign if different to avoid unneeded rendering.
-					finalValue = jQuery.trim( cur );
+					finalValue = stripAndCollapse( cur );
 					if ( curValue !== finalValue ) {
 						elem.setAttribute( "class", finalValue );
 					}
@@ -7876,7 +8112,7 @@ jQuery.fn.extend( {
 		var classes, elem, cur, curValue, clazz, j, finalValue,
 			i = 0;
 
-		if ( jQuery.isFunction( value ) ) {
+		if ( isFunction( value ) ) {
 			return this.each( function( j ) {
 				jQuery( this ).removeClass( value.call( this, j, getClass( this ) ) );
 			} );
@@ -7886,15 +8122,14 @@ jQuery.fn.extend( {
 			return this.attr( "class", "" );
 		}
 
-		if ( typeof value === "string" && value ) {
-			classes = value.match( rnotwhite ) || [];
+		classes = classesToArray( value );
 
+		if ( classes.length ) {
 			while ( ( elem = this[ i++ ] ) ) {
 				curValue = getClass( elem );
 
 				// This expression is here for better compressibility (see addClass)
-				cur = elem.nodeType === 1 &&
-					( " " + curValue + " " ).replace( rclass, " " );
+				cur = elem.nodeType === 1 && ( " " + stripAndCollapse( curValue ) + " " );
 
 				if ( cur ) {
 					j = 0;
@@ -7907,7 +8142,7 @@ jQuery.fn.extend( {
 					}
 
 					// Only assign if different to avoid unneeded rendering.
-					finalValue = jQuery.trim( cur );
+					finalValue = stripAndCollapse( cur );
 					if ( curValue !== finalValue ) {
 						elem.setAttribute( "class", finalValue );
 					}
@@ -7919,13 +8154,14 @@ jQuery.fn.extend( {
 	},
 
 	toggleClass: function( value, stateVal ) {
-		var type = typeof value;
+		var type = typeof value,
+			isValidValue = type === "string" || Array.isArray( value );
 
-		if ( typeof stateVal === "boolean" && type === "string" ) {
+		if ( typeof stateVal === "boolean" && isValidValue ) {
 			return stateVal ? this.addClass( value ) : this.removeClass( value );
 		}
 
-		if ( jQuery.isFunction( value ) ) {
+		if ( isFunction( value ) ) {
 			return this.each( function( i ) {
 				jQuery( this ).toggleClass(
 					value.call( this, i, getClass( this ), stateVal ),
@@ -7937,12 +8173,12 @@ jQuery.fn.extend( {
 		return this.each( function() {
 			var className, i, self, classNames;
 
-			if ( type === "string" ) {
+			if ( isValidValue ) {
 
 				// Toggle individual class names
 				i = 0;
 				self = jQuery( this );
-				classNames = value.match( rnotwhite ) || [];
+				classNames = classesToArray( value );
 
 				while ( ( className = classNames[ i++ ] ) ) {
 
@@ -7985,10 +8221,8 @@ jQuery.fn.extend( {
 		className = " " + selector + " ";
 		while ( ( elem = this[ i++ ] ) ) {
 			if ( elem.nodeType === 1 &&
-				( " " + getClass( elem ) + " " ).replace( rclass, " " )
-					.indexOf( className ) > -1
-			) {
-				return true;
+				( " " + stripAndCollapse( getClass( elem ) ) + " " ).indexOf( className ) > -1 ) {
+					return true;
 			}
 		}
 
@@ -7999,12 +8233,11 @@ jQuery.fn.extend( {
 
 
 
-var rreturn = /\r/g,
-	rspaces = /[\x20\t\r\n\f]+/g;
+var rreturn = /\r/g;
 
 jQuery.fn.extend( {
 	val: function( value ) {
-		var hooks, ret, isFunction,
+		var hooks, ret, valueIsFunction,
 			elem = this[ 0 ];
 
 		if ( !arguments.length ) {
@@ -8021,19 +8254,19 @@ jQuery.fn.extend( {
 
 				ret = elem.value;
 
-				return typeof ret === "string" ?
-
-					// Handle most common string cases
-					ret.replace( rreturn, "" ) :
+				// Handle most common string cases
+				if ( typeof ret === "string" ) {
+					return ret.replace( rreturn, "" );
+				}
 
-					// Handle cases where value is null/undef or number
-					ret == null ? "" : ret;
+				// Handle cases where value is null/undef or number
+				return ret == null ? "" : ret;
 			}
 
 			return;
 		}
 
-		isFunction = jQuery.isFunction( value );
+		valueIsFunction = isFunction( value );
 
 		return this.each( function( i ) {
 			var val;
@@ -8042,7 +8275,7 @@ jQuery.fn.extend( {
 				return;
 			}
 
-			if ( isFunction ) {
+			if ( valueIsFunction ) {
 				val = value.call( this, i, jQuery( this ).val() );
 			} else {
 				val = value;
@@ -8055,7 +8288,7 @@ jQuery.fn.extend( {
 			} else if ( typeof val === "number" ) {
 				val += "";
 
-			} else if ( jQuery.isArray( val ) ) {
+			} else if ( Array.isArray( val ) ) {
 				val = jQuery.map( val, function( value ) {
 					return value == null ? "" : value + "";
 				} );
@@ -8084,20 +8317,24 @@ jQuery.extend( {
 					// option.text throws exceptions (#14686, #14858)
 					// Strip and collapse whitespace
 					// https://html.spec.whatwg.org/#strip-and-collapse-whitespace
-					jQuery.trim( jQuery.text( elem ) ).replace( rspaces, " " );
+					stripAndCollapse( jQuery.text( elem ) );
 			}
 		},
 		select: {
 			get: function( elem ) {
-				var value, option,
+				var value, option, i,
 					options = elem.options,
 					index = elem.selectedIndex,
 					one = elem.type === "select-one",
 					values = one ? null : [],
-					max = one ? index + 1 : options.length,
-					i = index < 0 ?
-						max :
-						one ? index : 0;
+					max = one ? index + 1 : options.length;
+
+				if ( index < 0 ) {
+					i = max;
+
+				} else {
+					i = one ? index : 0;
+				}
 
 				// Loop through all the selected options
 				for ( ; i < max; i++ ) {
@@ -8110,7 +8347,7 @@ jQuery.extend( {
 							// Don't return options that are disabled or in a disabled optgroup
 							!option.disabled &&
 							( !option.parentNode.disabled ||
-								!jQuery.nodeName( option.parentNode, "optgroup" ) ) ) {
+								!nodeName( option.parentNode, "optgroup" ) ) ) {
 
 						// Get the specific value for the option
 						value = jQuery( option ).val();
@@ -8162,7 +8399,7 @@ jQuery.extend( {
 jQuery.each( [ "radio", "checkbox" ], function() {
 	jQuery.valHooks[ this ] = {
 		set: function( elem, value ) {
-			if ( jQuery.isArray( value ) ) {
+			if ( Array.isArray( value ) ) {
 				return ( elem.checked = jQuery.inArray( jQuery( elem ).val(), value ) > -1 );
 			}
 		}
@@ -8180,18 +8417,24 @@ jQuery.each( [ "radio", "checkbox" ], function() {
 // Return jQuery for attributes-only inclusion
 
 
-var rfocusMorph = /^(?:focusinfocus|focusoutblur)$/;
+support.focusin = "onfocusin" in window;
+
+
+var rfocusMorph = /^(?:focusinfocus|focusoutblur)$/,
+	stopPropagationCallback = function( e ) {
+		e.stopPropagation();
+	};
 
 jQuery.extend( jQuery.event, {
 
 	trigger: function( event, data, elem, onlyHandlers ) {
 
-		var i, cur, tmp, bubbleType, ontype, handle, special,
+		var i, cur, tmp, bubbleType, ontype, handle, special, lastElement,
 			eventPath = [ elem || document ],
 			type = hasOwn.call( event, "type" ) ? event.type : event,
 			namespaces = hasOwn.call( event, "namespace" ) ? event.namespace.split( "." ) : [];
 
-		cur = tmp = elem = elem || document;
+		cur = lastElement = tmp = elem = elem || document;
 
 		// Don't do events on text and comment nodes
 		if ( elem.nodeType === 3 || elem.nodeType === 8 ) {
@@ -8243,7 +8486,7 @@ jQuery.extend( jQuery.event, {
 
 		// Determine event propagation path in advance, per W3C events spec (#9951)
 		// Bubble up to document, then to window; watch for a global ownerDocument var (#9724)
-		if ( !onlyHandlers && !special.noBubble && !jQuery.isWindow( elem ) ) {
+		if ( !onlyHandlers && !special.noBubble && !isWindow( elem ) ) {
 
 			bubbleType = special.delegateType || type;
 			if ( !rfocusMorph.test( bubbleType + type ) ) {
@@ -8263,7 +8506,7 @@ jQuery.extend( jQuery.event, {
 		// Fire handlers on the event path
 		i = 0;
 		while ( ( cur = eventPath[ i++ ] ) && !event.isPropagationStopped() ) {
-
+			lastElement = cur;
 			event.type = i > 1 ?
 				bubbleType :
 				special.bindType || type;
@@ -8295,7 +8538,7 @@ jQuery.extend( jQuery.event, {
 
 				// Call a native DOM method on the target with the same name as the event.
 				// Don't do default actions on window, that's where global variables be (#6170)
-				if ( ontype && jQuery.isFunction( elem[ type ] ) && !jQuery.isWindow( elem ) ) {
+				if ( ontype && isFunction( elem[ type ] ) && !isWindow( elem ) ) {
 
 					// Don't re-trigger an onFOO event when we call its FOO() method
 					tmp = elem[ ontype ];
@@ -8306,7 +8549,17 @@ jQuery.extend( jQuery.event, {
 
 					// Prevent re-triggering of the same event, since we already bubbled it above
 					jQuery.event.triggered = type;
+
+					if ( event.isPropagationStopped() ) {
+						lastElement.addEventListener( type, stopPropagationCallback );
+					}
+
 					elem[ type ]();
+
+					if ( event.isPropagationStopped() ) {
+						lastElement.removeEventListener( type, stopPropagationCallback );
+					}
+
 					jQuery.event.triggered = undefined;
 
 					if ( tmp ) {
@@ -8352,31 +8605,6 @@ jQuery.fn.extend( {
 } );
 
 
-jQuery.each( ( "blur focus focusin focusout resize scroll click dblclick " +
-	"mousedown mouseup mousemove mouseover mouseout mouseenter mouseleave " +
-	"change select submit keydown keypress keyup contextmenu" ).split( " " ),
-	function( i, name ) {
-
-	// Handle event binding
-	jQuery.fn[ name ] = function( data, fn ) {
-		return arguments.length > 0 ?
-			this.on( name, null, data, fn ) :
-			this.trigger( name );
-	};
-} );
-
-jQuery.fn.extend( {
-	hover: function( fnOver, fnOut ) {
-		return this.mouseenter( fnOver ).mouseleave( fnOut || fnOver );
-	}
-} );
-
-
-
-
-support.focusin = "onfocusin" in window;
-
-
 // Support: Firefox <=44
 // Firefox doesn't have focus(in | out) events
 // Related ticket - https://bugzilla.mozilla.org/show_bug.cgi?id=687787
@@ -8420,7 +8648,7 @@ if ( !support.focusin ) {
 }
 var location = window.location;
 
-var nonce = jQuery.now();
+var nonce = Date.now();
 
 var rquery = ( /\?/ );
 
@@ -8457,7 +8685,7 @@ var
 function buildParams( prefix, obj, traditional, add ) {
 	var name;
 
-	if ( jQuery.isArray( obj ) ) {
+	if ( Array.isArray( obj ) ) {
 
 		// Serialize array item.
 		jQuery.each( obj, function( i, v ) {
@@ -8478,7 +8706,7 @@ function buildParams( prefix, obj, traditional, add ) {
 			}
 		} );
 
-	} else if ( !traditional && jQuery.type( obj ) === "object" ) {
+	} else if ( !traditional && toType( obj ) === "object" ) {
 
 		// Serialize object item.
 		for ( name in obj ) {
@@ -8500,7 +8728,7 @@ jQuery.param = function( a, traditional ) {
 		add = function( key, valueOrFunction ) {
 
 			// If value is a function, invoke it and use its return value
-			var value = jQuery.isFunction( valueOrFunction ) ?
+			var value = isFunction( valueOrFunction ) ?
 				valueOrFunction() :
 				valueOrFunction;
 
@@ -8509,7 +8737,7 @@ jQuery.param = function( a, traditional ) {
 		};
 
 	// If an array was passed in, assume that it is an array of form elements.
-	if ( jQuery.isArray( a ) || ( a.jquery && !jQuery.isPlainObject( a ) ) ) {
+	if ( Array.isArray( a ) || ( a.jquery && !jQuery.isPlainObject( a ) ) ) {
 
 		// Serialize the form elements
 		jQuery.each( a, function() {
@@ -8551,13 +8779,17 @@ jQuery.fn.extend( {
 		.map( function( i, elem ) {
 			var val = jQuery( this ).val();
 
-			return val == null ?
-				null :
-				jQuery.isArray( val ) ?
-					jQuery.map( val, function( val ) {
-						return { name: elem.name, value: val.replace( rCRLF, "\r\n" ) };
-					} ) :
-					{ name: elem.name, value: val.replace( rCRLF, "\r\n" ) };
+			if ( val == null ) {
+				return null;
+			}
+
+			if ( Array.isArray( val ) ) {
+				return jQuery.map( val, function( val ) {
+					return { name: elem.name, value: val.replace( rCRLF, "\r\n" ) };
+				} );
+			}
+
+			return { name: elem.name, value: val.replace( rCRLF, "\r\n" ) };
 		} ).get();
 	}
 } );
@@ -8566,7 +8798,7 @@ jQuery.fn.extend( {
 var
 	r20 = /%20/g,
 	rhash = /#.*$/,
-	rts = /([?&])_=[^&]*/,
+	rantiCache = /([?&])_=[^&]*/,
 	rheaders = /^(.*?):[ \t]*([^\r\n]*)$/mg,
 
 	// #7653, #8125, #8152: local protocol detection
@@ -8612,9 +8844,9 @@ function addToPrefiltersOrTransports( structure ) {
 
 		var dataType,
 			i = 0,
-			dataTypes = dataTypeExpression.toLowerCase().match( rnotwhite ) || [];
+			dataTypes = dataTypeExpression.toLowerCase().match( rnothtmlwhite ) || [];
 
-		if ( jQuery.isFunction( func ) ) {
+		if ( isFunction( func ) ) {
 
 			// For each dataType in the dataTypeExpression
 			while ( ( dataType = dataTypes[ i++ ] ) ) {
@@ -9080,13 +9312,13 @@ jQuery.extend( {
 		s.type = options.method || options.type || s.method || s.type;
 
 		// Extract dataTypes list
-		s.dataTypes = ( s.dataType || "*" ).toLowerCase().match( rnotwhite ) || [ "" ];
+		s.dataTypes = ( s.dataType || "*" ).toLowerCase().match( rnothtmlwhite ) || [ "" ];
 
 		// A cross-domain request is in order when the origin doesn't match the current origin.
 		if ( s.crossDomain == null ) {
 			urlAnchor = document.createElement( "a" );
 
-			// Support: IE <=8 - 11, Edge 12 - 13
+			// Support: IE <=8 - 11, Edge 12 - 15
 			// IE throws exception on accessing the href property if url is malformed,
 			// e.g. http://example.com:80x/
 			try {
@@ -9144,17 +9376,17 @@ jQuery.extend( {
 			// Remember the hash so we can put it back
 			uncached = s.url.slice( cacheURL.length );
 
-			// If data is available, append data to url
-			if ( s.data ) {
+			// If data is available and should be processed, append data to url
+			if ( s.data && ( s.processData || typeof s.data === "string" ) ) {
 				cacheURL += ( rquery.test( cacheURL ) ? "&" : "?" ) + s.data;
 
 				// #9682: remove data so that it's not used in an eventual retry
 				delete s.data;
 			}
 
-			// Add anti-cache in uncached url if needed
+			// Add or update anti-cache param if needed
 			if ( s.cache === false ) {
-				cacheURL = cacheURL.replace( rts, "" );
+				cacheURL = cacheURL.replace( rantiCache, "$1" );
 				uncached = ( rquery.test( cacheURL ) ? "&" : "?" ) + "_=" + ( nonce++ ) + uncached;
 			}
 
@@ -9382,7 +9614,7 @@ jQuery.each( [ "get", "post" ], function( i, method ) {
 	jQuery[ method ] = function( url, data, callback, type ) {
 
 		// Shift arguments if data argument was omitted
-		if ( jQuery.isFunction( data ) ) {
+		if ( isFunction( data ) ) {
 			type = type || callback;
 			callback = data;
 			data = undefined;
@@ -9420,7 +9652,7 @@ jQuery.fn.extend( {
 		var wrap;
 
 		if ( this[ 0 ] ) {
-			if ( jQuery.isFunction( html ) ) {
+			if ( isFunction( html ) ) {
 				html = html.call( this[ 0 ] );
 			}
 
@@ -9446,7 +9678,7 @@ jQuery.fn.extend( {
 	},
 
 	wrapInner: function( html ) {
-		if ( jQuery.isFunction( html ) ) {
+		if ( isFunction( html ) ) {
 			return this.each( function( i ) {
 				jQuery( this ).wrapInner( html.call( this, i ) );
 			} );
@@ -9466,10 +9698,10 @@ jQuery.fn.extend( {
 	},
 
 	wrap: function( html ) {
-		var isFunction = jQuery.isFunction( html );
+		var htmlIsFunction = isFunction( html );
 
 		return this.each( function( i ) {
-			jQuery( this ).wrapAll( isFunction ? html.call( this, i ) : html );
+			jQuery( this ).wrapAll( htmlIsFunction ? html.call( this, i ) : html );
 		} );
 	},
 
@@ -9561,7 +9793,8 @@ jQuery.ajaxTransport( function( options ) {
 					return function() {
 						if ( callback ) {
 							callback = errorCallback = xhr.onload =
-								xhr.onerror = xhr.onabort = xhr.onreadystatechange = null;
+								xhr.onerror = xhr.onabort = xhr.ontimeout =
+									xhr.onreadystatechange = null;
 
 							if ( type === "abort" ) {
 								xhr.abort();
@@ -9601,7 +9834,7 @@ jQuery.ajaxTransport( function( options ) {
 
 				// Listen to events
 				xhr.onload = callback();
-				errorCallback = xhr.onerror = callback( "error" );
+				errorCallback = xhr.onerror = xhr.ontimeout = callback( "error" );
 
 				// Support: IE 9 only
 				// Use onreadystatechange to replace onabort
@@ -9755,7 +9988,7 @@ jQuery.ajaxPrefilter( "json jsonp", function( s, originalSettings, jqXHR ) {
 	if ( jsonProp || s.dataTypes[ 0 ] === "jsonp" ) {
 
 		// Get callback name, remembering preexisting value associated with it
-		callbackName = s.jsonpCallback = jQuery.isFunction( s.jsonpCallback ) ?
+		callbackName = s.jsonpCallback = isFunction( s.jsonpCallback ) ?
 			s.jsonpCallback() :
 			s.jsonpCallback;
 
@@ -9806,7 +10039,7 @@ jQuery.ajaxPrefilter( "json jsonp", function( s, originalSettings, jqXHR ) {
 			}
 
 			// Call if it was a function and we have a response
-			if ( responseContainer && jQuery.isFunction( overwritten ) ) {
+			if ( responseContainer && isFunction( overwritten ) ) {
 				overwritten( responseContainer[ 0 ] );
 			}
 
@@ -9893,12 +10126,12 @@ jQuery.fn.load = function( url, params, callback ) {
 		off = url.indexOf( " " );
 
 	if ( off > -1 ) {
-		selector = jQuery.trim( url.slice( off ) );
+		selector = stripAndCollapse( url.slice( off ) );
 		url = url.slice( 0, off );
 	}
 
 	// If it's a function
-	if ( jQuery.isFunction( params ) ) {
+	if ( isFunction( params ) ) {
 
 		// We assume that it's the callback
 		callback = params;
@@ -9976,13 +10209,6 @@ jQuery.expr.pseudos.animated = function( elem ) {
 
 
 
-/**
- * Gets a window from an element
- */
-function getWindow( elem ) {
-	return jQuery.isWindow( elem ) ? elem : elem.nodeType === 9 && elem.defaultView;
-}
-
 jQuery.offset = {
 	setOffset: function( elem, options, i ) {
 		var curPosition, curLeft, curCSSTop, curTop, curOffset, curCSSLeft, calculatePosition,
@@ -10013,7 +10239,7 @@ jQuery.offset = {
 			curLeft = parseFloat( curCSSLeft ) || 0;
 		}
 
-		if ( jQuery.isFunction( options ) ) {
+		if ( isFunction( options ) ) {
 
 			// Use jQuery.extend here to allow modification of coordinates argument (gh-1848)
 			options = options.call( elem, i, jQuery.extend( {}, curOffset ) );
@@ -10036,6 +10262,8 @@ jQuery.offset = {
 };
 
 jQuery.fn.extend( {
+
+	// offset() relates an element's border box to the document origin
 	offset: function( options ) {
 
 		// Preserve chaining for setter
@@ -10047,13 +10275,14 @@ jQuery.fn.extend( {
 				} );
 		}
 
-		var docElem, win, rect, doc,
+		var rect, win,
 			elem = this[ 0 ];
 
 		if ( !elem ) {
 			return;
 		}
 
+		// Return zeros for disconnected and hidden (display: none) elements (gh-2310)
 		// Support: IE <=11 only
 		// Running getBoundingClientRect on a
 		// disconnected node in IE throws an error
@@ -10061,56 +10290,52 @@ jQuery.fn.extend( {
 			return { top: 0, left: 0 };
 		}
 
+		// Get document-relative position by adding viewport scroll to viewport-relative gBCR
 		rect = elem.getBoundingClientRect();
-
-		// Make sure element is not hidden (display: none)
-		if ( rect.width || rect.height ) {
-			doc = elem.ownerDocument;
-			win = getWindow( doc );
-			docElem = doc.documentElement;
-
-			return {
-				top: rect.top + win.pageYOffset - docElem.clientTop,
-				left: rect.left + win.pageXOffset - docElem.clientLeft
-			};
-		}
-
-		// Return zeros for disconnected and hidden elements (gh-2310)
-		return rect;
+		win = elem.ownerDocument.defaultView;
+		return {
+			top: rect.top + win.pageYOffset,
+			left: rect.left + win.pageXOffset
+		};
 	},
 
+	// position() relates an element's margin box to its offset parent's padding box
+	// This corresponds to the behavior of CSS absolute positioning
 	position: function() {
 		if ( !this[ 0 ] ) {
 			return;
 		}
 
-		var offsetParent, offset,
+		var offsetParent, offset, doc,
 			elem = this[ 0 ],
 			parentOffset = { top: 0, left: 0 };
 
-		// Fixed elements are offset from window (parentOffset = {top:0, left: 0},
-		// because it is its only offset parent
+		// position:fixed elements are offset from the viewport, which itself always has zero offset
 		if ( jQuery.css( elem, "position" ) === "fixed" ) {
 
-			// Assume getBoundingClientRect is there when computed position is fixed
+			// Assume position:fixed implies availability of getBoundingClientRect
 			offset = elem.getBoundingClientRect();
 
 		} else {
+			offset = this.offset();
 
-			// Get *real* offsetParent
-			offsetParent = this.offsetParent();
+			// Account for the *real* offset parent, which can be the document or its root element
+			// when a statically positioned element is identified
+			doc = elem.ownerDocument;
+			offsetParent = elem.offsetParent || doc.documentElement;
+			while ( offsetParent &&
+				( offsetParent === doc.body || offsetParent === doc.documentElement ) &&
+				jQuery.css( offsetParent, "position" ) === "static" ) {
 
-			// Get correct offsets
-			offset = this.offset();
-			if ( !jQuery.nodeName( offsetParent[ 0 ], "html" ) ) {
-				parentOffset = offsetParent.offset();
+				offsetParent = offsetParent.parentNode;
 			}
+			if ( offsetParent && offsetParent !== elem && offsetParent.nodeType === 1 ) {
 
-			// Add offsetParent borders
-			parentOffset = {
-				top: parentOffset.top + jQuery.css( offsetParent[ 0 ], "borderTopWidth", true ),
-				left: parentOffset.left + jQuery.css( offsetParent[ 0 ], "borderLeftWidth", true )
-			};
+				// Incorporate borders into its offset, since they are outside its content origin
+				parentOffset = jQuery( offsetParent ).offset();
+				parentOffset.top += jQuery.css( offsetParent, "borderTopWidth", true );
+				parentOffset.left += jQuery.css( offsetParent, "borderLeftWidth", true );
+			}
 		}
 
 		// Subtract parent offsets and element margins
@@ -10149,7 +10374,14 @@ jQuery.each( { scrollLeft: "pageXOffset", scrollTop: "pageYOffset" }, function(
 
 	jQuery.fn[ method ] = function( val ) {
 		return access( this, function( elem, method, val ) {
-			var win = getWindow( elem );
+
+			// Coalesce documents and windows
+			var win;
+			if ( isWindow( elem ) ) {
+				win = elem;
+			} else if ( elem.nodeType === 9 ) {
+				win = elem.defaultView;
+			}
 
 			if ( val === undefined ) {
 				return win ? win[ prop ] : elem[ method ];
@@ -10203,7 +10435,7 @@ jQuery.each( { Height: "height", Width: "width" }, function( name, type ) {
 			return access( this, function( elem, type, value ) {
 				var doc;
 
-				if ( jQuery.isWindow( elem ) ) {
+				if ( isWindow( elem ) ) {
 
 					// $( window ).outerWidth/Height return w/h including scrollbars (gh-1729)
 					return funcName.indexOf( "outer" ) === 0 ?
@@ -10237,6 +10469,28 @@ jQuery.each( { Height: "height", Width: "width" }, function( name, type ) {
 } );
 
 
+jQuery.each( ( "blur focus focusin focusout resize scroll click dblclick " +
+	"mousedown mouseup mousemove mouseover mouseout mouseenter mouseleave " +
+	"change select submit keydown keypress keyup contextmenu" ).split( " " ),
+	function( i, name ) {
+
+	// Handle event binding
+	jQuery.fn[ name ] = function( data, fn ) {
+		return arguments.length > 0 ?
+			this.on( name, null, data, fn ) :
+			this.trigger( name );
+	};
+} );
+
+jQuery.fn.extend( {
+	hover: function( fnOver, fnOut ) {
+		return this.mouseenter( fnOver ).mouseleave( fnOut || fnOver );
+	}
+} );
+
+
+
+
 jQuery.fn.extend( {
 
 	bind: function( types, data, fn ) {
@@ -10258,7 +10512,67 @@ jQuery.fn.extend( {
 	}
 } );
 
+// Bind a function to a context, optionally partially applying any
+// arguments.
+// jQuery.proxy is deprecated to promote standards (specifically Function#bind)
+// However, it is not slated for removal any time soon
+jQuery.proxy = function( fn, context ) {
+	var tmp, args, proxy;
+
+	if ( typeof context === "string" ) {
+		tmp = fn[ context ];
+		context = fn;
+		fn = tmp;
+	}
+
+	// Quick check to determine if target is callable, in the spec
+	// this throws a TypeError, but we will just return undefined.
+	if ( !isFunction( fn ) ) {
+		return undefined;
+	}
+
+	// Simulated bind
+	args = slice.call( arguments, 2 );
+	proxy = function() {
+		return fn.apply( context || this, args.concat( slice.call( arguments ) ) );
+	};
+
+	// Set the guid of unique handler to the same of original handler, so it can be removed
+	proxy.guid = fn.guid = fn.guid || jQuery.guid++;
+
+	return proxy;
+};
+
+jQuery.holdReady = function( hold ) {
+	if ( hold ) {
+		jQuery.readyWait++;
+	} else {
+		jQuery.ready( true );
+	}
+};
+jQuery.isArray = Array.isArray;
 jQuery.parseJSON = JSON.parse;
+jQuery.nodeName = nodeName;
+jQuery.isFunction = isFunction;
+jQuery.isWindow = isWindow;
+jQuery.camelCase = camelCase;
+jQuery.type = toType;
+
+jQuery.now = Date.now;
+
+jQuery.isNumeric = function( obj ) {
+
+	// As of jQuery 3.0, isNumeric is limited to
+	// strings and numbers (primitives or objects)
+	// that can be coerced to finite numbers (gh-2662)
+	var type = jQuery.type( obj );
+	return ( type === "number" || type === "string" ) &&
+
+		// parseFloat NaNs numeric-cast false positives ("")
+		// ...but misinterprets leading-number strings, particularly hex literals ("0x...")
+		// subtraction forces infinities to NaN
+		!isNaN( obj - parseFloat( obj ) );
+};
 
 
 
@@ -10285,7 +10599,6 @@ if ( typeof define === "function" && define.amd ) {
 
 
 
-
 var
 
 	// Map over jQuery in case of overwrite
@@ -10314,19210 +10627,20141 @@ if ( !noGlobal ) {
 }
 
 
+
+
 return jQuery;
 } );
 
 },{}],6:[function(require,module,exports){
-(function (global){
-/**
- * @license
- * lodash <https://lodash.com/>
- * Copyright jQuery Foundation and other contributors <https://jquery.org/>
- * Released under MIT license <https://lodash.com/license>
- * Based on Underscore.js 1.8.3 <http://underscorejs.org/LICENSE>
- * Copyright Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
- */
-;(function() {
+ /* eslint-env node */
+'use strict';
 
-  /** Used as a safe reference for `undefined` in pre-ES5 environments. */
-  var undefined;
+// SDP helpers.
+var SDPUtils = {};
 
-  /** Used as the semantic version number. */
-  var VERSION = '4.13.1';
+// Generate an alphanumeric identifier for cname or mids.
+// TODO: use UUIDs instead? https://gist.github.com/jed/982883
+SDPUtils.generateIdentifier = function() {
+  return Math.random().toString(36).substr(2, 10);
+};
 
-  /** Used as the size to enable large array optimizations. */
-  var LARGE_ARRAY_SIZE = 200;
+// The RTCP CNAME used by all peerconnections from the same JS.
+SDPUtils.localCName = SDPUtils.generateIdentifier();
 
-  /** Used as the `TypeError` message for "Functions" methods. */
-  var FUNC_ERROR_TEXT = 'Expected a function';
+// Splits SDP into lines, dealing with both CRLF and LF.
+SDPUtils.splitLines = function(blob) {
+  return blob.trim().split('\n').map(function(line) {
+    return line.trim();
+  });
+};
+// Splits SDP into sessionpart and mediasections. Ensures CRLF.
+SDPUtils.splitSections = function(blob) {
+  var parts = blob.split('\nm=');
+  return parts.map(function(part, index) {
+    return (index > 0 ? 'm=' + part : part).trim() + '\r\n';
+  });
+};
 
-  /** Used to stand-in for `undefined` hash values. */
-  var HASH_UNDEFINED = '__lodash_hash_undefined__';
+// Returns lines that start with a certain prefix.
+SDPUtils.matchPrefix = function(blob, prefix) {
+  return SDPUtils.splitLines(blob).filter(function(line) {
+    return line.indexOf(prefix) === 0;
+  });
+};
 
-  /** Used as the internal argument placeholder. */
-  var PLACEHOLDER = '__lodash_placeholder__';
+// Parses an ICE candidate line. Sample input:
+// candidate:702786350 2 udp 41819902 8.8.8.8 60769 typ relay raddr 8.8.8.8
+// rport 55996"
+SDPUtils.parseCandidate = function(line) {
+  var parts;
+  // Parse both variants.
+  if (line.indexOf('a=candidate:') === 0) {
+    parts = line.substring(12).split(' ');
+  } else {
+    parts = line.substring(10).split(' ');
+  }
 
-  /** Used to compose bitmasks for wrapper metadata. */
-  var BIND_FLAG = 1,
-      BIND_KEY_FLAG = 2,
-      CURRY_BOUND_FLAG = 4,
-      CURRY_FLAG = 8,
-      CURRY_RIGHT_FLAG = 16,
-      PARTIAL_FLAG = 32,
-      PARTIAL_RIGHT_FLAG = 64,
-      ARY_FLAG = 128,
-      REARG_FLAG = 256,
-      FLIP_FLAG = 512;
-
-  /** Used to compose bitmasks for comparison styles. */
-  var UNORDERED_COMPARE_FLAG = 1,
-      PARTIAL_COMPARE_FLAG = 2;
+  var candidate = {
+    foundation: parts[0],
+    component: parts[1],
+    protocol: parts[2].toLowerCase(),
+    priority: parseInt(parts[3], 10),
+    ip: parts[4],
+    port: parseInt(parts[5], 10),
+    // skip parts[6] == 'typ'
+    type: parts[7]
+  };
 
-  /** Used as default options for `_.truncate`. */
-  var DEFAULT_TRUNC_LENGTH = 30,
-      DEFAULT_TRUNC_OMISSION = '...';
+  for (var i = 8; i < parts.length; i += 2) {
+    switch (parts[i]) {
+      case 'raddr':
+        candidate.relatedAddress = parts[i + 1];
+        break;
+      case 'rport':
+        candidate.relatedPort = parseInt(parts[i + 1], 10);
+        break;
+      case 'tcptype':
+        candidate.tcpType = parts[i + 1];
+        break;
+      default: // extension handling, in particular ufrag
+        candidate[parts[i]] = parts[i + 1];
+        break;
+    }
+  }
+  return candidate;
+};
 
-  /** Used to detect hot functions by number of calls within a span of milliseconds. */
-  var HOT_COUNT = 150,
-      HOT_SPAN = 16;
+// Translates a candidate object into SDP candidate attribute.
+SDPUtils.writeCandidate = function(candidate) {
+  var sdp = [];
+  sdp.push(candidate.foundation);
+  sdp.push(candidate.component);
+  sdp.push(candidate.protocol.toUpperCase());
+  sdp.push(candidate.priority);
+  sdp.push(candidate.ip);
+  sdp.push(candidate.port);
 
-  /** Used to indicate the type of lazy iteratees. */
-  var LAZY_FILTER_FLAG = 1,
-      LAZY_MAP_FLAG = 2,
-      LAZY_WHILE_FLAG = 3;
+  var type = candidate.type;
+  sdp.push('typ');
+  sdp.push(type);
+  if (type !== 'host' && candidate.relatedAddress &&
+      candidate.relatedPort) {
+    sdp.push('raddr');
+    sdp.push(candidate.relatedAddress); // was: relAddr
+    sdp.push('rport');
+    sdp.push(candidate.relatedPort); // was: relPort
+  }
+  if (candidate.tcpType && candidate.protocol.toLowerCase() === 'tcp') {
+    sdp.push('tcptype');
+    sdp.push(candidate.tcpType);
+  }
+  return 'candidate:' + sdp.join(' ');
+};
 
-  /** Used as references for various `Number` constants. */
-  var INFINITY = 1 / 0,
-      MAX_SAFE_INTEGER = 9007199254740991,
-      MAX_INTEGER = 1.7976931348623157e+308,
-      NAN = 0 / 0;
-
-  /** Used as references for the maximum length and index of an array. */
-  var MAX_ARRAY_LENGTH = 4294967295,
-      MAX_ARRAY_INDEX = MAX_ARRAY_LENGTH - 1,
-      HALF_MAX_ARRAY_LENGTH = MAX_ARRAY_LENGTH >>> 1;
-
-  /** `Object#toString` result references. */
-  var argsTag = '[object Arguments]',
-      arrayTag = '[object Array]',
-      boolTag = '[object Boolean]',
-      dateTag = '[object Date]',
-      errorTag = '[object Error]',
-      funcTag = '[object Function]',
-      genTag = '[object GeneratorFunction]',
-      mapTag = '[object Map]',
-      numberTag = '[object Number]',
-      objectTag = '[object Object]',
-      promiseTag = '[object Promise]',
-      regexpTag = '[object RegExp]',
-      setTag = '[object Set]',
-      stringTag = '[object String]',
-      symbolTag = '[object Symbol]',
-      weakMapTag = '[object WeakMap]',
-      weakSetTag = '[object WeakSet]';
-
-  var arrayBufferTag = '[object ArrayBuffer]',
-      dataViewTag = '[object DataView]',
-      float32Tag = '[object Float32Array]',
-      float64Tag = '[object Float64Array]',
-      int8Tag = '[object Int8Array]',
-      int16Tag = '[object Int16Array]',
-      int32Tag = '[object Int32Array]',
-      uint8Tag = '[object Uint8Array]',
-      uint8ClampedTag = '[object Uint8ClampedArray]',
-      uint16Tag = '[object Uint16Array]',
-      uint32Tag = '[object Uint32Array]';
-
-  /** Used to match empty string literals in compiled template source. */
-  var reEmptyStringLeading = /\b__p \+= '';/g,
-      reEmptyStringMiddle = /\b(__p \+=) '' \+/g,
-      reEmptyStringTrailing = /(__e\(.*?\)|\b__t\)) \+\n'';/g;
-
-  /** Used to match HTML entities and HTML characters. */
-  var reEscapedHtml = /&(?:amp|lt|gt|quot|#39|#96);/g,
-      reUnescapedHtml = /[&<>"'`]/g,
-      reHasEscapedHtml = RegExp(reEscapedHtml.source),
-      reHasUnescapedHtml = RegExp(reUnescapedHtml.source);
-
-  /** Used to match template delimiters. */
-  var reEscape = /<%-([\s\S]+?)%>/g,
-      reEvaluate = /<%([\s\S]+?)%>/g,
-      reInterpolate = /<%=([\s\S]+?)%>/g;
-
-  /** Used to match property names within property paths. */
-  var reIsDeepProp = /\.|\[(?:[^[\]]*|(["'])(?:(?!\1)[^\\]|\\.)*?\1)\]/,
-      reIsPlainProp = /^\w*$/,
-      rePropName = /[^.[\]]+|\[(?:(-?\d+(?:\.\d+)?)|(["'])((?:(?!\2)[^\\]|\\.)*?)\2)\]|(?=(\.|\[\])(?:\4|$))/g;
-
-  /**
-   * Used to match `RegExp`
-   * [syntax characters](http://ecma-international.org/ecma-262/6.0/#sec-patterns).
-   */
-  var reRegExpChar = /[\\^$.*+?()[\]{}|]/g,
-      reHasRegExpChar = RegExp(reRegExpChar.source);
+// Parses an ice-options line, returns an array of option tags.
+// a=ice-options:foo bar
+SDPUtils.parseIceOptions = function(line) {
+  return line.substr(14).split(' ');
+}
 
-  /** Used to match leading and trailing whitespace. */
-  var reTrim = /^\s+|\s+$/g,
-      reTrimStart = /^\s+/,
-      reTrimEnd = /\s+$/;
+// Parses an rtpmap line, returns RTCRtpCoddecParameters. Sample input:
+// a=rtpmap:111 opus/48000/2
+SDPUtils.parseRtpMap = function(line) {
+  var parts = line.substr(9).split(' ');
+  var parsed = {
+    payloadType: parseInt(parts.shift(), 10) // was: id
+  };
 
-  /** Used to match non-compound words composed of alphanumeric characters. */
-  var reBasicWord = /[a-zA-Z0-9]+/g;
+  parts = parts[0].split('/');
 
-  /** Used to match backslashes in property paths. */
-  var reEscapeChar = /\\(\\)?/g;
+  parsed.name = parts[0];
+  parsed.clockRate = parseInt(parts[1], 10); // was: clockrate
+  // was: channels
+  parsed.numChannels = parts.length === 3 ? parseInt(parts[2], 10) : 1;
+  return parsed;
+};
 
-  /**
-   * Used to match
-   * [ES template delimiters](http://ecma-international.org/ecma-262/6.0/#sec-template-literal-lexical-components).
-   */
-  var reEsTemplate = /\$\{([^\\}]*(?:\\.[^\\}]*)*)\}/g;
+// Generate an a=rtpmap line from RTCRtpCodecCapability or
+// RTCRtpCodecParameters.
+SDPUtils.writeRtpMap = function(codec) {
+  var pt = codec.payloadType;
+  if (codec.preferredPayloadType !== undefined) {
+    pt = codec.preferredPayloadType;
+  }
+  return 'a=rtpmap:' + pt + ' ' + codec.name + '/' + codec.clockRate +
+      (codec.numChannels !== 1 ? '/' + codec.numChannels : '') + '\r\n';
+};
 
-  /** Used to match `RegExp` flags from their coerced string values. */
-  var reFlags = /\w*$/;
+// Parses an a=extmap line (headerextension from RFC 5285). Sample input:
+// a=extmap:2 urn:ietf:params:rtp-hdrext:toffset
+// a=extmap:2/sendonly urn:ietf:params:rtp-hdrext:toffset
+SDPUtils.parseExtmap = function(line) {
+  var parts = line.substr(9).split(' ');
+  return {
+    id: parseInt(parts[0], 10),
+    direction: parts[0].indexOf('/') > 0 ? parts[0].split('/')[1] : 'sendrecv',
+    uri: parts[1]
+  };
+};
 
-  /** Used to detect hexadecimal string values. */
-  var reHasHexPrefix = /^0x/i;
+// Generates a=extmap line from RTCRtpHeaderExtensionParameters or
+// RTCRtpHeaderExtension.
+SDPUtils.writeExtmap = function(headerExtension) {
+  return 'a=extmap:' + (headerExtension.id || headerExtension.preferredId) +
+      (headerExtension.direction && headerExtension.direction !== 'sendrecv'
+          ? '/' + headerExtension.direction
+          : '') +
+      ' ' + headerExtension.uri + '\r\n';
+};
 
-  /** Used to detect bad signed hexadecimal string values. */
-  var reIsBadHex = /^[-+]0x[0-9a-f]+$/i;
+// Parses an ftmp line, returns dictionary. Sample input:
+// a=fmtp:96 vbr=on;cng=on
+// Also deals with vbr=on; cng=on
+SDPUtils.parseFmtp = function(line) {
+  var parsed = {};
+  var kv;
+  var parts = line.substr(line.indexOf(' ') + 1).split(';');
+  for (var j = 0; j < parts.length; j++) {
+    kv = parts[j].trim().split('=');
+    parsed[kv[0].trim()] = kv[1];
+  }
+  return parsed;
+};
 
-  /** Used to detect binary string values. */
-  var reIsBinary = /^0b[01]+$/i;
+// Generates an a=ftmp line from RTCRtpCodecCapability or RTCRtpCodecParameters.
+SDPUtils.writeFmtp = function(codec) {
+  var line = '';
+  var pt = codec.payloadType;
+  if (codec.preferredPayloadType !== undefined) {
+    pt = codec.preferredPayloadType;
+  }
+  if (codec.parameters && Object.keys(codec.parameters).length) {
+    var params = [];
+    Object.keys(codec.parameters).forEach(function(param) {
+      params.push(param + '=' + codec.parameters[param]);
+    });
+    line += 'a=fmtp:' + pt + ' ' + params.join(';') + '\r\n';
+  }
+  return line;
+};
 
-  /** Used to detect host constructors (Safari). */
-  var reIsHostCtor = /^\[object .+?Constructor\]$/;
+// Parses an rtcp-fb line, returns RTCPRtcpFeedback object. Sample input:
+// a=rtcp-fb:98 nack rpsi
+SDPUtils.parseRtcpFb = function(line) {
+  var parts = line.substr(line.indexOf(' ') + 1).split(' ');
+  return {
+    type: parts.shift(),
+    parameter: parts.join(' ')
+  };
+};
+// Generate a=rtcp-fb lines from RTCRtpCodecCapability or RTCRtpCodecParameters.
+SDPUtils.writeRtcpFb = function(codec) {
+  var lines = '';
+  var pt = codec.payloadType;
+  if (codec.preferredPayloadType !== undefined) {
+    pt = codec.preferredPayloadType;
+  }
+  if (codec.rtcpFeedback && codec.rtcpFeedback.length) {
+    // FIXME: special handling for trr-int?
+    codec.rtcpFeedback.forEach(function(fb) {
+      lines += 'a=rtcp-fb:' + pt + ' ' + fb.type +
+      (fb.parameter && fb.parameter.length ? ' ' + fb.parameter : '') +
+          '\r\n';
+    });
+  }
+  return lines;
+};
 
-  /** Used to detect octal string values. */
-  var reIsOctal = /^0o[0-7]+$/i;
+// Parses an RFC 5576 ssrc media attribute. Sample input:
+// a=ssrc:3735928559 cname:something
+SDPUtils.parseSsrcMedia = function(line) {
+  var sp = line.indexOf(' ');
+  var parts = {
+    ssrc: parseInt(line.substr(7, sp - 7), 10)
+  };
+  var colon = line.indexOf(':', sp);
+  if (colon > -1) {
+    parts.attribute = line.substr(sp + 1, colon - sp - 1);
+    parts.value = line.substr(colon + 1);
+  } else {
+    parts.attribute = line.substr(sp + 1);
+  }
+  return parts;
+};
 
-  /** Used to detect unsigned integer values. */
-  var reIsUint = /^(?:0|[1-9]\d*)$/;
+// Extracts the MID (RFC 5888) from a media section.
+// returns the MID or undefined if no mid line was found.
+SDPUtils.getMid = function(mediaSection) {
+  var mid = SDPUtils.matchPrefix(mediaSection, 'a=mid:')[0];
+  if (mid) {
+    return mid.substr(6);
+  }
+}
 
-  /** Used to match latin-1 supplementary letters (excluding mathematical operators). */
-  var reLatin1 = /[\xc0-\xd6\xd8-\xde\xdf-\xf6\xf8-\xff]/g;
+SDPUtils.parseFingerprint = function(line) {
+  var parts = line.substr(14).split(' ');
+  return {
+    algorithm: parts[0].toLowerCase(), // algorithm is case-sensitive in Edge.
+    value: parts[1]
+  };
+};
 
-  /** Used to ensure capturing order of template delimiters. */
-  var reNoMatch = /($^)/;
+// Extracts DTLS parameters from SDP media section or sessionpart.
+// FIXME: for consistency with other functions this should only
+//   get the fingerprint line as input. See also getIceParameters.
+SDPUtils.getDtlsParameters = function(mediaSection, sessionpart) {
+  var lines = SDPUtils.matchPrefix(mediaSection + sessionpart,
+      'a=fingerprint:');
+  // Note: a=setup line is ignored since we use the 'auto' role.
+  // Note2: 'algorithm' is not case sensitive except in Edge.
+  return {
+    role: 'auto',
+    fingerprints: lines.map(SDPUtils.parseFingerprint)
+  };
+};
 
-  /** Used to match unescaped characters in compiled string literals. */
-  var reUnescapedString = /['\n\r\u2028\u2029\\]/g;
+// Serializes DTLS parameters to SDP.
+SDPUtils.writeDtlsParameters = function(params, setupType) {
+  var sdp = 'a=setup:' + setupType + '\r\n';
+  params.fingerprints.forEach(function(fp) {
+    sdp += 'a=fingerprint:' + fp.algorithm + ' ' + fp.value + '\r\n';
+  });
+  return sdp;
+};
+// Parses ICE information from SDP media section or sessionpart.
+// FIXME: for consistency with other functions this should only
+//   get the ice-ufrag and ice-pwd lines as input.
+SDPUtils.getIceParameters = function(mediaSection, sessionpart) {
+  var lines = SDPUtils.splitLines(mediaSection);
+  // Search in session part, too.
+  lines = lines.concat(SDPUtils.splitLines(sessionpart));
+  var iceParameters = {
+    usernameFragment: lines.filter(function(line) {
+      return line.indexOf('a=ice-ufrag:') === 0;
+    })[0].substr(12),
+    password: lines.filter(function(line) {
+      return line.indexOf('a=ice-pwd:') === 0;
+    })[0].substr(10)
+  };
+  return iceParameters;
+};
 
-  /** Used to compose unicode character classes. */
-  var rsAstralRange = '\\ud800-\\udfff',
-      rsComboMarksRange = '\\u0300-\\u036f\\ufe20-\\ufe23',
-      rsComboSymbolsRange = '\\u20d0-\\u20f0',
-      rsDingbatRange = '\\u2700-\\u27bf',
-      rsLowerRange = 'a-z\\xdf-\\xf6\\xf8-\\xff',
-      rsMathOpRange = '\\xac\\xb1\\xd7\\xf7',
-      rsNonCharRange = '\\x00-\\x2f\\x3a-\\x40\\x5b-\\x60\\x7b-\\xbf',
-      rsPunctuationRange = '\\u2000-\\u206f',
-      rsSpaceRange = ' \\t\\x0b\\f\\xa0\\ufeff\\n\\r\\u2028\\u2029\\u1680\\u180e\\u2000\\u2001\\u2002\\u2003\\u2004\\u2005\\u2006\\u2007\\u2008\\u2009\\u200a\\u202f\\u205f\\u3000',
-      rsUpperRange = 'A-Z\\xc0-\\xd6\\xd8-\\xde',
-      rsVarRange = '\\ufe0e\\ufe0f',
-      rsBreakRange = rsMathOpRange + rsNonCharRange + rsPunctuationRange + rsSpaceRange;
+// Serializes ICE parameters to SDP.
+SDPUtils.writeIceParameters = function(params) {
+  return 'a=ice-ufrag:' + params.usernameFragment + '\r\n' +
+      'a=ice-pwd:' + params.password + '\r\n';
+};
 
-  /** Used to compose unicode capture groups. */
-  var rsApos = "['\u2019]",
-      rsAstral = '[' + rsAstralRange + ']',
-      rsBreak = '[' + rsBreakRange + ']',
-      rsCombo = '[' + rsComboMarksRange + rsComboSymbolsRange + ']',
-      rsDigits = '\\d+',
-      rsDingbat = '[' + rsDingbatRange + ']',
-      rsLower = '[' + rsLowerRange + ']',
-      rsMisc = '[^' + rsAstralRange + rsBreakRange + rsDigits + rsDingbatRange + rsLowerRange + rsUpperRange + ']',
-      rsFitz = '\\ud83c[\\udffb-\\udfff]',
-      rsModifier = '(?:' + rsCombo + '|' + rsFitz + ')',
-      rsNonAstral = '[^' + rsAstralRange + ']',
-      rsRegional = '(?:\\ud83c[\\udde6-\\uddff]){2}',
-      rsSurrPair = '[\\ud800-\\udbff][\\udc00-\\udfff]',
-      rsUpper = '[' + rsUpperRange + ']',
-      rsZWJ = '\\u200d';
-
-  /** Used to compose unicode regexes. */
-  var rsLowerMisc = '(?:' + rsLower + '|' + rsMisc + ')',
-      rsUpperMisc = '(?:' + rsUpper + '|' + rsMisc + ')',
-      rsOptLowerContr = '(?:' + rsApos + '(?:d|ll|m|re|s|t|ve))?',
-      rsOptUpperContr = '(?:' + rsApos + '(?:D|LL|M|RE|S|T|VE))?',
-      reOptMod = rsModifier + '?',
-      rsOptVar = '[' + rsVarRange + ']?',
-      rsOptJoin = '(?:' + rsZWJ + '(?:' + [rsNonAstral, rsRegional, rsSurrPair].join('|') + ')' + rsOptVar + reOptMod + ')*',
-      rsSeq = rsOptVar + reOptMod + rsOptJoin,
-      rsEmoji = '(?:' + [rsDingbat, rsRegional, rsSurrPair].join('|') + ')' + rsSeq,
-      rsSymbol = '(?:' + [rsNonAstral + rsCombo + '?', rsCombo, rsRegional, rsSurrPair, rsAstral].join('|') + ')';
+// Parses the SDP media section and returns RTCRtpParameters.
+SDPUtils.parseRtpParameters = function(mediaSection) {
+  var description = {
+    codecs: [],
+    headerExtensions: [],
+    fecMechanisms: [],
+    rtcp: []
+  };
+  var lines = SDPUtils.splitLines(mediaSection);
+  var mline = lines[0].split(' ');
+  for (var i = 3; i < mline.length; i++) { // find all codecs from mline[3..]
+    var pt = mline[i];
+    var rtpmapline = SDPUtils.matchPrefix(
+        mediaSection, 'a=rtpmap:' + pt + ' ')[0];
+    if (rtpmapline) {
+      var codec = SDPUtils.parseRtpMap(rtpmapline);
+      var fmtps = SDPUtils.matchPrefix(
+          mediaSection, 'a=fmtp:' + pt + ' ');
+      // Only the first a=fmtp:<pt> is considered.
+      codec.parameters = fmtps.length ? SDPUtils.parseFmtp(fmtps[0]) : {};
+      codec.rtcpFeedback = SDPUtils.matchPrefix(
+          mediaSection, 'a=rtcp-fb:' + pt + ' ')
+        .map(SDPUtils.parseRtcpFb);
+      description.codecs.push(codec);
+      // parse FEC mechanisms from rtpmap lines.
+      switch (codec.name.toUpperCase()) {
+        case 'RED':
+        case 'ULPFEC':
+          description.fecMechanisms.push(codec.name.toUpperCase());
+          break;
+        default: // only RED and ULPFEC are recognized as FEC mechanisms.
+          break;
+      }
+    }
+  }
+  SDPUtils.matchPrefix(mediaSection, 'a=extmap:').forEach(function(line) {
+    description.headerExtensions.push(SDPUtils.parseExtmap(line));
+  });
+  // FIXME: parse rtcp.
+  return description;
+};
 
-  /** Used to match apostrophes. */
-  var reApos = RegExp(rsApos, 'g');
+// Generates parts of the SDP media section describing the capabilities /
+// parameters.
+SDPUtils.writeRtpDescription = function(kind, caps) {
+  var sdp = '';
 
-  /**
-   * Used to match [combining diacritical marks](https://en.wikipedia.org/wiki/Combining_Diacritical_Marks) and
-   * [combining diacritical marks for symbols](https://en.wikipedia.org/wiki/Combining_Diacritical_Marks_for_Symbols).
-   */
-  var reComboMark = RegExp(rsCombo, 'g');
+  // Build the mline.
+  sdp += 'm=' + kind + ' ';
+  sdp += caps.codecs.length > 0 ? '9' : '0'; // reject if no codecs.
+  sdp += ' UDP/TLS/RTP/SAVPF ';
+  sdp += caps.codecs.map(function(codec) {
+    if (codec.preferredPayloadType !== undefined) {
+      return codec.preferredPayloadType;
+    }
+    return codec.payloadType;
+  }).join(' ') + '\r\n';
 
-  /** Used to match [string symbols](https://mathiasbynens.be/notes/javascript-unicode). */
-  var reComplexSymbol = RegExp(rsFitz + '(?=' + rsFitz + ')|' + rsSymbol + rsSeq, 'g');
+  sdp += 'c=IN IP4 0.0.0.0\r\n';
+  sdp += 'a=rtcp:9 IN IP4 0.0.0.0\r\n';
 
-  /** Used to match complex or compound words. */
-  var reComplexWord = RegExp([
-    rsUpper + '?' + rsLower + '+' + rsOptLowerContr + '(?=' + [rsBreak, rsUpper, '$'].join('|') + ')',
-    rsUpperMisc + '+' + rsOptUpperContr + '(?=' + [rsBreak, rsUpper + rsLowerMisc, '$'].join('|') + ')',
-    rsUpper + '?' + rsLowerMisc + '+' + rsOptLowerContr,
-    rsUpper + '+' + rsOptUpperContr,
-    rsDigits,
-    rsEmoji
-  ].join('|'), 'g');
+  // Add a=rtpmap lines for each codec. Also fmtp and rtcp-fb.
+  caps.codecs.forEach(function(codec) {
+    sdp += SDPUtils.writeRtpMap(codec);
+    sdp += SDPUtils.writeFmtp(codec);
+    sdp += SDPUtils.writeRtcpFb(codec);
+  });
+  var maxptime = 0;
+  caps.codecs.forEach(function(codec) {
+    if (codec.maxptime > maxptime) {
+      maxptime = codec.maxptime;
+    }
+  });
+  if (maxptime > 0) {
+    sdp += 'a=maxptime:' + maxptime + '\r\n';
+  }
+  sdp += 'a=rtcp-mux\r\n';
 
-  /** Used to detect strings with [zero-width joiners or code points from the astral planes](http://eev.ee/blog/2015/09/12/dark-corners-of-unicode/). */
-  var reHasComplexSymbol = RegExp('[' + rsZWJ + rsAstralRange  + rsComboMarksRange + rsComboSymbolsRange + rsVarRange + ']');
+  caps.headerExtensions.forEach(function(extension) {
+    sdp += SDPUtils.writeExtmap(extension);
+  });
+  // FIXME: write fecMechanisms.
+  return sdp;
+};
 
-  /** Used to detect strings that need a more robust regexp to match words. */
-  var reHasComplexWord = /[a-z][A-Z]|[A-Z]{2,}[a-z]|[0-9][a-zA-Z]|[a-zA-Z][0-9]|[^a-zA-Z0-9 ]/;
+// Parses the SDP media section and returns an array of
+// RTCRtpEncodingParameters.
+SDPUtils.parseRtpEncodingParameters = function(mediaSection) {
+  var encodingParameters = [];
+  var description = SDPUtils.parseRtpParameters(mediaSection);
+  var hasRed = description.fecMechanisms.indexOf('RED') !== -1;
+  var hasUlpfec = description.fecMechanisms.indexOf('ULPFEC') !== -1;
 
-  /** Used to assign default `context` object properties. */
-  var contextProps = [
-    'Array', 'Buffer', 'DataView', 'Date', 'Error', 'Float32Array', 'Float64Array',
-    'Function', 'Int8Array', 'Int16Array', 'Int32Array', 'Map', 'Math', 'Object',
-    'Promise', 'Reflect', 'RegExp', 'Set', 'String', 'Symbol', 'TypeError',
-    'Uint8Array', 'Uint8ClampedArray', 'Uint16Array', 'Uint32Array', 'WeakMap',
-    '_', 'isFinite', 'parseInt', 'setTimeout'
-  ];
+  // filter a=ssrc:... cname:, ignore PlanB-msid
+  var ssrcs = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
+  .map(function(line) {
+    return SDPUtils.parseSsrcMedia(line);
+  })
+  .filter(function(parts) {
+    return parts.attribute === 'cname';
+  });
+  var primarySsrc = ssrcs.length > 0 && ssrcs[0].ssrc;
+  var secondarySsrc;
 
-  /** Used to make template sourceURLs easier to identify. */
-  var templateCounter = -1;
+  var flows = SDPUtils.matchPrefix(mediaSection, 'a=ssrc-group:FID')
+  .map(function(line) {
+    var parts = line.split(' ');
+    parts.shift();
+    return parts.map(function(part) {
+      return parseInt(part, 10);
+    });
+  });
+  if (flows.length > 0 && flows[0].length > 1 && flows[0][0] === primarySsrc) {
+    secondarySsrc = flows[0][1];
+  }
 
-  /** Used to identify `toStringTag` values of typed arrays. */
-  var typedArrayTags = {};
-  typedArrayTags[float32Tag] = typedArrayTags[float64Tag] =
-  typedArrayTags[int8Tag] = typedArrayTags[int16Tag] =
-  typedArrayTags[int32Tag] = typedArrayTags[uint8Tag] =
-  typedArrayTags[uint8ClampedTag] = typedArrayTags[uint16Tag] =
-  typedArrayTags[uint32Tag] = true;
-  typedArrayTags[argsTag] = typedArrayTags[arrayTag] =
-  typedArrayTags[arrayBufferTag] = typedArrayTags[boolTag] =
-  typedArrayTags[dataViewTag] = typedArrayTags[dateTag] =
-  typedArrayTags[errorTag] = typedArrayTags[funcTag] =
-  typedArrayTags[mapTag] = typedArrayTags[numberTag] =
-  typedArrayTags[objectTag] = typedArrayTags[regexpTag] =
-  typedArrayTags[setTag] = typedArrayTags[stringTag] =
-  typedArrayTags[weakMapTag] = false;
+  description.codecs.forEach(function(codec) {
+    if (codec.name.toUpperCase() === 'RTX' && codec.parameters.apt) {
+      var encParam = {
+        ssrc: primarySsrc,
+        codecPayloadType: parseInt(codec.parameters.apt, 10),
+        rtx: {
+          ssrc: secondarySsrc
+        }
+      };
+      encodingParameters.push(encParam);
+      if (hasRed) {
+        encParam = JSON.parse(JSON.stringify(encParam));
+        encParam.fec = {
+          ssrc: secondarySsrc,
+          mechanism: hasUlpfec ? 'red+ulpfec' : 'red'
+        };
+        encodingParameters.push(encParam);
+      }
+    }
+  });
+  if (encodingParameters.length === 0 && primarySsrc) {
+    encodingParameters.push({
+      ssrc: primarySsrc
+    });
+  }
 
-  /** Used to identify `toStringTag` values supported by `_.clone`. */
-  var cloneableTags = {};
-  cloneableTags[argsTag] = cloneableTags[arrayTag] =
-  cloneableTags[arrayBufferTag] = cloneableTags[dataViewTag] =
-  cloneableTags[boolTag] = cloneableTags[dateTag] =
-  cloneableTags[float32Tag] = cloneableTags[float64Tag] =
-  cloneableTags[int8Tag] = cloneableTags[int16Tag] =
-  cloneableTags[int32Tag] = cloneableTags[mapTag] =
-  cloneableTags[numberTag] = cloneableTags[objectTag] =
-  cloneableTags[regexpTag] = cloneableTags[setTag] =
-  cloneableTags[stringTag] = cloneableTags[symbolTag] =
-  cloneableTags[uint8Tag] = cloneableTags[uint8ClampedTag] =
-  cloneableTags[uint16Tag] = cloneableTags[uint32Tag] = true;
-  cloneableTags[errorTag] = cloneableTags[funcTag] =
-  cloneableTags[weakMapTag] = false;
+  // we support both b=AS and b=TIAS but interpret AS as TIAS.
+  var bandwidth = SDPUtils.matchPrefix(mediaSection, 'b=');
+  if (bandwidth.length) {
+    if (bandwidth[0].indexOf('b=TIAS:') === 0) {
+      bandwidth = parseInt(bandwidth[0].substr(7), 10);
+    } else if (bandwidth[0].indexOf('b=AS:') === 0) {
+      bandwidth = parseInt(bandwidth[0].substr(5), 10);
+    }
+    encodingParameters.forEach(function(params) {
+      params.maxBitrate = bandwidth;
+    });
+  }
+  return encodingParameters;
+};
 
-  /** Used to map latin-1 supplementary letters to basic latin letters. */
-  var deburredLetters = {
-    '\xc0': 'A',  '\xc1': 'A', '\xc2': 'A', '\xc3': 'A', '\xc4': 'A', '\xc5': 'A',
-    '\xe0': 'a',  '\xe1': 'a', '\xe2': 'a', '\xe3': 'a', '\xe4': 'a', '\xe5': 'a',
-    '\xc7': 'C',  '\xe7': 'c',
-    '\xd0': 'D',  '\xf0': 'd',
-    '\xc8': 'E',  '\xc9': 'E', '\xca': 'E', '\xcb': 'E',
-    '\xe8': 'e',  '\xe9': 'e', '\xea': 'e', '\xeb': 'e',
-    '\xcC': 'I',  '\xcd': 'I', '\xce': 'I', '\xcf': 'I',
-    '\xeC': 'i',  '\xed': 'i', '\xee': 'i', '\xef': 'i',
-    '\xd1': 'N',  '\xf1': 'n',
-    '\xd2': 'O',  '\xd3': 'O', '\xd4': 'O', '\xd5': 'O', '\xd6': 'O', '\xd8': 'O',
-    '\xf2': 'o',  '\xf3': 'o', '\xf4': 'o', '\xf5': 'o', '\xf6': 'o', '\xf8': 'o',
-    '\xd9': 'U',  '\xda': 'U', '\xdb': 'U', '\xdc': 'U',
-    '\xf9': 'u',  '\xfa': 'u', '\xfb': 'u', '\xfc': 'u',
-    '\xdd': 'Y',  '\xfd': 'y', '\xff': 'y',
-    '\xc6': 'Ae', '\xe6': 'ae',
-    '\xde': 'Th', '\xfe': 'th',
-    '\xdf': 'ss'
-  };
+// parses http://draft.ortc.org/#rtcrtcpparameters*
+SDPUtils.parseRtcpParameters = function(mediaSection) {
+  var rtcpParameters = {};
 
-  /** Used to map characters to HTML entities. */
-  var htmlEscapes = {
-    '&': '&amp;',
-    '<': '&lt;',
-    '>': '&gt;',
-    '"': '&quot;',
-    "'": '&#39;',
-    '`': '&#96;'
-  };
+  var cname;
+  // Gets the first SSRC. Note that with RTX there might be multiple
+  // SSRCs.
+  var remoteSsrc = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
+      .map(function(line) {
+        return SDPUtils.parseSsrcMedia(line);
+      })
+      .filter(function(obj) {
+        return obj.attribute === 'cname';
+      })[0];
+  if (remoteSsrc) {
+    rtcpParameters.cname = remoteSsrc.value;
+    rtcpParameters.ssrc = remoteSsrc.ssrc;
+  }
 
-  /** Used to map HTML entities to characters. */
-  var htmlUnescapes = {
-    '&amp;': '&',
-    '&lt;': '<',
-    '&gt;': '>',
-    '&quot;': '"',
-    '&#39;': "'",
-    '&#96;': '`'
-  };
+  // Edge uses the compound attribute instead of reducedSize
+  // compound is !reducedSize
+  var rsize = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-rsize');
+  rtcpParameters.reducedSize = rsize.length > 0;
+  rtcpParameters.compound = rsize.length === 0;
 
-  /** Used to escape characters for inclusion in compiled string literals. */
-  var stringEscapes = {
-    '\\': '\\',
-    "'": "'",
-    '\n': 'n',
-    '\r': 'r',
-    '\u2028': 'u2028',
-    '\u2029': 'u2029'
-  };
+  // parses the rtcp-mux attrіbute.
+  // Note that Edge does not support unmuxed RTCP.
+  var mux = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-mux');
+  rtcpParameters.mux = mux.length > 0;
 
-  /** Built-in method references without a dependency on `root`. */
-  var freeParseFloat = parseFloat,
-      freeParseInt = parseInt;
+  return rtcpParameters;
+};
 
-  /** Detect free variable `exports`. */
-  var freeExports = typeof exports == 'object' && exports;
+// parses either a=msid: or a=ssrc:... msid lines and returns
+// the id of the MediaStream and MediaStreamTrack.
+SDPUtils.parseMsid = function(mediaSection) {
+  var parts;
+  var spec = SDPUtils.matchPrefix(mediaSection, 'a=msid:');
+  if (spec.length === 1) {
+    parts = spec[0].substr(7).split(' ');
+    return {stream: parts[0], track: parts[1]};
+  }
+  var planB = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
+  .map(function(line) {
+    return SDPUtils.parseSsrcMedia(line);
+  })
+  .filter(function(parts) {
+    return parts.attribute === 'msid';
+  });
+  if (planB.length > 0) {
+    parts = planB[0].value.split(' ');
+    return {stream: parts[0], track: parts[1]};
+  }
+};
 
-  /** Detect free variable `module`. */
-  var freeModule = freeExports && typeof module == 'object' && module;
+SDPUtils.writeSessionBoilerplate = function() {
+  // FIXME: sess-id should be an NTP timestamp.
+  return 'v=0\r\n' +
+      'o=thisisadapterortc 8169639915646943137 2 IN IP4 127.0.0.1\r\n' +
+      's=-\r\n' +
+      't=0 0\r\n';
+};
 
-  /** Detect the popular CommonJS extension `module.exports`. */
-  var moduleExports = freeModule && freeModule.exports === freeExports;
+SDPUtils.writeMediaSection = function(transceiver, caps, type, stream) {
+  var sdp = SDPUtils.writeRtpDescription(transceiver.kind, caps);
 
-  /** Detect free variable `global` from Node.js. */
-  var freeGlobal = checkGlobal(typeof global == 'object' && global);
+  // Map ICE parameters (ufrag, pwd) to SDP.
+  sdp += SDPUtils.writeIceParameters(
+      transceiver.iceGatherer.getLocalParameters());
 
-  /** Detect free variable `self`. */
-  var freeSelf = checkGlobal(typeof self == 'object' && self);
+  // Map DTLS parameters to SDP.
+  sdp += SDPUtils.writeDtlsParameters(
+      transceiver.dtlsTransport.getLocalParameters(),
+      type === 'offer' ? 'actpass' : 'active');
 
-  /** Detect `this` as the global object. */
-  var thisGlobal = checkGlobal(typeof this == 'object' && this);
+  sdp += 'a=mid:' + transceiver.mid + '\r\n';
 
-  /** Used as a reference to the global object. */
-  var root = freeGlobal || freeSelf || thisGlobal || Function('return this')();
+  if (transceiver.direction) {
+    sdp += 'a=' + transceiver.direction + '\r\n';
+  } else if (transceiver.rtpSender && transceiver.rtpReceiver) {
+    sdp += 'a=sendrecv\r\n';
+  } else if (transceiver.rtpSender) {
+    sdp += 'a=sendonly\r\n';
+  } else if (transceiver.rtpReceiver) {
+    sdp += 'a=recvonly\r\n';
+  } else {
+    sdp += 'a=inactive\r\n';
+  }
 
-  /*--------------------------------------------------------------------------*/
+  if (transceiver.rtpSender) {
+    // spec.
+    var msid = 'msid:' + stream.id + ' ' +
+        transceiver.rtpSender.track.id + '\r\n';
+    sdp += 'a=' + msid;
 
-  /**
-   * Adds the key-value `pair` to `map`.
-   *
-   * @private
-   * @param {Object} map The map to modify.
-   * @param {Array} pair The key-value pair to add.
-   * @returns {Object} Returns `map`.
-   */
-  function addMapEntry(map, pair) {
-    // Don't return `Map#set` because it doesn't return the map instance in IE 11.
-    map.set(pair[0], pair[1]);
-    return map;
+    // for Chrome.
+    sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
+        ' ' + msid;
+    if (transceiver.sendEncodingParameters[0].rtx) {
+      sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
+          ' ' + msid;
+      sdp += 'a=ssrc-group:FID ' +
+          transceiver.sendEncodingParameters[0].ssrc + ' ' +
+          transceiver.sendEncodingParameters[0].rtx.ssrc +
+          '\r\n';
+    }
   }
-
-  /**
-   * Adds `value` to `set`.
-   *
-   * @private
-   * @param {Object} set The set to modify.
-   * @param {*} value The value to add.
-   * @returns {Object} Returns `set`.
-   */
-  function addSetEntry(set, value) {
-    set.add(value);
-    return set;
+  // FIXME: this should be written by writeRtpDescription.
+  sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
+      ' cname:' + SDPUtils.localCName + '\r\n';
+  if (transceiver.rtpSender && transceiver.sendEncodingParameters[0].rtx) {
+    sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
+        ' cname:' + SDPUtils.localCName + '\r\n';
   }
+  return sdp;
+};
 
-  /**
-   * A faster alternative to `Function#apply`, this function invokes `func`
-   * with the `this` binding of `thisArg` and the arguments of `args`.
-   *
-   * @private
-   * @param {Function} func The function to invoke.
-   * @param {*} thisArg The `this` binding of `func`.
-   * @param {Array} args The arguments to invoke `func` with.
-   * @returns {*} Returns the result of `func`.
-   */
-  function apply(func, thisArg, args) {
-    var length = args.length;
-    switch (length) {
-      case 0: return func.call(thisArg);
-      case 1: return func.call(thisArg, args[0]);
-      case 2: return func.call(thisArg, args[0], args[1]);
-      case 3: return func.call(thisArg, args[0], args[1], args[2]);
+// Gets the direction from the mediaSection or the sessionpart.
+SDPUtils.getDirection = function(mediaSection, sessionpart) {
+  // Look for sendrecv, sendonly, recvonly, inactive, default to sendrecv.
+  var lines = SDPUtils.splitLines(mediaSection);
+  for (var i = 0; i < lines.length; i++) {
+    switch (lines[i]) {
+      case 'a=sendrecv':
+      case 'a=sendonly':
+      case 'a=recvonly':
+      case 'a=inactive':
+        return lines[i].substr(2);
+      default:
+        // FIXME: What should happen here?
     }
-    return func.apply(thisArg, args);
   }
+  if (sessionpart) {
+    return SDPUtils.getDirection(sessionpart);
+  }
+  return 'sendrecv';
+};
 
-  /**
-   * A specialized version of `baseAggregator` for arrays.
-   *
-   * @private
-   * @param {Array} [array] The array to iterate over.
-   * @param {Function} setter The function to set `accumulator` values.
-   * @param {Function} iteratee The iteratee to transform keys.
-   * @param {Object} accumulator The initial aggregated object.
-   * @returns {Function} Returns `accumulator`.
-   */
-  function arrayAggregator(array, setter, iteratee, accumulator) {
-    var index = -1,
-        length = array ? array.length : 0;
+SDPUtils.getKind = function(mediaSection) {
+  var lines = SDPUtils.splitLines(mediaSection);
+  var mline = lines[0].split(' ');
+  return mline[0].substr(2);
+};
 
-    while (++index < length) {
-      var value = array[index];
-      setter(accumulator, value, iteratee(value), array);
-    }
-    return accumulator;
-  }
+SDPUtils.isRejected = function(mediaSection) {
+  return mediaSection.split(' ', 2)[1] === '0';
+};
 
-  /**
-   * A specialized version of `_.forEach` for arrays without support for
-   * iteratee shorthands.
-   *
-   * @private
-   * @param {Array} [array] The array to iterate over.
-   * @param {Function} iteratee The function invoked per iteration.
-   * @returns {Array} Returns `array`.
-   */
-  function arrayEach(array, iteratee) {
-    var index = -1,
-        length = array ? array.length : 0;
+// Expose public methods.
+module.exports = SDPUtils;
 
-    while (++index < length) {
-      if (iteratee(array[index], index, array) === false) {
-        break;
-      }
-    }
-    return array;
-  }
+},{}],7:[function(require,module,exports){
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree.
+ */
+ /* eslint-env node */
 
-  /**
-   * A specialized version of `_.forEachRight` for arrays without support for
-   * iteratee shorthands.
-   *
-   * @private
-   * @param {Array} [array] The array to iterate over.
-   * @param {Function} iteratee The function invoked per iteration.
-   * @returns {Array} Returns `array`.
-   */
-  function arrayEachRight(array, iteratee) {
-    var length = array ? array.length : 0;
+'use strict';
 
-    while (length--) {
-      if (iteratee(array[length], length, array) === false) {
-        break;
-      }
-    }
-    return array;
-  }
+// Shimming starts here.
+(function() {
+  // Utils.
+  var logging = require('./utils').log;
+  var browserDetails = require('./utils').browserDetails;
+  // Export to the adapter global object visible in the browser.
+  module.exports.browserDetails = browserDetails;
+  module.exports.extractVersion = require('./utils').extractVersion;
+  module.exports.disableLog = require('./utils').disableLog;
 
-  /**
-   * A specialized version of `_.every` for arrays without support for
-   * iteratee shorthands.
-   *
-   * @private
-   * @param {Array} [array] The array to iterate over.
-   * @param {Function} predicate The function invoked per iteration.
-   * @returns {boolean} Returns `true` if all elements pass the predicate check,
-   *  else `false`.
-   */
-  function arrayEvery(array, predicate) {
-    var index = -1,
-        length = array ? array.length : 0;
+  // Uncomment the line below if you want logging to occur, including logging
+  // for the switch statement below. Can also be turned on in the browser via
+  // adapter.disableLog(false), but then logging from the switch statement below
+  // will not appear.
+  // require('./utils').disableLog(false);
 
-    while (++index < length) {
-      if (!predicate(array[index], index, array)) {
-        return false;
-      }
-    }
-    return true;
-  }
+  // Browser shims.
+  var chromeShim = require('./chrome/chrome_shim') || null;
+  var edgeShim = require('./edge/edge_shim') || null;
+  var firefoxShim = require('./firefox/firefox_shim') || null;
+  var safariShim = require('./safari/safari_shim') || null;
 
-  /**
-   * A specialized version of `_.filter` for arrays without support for
-   * iteratee shorthands.
-   *
-   * @private
-   * @param {Array} [array] The array to iterate over.
-   * @param {Function} predicate The function invoked per iteration.
-   * @returns {Array} Returns the new filtered array.
-   */
-  function arrayFilter(array, predicate) {
-    var index = -1,
-        length = array ? array.length : 0,
-        resIndex = 0,
-        result = [];
+  // Shim browser if found.
+  switch (browserDetails.browser) {
+    case 'opera': // fallthrough as it uses chrome shims
+    case 'chrome':
+      if (!chromeShim || !chromeShim.shimPeerConnection) {
+        logging('Chrome shim is not included in this adapter release.');
+        return;
+      }
+      logging('adapter.js shimming chrome.');
+      // Export to the adapter global object visible in the browser.
+      module.exports.browserShim = chromeShim;
 
-    while (++index < length) {
-      var value = array[index];
-      if (predicate(value, index, array)) {
-        result[resIndex++] = value;
+      chromeShim.shimGetUserMedia();
+      chromeShim.shimMediaStream();
+      chromeShim.shimSourceObject();
+      chromeShim.shimPeerConnection();
+      chromeShim.shimOnTrack();
+      break;
+    case 'firefox':
+      if (!firefoxShim || !firefoxShim.shimPeerConnection) {
+        logging('Firefox shim is not included in this adapter release.');
+        return;
       }
-    }
-    return result;
-  }
+      logging('adapter.js shimming firefox.');
+      // Export to the adapter global object visible in the browser.
+      module.exports.browserShim = firefoxShim;
 
-  /**
-   * A specialized version of `_.includes` for arrays without support for
-   * specifying an index to search from.
-   *
-   * @private
-   * @param {Array} [array] The array to search.
-   * @param {*} target The value to search for.
-   * @returns {boolean} Returns `true` if `target` is found, else `false`.
-   */
-  function arrayIncludes(array, value) {
-    var length = array ? array.length : 0;
-    return !!length && baseIndexOf(array, value, 0) > -1;
-  }
-
-  /**
-   * This function is like `arrayIncludes` except that it accepts a comparator.
-   *
-   * @private
-   * @param {Array} [array] The array to search.
-   * @param {*} target The value to search for.
-   * @param {Function} comparator The comparator invoked per element.
-   * @returns {boolean} Returns `true` if `target` is found, else `false`.
-   */
-  function arrayIncludesWith(array, value, comparator) {
-    var index = -1,
-        length = array ? array.length : 0;
-
-    while (++index < length) {
-      if (comparator(value, array[index])) {
-        return true;
+      firefoxShim.shimGetUserMedia();
+      firefoxShim.shimSourceObject();
+      firefoxShim.shimPeerConnection();
+      firefoxShim.shimOnTrack();
+      break;
+    case 'edge':
+      if (!edgeShim || !edgeShim.shimPeerConnection) {
+        logging('MS edge shim is not included in this adapter release.');
+        return;
       }
-    }
-    return false;
-  }
+      logging('adapter.js shimming edge.');
+      // Export to the adapter global object visible in the browser.
+      module.exports.browserShim = edgeShim;
 
-  /**
-   * A specialized version of `_.map` for arrays without support for iteratee
-   * shorthands.
-   *
-   * @private
-   * @param {Array} [array] The array to iterate over.
-   * @param {Function} iteratee The function invoked per iteration.
-   * @returns {Array} Returns the new mapped array.
-   */
-  function arrayMap(array, iteratee) {
-    var index = -1,
-        length = array ? array.length : 0,
-        result = Array(length);
+      edgeShim.shimGetUserMedia();
+      edgeShim.shimPeerConnection();
+      break;
+    case 'safari':
+      if (!safariShim) {
+        logging('Safari shim is not included in this adapter release.');
+        return;
+      }
+      logging('adapter.js shimming safari.');
+      // Export to the adapter global object visible in the browser.
+      module.exports.browserShim = safariShim;
 
-    while (++index < length) {
-      result[index] = iteratee(array[index], index, array);
-    }
-    return result;
+      safariShim.shimGetUserMedia();
+      break;
+    default:
+      logging('Unsupported browser!');
   }
+})();
 
-  /**
-   * Appends the elements of `values` to `array`.
-   *
-   * @private
-   * @param {Array} array The array to modify.
-   * @param {Array} values The values to append.
-   * @returns {Array} Returns `array`.
-   */
-  function arrayPush(array, values) {
-    var index = -1,
-        length = values.length,
-        offset = array.length;
-
-    while (++index < length) {
-      array[offset + index] = values[index];
-    }
-    return array;
-  }
+},{"./chrome/chrome_shim":8,"./edge/edge_shim":10,"./firefox/firefox_shim":12,"./safari/safari_shim":14,"./utils":15}],8:[function(require,module,exports){
 
-  /**
-   * A specialized version of `_.reduce` for arrays without support for
-   * iteratee shorthands.
-   *
-   * @private
-   * @param {Array} [array] The array to iterate over.
-   * @param {Function} iteratee The function invoked per iteration.
-   * @param {*} [accumulator] The initial value.
-   * @param {boolean} [initAccum] Specify using the first element of `array` as
-   *  the initial value.
-   * @returns {*} Returns the accumulated value.
-   */
-  function arrayReduce(array, iteratee, accumulator, initAccum) {
-    var index = -1,
-        length = array ? array.length : 0;
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree.
+ */
+ /* eslint-env node */
+'use strict';
+var logging = require('../utils.js').log;
+var browserDetails = require('../utils.js').browserDetails;
 
-    if (initAccum && length) {
-      accumulator = array[++index];
-    }
-    while (++index < length) {
-      accumulator = iteratee(accumulator, array[index], index, array);
-    }
-    return accumulator;
-  }
+var chromeShim = {
+  shimMediaStream: function() {
+    window.MediaStream = window.MediaStream || window.webkitMediaStream;
+  },
 
-  /**
-   * A specialized version of `_.reduceRight` for arrays without support for
-   * iteratee shorthands.
-   *
-   * @private
-   * @param {Array} [array] The array to iterate over.
-   * @param {Function} iteratee The function invoked per iteration.
-   * @param {*} [accumulator] The initial value.
-   * @param {boolean} [initAccum] Specify using the last element of `array` as
-   *  the initial value.
-   * @returns {*} Returns the accumulated value.
-   */
-  function arrayReduceRight(array, iteratee, accumulator, initAccum) {
-    var length = array ? array.length : 0;
-    if (initAccum && length) {
-      accumulator = array[--length];
-    }
-    while (length--) {
-      accumulator = iteratee(accumulator, array[length], length, array);
+  shimOnTrack: function() {
+    if (typeof window === 'object' && window.RTCPeerConnection && !('ontrack' in
+        window.RTCPeerConnection.prototype)) {
+      Object.defineProperty(window.RTCPeerConnection.prototype, 'ontrack', {
+        get: function() {
+          return this._ontrack;
+        },
+        set: function(f) {
+          var self = this;
+          if (this._ontrack) {
+            this.removeEventListener('track', this._ontrack);
+            this.removeEventListener('addstream', this._ontrackpoly);
+          }
+          this.addEventListener('track', this._ontrack = f);
+          this.addEventListener('addstream', this._ontrackpoly = function(e) {
+            // onaddstream does not fire when a track is added to an existing
+            // stream. But stream.onaddtrack is implemented so we use that.
+            e.stream.addEventListener('addtrack', function(te) {
+              var event = new Event('track');
+              event.track = te.track;
+              event.receiver = {track: te.track};
+              event.streams = [e.stream];
+              self.dispatchEvent(event);
+            });
+            e.stream.getTracks().forEach(function(track) {
+              var event = new Event('track');
+              event.track = track;
+              event.receiver = {track: track};
+              event.streams = [e.stream];
+              this.dispatchEvent(event);
+            }.bind(this));
+          }.bind(this));
+        }
+      });
     }
-    return accumulator;
-  }
+  },
 
-  /**
-   * A specialized version of `_.some` for arrays without support for iteratee
-   * shorthands.
-   *
-   * @private
-   * @param {Array} [array] The array to iterate over.
-   * @param {Function} predicate The function invoked per iteration.
-   * @returns {boolean} Returns `true` if any element passes the predicate check,
-   *  else `false`.
-   */
-  function arraySome(array, predicate) {
-    var index = -1,
-        length = array ? array.length : 0;
+  shimSourceObject: function() {
+    if (typeof window === 'object') {
+      if (window.HTMLMediaElement &&
+        !('srcObject' in window.HTMLMediaElement.prototype)) {
+        // Shim the srcObject property, once, when HTMLMediaElement is found.
+        Object.defineProperty(window.HTMLMediaElement.prototype, 'srcObject', {
+          get: function() {
+            return this._srcObject;
+          },
+          set: function(stream) {
+            var self = this;
+            // Use _srcObject as a private property for this shim
+            this._srcObject = stream;
+            if (this.src) {
+              URL.revokeObjectURL(this.src);
+            }
 
-    while (++index < length) {
-      if (predicate(array[index], index, array)) {
-        return true;
+            if (!stream) {
+              this.src = '';
+              return;
+            }
+            this.src = URL.createObjectURL(stream);
+            // We need to recreate the blob url when a track is added or
+            // removed. Doing it manually since we want to avoid a recursion.
+            stream.addEventListener('addtrack', function() {
+              if (self.src) {
+                URL.revokeObjectURL(self.src);
+              }
+              self.src = URL.createObjectURL(stream);
+            });
+            stream.addEventListener('removetrack', function() {
+              if (self.src) {
+                URL.revokeObjectURL(self.src);
+              }
+              self.src = URL.createObjectURL(stream);
+            });
+          }
+        });
       }
     }
-    return false;
-  }
+  },
 
-  /**
-   * The base implementation of methods like `_.findKey` and `_.findLastKey`,
-   * without support for iteratee shorthands, which iterates over `collection`
-   * using `eachFunc`.
-   *
-   * @private
-   * @param {Array|Object} collection The collection to search.
-   * @param {Function} predicate The function invoked per iteration.
-   * @param {Function} eachFunc The function to iterate over `collection`.
-   * @returns {*} Returns the found element or its key, else `undefined`.
-   */
-  function baseFindKey(collection, predicate, eachFunc) {
-    var result;
-    eachFunc(collection, function(value, key, collection) {
-      if (predicate(value, key, collection)) {
-        result = key;
-        return false;
+  shimPeerConnection: function() {
+    // The RTCPeerConnection object.
+    window.RTCPeerConnection = function(pcConfig, pcConstraints) {
+      // Translate iceTransportPolicy to iceTransports,
+      // see https://code.google.com/p/webrtc/issues/detail?id=4869
+      logging('PeerConnection');
+      if (pcConfig && pcConfig.iceTransportPolicy) {
+        pcConfig.iceTransports = pcConfig.iceTransportPolicy;
       }
-    });
-    return result;
-  }
 
-  /**
-   * The base implementation of `_.findIndex` and `_.findLastIndex` without
-   * support for iteratee shorthands.
-   *
-   * @private
-   * @param {Array} array The array to search.
-   * @param {Function} predicate The function invoked per iteration.
-   * @param {number} fromIndex The index to search from.
-   * @param {boolean} [fromRight] Specify iterating from right to left.
-   * @returns {number} Returns the index of the matched value, else `-1`.
-   */
-  function baseFindIndex(array, predicate, fromIndex, fromRight) {
-    var length = array.length,
-        index = fromIndex + (fromRight ? 1 : -1);
+      var pc = new webkitRTCPeerConnection(pcConfig, pcConstraints);
+      var origGetStats = pc.getStats.bind(pc);
+      pc.getStats = function(selector, successCallback, errorCallback) {
+        var self = this;
+        var args = arguments;
 
-    while ((fromRight ? index-- : ++index < length)) {
-      if (predicate(array[index], index, array)) {
-        return index;
-      }
-    }
-    return -1;
-  }
+        // If selector is a function then we are in the old style stats so just
+        // pass back the original getStats format to avoid breaking old users.
+        if (arguments.length > 0 && typeof selector === 'function') {
+          return origGetStats(selector, successCallback);
+        }
 
-  /**
-   * The base implementation of `_.indexOf` without `fromIndex` bounds checks.
-   *
-   * @private
-   * @param {Array} array The array to search.
-   * @param {*} value The value to search for.
-   * @param {number} fromIndex The index to search from.
-   * @returns {number} Returns the index of the matched value, else `-1`.
-   */
-  function baseIndexOf(array, value, fromIndex) {
-    if (value !== value) {
-      return indexOfNaN(array, fromIndex);
-    }
-    var index = fromIndex - 1,
-        length = array.length;
+        var fixChromeStats_ = function(response) {
+          var standardReport = {};
+          var reports = response.result();
+          reports.forEach(function(report) {
+            var standardStats = {
+              id: report.id,
+              timestamp: report.timestamp,
+              type: report.type
+            };
+            report.names().forEach(function(name) {
+              standardStats[name] = report.stat(name);
+            });
+            standardReport[standardStats.id] = standardStats;
+          });
 
-    while (++index < length) {
-      if (array[index] === value) {
-        return index;
-      }
-    }
-    return -1;
-  }
+          return standardReport;
+        };
 
-  /**
-   * This function is like `baseIndexOf` except that it accepts a comparator.
-   *
-   * @private
-   * @param {Array} array The array to search.
-   * @param {*} value The value to search for.
-   * @param {number} fromIndex The index to search from.
-   * @param {Function} comparator The comparator invoked per element.
-   * @returns {number} Returns the index of the matched value, else `-1`.
-   */
-  function baseIndexOfWith(array, value, fromIndex, comparator) {
-    var index = fromIndex - 1,
-        length = array.length;
+        // shim getStats with maplike support
+        var makeMapStats = function(stats, legacyStats) {
+          var map = new Map(Object.keys(stats).map(function(key) {
+            return[key, stats[key]];
+          }));
+          legacyStats = legacyStats || stats;
+          Object.keys(legacyStats).forEach(function(key) {
+            map[key] = legacyStats[key];
+          });
+          return map;
+        };
 
-    while (++index < length) {
-      if (comparator(array[index], value)) {
-        return index;
-      }
-    }
-    return -1;
-  }
+        if (arguments.length >= 2) {
+          var successCallbackWrapper_ = function(response) {
+            args[1](makeMapStats(fixChromeStats_(response)));
+          };
 
-  /**
-   * The base implementation of `_.mean` and `_.meanBy` without support for
-   * iteratee shorthands.
-   *
-   * @private
-   * @param {Array} array The array to iterate over.
-   * @param {Function} iteratee The function invoked per iteration.
-   * @returns {number} Returns the mean.
-   */
-  function baseMean(array, iteratee) {
-    var length = array ? array.length : 0;
-    return length ? (baseSum(array, iteratee) / length) : NAN;
-  }
+          return origGetStats.apply(this, [successCallbackWrapper_,
+              arguments[0]]);
+        }
 
-  /**
-   * The base implementation of `_.reduce` and `_.reduceRight`, without support
-   * for iteratee shorthands, which iterates over `collection` using `eachFunc`.
-   *
-   * @private
-   * @param {Array|Object} collection The collection to iterate over.
-   * @param {Function} iteratee The function invoked per iteration.
-   * @param {*} accumulator The initial value.
-   * @param {boolean} initAccum Specify using the first or last element of
-   *  `collection` as the initial value.
-   * @param {Function} eachFunc The function to iterate over `collection`.
-   * @returns {*} Returns the accumulated value.
-   */
-  function baseReduce(collection, iteratee, accumulator, initAccum, eachFunc) {
-    eachFunc(collection, function(value, index, collection) {
-      accumulator = initAccum
-        ? (initAccum = false, value)
-        : iteratee(accumulator, value, index, collection);
-    });
-    return accumulator;
-  }
+        // promise-support
+        return new Promise(function(resolve, reject) {
+          if (args.length === 1 && typeof selector === 'object') {
+            origGetStats.apply(self, [
+              function(response) {
+                resolve(makeMapStats(fixChromeStats_(response)));
+              }, reject]);
+          } else {
+            // Preserve legacy chrome stats only on legacy access of stats obj
+            origGetStats.apply(self, [
+              function(response) {
+                resolve(makeMapStats(fixChromeStats_(response),
+                    response.result()));
+              }, reject]);
+          }
+        }).then(successCallback, errorCallback);
+      };
 
-  /**
-   * The base implementation of `_.sortBy` which uses `comparer` to define the
-   * sort order of `array` and replaces criteria objects with their corresponding
-   * values.
-   *
-   * @private
-   * @param {Array} array The array to sort.
-   * @param {Function} comparer The function to define sort order.
-   * @returns {Array} Returns `array`.
-   */
-  function baseSortBy(array, comparer) {
-    var length = array.length;
+      return pc;
+    };
+    window.RTCPeerConnection.prototype = webkitRTCPeerConnection.prototype;
 
-    array.sort(comparer);
-    while (length--) {
-      array[length] = array[length].value;
+    // wrap static methods. Currently just generateCertificate.
+    if (webkitRTCPeerConnection.generateCertificate) {
+      Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
+        get: function() {
+          return webkitRTCPeerConnection.generateCertificate;
+        }
+      });
     }
-    return array;
-  }
 
-  /**
-   * The base implementation of `_.sum` and `_.sumBy` without support for
-   * iteratee shorthands.
-   *
-   * @private
-   * @param {Array} array The array to iterate over.
-   * @param {Function} iteratee The function invoked per iteration.
-   * @returns {number} Returns the sum.
-   */
-  function baseSum(array, iteratee) {
-    var result,
-        index = -1,
-        length = array.length;
+    ['createOffer', 'createAnswer'].forEach(function(method) {
+      var nativeMethod = webkitRTCPeerConnection.prototype[method];
+      webkitRTCPeerConnection.prototype[method] = function() {
+        var self = this;
+        if (arguments.length < 1 || (arguments.length === 1 &&
+            typeof arguments[0] === 'object')) {
+          var opts = arguments.length === 1 ? arguments[0] : undefined;
+          return new Promise(function(resolve, reject) {
+            nativeMethod.apply(self, [resolve, reject, opts]);
+          });
+        }
+        return nativeMethod.apply(this, arguments);
+      };
+    });
 
-    while (++index < length) {
-      var current = iteratee(array[index]);
-      if (current !== undefined) {
-        result = result === undefined ? current : (result + current);
-      }
+    // add promise support -- natively available in Chrome 51
+    if (browserDetails.version < 51) {
+      ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate']
+          .forEach(function(method) {
+            var nativeMethod = webkitRTCPeerConnection.prototype[method];
+            webkitRTCPeerConnection.prototype[method] = function() {
+              var args = arguments;
+              var self = this;
+              var promise = new Promise(function(resolve, reject) {
+                nativeMethod.apply(self, [args[0], resolve, reject]);
+              });
+              if (args.length < 2) {
+                return promise;
+              }
+              return promise.then(function() {
+                args[1].apply(null, []);
+              },
+              function(err) {
+                if (args.length >= 3) {
+                  args[2].apply(null, [err]);
+                }
+              });
+            };
+          });
     }
-    return result;
-  }
-
-  /**
-   * The base implementation of `_.times` without support for iteratee shorthands
-   * or max array length checks.
-   *
-   * @private
-   * @param {number} n The number of times to invoke `iteratee`.
-   * @param {Function} iteratee The function invoked per iteration.
-   * @returns {Array} Returns the array of results.
-   */
-  function baseTimes(n, iteratee) {
-    var index = -1,
-        result = Array(n);
 
-    while (++index < n) {
-      result[index] = iteratee(index);
-    }
-    return result;
-  }
-
-  /**
-   * The base implementation of `_.toPairs` and `_.toPairsIn` which creates an array
-   * of key-value pairs for `object` corresponding to the property names of `props`.
-   *
-   * @private
-   * @param {Object} object The object to query.
-   * @param {Array} props The property names to get values for.
-   * @returns {Object} Returns the key-value pairs.
-   */
-  function baseToPairs(object, props) {
-    return arrayMap(props, function(key) {
-      return [key, object[key]];
-    });
-  }
+    // shim implicit creation of RTCSessionDescription/RTCIceCandidate
+    ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate']
+        .forEach(function(method) {
+          var nativeMethod = webkitRTCPeerConnection.prototype[method];
+          webkitRTCPeerConnection.prototype[method] = function() {
+            arguments[0] = new ((method === 'addIceCandidate') ?
+                RTCIceCandidate : RTCSessionDescription)(arguments[0]);
+            return nativeMethod.apply(this, arguments);
+          };
+        });
 
-  /**
-   * The base implementation of `_.unary` without support for storing wrapper metadata.
-   *
-   * @private
-   * @param {Function} func The function to cap arguments for.
-   * @returns {Function} Returns the new capped function.
-   */
-  function baseUnary(func) {
-    return function(value) {
-      return func(value);
+    // support for addIceCandidate(null or undefined)
+    var nativeAddIceCandidate =
+        RTCPeerConnection.prototype.addIceCandidate;
+    RTCPeerConnection.prototype.addIceCandidate = function() {
+      if (!arguments[0]) {
+        if (arguments[1]) {
+          arguments[1].apply(null);
+        }
+        return Promise.resolve();
+      }
+      return nativeAddIceCandidate.apply(this, arguments);
     };
   }
+};
 
-  /**
-   * The base implementation of `_.values` and `_.valuesIn` which creates an
-   * array of `object` property values corresponding to the property names
-   * of `props`.
-   *
-   * @private
-   * @param {Object} object The object to query.
-   * @param {Array} props The property names to get values for.
-   * @returns {Object} Returns the array of property values.
-   */
-  function baseValues(object, props) {
-    return arrayMap(props, function(key) {
-      return object[key];
-    });
-  }
-
-  /**
-   * Checks if a cache value for `key` exists.
-   *
-   * @private
-   * @param {Object} cache The cache to query.
-   * @param {string} key The key of the entry to check.
-   * @returns {boolean} Returns `true` if an entry for `key` exists, else `false`.
-   */
-  function cacheHas(cache, key) {
-    return cache.has(key);
-  }
-
-  /**
-   * Used by `_.trim` and `_.trimStart` to get the index of the first string symbol
-   * that is not found in the character symbols.
-   *
-   * @private
-   * @param {Array} strSymbols The string symbols to inspect.
-   * @param {Array} chrSymbols The character symbols to find.
-   * @returns {number} Returns the index of the first unmatched string symbol.
-   */
-  function charsStartIndex(strSymbols, chrSymbols) {
-    var index = -1,
-        length = strSymbols.length;
-
-    while (++index < length && baseIndexOf(chrSymbols, strSymbols[index], 0) > -1) {}
-    return index;
-  }
 
-  /**
-   * Used by `_.trim` and `_.trimEnd` to get the index of the last string symbol
-   * that is not found in the character symbols.
-   *
-   * @private
-   * @param {Array} strSymbols The string symbols to inspect.
-   * @param {Array} chrSymbols The character symbols to find.
-   * @returns {number} Returns the index of the last unmatched string symbol.
-   */
-  function charsEndIndex(strSymbols, chrSymbols) {
-    var index = strSymbols.length;
+// Expose public methods.
+module.exports = {
+  shimMediaStream: chromeShim.shimMediaStream,
+  shimOnTrack: chromeShim.shimOnTrack,
+  shimSourceObject: chromeShim.shimSourceObject,
+  shimPeerConnection: chromeShim.shimPeerConnection,
+  shimGetUserMedia: require('./getusermedia')
+};
 
-    while (index-- && baseIndexOf(chrSymbols, strSymbols[index], 0) > -1) {}
-    return index;
-  }
+},{"../utils.js":15,"./getusermedia":9}],9:[function(require,module,exports){
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree.
+ */
+ /* eslint-env node */
+'use strict';
+var logging = require('../utils.js').log;
 
-  /**
-   * Checks if `value` is a global object.
-   *
-   * @private
-   * @param {*} value The value to check.
-   * @returns {null|Object} Returns `value` if it's a global object, else `null`.
-   */
-  function checkGlobal(value) {
-    return (value && value.Object === Object) ? value : null;
-  }
+// Expose public methods.
+module.exports = function() {
+  var constraintsToChrome_ = function(c) {
+    if (typeof c !== 'object' || c.mandatory || c.optional) {
+      return c;
+    }
+    var cc = {};
+    Object.keys(c).forEach(function(key) {
+      if (key === 'require' || key === 'advanced' || key === 'mediaSource') {
+        return;
+      }
+      var r = (typeof c[key] === 'object') ? c[key] : {ideal: c[key]};
+      if (r.exact !== undefined && typeof r.exact === 'number') {
+        r.min = r.max = r.exact;
+      }
+      var oldname_ = function(prefix, name) {
+        if (prefix) {
+          return prefix + name.charAt(0).toUpperCase() + name.slice(1);
+        }
+        return (name === 'deviceId') ? 'sourceId' : name;
+      };
+      if (r.ideal !== undefined) {
+        cc.optional = cc.optional || [];
+        var oc = {};
+        if (typeof r.ideal === 'number') {
+          oc[oldname_('min', key)] = r.ideal;
+          cc.optional.push(oc);
+          oc = {};
+          oc[oldname_('max', key)] = r.ideal;
+          cc.optional.push(oc);
+        } else {
+          oc[oldname_('', key)] = r.ideal;
+          cc.optional.push(oc);
+        }
+      }
+      if (r.exact !== undefined && typeof r.exact !== 'number') {
+        cc.mandatory = cc.mandatory || {};
+        cc.mandatory[oldname_('', key)] = r.exact;
+      } else {
+        ['min', 'max'].forEach(function(mix) {
+          if (r[mix] !== undefined) {
+            cc.mandatory = cc.mandatory || {};
+            cc.mandatory[oldname_(mix, key)] = r[mix];
+          }
+        });
+      }
+    });
+    if (c.advanced) {
+      cc.optional = (cc.optional || []).concat(c.advanced);
+    }
+    return cc;
+  };
 
-  /**
-   * Gets the number of `placeholder` occurrences in `array`.
-   *
-   * @private
-   * @param {Array} array The array to inspect.
-   * @param {*} placeholder The placeholder to search for.
-   * @returns {number} Returns the placeholder count.
-   */
-  function countHolders(array, placeholder) {
-    var length = array.length,
-        result = 0;
+  var shimConstraints_ = function(constraints, func) {
+    constraints = JSON.parse(JSON.stringify(constraints));
+    if (constraints && constraints.audio) {
+      constraints.audio = constraintsToChrome_(constraints.audio);
+    }
+    if (constraints && typeof constraints.video === 'object') {
+      // Shim facingMode for mobile, where it defaults to "user".
+      var face = constraints.video.facingMode;
+      face = face && ((typeof face === 'object') ? face : {ideal: face});
 
-    while (length--) {
-      if (array[length] === placeholder) {
-        result++;
+      if ((face && (face.exact === 'user' || face.exact === 'environment' ||
+                    face.ideal === 'user' || face.ideal === 'environment')) &&
+          !(navigator.mediaDevices.getSupportedConstraints &&
+            navigator.mediaDevices.getSupportedConstraints().facingMode)) {
+        delete constraints.video.facingMode;
+        if (face.exact === 'environment' || face.ideal === 'environment') {
+          // Look for "back" in label, or use last cam (typically back cam).
+          return navigator.mediaDevices.enumerateDevices()
+          .then(function(devices) {
+            devices = devices.filter(function(d) {
+              return d.kind === 'videoinput';
+            });
+            var back = devices.find(function(d) {
+              return d.label.toLowerCase().indexOf('back') !== -1;
+            }) || (devices.length && devices[devices.length - 1]);
+            if (back) {
+              constraints.video.deviceId = face.exact ? {exact: back.deviceId} :
+                                                        {ideal: back.deviceId};
+            }
+            constraints.video = constraintsToChrome_(constraints.video);
+            logging('chrome: ' + JSON.stringify(constraints));
+            return func(constraints);
+          });
+        }
       }
+      constraints.video = constraintsToChrome_(constraints.video);
     }
-    return result;
-  }
-
-  /**
-   * Used by `_.deburr` to convert latin-1 supplementary letters to basic latin letters.
-   *
-   * @private
-   * @param {string} letter The matched letter to deburr.
-   * @returns {string} Returns the deburred letter.
-   */
-  function deburrLetter(letter) {
-    return deburredLetters[letter];
-  }
+    logging('chrome: ' + JSON.stringify(constraints));
+    return func(constraints);
+  };
 
-  /**
-   * Used by `_.escape` to convert characters to HTML entities.
-   *
-   * @private
-   * @param {string} chr The matched character to escape.
-   * @returns {string} Returns the escaped character.
-   */
-  function escapeHtmlChar(chr) {
-    return htmlEscapes[chr];
-  }
+  var shimError_ = function(e) {
+    return {
+      name: {
+        PermissionDeniedError: 'NotAllowedError',
+        ConstraintNotSatisfiedError: 'OverconstrainedError'
+      }[e.name] || e.name,
+      message: e.message,
+      constraint: e.constraintName,
+      toString: function() {
+        return this.name + (this.message && ': ') + this.message;
+      }
+    };
+  };
 
-  /**
-   * Used by `_.template` to escape characters for inclusion in compiled string literals.
-   *
-   * @private
-   * @param {string} chr The matched character to escape.
-   * @returns {string} Returns the escaped character.
-   */
-  function escapeStringChar(chr) {
-    return '\\' + stringEscapes[chr];
-  }
+  var getUserMedia_ = function(constraints, onSuccess, onError) {
+    shimConstraints_(constraints, function(c) {
+      navigator.webkitGetUserMedia(c, onSuccess, function(e) {
+        onError(shimError_(e));
+      });
+    });
+  };
 
-  /**
-   * Gets the value at `key` of `object`.
-   *
-   * @private
-   * @param {Object} [object] The object to query.
-   * @param {string} key The key of the property to get.
-   * @returns {*} Returns the property value.
-   */
-  function getValue(object, key) {
-    return object == null ? undefined : object[key];
-  }
+  navigator.getUserMedia = getUserMedia_;
 
-  /**
-   * Gets the index at which the first occurrence of `NaN` is found in `array`.
-   *
-   * @private
-   * @param {Array} array The array to search.
-   * @param {number} fromIndex The index to search from.
-   * @param {boolean} [fromRight] Specify iterating from right to left.
-   * @returns {number} Returns the index of the matched `NaN`, else `-1`.
-   */
-  function indexOfNaN(array, fromIndex, fromRight) {
-    var length = array.length,
-        index = fromIndex + (fromRight ? 1 : -1);
+  // Returns the result of getUserMedia as a Promise.
+  var getUserMediaPromise_ = function(constraints) {
+    return new Promise(function(resolve, reject) {
+      navigator.getUserMedia(constraints, resolve, reject);
+    });
+  };
 
-    while ((fromRight ? index-- : ++index < length)) {
-      var other = array[index];
-      if (other !== other) {
-        return index;
+  if (!navigator.mediaDevices) {
+    navigator.mediaDevices = {
+      getUserMedia: getUserMediaPromise_,
+      enumerateDevices: function() {
+        return new Promise(function(resolve) {
+          var kinds = {audio: 'audioinput', video: 'videoinput'};
+          return MediaStreamTrack.getSources(function(devices) {
+            resolve(devices.map(function(device) {
+              return {label: device.label,
+                      kind: kinds[device.kind],
+                      deviceId: device.id,
+                      groupId: ''};
+            }));
+          });
+        });
       }
-    }
-    return -1;
+    };
   }
 
-  /**
-   * Checks if `value` is a host object in IE < 9.
-   *
-   * @private
-   * @param {*} value The value to check.
-   * @returns {boolean} Returns `true` if `value` is a host object, else `false`.
-   */
-  function isHostObject(value) {
-    // Many host objects are `Object` objects that can coerce to strings
-    // despite having improperly defined `toString` methods.
-    var result = false;
-    if (value != null && typeof value.toString != 'function') {
-      try {
-        result = !!(value + '');
-      } catch (e) {}
-    }
-    return result;
+  // A shim for getUserMedia method on the mediaDevices object.
+  // TODO(KaptenJansson) remove once implemented in Chrome stable.
+  if (!navigator.mediaDevices.getUserMedia) {
+    navigator.mediaDevices.getUserMedia = function(constraints) {
+      return getUserMediaPromise_(constraints);
+    };
+  } else {
+    // Even though Chrome 45 has navigator.mediaDevices and a getUserMedia
+    // function which returns a Promise, it does not accept spec-style
+    // constraints.
+    var origGetUserMedia = navigator.mediaDevices.getUserMedia.
+        bind(navigator.mediaDevices);
+    navigator.mediaDevices.getUserMedia = function(cs) {
+      return shimConstraints_(cs, function(c) {
+        return origGetUserMedia(c).then(function(stream) {
+          if (c.audio && !stream.getAudioTracks().length ||
+              c.video && !stream.getVideoTracks().length) {
+            stream.getTracks().forEach(function(track) {
+              track.stop();
+            });
+            throw new DOMException('', 'NotFoundError');
+          }
+          return stream;
+        }, function(e) {
+          return Promise.reject(shimError_(e));
+        });
+      });
+    };
   }
 
-  /**
-   * Converts `iterator` to an array.
-   *
-   * @private
-   * @param {Object} iterator The iterator to convert.
-   * @returns {Array} Returns the converted array.
-   */
-  function iteratorToArray(iterator) {
-    var data,
-        result = [];
-
-    while (!(data = iterator.next()).done) {
-      result.push(data.value);
-    }
-    return result;
+  // Dummy devicechange event methods.
+  // TODO(KaptenJansson) remove once implemented in Chrome stable.
+  if (typeof navigator.mediaDevices.addEventListener === 'undefined') {
+    navigator.mediaDevices.addEventListener = function() {
+      logging('Dummy mediaDevices.addEventListener called.');
+    };
   }
-
-  /**
-   * Converts `map` to its key-value pairs.
-   *
-   * @private
-   * @param {Object} map The map to convert.
-   * @returns {Array} Returns the key-value pairs.
-   */
-  function mapToArray(map) {
-    var index = -1,
-        result = Array(map.size);
-
-    map.forEach(function(value, key) {
-      result[++index] = [key, value];
-    });
-    return result;
+  if (typeof navigator.mediaDevices.removeEventListener === 'undefined') {
+    navigator.mediaDevices.removeEventListener = function() {
+      logging('Dummy mediaDevices.removeEventListener called.');
+    };
   }
+};
 
-  /**
-   * Replaces all `placeholder` elements in `array` with an internal placeholder
-   * and returns an array of their indexes.
-   *
-   * @private
-   * @param {Array} array The array to modify.
-   * @param {*} placeholder The placeholder to replace.
-   * @returns {Array} Returns the new array of placeholder indexes.
-   */
-  function replaceHolders(array, placeholder) {
-    var index = -1,
-        length = array.length,
-        resIndex = 0,
-        result = [];
+},{"../utils.js":15}],10:[function(require,module,exports){
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree.
+ */
+ /* eslint-env node */
+'use strict';
 
-    while (++index < length) {
-      var value = array[index];
-      if (value === placeholder || value === PLACEHOLDER) {
-        array[index] = PLACEHOLDER;
-        result[resIndex++] = index;
+var SDPUtils = require('sdp');
+var browserDetails = require('../utils').browserDetails;
+
+var edgeShim = {
+  shimPeerConnection: function() {
+    if (window.RTCIceGatherer) {
+      // ORTC defines an RTCIceCandidate object but no constructor.
+      // Not implemented in Edge.
+      if (!window.RTCIceCandidate) {
+        window.RTCIceCandidate = function(args) {
+          return args;
+        };
+      }
+      // ORTC does not have a session description object but
+      // other browsers (i.e. Chrome) that will support both PC and ORTC
+      // in the future might have this defined already.
+      if (!window.RTCSessionDescription) {
+        window.RTCSessionDescription = function(args) {
+          return args;
+        };
       }
+      // this adds an additional event listener to MediaStrackTrack that signals
+      // when a tracks enabled property was changed.
+      var origMSTEnabled = Object.getOwnPropertyDescriptor(
+          MediaStreamTrack.prototype, 'enabled');
+      Object.defineProperty(MediaStreamTrack.prototype, 'enabled', {
+        set: function(value) {
+          origMSTEnabled.set.call(this, value);
+          var ev = new Event('enabled');
+          ev.enabled = value;
+          this.dispatchEvent(ev);
+        }
+      });
     }
-    return result;
-  }
-
-  /**
-   * Converts `set` to an array of its values.
-   *
-   * @private
-   * @param {Object} set The set to convert.
-   * @returns {Array} Returns the values.
-   */
-  function setToArray(set) {
-    var index = -1,
-        result = Array(set.size);
 
-    set.forEach(function(value) {
-      result[++index] = value;
-    });
-    return result;
-  }
+    window.RTCPeerConnection = function(config) {
+      var self = this;
 
-  /**
-   * Converts `set` to its value-value pairs.
-   *
-   * @private
-   * @param {Object} set The set to convert.
-   * @returns {Array} Returns the value-value pairs.
-   */
-  function setToPairs(set) {
-    var index = -1,
-        result = Array(set.size);
+      var _eventTarget = document.createDocumentFragment();
+      ['addEventListener', 'removeEventListener', 'dispatchEvent']
+          .forEach(function(method) {
+            self[method] = _eventTarget[method].bind(_eventTarget);
+          });
 
-    set.forEach(function(value) {
-      result[++index] = [value, value];
-    });
-    return result;
-  }
+      this.onicecandidate = null;
+      this.onaddstream = null;
+      this.ontrack = null;
+      this.onremovestream = null;
+      this.onsignalingstatechange = null;
+      this.oniceconnectionstatechange = null;
+      this.onnegotiationneeded = null;
+      this.ondatachannel = null;
 
-  /**
-   * Gets the number of symbols in `string`.
-   *
-   * @private
-   * @param {string} string The string to inspect.
-   * @returns {number} Returns the string size.
-   */
-  function stringSize(string) {
-    if (!(string && reHasComplexSymbol.test(string))) {
-      return string.length;
-    }
-    var result = reComplexSymbol.lastIndex = 0;
-    while (reComplexSymbol.test(string)) {
-      result++;
-    }
-    return result;
-  }
+      this.localStreams = [];
+      this.remoteStreams = [];
+      this.getLocalStreams = function() {
+        return self.localStreams;
+      };
+      this.getRemoteStreams = function() {
+        return self.remoteStreams;
+      };
 
-  /**
-   * Converts `string` to an array.
-   *
-   * @private
-   * @param {string} string The string to convert.
-   * @returns {Array} Returns the converted array.
-   */
-  function stringToArray(string) {
-    return string.match(reComplexSymbol);
-  }
+      this.localDescription = new RTCSessionDescription({
+        type: '',
+        sdp: ''
+      });
+      this.remoteDescription = new RTCSessionDescription({
+        type: '',
+        sdp: ''
+      });
+      this.signalingState = 'stable';
+      this.iceConnectionState = 'new';
+      this.iceGatheringState = 'new';
 
-  /**
-   * Used by `_.unescape` to convert HTML entities to characters.
-   *
-   * @private
-   * @param {string} chr The matched character to unescape.
-   * @returns {string} Returns the unescaped character.
-   */
-  function unescapeHtmlChar(chr) {
-    return htmlUnescapes[chr];
-  }
+      this.iceOptions = {
+        gatherPolicy: 'all',
+        iceServers: []
+      };
+      if (config && config.iceTransportPolicy) {
+        switch (config.iceTransportPolicy) {
+          case 'all':
+          case 'relay':
+            this.iceOptions.gatherPolicy = config.iceTransportPolicy;
+            break;
+          case 'none':
+            // FIXME: remove once implementation and spec have added this.
+            throw new TypeError('iceTransportPolicy "none" not supported');
+          default:
+            // don't set iceTransportPolicy.
+            break;
+        }
+      }
+      this.usingBundle = config && config.bundlePolicy === 'max-bundle';
 
-  /*--------------------------------------------------------------------------*/
+      if (config && config.iceServers) {
+        // Edge does not like
+        // 1) stun:
+        // 2) turn: that does not have all of turn:host:port?transport=udp
+        // 3) turn: with ipv6 addresses
+        var iceServers = JSON.parse(JSON.stringify(config.iceServers));
+        this.iceOptions.iceServers = iceServers.filter(function(server) {
+          if (server && server.urls) {
+            var urls = server.urls;
+            if (typeof urls === 'string') {
+              urls = [urls];
+            }
+            urls = urls.filter(function(url) {
+              return (url.indexOf('turn:') === 0 &&
+                  url.indexOf('transport=udp') !== -1 &&
+                  url.indexOf('turn:[') === -1) ||
+                  (url.indexOf('stun:') === 0 &&
+                    browserDetails.version >= 14393);
+            })[0];
+            return !!urls;
+          }
+          return false;
+        });
+      }
+      this._config = config;
 
-  /**
-   * Create a new pristine `lodash` function using the `context` object.
-   *
-   * @static
-   * @memberOf _
-   * @since 1.1.0
-   * @category Util
-   * @param {Object} [context=root] The context object.
-   * @returns {Function} Returns a new `lodash` function.
-   * @example
-   *
-   * _.mixin({ 'foo': _.constant('foo') });
-   *
-   * var lodash = _.runInContext();
-   * lodash.mixin({ 'bar': lodash.constant('bar') });
-   *
-   * _.isFunction(_.foo);
-   * // => true
-   * _.isFunction(_.bar);
-   * // => false
-   *
-   * lodash.isFunction(lodash.foo);
-   * // => false
-   * lodash.isFunction(lodash.bar);
-   * // => true
-   *
-   * // Use `context` to stub `Date#getTime` use in `_.now`.
-   * var stubbed = _.runInContext({
-   *   'Date': function() {
-   *     return { 'getTime': stubGetTime };
-   *   }
-   * });
-   *
-   * // Create a suped-up `defer` in Node.js.
-   * var defer = _.runInContext({ 'setTimeout': setImmediate }).defer;
-   */
-  function runInContext(context) {
-    context = context ? _.defaults({}, context, _.pick(root, contextProps)) : root;
+      // per-track iceGathers, iceTransports, dtlsTransports, rtpSenders, ...
+      // everything that is needed to describe a SDP m-line.
+      this.transceivers = [];
 
-    /** Built-in constructor references. */
-    var Date = context.Date,
-        Error = context.Error,
-        Math = context.Math,
-        RegExp = context.RegExp,
-        TypeError = context.TypeError;
+      // since the iceGatherer is currently created in createOffer but we
+      // must not emit candidates until after setLocalDescription we buffer
+      // them in this array.
+      this._localIceCandidatesBuffer = [];
+    };
 
-    /** Used for built-in method references. */
-    var arrayProto = context.Array.prototype,
-        objectProto = context.Object.prototype,
-        stringProto = context.String.prototype;
+    window.RTCPeerConnection.prototype._emitBufferedCandidates = function() {
+      var self = this;
+      var sections = SDPUtils.splitSections(self.localDescription.sdp);
+      // FIXME: need to apply ice candidates in a way which is async but
+      // in-order
+      this._localIceCandidatesBuffer.forEach(function(event) {
+        var end = !event.candidate || Object.keys(event.candidate).length === 0;
+        if (end) {
+          for (var j = 1; j < sections.length; j++) {
+            if (sections[j].indexOf('\r\na=end-of-candidates\r\n') === -1) {
+              sections[j] += 'a=end-of-candidates\r\n';
+            }
+          }
+        } else if (event.candidate.candidate.indexOf('typ endOfCandidates')
+            === -1) {
+          sections[event.candidate.sdpMLineIndex + 1] +=
+              'a=' + event.candidate.candidate + '\r\n';
+        }
+        self.localDescription.sdp = sections.join('');
+        self.dispatchEvent(event);
+        if (self.onicecandidate !== null) {
+          self.onicecandidate(event);
+        }
+        if (!event.candidate && self.iceGatheringState !== 'complete') {
+          var complete = self.transceivers.every(function(transceiver) {
+            return transceiver.iceGatherer &&
+                transceiver.iceGatherer.state === 'completed';
+          });
+          if (complete) {
+            self.iceGatheringState = 'complete';
+          }
+        }
+      });
+      this._localIceCandidatesBuffer = [];
+    };
 
-    /** Used to detect overreaching core-js shims. */
-    var coreJsData = context['__core-js_shared__'];
+    window.RTCPeerConnection.prototype.getConfiguration = function() {
+      return this._config;
+    };
 
-    /** Used to detect methods masquerading as native. */
-    var maskSrcKey = (function() {
-      var uid = /[^.]+$/.exec(coreJsData && coreJsData.keys && coreJsData.keys.IE_PROTO || '');
-      return uid ? ('Symbol(src)_1.' + uid) : '';
-    }());
+    window.RTCPeerConnection.prototype.addStream = function(stream) {
+      // Clone is necessary for local demos mostly, attaching directly
+      // to two different senders does not work (build 10547).
+      var clonedStream = stream.clone();
+      stream.getTracks().forEach(function(track, idx) {
+        var clonedTrack = clonedStream.getTracks()[idx];
+        track.addEventListener('enabled', function(event) {
+          clonedTrack.enabled = event.enabled;
+        });
+      });
+      this.localStreams.push(clonedStream);
+      this._maybeFireNegotiationNeeded();
+    };
 
-    /** Used to resolve the decompiled source of functions. */
-    var funcToString = context.Function.prototype.toString;
+    window.RTCPeerConnection.prototype.removeStream = function(stream) {
+      var idx = this.localStreams.indexOf(stream);
+      if (idx > -1) {
+        this.localStreams.splice(idx, 1);
+        this._maybeFireNegotiationNeeded();
+      }
+    };
 
-    /** Used to check objects for own properties. */
-    var hasOwnProperty = objectProto.hasOwnProperty;
+    window.RTCPeerConnection.prototype.getSenders = function() {
+      return this.transceivers.filter(function(transceiver) {
+        return !!transceiver.rtpSender;
+      })
+      .map(function(transceiver) {
+        return transceiver.rtpSender;
+      });
+    };
 
-    /** Used to generate unique IDs. */
-    var idCounter = 0;
+    window.RTCPeerConnection.prototype.getReceivers = function() {
+      return this.transceivers.filter(function(transceiver) {
+        return !!transceiver.rtpReceiver;
+      })
+      .map(function(transceiver) {
+        return transceiver.rtpReceiver;
+      });
+    };
 
-    /** Used to infer the `Object` constructor. */
-    var objectCtorString = funcToString.call(Object);
+    // Determines the intersection of local and remote capabilities.
+    window.RTCPeerConnection.prototype._getCommonCapabilities =
+        function(localCapabilities, remoteCapabilities) {
+          var commonCapabilities = {
+            codecs: [],
+            headerExtensions: [],
+            fecMechanisms: []
+          };
+          localCapabilities.codecs.forEach(function(lCodec) {
+            for (var i = 0; i < remoteCapabilities.codecs.length; i++) {
+              var rCodec = remoteCapabilities.codecs[i];
+              if (lCodec.name.toLowerCase() === rCodec.name.toLowerCase() &&
+                  lCodec.clockRate === rCodec.clockRate) {
+                // number of channels is the highest common number of channels
+                rCodec.numChannels = Math.min(lCodec.numChannels,
+                    rCodec.numChannels);
+                // push rCodec so we reply with offerer payload type
+                commonCapabilities.codecs.push(rCodec);
 
-    /**
-     * Used to resolve the
-     * [`toStringTag`](http://ecma-international.org/ecma-262/6.0/#sec-object.prototype.tostring)
-     * of values.
-     */
-    var objectToString = objectProto.toString;
+                // determine common feedback mechanisms
+                rCodec.rtcpFeedback = rCodec.rtcpFeedback.filter(function(fb) {
+                  for (var j = 0; j < lCodec.rtcpFeedback.length; j++) {
+                    if (lCodec.rtcpFeedback[j].type === fb.type &&
+                        lCodec.rtcpFeedback[j].parameter === fb.parameter) {
+                      return true;
+                    }
+                  }
+                  return false;
+                });
+                // FIXME: also need to determine .parameters
+                //  see https://github.com/openpeer/ortc/issues/569
+                break;
+              }
+            }
+          });
 
-    /** Used to restore the original `_` reference in `_.noConflict`. */
-    var oldDash = root._;
+          localCapabilities.headerExtensions
+              .forEach(function(lHeaderExtension) {
+                for (var i = 0; i < remoteCapabilities.headerExtensions.length;
+                     i++) {
+                  var rHeaderExtension = remoteCapabilities.headerExtensions[i];
+                  if (lHeaderExtension.uri === rHeaderExtension.uri) {
+                    commonCapabilities.headerExtensions.push(rHeaderExtension);
+                    break;
+                  }
+                }
+              });
 
-    /** Used to detect if a method is native. */
-    var reIsNative = RegExp('^' +
-      funcToString.call(hasOwnProperty).replace(reRegExpChar, '\\$&')
-      .replace(/hasOwnProperty|(function).*?(?=\\\()| for .+?(?=\\\])/g, '$1.*?') + '$'
-    );
+          // FIXME: fecMechanisms
+          return commonCapabilities;
+        };
 
-    /** Built-in value references. */
-    var Buffer = moduleExports ? context.Buffer : undefined,
-        Reflect = context.Reflect,
-        Symbol = context.Symbol,
-        Uint8Array = context.Uint8Array,
-        enumerate = Reflect ? Reflect.enumerate : undefined,
-        getOwnPropertySymbols = Object.getOwnPropertySymbols,
-        iteratorSymbol = typeof (iteratorSymbol = Symbol && Symbol.iterator) == 'symbol' ? iteratorSymbol : undefined,
-        objectCreate = Object.create,
-        propertyIsEnumerable = objectProto.propertyIsEnumerable,
-        splice = arrayProto.splice;
+    // Create ICE gatherer, ICE transport and DTLS transport.
+    window.RTCPeerConnection.prototype._createIceAndDtlsTransports =
+        function(mid, sdpMLineIndex) {
+          var self = this;
+          var iceGatherer = new RTCIceGatherer(self.iceOptions);
+          var iceTransport = new RTCIceTransport(iceGatherer);
+          iceGatherer.onlocalcandidate = function(evt) {
+            var event = new Event('icecandidate');
+            event.candidate = {sdpMid: mid, sdpMLineIndex: sdpMLineIndex};
 
-    /** Built-in method references that are mockable. */
-    var setTimeout = function(func, wait) { return context.setTimeout.call(root, func, wait); };
+            var cand = evt.candidate;
+            var end = !cand || Object.keys(cand).length === 0;
+            // Edge emits an empty object for RTCIceCandidateComplete‥
+            if (end) {
+              // polyfill since RTCIceGatherer.state is not implemented in
+              // Edge 10547 yet.
+              if (iceGatherer.state === undefined) {
+                iceGatherer.state = 'completed';
+              }
 
-    /* Built-in method references for those with the same name as other `lodash` methods. */
-    var nativeCeil = Math.ceil,
-        nativeFloor = Math.floor,
-        nativeGetPrototype = Object.getPrototypeOf,
-        nativeIsFinite = context.isFinite,
-        nativeJoin = arrayProto.join,
-        nativeKeys = Object.keys,
-        nativeMax = Math.max,
-        nativeMin = Math.min,
-        nativeParseInt = context.parseInt,
-        nativeRandom = Math.random,
-        nativeReplace = stringProto.replace,
-        nativeReverse = arrayProto.reverse,
-        nativeSplit = stringProto.split;
-
-    /* Built-in method references that are verified to be native. */
-    var DataView = getNative(context, 'DataView'),
-        Map = getNative(context, 'Map'),
-        Promise = getNative(context, 'Promise'),
-        Set = getNative(context, 'Set'),
-        WeakMap = getNative(context, 'WeakMap'),
-        nativeCreate = getNative(Object, 'create');
-
-    /** Used to store function metadata. */
-    var metaMap = WeakMap && new WeakMap;
+              // Emit a candidate with type endOfCandidates to make the samples
+              // work. Edge requires addIceCandidate with this empty candidate
+              // to start checking. The real solution is to signal
+              // end-of-candidates to the other side when getting the null
+              // candidate but some apps (like the samples) don't do that.
+              event.candidate.candidate =
+                  'candidate:1 1 udp 1 0.0.0.0 9 typ endOfCandidates';
+            } else {
+              // RTCIceCandidate doesn't have a component, needs to be added
+              cand.component = iceTransport.component === 'RTCP' ? 2 : 1;
+              event.candidate.candidate = SDPUtils.writeCandidate(cand);
+            }
 
-    /** Detect if properties shadowing those on `Object.prototype` are non-enumerable. */
-    var nonEnumShadows = !propertyIsEnumerable.call({ 'valueOf': 1 }, 'valueOf');
+            // update local description.
+            var sections = SDPUtils.splitSections(self.localDescription.sdp);
+            if (event.candidate.candidate.indexOf('typ endOfCandidates')
+                === -1) {
+              sections[event.candidate.sdpMLineIndex + 1] +=
+                  'a=' + event.candidate.candidate + '\r\n';
+            } else {
+              sections[event.candidate.sdpMLineIndex + 1] +=
+                  'a=end-of-candidates\r\n';
+            }
+            self.localDescription.sdp = sections.join('');
 
-    /** Used to lookup unminified function names. */
-    var realNames = {};
+            var complete = self.transceivers.every(function(transceiver) {
+              return transceiver.iceGatherer &&
+                  transceiver.iceGatherer.state === 'completed';
+            });
 
-    /** Used to detect maps, sets, and weakmaps. */
-    var dataViewCtorString = toSource(DataView),
-        mapCtorString = toSource(Map),
-        promiseCtorString = toSource(Promise),
-        setCtorString = toSource(Set),
-        weakMapCtorString = toSource(WeakMap);
+            // Emit candidate if localDescription is set.
+            // Also emits null candidate when all gatherers are complete.
+            switch (self.iceGatheringState) {
+              case 'new':
+                self._localIceCandidatesBuffer.push(event);
+                if (end && complete) {
+                  self._localIceCandidatesBuffer.push(
+                      new Event('icecandidate'));
+                }
+                break;
+              case 'gathering':
+                self._emitBufferedCandidates();
+                self.dispatchEvent(event);
+                if (self.onicecandidate !== null) {
+                  self.onicecandidate(event);
+                }
+                if (complete) {
+                  self.dispatchEvent(new Event('icecandidate'));
+                  if (self.onicecandidate !== null) {
+                    self.onicecandidate(new Event('icecandidate'));
+                  }
+                  self.iceGatheringState = 'complete';
+                }
+                break;
+              case 'complete':
+                // should not happen... currently!
+                break;
+              default: // no-op.
+                break;
+            }
+          };
+          iceTransport.onicestatechange = function() {
+            self._updateConnectionState();
+          };
 
-    /** Used to convert symbols to primitives and strings. */
-    var symbolProto = Symbol ? Symbol.prototype : undefined,
-        symbolValueOf = symbolProto ? symbolProto.valueOf : undefined,
-        symbolToString = symbolProto ? symbolProto.toString : undefined;
+          var dtlsTransport = new RTCDtlsTransport(iceTransport);
+          dtlsTransport.ondtlsstatechange = function() {
+            self._updateConnectionState();
+          };
+          dtlsTransport.onerror = function() {
+            // onerror does not set state to failed by itself.
+            dtlsTransport.state = 'failed';
+            self._updateConnectionState();
+          };
 
-    /*------------------------------------------------------------------------*/
+          return {
+            iceGatherer: iceGatherer,
+            iceTransport: iceTransport,
+            dtlsTransport: dtlsTransport
+          };
+        };
 
-    /**
-     * Creates a `lodash` object which wraps `value` to enable implicit method
-     * chain sequences. Methods that operate on and return arrays, collections,
-     * and functions can be chained together. Methods that retrieve a single value
-     * or may return a primitive value will automatically end the chain sequence
-     * and return the unwrapped value. Otherwise, the value must be unwrapped
-     * with `_#value`.
-     *
-     * Explicit chain sequences, which must be unwrapped with `_#value`, may be
-     * enabled using `_.chain`.
-     *
-     * The execution of chained methods is lazy, that is, it's deferred until
-     * `_#value` is implicitly or explicitly called.
-     *
-     * Lazy evaluation allows several methods to support shortcut fusion.
-     * Shortcut fusion is an optimization to merge iteratee calls; this avoids
-     * the creation of intermediate arrays and can greatly reduce the number of
-     * iteratee executions. Sections of a chain sequence qualify for shortcut
-     * fusion if the section is applied to an array of at least `200` elements
-     * and any iteratees accept only one argument. The heuristic for whether a
-     * section qualifies for shortcut fusion is subject to change.
-     *
-     * Chaining is supported in custom builds as long as the `_#value` method is
-     * directly or indirectly included in the build.
-     *
-     * In addition to lodash methods, wrappers have `Array` and `String` methods.
-     *
-     * The wrapper `Array` methods are:
-     * `concat`, `join`, `pop`, `push`, `shift`, `sort`, `splice`, and `unshift`
-     *
-     * The wrapper `String` methods are:
-     * `replace` and `split`
-     *
-     * The wrapper methods that support shortcut fusion are:
-     * `at`, `compact`, `drop`, `dropRight`, `dropWhile`, `filter`, `find`,
-     * `findLast`, `head`, `initial`, `last`, `map`, `reject`, `reverse`, `slice`,
-     * `tail`, `take`, `takeRight`, `takeRightWhile`, `takeWhile`, and `toArray`
-     *
-     * The chainable wrapper methods are:
-     * `after`, `ary`, `assign`, `assignIn`, `assignInWith`, `assignWith`, `at`,
-     * `before`, `bind`, `bindAll`, `bindKey`, `castArray`, `chain`, `chunk`,
-     * `commit`, `compact`, `concat`, `conforms`, `constant`, `countBy`, `create`,
-     * `curry`, `debounce`, `defaults`, `defaultsDeep`, `defer`, `delay`,
-     * `difference`, `differenceBy`, `differenceWith`, `drop`, `dropRight`,
-     * `dropRightWhile`, `dropWhile`, `extend`, `extendWith`, `fill`, `filter`,
-     * `flatMap`, `flatMapDeep`, `flatMapDepth`, `flatten`, `flattenDeep`,
-     * `flattenDepth`, `flip`, `flow`, `flowRight`, `fromPairs`, `functions`,
-     * `functionsIn`, `groupBy`, `initial`, `intersection`, `intersectionBy`,
-     * `intersectionWith`, `invert`, `invertBy`, `invokeMap`, `iteratee`, `keyBy`,
-     * `keys`, `keysIn`, `map`, `mapKeys`, `mapValues`, `matches`, `matchesProperty`,
-     * `memoize`, `merge`, `mergeWith`, `method`, `methodOf`, `mixin`, `negate`,
-     * `nthArg`, `omit`, `omitBy`, `once`, `orderBy`, `over`, `overArgs`,
-     * `overEvery`, `overSome`, `partial`, `partialRight`, `partition`, `pick`,
-     * `pickBy`, `plant`, `property`, `propertyOf`, `pull`, `pullAll`, `pullAllBy`,
-     * `pullAllWith`, `pullAt`, `push`, `range`, `rangeRight`, `rearg`, `reject`,
-     * `remove`, `rest`, `reverse`, `sampleSize`, `set`, `setWith`, `shuffle`,
-     * `slice`, `sort`, `sortBy`, `splice`, `spread`, `tail`, `take`, `takeRight`,
-     * `takeRightWhile`, `takeWhile`, `tap`, `throttle`, `thru`, `toArray`,
-     * `toPairs`, `toPairsIn`, `toPath`, `toPlainObject`, `transform`, `unary`,
-     * `union`, `unionBy`, `unionWith`, `uniq`, `uniqBy`, `uniqWith`, `unset`,
-     * `unshift`, `unzip`, `unzipWith`, `update`, `updateWith`, `values`,
-     * `valuesIn`, `without`, `wrap`, `xor`, `xorBy`, `xorWith`, `zip`,
-     * `zipObject`, `zipObjectDeep`, and `zipWith`
-     *
-     * The wrapper methods that are **not** chainable by default are:
-     * `add`, `attempt`, `camelCase`, `capitalize`, `ceil`, `clamp`, `clone`,
-     * `cloneDeep`, `cloneDeepWith`, `cloneWith`, `deburr`, `divide`, `each`,
-     * `eachRight`, `endsWith`, `eq`, `escape`, `escapeRegExp`, `every`, `find`,
-     * `findIndex`, `findKey`, `findLast`, `findLastIndex`, `findLastKey`, `first`,
-     * `floor`, `forEach`, `forEachRight`, `forIn`, `forInRight`, `forOwn`,
-     * `forOwnRight`, `get`, `gt`, `gte`, `has`, `hasIn`, `head`, `identity`,
-     * `includes`, `indexOf`, `inRange`, `invoke`, `isArguments`, `isArray`,
-     * `isArrayBuffer`, `isArrayLike`, `isArrayLikeObject`, `isBoolean`,
-     * `isBuffer`, `isDate`, `isElement`, `isEmpty`, `isEqual`, `isEqualWith`,
-     * `isError`, `isFinite`, `isFunction`, `isInteger`, `isLength`, `isMap`,
-     * `isMatch`, `isMatchWith`, `isNaN`, `isNative`, `isNil`, `isNull`,
-     * `isNumber`, `isObject`, `isObjectLike`, `isPlainObject`, `isRegExp`,
-     * `isSafeInteger`, `isSet`, `isString`, `isUndefined`, `isTypedArray`,
-     * `isWeakMap`, `isWeakSet`, `join`, `kebabCase`, `last`, `lastIndexOf`,
-     * `lowerCase`, `lowerFirst`, `lt`, `lte`, `max`, `maxBy`, `mean`, `meanBy`,
-     * `min`, `minBy`, `multiply`, `noConflict`, `noop`, `now`, `nth`, `pad`,
-     * `padEnd`, `padStart`, `parseInt`, `pop`, `random`, `reduce`, `reduceRight`,
-     * `repeat`, `result`, `round`, `runInContext`, `sample`, `shift`, `size`,
-     * `snakeCase`, `some`, `sortedIndex`, `sortedIndexBy`, `sortedLastIndex`,
-     * `sortedLastIndexBy`, `startCase`, `startsWith`, `stubArray`, `stubFalse`,
-     * `stubObject`, `stubString`, `stubTrue`, `subtract`, `sum`, `sumBy`,
-     * `template`, `times`, `toFinite`, `toInteger`, `toJSON`, `toLength`,
-     * `toLower`, `toNumber`, `toSafeInteger`, `toString`, `toUpper`, `trim`,
-     * `trimEnd`, `trimStart`, `truncate`, `unescape`, `uniqueId`, `upperCase`,
-     * `upperFirst`, `value`, and `words`
-     *
-     * @name _
-     * @constructor
-     * @category Seq
-     * @param {*} value The value to wrap in a `lodash` instance.
-     * @returns {Object} Returns the new `lodash` wrapper instance.
-     * @example
-     *
-     * function square(n) {
-     *   return n * n;
-     * }
-     *
-     * var wrapped = _([1, 2, 3]);
-     *
-     * // Returns an unwrapped value.
-     * wrapped.reduce(_.add);
-     * // => 6
-     *
-     * // Returns a wrapped value.
-     * var squares = wrapped.map(square);
-     *
-     * _.isArray(squares);
-     * // => false
-     *
-     * _.isArray(squares.value());
-     * // => true
-     */
-    function lodash(value) {
-      if (isObjectLike(value) && !isArray(value) && !(value instanceof LazyWrapper)) {
-        if (value instanceof LodashWrapper) {
-          return value;
+    // Start the RTP Sender and Receiver for a transceiver.
+    window.RTCPeerConnection.prototype._transceive = function(transceiver,
+        send, recv) {
+      var params = this._getCommonCapabilities(transceiver.localCapabilities,
+          transceiver.remoteCapabilities);
+      if (send && transceiver.rtpSender) {
+        params.encodings = transceiver.sendEncodingParameters;
+        params.rtcp = {
+          cname: SDPUtils.localCName
+        };
+        if (transceiver.recvEncodingParameters.length) {
+          params.rtcp.ssrc = transceiver.recvEncodingParameters[0].ssrc;
         }
-        if (hasOwnProperty.call(value, '__wrapped__')) {
-          return wrapperClone(value);
+        transceiver.rtpSender.send(params);
+      }
+      if (recv && transceiver.rtpReceiver) {
+        // remove RTX field in Edge 14942
+        if (transceiver.kind === 'video'
+            && transceiver.recvEncodingParameters) {
+          transceiver.recvEncodingParameters.forEach(function(p) {
+            delete p.rtx;
+          });
         }
+        params.encodings = transceiver.recvEncodingParameters;
+        params.rtcp = {
+          cname: transceiver.cname
+        };
+        if (transceiver.sendEncodingParameters.length) {
+          params.rtcp.ssrc = transceiver.sendEncodingParameters[0].ssrc;
+        }
+        transceiver.rtpReceiver.receive(params);
       }
-      return new LodashWrapper(value);
-    }
-
-    /**
-     * The function whose prototype chain sequence wrappers inherit from.
-     *
-     * @private
-     */
-    function baseLodash() {
-      // No operation performed.
-    }
+    };
 
-    /**
-     * The base constructor for creating `lodash` wrapper objects.
-     *
-     * @private
-     * @param {*} value The value to wrap.
-     * @param {boolean} [chainAll] Enable explicit method chain sequences.
-     */
-    function LodashWrapper(value, chainAll) {
-      this.__wrapped__ = value;
-      this.__actions__ = [];
-      this.__chain__ = !!chainAll;
-      this.__index__ = 0;
-      this.__values__ = undefined;
-    }
-
-    /**
-     * By default, the template delimiters used by lodash are like those in
-     * embedded Ruby (ERB). Change the following template settings to use
-     * alternative delimiters.
-     *
-     * @static
-     * @memberOf _
-     * @type {Object}
-     */
-    lodash.templateSettings = {
+    window.RTCPeerConnection.prototype.setLocalDescription =
+        function(description) {
+          var self = this;
+          var sections;
+          var sessionpart;
+          if (description.type === 'offer') {
+            // FIXME: What was the purpose of this empty if statement?
+            // if (!this._pendingOffer) {
+            // } else {
+            if (this._pendingOffer) {
+              // VERY limited support for SDP munging. Limited to:
+              // * changing the order of codecs
+              sections = SDPUtils.splitSections(description.sdp);
+              sessionpart = sections.shift();
+              sections.forEach(function(mediaSection, sdpMLineIndex) {
+                var caps = SDPUtils.parseRtpParameters(mediaSection);
+                self._pendingOffer[sdpMLineIndex].localCapabilities = caps;
+              });
+              this.transceivers = this._pendingOffer;
+              delete this._pendingOffer;
+            }
+          } else if (description.type === 'answer') {
+            sections = SDPUtils.splitSections(self.remoteDescription.sdp);
+            sessionpart = sections.shift();
+            var isIceLite = SDPUtils.matchPrefix(sessionpart,
+                'a=ice-lite').length > 0;
+            sections.forEach(function(mediaSection, sdpMLineIndex) {
+              var transceiver = self.transceivers[sdpMLineIndex];
+              var iceGatherer = transceiver.iceGatherer;
+              var iceTransport = transceiver.iceTransport;
+              var dtlsTransport = transceiver.dtlsTransport;
+              var localCapabilities = transceiver.localCapabilities;
+              var remoteCapabilities = transceiver.remoteCapabilities;
 
-      /**
-       * Used to detect `data` property values to be HTML-escaped.
-       *
-       * @memberOf _.templateSettings
-       * @type {RegExp}
-       */
-      'escape': reEscape,
+              var rejected = mediaSection.split('\n', 1)[0]
+                  .split(' ', 2)[1] === '0';
 
-      /**
-       * Used to detect code to be evaluated.
-       *
-       * @memberOf _.templateSettings
-       * @type {RegExp}
-       */
-      'evaluate': reEvaluate,
+              if (!rejected && !transceiver.isDatachannel) {
+                var remoteIceParameters = SDPUtils.getIceParameters(
+                    mediaSection, sessionpart);
+                if (isIceLite) {
+                  var cands = SDPUtils.matchPrefix(mediaSection, 'a=candidate:')
+                  .map(function(cand) {
+                    return SDPUtils.parseCandidate(cand);
+                  })
+                  .filter(function(cand) {
+                    return cand.component === '1';
+                  });
+                  // ice-lite only includes host candidates in the SDP so we can
+                  // use setRemoteCandidates (which implies an
+                  // RTCIceCandidateComplete)
+                  if (cands.length) {
+                    iceTransport.setRemoteCandidates(cands);
+                  }
+                }
+                var remoteDtlsParameters = SDPUtils.getDtlsParameters(
+                    mediaSection, sessionpart);
+                if (isIceLite) {
+                  remoteDtlsParameters.role = 'server';
+                }
 
-      /**
-       * Used to detect `data` property values to inject.
-       *
-       * @memberOf _.templateSettings
-       * @type {RegExp}
-       */
-      'interpolate': reInterpolate,
+                if (!self.usingBundle || sdpMLineIndex === 0) {
+                  iceTransport.start(iceGatherer, remoteIceParameters,
+                      isIceLite ? 'controlling' : 'controlled');
+                  dtlsTransport.start(remoteDtlsParameters);
+                }
 
-      /**
-       * Used to reference the data object in the template text.
-       *
-       * @memberOf _.templateSettings
-       * @type {string}
-       */
-      'variable': '',
+                // Calculate intersection of capabilities.
+                var params = self._getCommonCapabilities(localCapabilities,
+                    remoteCapabilities);
 
-      /**
-       * Used to import variables into the compiled template.
-       *
-       * @memberOf _.templateSettings
-       * @type {Object}
-       */
-      'imports': {
+                // Start the RTCRtpSender. The RTCRtpReceiver for this
+                // transceiver has already been started in setRemoteDescription.
+                self._transceive(transceiver,
+                    params.codecs.length > 0,
+                    false);
+              }
+            });
+          }
 
-        /**
-         * A reference to the `lodash` function.
-         *
-         * @memberOf _.templateSettings.imports
-         * @type {Function}
-         */
-        '_': lodash
-      }
-    };
+          this.localDescription = {
+            type: description.type,
+            sdp: description.sdp
+          };
+          switch (description.type) {
+            case 'offer':
+              this._updateSignalingState('have-local-offer');
+              break;
+            case 'answer':
+              this._updateSignalingState('stable');
+              break;
+            default:
+              throw new TypeError('unsupported type "' + description.type +
+                  '"');
+          }
 
-    // Ensure wrappers are instances of `baseLodash`.
-    lodash.prototype = baseLodash.prototype;
-    lodash.prototype.constructor = lodash;
+          // If a success callback was provided, emit ICE candidates after it
+          // has been executed. Otherwise, emit callback after the Promise is
+          // resolved.
+          var hasCallback = arguments.length > 1 &&
+            typeof arguments[1] === 'function';
+          if (hasCallback) {
+            var cb = arguments[1];
+            window.setTimeout(function() {
+              cb();
+              if (self.iceGatheringState === 'new') {
+                self.iceGatheringState = 'gathering';
+              }
+              self._emitBufferedCandidates();
+            }, 0);
+          }
+          var p = Promise.resolve();
+          p.then(function() {
+            if (!hasCallback) {
+              if (self.iceGatheringState === 'new') {
+                self.iceGatheringState = 'gathering';
+              }
+              // Usually candidates will be emitted earlier.
+              window.setTimeout(self._emitBufferedCandidates.bind(self), 500);
+            }
+          });
+          return p;
+        };
 
-    LodashWrapper.prototype = baseCreate(baseLodash.prototype);
-    LodashWrapper.prototype.constructor = LodashWrapper;
+    window.RTCPeerConnection.prototype.setRemoteDescription =
+        function(description) {
+          var self = this;
+          var stream = new MediaStream();
+          var receiverList = [];
+          var sections = SDPUtils.splitSections(description.sdp);
+          var sessionpart = sections.shift();
+          var isIceLite = SDPUtils.matchPrefix(sessionpart,
+              'a=ice-lite').length > 0;
+          this.usingBundle = SDPUtils.matchPrefix(sessionpart,
+              'a=group:BUNDLE ').length > 0;
+          sections.forEach(function(mediaSection, sdpMLineIndex) {
+            var lines = SDPUtils.splitLines(mediaSection);
+            var mline = lines[0].substr(2).split(' ');
+            var kind = mline[0];
+            var rejected = mline[1] === '0';
+            var direction = SDPUtils.getDirection(mediaSection, sessionpart);
 
-    /*------------------------------------------------------------------------*/
+            var mid = SDPUtils.matchPrefix(mediaSection, 'a=mid:');
+            if (mid.length) {
+              mid = mid[0].substr(6);
+            } else {
+              mid = SDPUtils.generateIdentifier();
+            }
 
-    /**
-     * Creates a lazy wrapper object which wraps `value` to enable lazy evaluation.
-     *
-     * @private
-     * @constructor
-     * @param {*} value The value to wrap.
-     */
-    function LazyWrapper(value) {
-      this.__wrapped__ = value;
-      this.__actions__ = [];
-      this.__dir__ = 1;
-      this.__filtered__ = false;
-      this.__iteratees__ = [];
-      this.__takeCount__ = MAX_ARRAY_LENGTH;
-      this.__views__ = [];
-    }
+            // Reject datachannels which are not implemented yet.
+            if (kind === 'application' && mline[2] === 'DTLS/SCTP') {
+              self.transceivers[sdpMLineIndex] = {
+                mid: mid,
+                isDatachannel: true
+              };
+              return;
+            }
 
-    /**
-     * Creates a clone of the lazy wrapper object.
-     *
-     * @private
-     * @name clone
-     * @memberOf LazyWrapper
-     * @returns {Object} Returns the cloned `LazyWrapper` object.
-     */
-    function lazyClone() {
-      var result = new LazyWrapper(this.__wrapped__);
-      result.__actions__ = copyArray(this.__actions__);
-      result.__dir__ = this.__dir__;
-      result.__filtered__ = this.__filtered__;
-      result.__iteratees__ = copyArray(this.__iteratees__);
-      result.__takeCount__ = this.__takeCount__;
-      result.__views__ = copyArray(this.__views__);
-      return result;
-    }
+            var transceiver;
+            var iceGatherer;
+            var iceTransport;
+            var dtlsTransport;
+            var rtpSender;
+            var rtpReceiver;
+            var sendEncodingParameters;
+            var recvEncodingParameters;
+            var localCapabilities;
 
-    /**
-     * Reverses the direction of lazy iteration.
-     *
-     * @private
-     * @name reverse
-     * @memberOf LazyWrapper
-     * @returns {Object} Returns the new reversed `LazyWrapper` object.
-     */
-    function lazyReverse() {
-      if (this.__filtered__) {
-        var result = new LazyWrapper(this);
-        result.__dir__ = -1;
-        result.__filtered__ = true;
-      } else {
-        result = this.clone();
-        result.__dir__ *= -1;
-      }
-      return result;
-    }
+            var track;
+            // FIXME: ensure the mediaSection has rtcp-mux set.
+            var remoteCapabilities = SDPUtils.parseRtpParameters(mediaSection);
+            var remoteIceParameters;
+            var remoteDtlsParameters;
+            if (!rejected) {
+              remoteIceParameters = SDPUtils.getIceParameters(mediaSection,
+                  sessionpart);
+              remoteDtlsParameters = SDPUtils.getDtlsParameters(mediaSection,
+                  sessionpart);
+              remoteDtlsParameters.role = 'client';
+            }
+            recvEncodingParameters =
+                SDPUtils.parseRtpEncodingParameters(mediaSection);
 
-    /**
-     * Extracts the unwrapped value from its lazy wrapper.
-     *
-     * @private
-     * @name value
-     * @memberOf LazyWrapper
-     * @returns {*} Returns the unwrapped value.
-     */
-    function lazyValue() {
-      var array = this.__wrapped__.value(),
-          dir = this.__dir__,
-          isArr = isArray(array),
-          isRight = dir < 0,
-          arrLength = isArr ? array.length : 0,
-          view = getView(0, arrLength, this.__views__),
-          start = view.start,
-          end = view.end,
-          length = end - start,
-          index = isRight ? end : (start - 1),
-          iteratees = this.__iteratees__,
-          iterLength = iteratees.length,
-          resIndex = 0,
-          takeCount = nativeMin(length, this.__takeCount__);
+            var cname;
+            // Gets the first SSRC. Note that with RTX there might be multiple
+            // SSRCs.
+            var remoteSsrc = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
+                .map(function(line) {
+                  return SDPUtils.parseSsrcMedia(line);
+                })
+                .filter(function(obj) {
+                  return obj.attribute === 'cname';
+                })[0];
+            if (remoteSsrc) {
+              cname = remoteSsrc.value;
+            }
 
-      if (!isArr || arrLength < LARGE_ARRAY_SIZE ||
-          (arrLength == length && takeCount == length)) {
-        return baseWrapperValue(array, this.__actions__);
-      }
-      var result = [];
+            var isComplete = SDPUtils.matchPrefix(mediaSection,
+                'a=end-of-candidates', sessionpart).length > 0;
+            var cands = SDPUtils.matchPrefix(mediaSection, 'a=candidate:')
+                .map(function(cand) {
+                  return SDPUtils.parseCandidate(cand);
+                })
+                .filter(function(cand) {
+                  return cand.component === '1';
+                });
+            if (description.type === 'offer' && !rejected) {
+              var transports = self.usingBundle && sdpMLineIndex > 0 ? {
+                iceGatherer: self.transceivers[0].iceGatherer,
+                iceTransport: self.transceivers[0].iceTransport,
+                dtlsTransport: self.transceivers[0].dtlsTransport
+              } : self._createIceAndDtlsTransports(mid, sdpMLineIndex);
 
-      outer:
-      while (length-- && resIndex < takeCount) {
-        index += dir;
+              if (isComplete) {
+                transports.iceTransport.setRemoteCandidates(cands);
+              }
 
-        var iterIndex = -1,
-            value = array[index];
+              localCapabilities = RTCRtpReceiver.getCapabilities(kind);
 
-        while (++iterIndex < iterLength) {
-          var data = iteratees[iterIndex],
-              iteratee = data.iteratee,
-              type = data.type,
-              computed = iteratee(value);
+              // filter RTX until additional stuff needed for RTX is implemented
+              // in adapter.js
+              localCapabilities.codecs = localCapabilities.codecs.filter(
+                  function(codec) {
+                    return codec.name !== 'rtx';
+                  });
 
-          if (type == LAZY_MAP_FLAG) {
-            value = computed;
-          } else if (!computed) {
-            if (type == LAZY_FILTER_FLAG) {
-              continue outer;
-            } else {
-              break outer;
-            }
-          }
-        }
-        result[resIndex++] = value;
-      }
-      return result;
-    }
+              sendEncodingParameters = [{
+                ssrc: (2 * sdpMLineIndex + 2) * 1001
+              }];
 
-    // Ensure `LazyWrapper` is an instance of `baseLodash`.
-    LazyWrapper.prototype = baseCreate(baseLodash.prototype);
-    LazyWrapper.prototype.constructor = LazyWrapper;
+              rtpReceiver = new RTCRtpReceiver(transports.dtlsTransport, kind);
 
-    /*------------------------------------------------------------------------*/
+              track = rtpReceiver.track;
+              receiverList.push([track, rtpReceiver]);
+              // FIXME: not correct when there are multiple streams but that is
+              // not currently supported in this shim.
+              stream.addTrack(track);
 
-    /**
-     * Creates a hash object.
-     *
-     * @private
-     * @constructor
-     * @param {Array} [entries] The key-value pairs to cache.
-     */
-    function Hash(entries) {
-      var index = -1,
-          length = entries ? entries.length : 0;
+              // FIXME: look at direction.
+              if (self.localStreams.length > 0 &&
+                  self.localStreams[0].getTracks().length >= sdpMLineIndex) {
+                var localTrack;
+                if (kind === 'audio') {
+                  localTrack = self.localStreams[0].getAudioTracks()[0];
+                } else if (kind === 'video') {
+                  localTrack = self.localStreams[0].getVideoTracks()[0];
+                }
+                if (localTrack) {
+                  rtpSender = new RTCRtpSender(localTrack,
+                      transports.dtlsTransport);
+                }
+              }
 
-      this.clear();
-      while (++index < length) {
-        var entry = entries[index];
-        this.set(entry[0], entry[1]);
-      }
-    }
+              self.transceivers[sdpMLineIndex] = {
+                iceGatherer: transports.iceGatherer,
+                iceTransport: transports.iceTransport,
+                dtlsTransport: transports.dtlsTransport,
+                localCapabilities: localCapabilities,
+                remoteCapabilities: remoteCapabilities,
+                rtpSender: rtpSender,
+                rtpReceiver: rtpReceiver,
+                kind: kind,
+                mid: mid,
+                cname: cname,
+                sendEncodingParameters: sendEncodingParameters,
+                recvEncodingParameters: recvEncodingParameters
+              };
+              // Start the RTCRtpReceiver now. The RTPSender is started in
+              // setLocalDescription.
+              self._transceive(self.transceivers[sdpMLineIndex],
+                  false,
+                  direction === 'sendrecv' || direction === 'sendonly');
+            } else if (description.type === 'answer' && !rejected) {
+              transceiver = self.transceivers[sdpMLineIndex];
+              iceGatherer = transceiver.iceGatherer;
+              iceTransport = transceiver.iceTransport;
+              dtlsTransport = transceiver.dtlsTransport;
+              rtpSender = transceiver.rtpSender;
+              rtpReceiver = transceiver.rtpReceiver;
+              sendEncodingParameters = transceiver.sendEncodingParameters;
+              localCapabilities = transceiver.localCapabilities;
 
-    /**
-     * Removes all key-value entries from the hash.
-     *
-     * @private
-     * @name clear
-     * @memberOf Hash
-     */
-    function hashClear() {
-      this.__data__ = nativeCreate ? nativeCreate(null) : {};
-    }
+              self.transceivers[sdpMLineIndex].recvEncodingParameters =
+                  recvEncodingParameters;
+              self.transceivers[sdpMLineIndex].remoteCapabilities =
+                  remoteCapabilities;
+              self.transceivers[sdpMLineIndex].cname = cname;
 
-    /**
-     * Removes `key` and its value from the hash.
-     *
-     * @private
-     * @name delete
-     * @memberOf Hash
-     * @param {Object} hash The hash to modify.
-     * @param {string} key The key of the value to remove.
-     * @returns {boolean} Returns `true` if the entry was removed, else `false`.
-     */
-    function hashDelete(key) {
-      return this.has(key) && delete this.__data__[key];
-    }
+              if ((isIceLite || isComplete) && cands.length) {
+                iceTransport.setRemoteCandidates(cands);
+              }
+              if (!self.usingBundle || sdpMLineIndex === 0) {
+                iceTransport.start(iceGatherer, remoteIceParameters,
+                    'controlling');
+                dtlsTransport.start(remoteDtlsParameters);
+              }
 
-    /**
-     * Gets the hash value for `key`.
-     *
-     * @private
-     * @name get
-     * @memberOf Hash
-     * @param {string} key The key of the value to get.
-     * @returns {*} Returns the entry value.
-     */
-    function hashGet(key) {
-      var data = this.__data__;
-      if (nativeCreate) {
-        var result = data[key];
-        return result === HASH_UNDEFINED ? undefined : result;
-      }
-      return hasOwnProperty.call(data, key) ? data[key] : undefined;
-    }
+              self._transceive(transceiver,
+                  direction === 'sendrecv' || direction === 'recvonly',
+                  direction === 'sendrecv' || direction === 'sendonly');
 
-    /**
-     * Checks if a hash value for `key` exists.
-     *
-     * @private
-     * @name has
-     * @memberOf Hash
-     * @param {string} key The key of the entry to check.
-     * @returns {boolean} Returns `true` if an entry for `key` exists, else `false`.
-     */
-    function hashHas(key) {
-      var data = this.__data__;
-      return nativeCreate ? data[key] !== undefined : hasOwnProperty.call(data, key);
-    }
+              if (rtpReceiver &&
+                  (direction === 'sendrecv' || direction === 'sendonly')) {
+                track = rtpReceiver.track;
+                receiverList.push([track, rtpReceiver]);
+                stream.addTrack(track);
+              } else {
+                // FIXME: actually the receiver should be created later.
+                delete transceiver.rtpReceiver;
+              }
+            }
+          });
 
-    /**
-     * Sets the hash `key` to `value`.
-     *
-     * @private
-     * @name set
-     * @memberOf Hash
-     * @param {string} key The key of the value to set.
-     * @param {*} value The value to set.
-     * @returns {Object} Returns the hash instance.
-     */
-    function hashSet(key, value) {
-      var data = this.__data__;
-      data[key] = (nativeCreate && value === undefined) ? HASH_UNDEFINED : value;
-      return this;
-    }
-
-    // Add methods to `Hash`.
-    Hash.prototype.clear = hashClear;
-    Hash.prototype['delete'] = hashDelete;
-    Hash.prototype.get = hashGet;
-    Hash.prototype.has = hashHas;
-    Hash.prototype.set = hashSet;
+          this.remoteDescription = {
+            type: description.type,
+            sdp: description.sdp
+          };
+          switch (description.type) {
+            case 'offer':
+              this._updateSignalingState('have-remote-offer');
+              break;
+            case 'answer':
+              this._updateSignalingState('stable');
+              break;
+            default:
+              throw new TypeError('unsupported type "' + description.type +
+                  '"');
+          }
+          if (stream.getTracks().length) {
+            self.remoteStreams.push(stream);
+            window.setTimeout(function() {
+              var event = new Event('addstream');
+              event.stream = stream;
+              self.dispatchEvent(event);
+              if (self.onaddstream !== null) {
+                window.setTimeout(function() {
+                  self.onaddstream(event);
+                }, 0);
+              }
 
-    /*------------------------------------------------------------------------*/
+              receiverList.forEach(function(item) {
+                var track = item[0];
+                var receiver = item[1];
+                var trackEvent = new Event('track');
+                trackEvent.track = track;
+                trackEvent.receiver = receiver;
+                trackEvent.streams = [stream];
+                self.dispatchEvent(event);
+                if (self.ontrack !== null) {
+                  window.setTimeout(function() {
+                    self.ontrack(trackEvent);
+                  }, 0);
+                }
+              });
+            }, 0);
+          }
+          if (arguments.length > 1 && typeof arguments[1] === 'function') {
+            window.setTimeout(arguments[1], 0);
+          }
+          return Promise.resolve();
+        };
 
-    /**
-     * Creates an list cache object.
-     *
-     * @private
-     * @constructor
-     * @param {Array} [entries] The key-value pairs to cache.
-     */
-    function ListCache(entries) {
-      var index = -1,
-          length = entries ? entries.length : 0;
+    window.RTCPeerConnection.prototype.close = function() {
+      this.transceivers.forEach(function(transceiver) {
+        /* not yet
+        if (transceiver.iceGatherer) {
+          transceiver.iceGatherer.close();
+        }
+        */
+        if (transceiver.iceTransport) {
+          transceiver.iceTransport.stop();
+        }
+        if (transceiver.dtlsTransport) {
+          transceiver.dtlsTransport.stop();
+        }
+        if (transceiver.rtpSender) {
+          transceiver.rtpSender.stop();
+        }
+        if (transceiver.rtpReceiver) {
+          transceiver.rtpReceiver.stop();
+        }
+      });
+      // FIXME: clean up tracks, local streams, remote streams, etc
+      this._updateSignalingState('closed');
+    };
 
-      this.clear();
-      while (++index < length) {
-        var entry = entries[index];
-        this.set(entry[0], entry[1]);
-      }
-    }
+    // Update the signaling state.
+    window.RTCPeerConnection.prototype._updateSignalingState =
+        function(newState) {
+          this.signalingState = newState;
+          var event = new Event('signalingstatechange');
+          this.dispatchEvent(event);
+          if (this.onsignalingstatechange !== null) {
+            this.onsignalingstatechange(event);
+          }
+        };
 
-    /**
-     * Removes all key-value entries from the list cache.
-     *
-     * @private
-     * @name clear
-     * @memberOf ListCache
-     */
-    function listCacheClear() {
-      this.__data__ = [];
-    }
+    // Determine whether to fire the negotiationneeded event.
+    window.RTCPeerConnection.prototype._maybeFireNegotiationNeeded =
+        function() {
+          // Fire away (for now).
+          var event = new Event('negotiationneeded');
+          this.dispatchEvent(event);
+          if (this.onnegotiationneeded !== null) {
+            this.onnegotiationneeded(event);
+          }
+        };
 
-    /**
-     * Removes `key` and its value from the list cache.
-     *
-     * @private
-     * @name delete
-     * @memberOf ListCache
-     * @param {string} key The key of the value to remove.
-     * @returns {boolean} Returns `true` if the entry was removed, else `false`.
-     */
-    function listCacheDelete(key) {
-      var data = this.__data__,
-          index = assocIndexOf(data, key);
+    // Update the connection state.
+    window.RTCPeerConnection.prototype._updateConnectionState = function() {
+      var self = this;
+      var newState;
+      var states = {
+        'new': 0,
+        closed: 0,
+        connecting: 0,
+        checking: 0,
+        connected: 0,
+        completed: 0,
+        failed: 0
+      };
+      this.transceivers.forEach(function(transceiver) {
+        states[transceiver.iceTransport.state]++;
+        states[transceiver.dtlsTransport.state]++;
+      });
+      // ICETransport.completed and connected are the same for this purpose.
+      states.connected += states.completed;
 
-      if (index < 0) {
-        return false;
-      }
-      var lastIndex = data.length - 1;
-      if (index == lastIndex) {
-        data.pop();
-      } else {
-        splice.call(data, index, 1);
+      newState = 'new';
+      if (states.failed > 0) {
+        newState = 'failed';
+      } else if (states.connecting > 0 || states.checking > 0) {
+        newState = 'connecting';
+      } else if (states.disconnected > 0) {
+        newState = 'disconnected';
+      } else if (states.new > 0) {
+        newState = 'new';
+      } else if (states.connected > 0 || states.completed > 0) {
+        newState = 'connected';
       }
-      return true;
-    }
-
-    /**
-     * Gets the list cache value for `key`.
-     *
-     * @private
-     * @name get
-     * @memberOf ListCache
-     * @param {string} key The key of the value to get.
-     * @returns {*} Returns the entry value.
-     */
-    function listCacheGet(key) {
-      var data = this.__data__,
-          index = assocIndexOf(data, key);
-
-      return index < 0 ? undefined : data[index][1];
-    }
-
-    /**
-     * Checks if a list cache value for `key` exists.
-     *
-     * @private
-     * @name has
-     * @memberOf ListCache
-     * @param {string} key The key of the entry to check.
-     * @returns {boolean} Returns `true` if an entry for `key` exists, else `false`.
-     */
-    function listCacheHas(key) {
-      return assocIndexOf(this.__data__, key) > -1;
-    }
 
-    /**
-     * Sets the list cache `key` to `value`.
-     *
-     * @private
-     * @name set
-     * @memberOf ListCache
-     * @param {string} key The key of the value to set.
-     * @param {*} value The value to set.
-     * @returns {Object} Returns the list cache instance.
-     */
-    function listCacheSet(key, value) {
-      var data = this.__data__,
-          index = assocIndexOf(data, key);
+      if (newState !== self.iceConnectionState) {
+        self.iceConnectionState = newState;
+        var event = new Event('iceconnectionstatechange');
+        this.dispatchEvent(event);
+        if (this.oniceconnectionstatechange !== null) {
+          this.oniceconnectionstatechange(event);
+        }
+      }
+    };
 
-      if (index < 0) {
-        data.push([key, value]);
-      } else {
-        data[index][1] = value;
+    window.RTCPeerConnection.prototype.createOffer = function() {
+      var self = this;
+      if (this._pendingOffer) {
+        throw new Error('createOffer called while there is a pending offer.');
+      }
+      var offerOptions;
+      if (arguments.length === 1 && typeof arguments[0] !== 'function') {
+        offerOptions = arguments[0];
+      } else if (arguments.length === 3) {
+        offerOptions = arguments[2];
       }
-      return this;
-    }
 
-    // Add methods to `ListCache`.
-    ListCache.prototype.clear = listCacheClear;
-    ListCache.prototype['delete'] = listCacheDelete;
-    ListCache.prototype.get = listCacheGet;
-    ListCache.prototype.has = listCacheHas;
-    ListCache.prototype.set = listCacheSet;
+      var tracks = [];
+      var numAudioTracks = 0;
+      var numVideoTracks = 0;
+      // Default to sendrecv.
+      if (this.localStreams.length) {
+        numAudioTracks = this.localStreams[0].getAudioTracks().length;
+        numVideoTracks = this.localStreams[0].getVideoTracks().length;
+      }
+      // Determine number of audio and video tracks we need to send/recv.
+      if (offerOptions) {
+        // Reject Chrome legacy constraints.
+        if (offerOptions.mandatory || offerOptions.optional) {
+          throw new TypeError(
+              'Legacy mandatory/optional constraints not supported.');
+        }
+        if (offerOptions.offerToReceiveAudio !== undefined) {
+          numAudioTracks = offerOptions.offerToReceiveAudio;
+        }
+        if (offerOptions.offerToReceiveVideo !== undefined) {
+          numVideoTracks = offerOptions.offerToReceiveVideo;
+        }
+      }
+      if (this.localStreams.length) {
+        // Push local streams.
+        this.localStreams[0].getTracks().forEach(function(track) {
+          tracks.push({
+            kind: track.kind,
+            track: track,
+            wantReceive: track.kind === 'audio' ?
+                numAudioTracks > 0 : numVideoTracks > 0
+          });
+          if (track.kind === 'audio') {
+            numAudioTracks--;
+          } else if (track.kind === 'video') {
+            numVideoTracks--;
+          }
+        });
+      }
+      // Create M-lines for recvonly streams.
+      while (numAudioTracks > 0 || numVideoTracks > 0) {
+        if (numAudioTracks > 0) {
+          tracks.push({
+            kind: 'audio',
+            wantReceive: true
+          });
+          numAudioTracks--;
+        }
+        if (numVideoTracks > 0) {
+          tracks.push({
+            kind: 'video',
+            wantReceive: true
+          });
+          numVideoTracks--;
+        }
+      }
 
-    /*------------------------------------------------------------------------*/
+      var sdp = SDPUtils.writeSessionBoilerplate();
+      var transceivers = [];
+      tracks.forEach(function(mline, sdpMLineIndex) {
+        // For each track, create an ice gatherer, ice transport,
+        // dtls transport, potentially rtpsender and rtpreceiver.
+        var track = mline.track;
+        var kind = mline.kind;
+        var mid = SDPUtils.generateIdentifier();
 
-    /**
-     * Creates a map cache object to store key-value pairs.
-     *
-     * @private
-     * @constructor
-     * @param {Array} [entries] The key-value pairs to cache.
-     */
-    function MapCache(entries) {
-      var index = -1,
-          length = entries ? entries.length : 0;
+        var transports = self.usingBundle && sdpMLineIndex > 0 ? {
+          iceGatherer: transceivers[0].iceGatherer,
+          iceTransport: transceivers[0].iceTransport,
+          dtlsTransport: transceivers[0].dtlsTransport
+        } : self._createIceAndDtlsTransports(mid, sdpMLineIndex);
 
-      this.clear();
-      while (++index < length) {
-        var entry = entries[index];
-        this.set(entry[0], entry[1]);
-      }
-    }
+        var localCapabilities = RTCRtpSender.getCapabilities(kind);
+        // filter RTX until additional stuff needed for RTX is implemented
+        // in adapter.js
+        localCapabilities.codecs = localCapabilities.codecs.filter(
+            function(codec) {
+              return codec.name !== 'rtx';
+            });
+        localCapabilities.codecs.forEach(function(codec) {
+          // work around https://bugs.chromium.org/p/webrtc/issues/detail?id=6552
+          // by adding level-asymmetry-allowed=1
+          if (codec.name === 'H264' &&
+              codec.parameters['level-asymmetry-allowed'] === undefined) {
+            codec.parameters['level-asymmetry-allowed'] = '1';
+          }
+        });
 
-    /**
-     * Removes all key-value entries from the map.
-     *
-     * @private
-     * @name clear
-     * @memberOf MapCache
-     */
-    function mapCacheClear() {
-      this.__data__ = {
-        'hash': new Hash,
-        'map': new (Map || ListCache),
-        'string': new Hash
-      };
-    }
+        var rtpSender;
+        var rtpReceiver;
 
-    /**
-     * Removes `key` and its value from the map.
-     *
-     * @private
-     * @name delete
-     * @memberOf MapCache
-     * @param {string} key The key of the value to remove.
-     * @returns {boolean} Returns `true` if the entry was removed, else `false`.
-     */
-    function mapCacheDelete(key) {
-      return getMapData(this, key)['delete'](key);
-    }
+        // generate an ssrc now, to be used later in rtpSender.send
+        var sendEncodingParameters = [{
+          ssrc: (2 * sdpMLineIndex + 1) * 1001
+        }];
+        if (track) {
+          rtpSender = new RTCRtpSender(track, transports.dtlsTransport);
+        }
 
-    /**
-     * Gets the map value for `key`.
-     *
-     * @private
-     * @name get
-     * @memberOf MapCache
-     * @param {string} key The key of the value to get.
-     * @returns {*} Returns the entry value.
-     */
-    function mapCacheGet(key) {
-      return getMapData(this, key).get(key);
-    }
+        if (mline.wantReceive) {
+          rtpReceiver = new RTCRtpReceiver(transports.dtlsTransport, kind);
+        }
 
-    /**
-     * Checks if a map value for `key` exists.
-     *
-     * @private
-     * @name has
-     * @memberOf MapCache
-     * @param {string} key The key of the entry to check.
-     * @returns {boolean} Returns `true` if an entry for `key` exists, else `false`.
-     */
-    function mapCacheHas(key) {
-      return getMapData(this, key).has(key);
-    }
+        transceivers[sdpMLineIndex] = {
+          iceGatherer: transports.iceGatherer,
+          iceTransport: transports.iceTransport,
+          dtlsTransport: transports.dtlsTransport,
+          localCapabilities: localCapabilities,
+          remoteCapabilities: null,
+          rtpSender: rtpSender,
+          rtpReceiver: rtpReceiver,
+          kind: kind,
+          mid: mid,
+          sendEncodingParameters: sendEncodingParameters,
+          recvEncodingParameters: null
+        };
+      });
+      if (this.usingBundle) {
+        sdp += 'a=group:BUNDLE ' + transceivers.map(function(t) {
+          return t.mid;
+        }).join(' ') + '\r\n';
+      }
+      tracks.forEach(function(mline, sdpMLineIndex) {
+        var transceiver = transceivers[sdpMLineIndex];
+        sdp += SDPUtils.writeMediaSection(transceiver,
+            transceiver.localCapabilities, 'offer', self.localStreams[0]);
+      });
 
-    /**
-     * Sets the map `key` to `value`.
-     *
-     * @private
-     * @name set
-     * @memberOf MapCache
-     * @param {string} key The key of the value to set.
-     * @param {*} value The value to set.
-     * @returns {Object} Returns the map cache instance.
-     */
-    function mapCacheSet(key, value) {
-      getMapData(this, key).set(key, value);
-      return this;
-    }
+      this._pendingOffer = transceivers;
+      var desc = new RTCSessionDescription({
+        type: 'offer',
+        sdp: sdp
+      });
+      if (arguments.length && typeof arguments[0] === 'function') {
+        window.setTimeout(arguments[0], 0, desc);
+      }
+      return Promise.resolve(desc);
+    };
 
-    // Add methods to `MapCache`.
-    MapCache.prototype.clear = mapCacheClear;
-    MapCache.prototype['delete'] = mapCacheDelete;
-    MapCache.prototype.get = mapCacheGet;
-    MapCache.prototype.has = mapCacheHas;
-    MapCache.prototype.set = mapCacheSet;
+    window.RTCPeerConnection.prototype.createAnswer = function() {
+      var self = this;
 
-    /*------------------------------------------------------------------------*/
+      var sdp = SDPUtils.writeSessionBoilerplate();
+      if (this.usingBundle) {
+        sdp += 'a=group:BUNDLE ' + this.transceivers.map(function(t) {
+          return t.mid;
+        }).join(' ') + '\r\n';
+      }
+      this.transceivers.forEach(function(transceiver) {
+        if (transceiver.isDatachannel) {
+          sdp += 'm=application 0 DTLS/SCTP 5000\r\n' +
+              'c=IN IP4 0.0.0.0\r\n' +
+              'a=mid:' + transceiver.mid + '\r\n';
+          return;
+        }
+        // Calculate intersection of capabilities.
+        var commonCapabilities = self._getCommonCapabilities(
+            transceiver.localCapabilities,
+            transceiver.remoteCapabilities);
 
-    /**
-     *
-     * Creates an array cache object to store unique values.
-     *
-     * @private
-     * @constructor
-     * @param {Array} [values] The values to cache.
-     */
-    function SetCache(values) {
-      var index = -1,
-          length = values ? values.length : 0;
+        sdp += SDPUtils.writeMediaSection(transceiver, commonCapabilities,
+            'answer', self.localStreams[0]);
+      });
 
-      this.__data__ = new MapCache;
-      while (++index < length) {
-        this.add(values[index]);
+      var desc = new RTCSessionDescription({
+        type: 'answer',
+        sdp: sdp
+      });
+      if (arguments.length && typeof arguments[0] === 'function') {
+        window.setTimeout(arguments[0], 0, desc);
       }
-    }
+      return Promise.resolve(desc);
+    };
 
-    /**
-     * Adds `value` to the array cache.
-     *
-     * @private
-     * @name add
-     * @memberOf SetCache
-     * @alias push
-     * @param {*} value The value to cache.
-     * @returns {Object} Returns the cache instance.
-     */
-    function setCacheAdd(value) {
-      this.__data__.set(value, HASH_UNDEFINED);
-      return this;
-    }
+    window.RTCPeerConnection.prototype.addIceCandidate = function(candidate) {
+      if (!candidate) {
+        this.transceivers.forEach(function(transceiver) {
+          transceiver.iceTransport.addRemoteCandidate({});
+        });
+      } else {
+        var mLineIndex = candidate.sdpMLineIndex;
+        if (candidate.sdpMid) {
+          for (var i = 0; i < this.transceivers.length; i++) {
+            if (this.transceivers[i].mid === candidate.sdpMid) {
+              mLineIndex = i;
+              break;
+            }
+          }
+        }
+        var transceiver = this.transceivers[mLineIndex];
+        if (transceiver) {
+          var cand = Object.keys(candidate.candidate).length > 0 ?
+              SDPUtils.parseCandidate(candidate.candidate) : {};
+          // Ignore Chrome's invalid candidates since Edge does not like them.
+          if (cand.protocol === 'tcp' && (cand.port === 0 || cand.port === 9)) {
+            return;
+          }
+          // Ignore RTCP candidates, we assume RTCP-MUX.
+          if (cand.component !== '1') {
+            return;
+          }
+          // A dirty hack to make samples work.
+          if (cand.type === 'endOfCandidates') {
+            cand = {};
+          }
+          transceiver.iceTransport.addRemoteCandidate(cand);
 
-    /**
-     * Checks if `value` is in the array cache.
-     *
-     * @private
-     * @name has
-     * @memberOf SetCache
-     * @param {*} value The value to search for.
-     * @returns {number} Returns `true` if `value` is found, else `false`.
-     */
-    function setCacheHas(value) {
-      return this.__data__.has(value);
-    }
+          // update the remoteDescription.
+          var sections = SDPUtils.splitSections(this.remoteDescription.sdp);
+          sections[mLineIndex + 1] += (cand.type ? candidate.candidate.trim()
+              : 'a=end-of-candidates') + '\r\n';
+          this.remoteDescription.sdp = sections.join('');
+        }
+      }
+      if (arguments.length > 1 && typeof arguments[1] === 'function') {
+        window.setTimeout(arguments[1], 0);
+      }
+      return Promise.resolve();
+    };
 
-    // Add methods to `SetCache`.
-    SetCache.prototype.add = SetCache.prototype.push = setCacheAdd;
-    SetCache.prototype.has = setCacheHas;
+    window.RTCPeerConnection.prototype.getStats = function() {
+      var promises = [];
+      this.transceivers.forEach(function(transceiver) {
+        ['rtpSender', 'rtpReceiver', 'iceGatherer', 'iceTransport',
+            'dtlsTransport'].forEach(function(method) {
+              if (transceiver[method]) {
+                promises.push(transceiver[method].getStats());
+              }
+            });
+      });
+      var cb = arguments.length > 1 && typeof arguments[1] === 'function' &&
+          arguments[1];
+      return new Promise(function(resolve) {
+        // shim getStats with maplike support
+        var results = new Map();
+        Promise.all(promises).then(function(res) {
+          res.forEach(function(result) {
+            Object.keys(result).forEach(function(id) {
+              results.set(id, result[id]);
+              results[id] = result[id];
+            });
+          });
+          if (cb) {
+            window.setTimeout(cb, 0, results);
+          }
+          resolve(results);
+        });
+      });
+    };
+  }
+};
 
-    /*------------------------------------------------------------------------*/
+// Expose public methods.
+module.exports = {
+  shimPeerConnection: edgeShim.shimPeerConnection,
+  shimGetUserMedia: require('./getusermedia')
+};
 
-    /**
-     * Creates a stack cache object to store key-value pairs.
-     *
-     * @private
-     * @constructor
-     * @param {Array} [entries] The key-value pairs to cache.
-     */
-    function Stack(entries) {
-      this.__data__ = new ListCache(entries);
-    }
+},{"../utils":15,"./getusermedia":11,"sdp":6}],11:[function(require,module,exports){
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree.
+ */
+ /* eslint-env node */
+'use strict';
 
-    /**
-     * Removes all key-value entries from the stack.
-     *
-     * @private
-     * @name clear
-     * @memberOf Stack
-     */
-    function stackClear() {
-      this.__data__ = new ListCache;
-    }
+// Expose public methods.
+module.exports = function() {
+  var shimError_ = function(e) {
+    return {
+      name: {PermissionDeniedError: 'NotAllowedError'}[e.name] || e.name,
+      message: e.message,
+      constraint: e.constraint,
+      toString: function() {
+        return this.name;
+      }
+    };
+  };
 
-    /**
-     * Removes `key` and its value from the stack.
-     *
-     * @private
-     * @name delete
-     * @memberOf Stack
-     * @param {string} key The key of the value to remove.
-     * @returns {boolean} Returns `true` if the entry was removed, else `false`.
-     */
-    function stackDelete(key) {
-      return this.__data__['delete'](key);
-    }
+  // getUserMedia error shim.
+  var origGetUserMedia = navigator.mediaDevices.getUserMedia.
+      bind(navigator.mediaDevices);
+  navigator.mediaDevices.getUserMedia = function(c) {
+    return origGetUserMedia(c).catch(function(e) {
+      return Promise.reject(shimError_(e));
+    });
+  };
+};
 
-    /**
-     * Gets the stack value for `key`.
-     *
-     * @private
-     * @name get
-     * @memberOf Stack
-     * @param {string} key The key of the value to get.
-     * @returns {*} Returns the entry value.
-     */
-    function stackGet(key) {
-      return this.__data__.get(key);
-    }
+},{}],12:[function(require,module,exports){
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree.
+ */
+ /* eslint-env node */
+'use strict';
 
-    /**
-     * Checks if a stack value for `key` exists.
-     *
-     * @private
-     * @name has
-     * @memberOf Stack
-     * @param {string} key The key of the entry to check.
-     * @returns {boolean} Returns `true` if an entry for `key` exists, else `false`.
-     */
-    function stackHas(key) {
-      return this.__data__.has(key);
+var browserDetails = require('../utils').browserDetails;
+
+var firefoxShim = {
+  shimOnTrack: function() {
+    if (typeof window === 'object' && window.RTCPeerConnection && !('ontrack' in
+        window.RTCPeerConnection.prototype)) {
+      Object.defineProperty(window.RTCPeerConnection.prototype, 'ontrack', {
+        get: function() {
+          return this._ontrack;
+        },
+        set: function(f) {
+          if (this._ontrack) {
+            this.removeEventListener('track', this._ontrack);
+            this.removeEventListener('addstream', this._ontrackpoly);
+          }
+          this.addEventListener('track', this._ontrack = f);
+          this.addEventListener('addstream', this._ontrackpoly = function(e) {
+            e.stream.getTracks().forEach(function(track) {
+              var event = new Event('track');
+              event.track = track;
+              event.receiver = {track: track};
+              event.streams = [e.stream];
+              this.dispatchEvent(event);
+            }.bind(this));
+          }.bind(this));
+        }
+      });
     }
+  },
 
-    /**
-     * Sets the stack `key` to `value`.
-     *
-     * @private
-     * @name set
-     * @memberOf Stack
-     * @param {string} key The key of the value to set.
-     * @param {*} value The value to set.
-     * @returns {Object} Returns the stack cache instance.
-     */
-    function stackSet(key, value) {
-      var cache = this.__data__;
-      if (cache instanceof ListCache && cache.__data__.length == LARGE_ARRAY_SIZE) {
-        cache = this.__data__ = new MapCache(cache.__data__);
+  shimSourceObject: function() {
+    // Firefox has supported mozSrcObject since FF22, unprefixed in 42.
+    if (typeof window === 'object') {
+      if (window.HTMLMediaElement &&
+        !('srcObject' in window.HTMLMediaElement.prototype)) {
+        // Shim the srcObject property, once, when HTMLMediaElement is found.
+        Object.defineProperty(window.HTMLMediaElement.prototype, 'srcObject', {
+          get: function() {
+            return this.mozSrcObject;
+          },
+          set: function(stream) {
+            this.mozSrcObject = stream;
+          }
+        });
       }
-      cache.set(key, value);
-      return this;
     }
+  },
 
-    // Add methods to `Stack`.
-    Stack.prototype.clear = stackClear;
-    Stack.prototype['delete'] = stackDelete;
-    Stack.prototype.get = stackGet;
-    Stack.prototype.has = stackHas;
-    Stack.prototype.set = stackSet;
-
-    /*------------------------------------------------------------------------*/
-
-    /**
-     * Used by `_.defaults` to customize its `_.assignIn` use.
-     *
-     * @private
-     * @param {*} objValue The destination value.
-     * @param {*} srcValue The source value.
-     * @param {string} key The key of the property to assign.
-     * @param {Object} object The parent object of `objValue`.
-     * @returns {*} Returns the value to assign.
-     */
-    function assignInDefaults(objValue, srcValue, key, object) {
-      if (objValue === undefined ||
-          (eq(objValue, objectProto[key]) && !hasOwnProperty.call(object, key))) {
-        return srcValue;
-      }
-      return objValue;
+  shimPeerConnection: function() {
+    if (typeof window !== 'object' || !(window.RTCPeerConnection ||
+        window.mozRTCPeerConnection)) {
+      return; // probably media.peerconnection.enabled=false in about:config
     }
+    // The RTCPeerConnection object.
+    if (!window.RTCPeerConnection) {
+      window.RTCPeerConnection = function(pcConfig, pcConstraints) {
+        if (browserDetails.version < 38) {
+          // .urls is not supported in FF < 38.
+          // create RTCIceServers with a single url.
+          if (pcConfig && pcConfig.iceServers) {
+            var newIceServers = [];
+            for (var i = 0; i < pcConfig.iceServers.length; i++) {
+              var server = pcConfig.iceServers[i];
+              if (server.hasOwnProperty('urls')) {
+                for (var j = 0; j < server.urls.length; j++) {
+                  var newServer = {
+                    url: server.urls[j]
+                  };
+                  if (server.urls[j].indexOf('turn') === 0) {
+                    newServer.username = server.username;
+                    newServer.credential = server.credential;
+                  }
+                  newIceServers.push(newServer);
+                }
+              } else {
+                newIceServers.push(pcConfig.iceServers[i]);
+              }
+            }
+            pcConfig.iceServers = newIceServers;
+          }
+        }
+        return new mozRTCPeerConnection(pcConfig, pcConstraints);
+      };
+      window.RTCPeerConnection.prototype = mozRTCPeerConnection.prototype;
 
-    /**
-     * This function is like `assignValue` except that it doesn't assign
-     * `undefined` values.
-     *
-     * @private
-     * @param {Object} object The object to modify.
-     * @param {string} key The key of the property to assign.
-     * @param {*} value The value to assign.
-     */
-    function assignMergeValue(object, key, value) {
-      if ((value !== undefined && !eq(object[key], value)) ||
-          (typeof key == 'number' && value === undefined && !(key in object))) {
-        object[key] = value;
+      // wrap static methods. Currently just generateCertificate.
+      if (mozRTCPeerConnection.generateCertificate) {
+        Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
+          get: function() {
+            return mozRTCPeerConnection.generateCertificate;
+          }
+        });
       }
-    }
 
-    /**
-     * Assigns `value` to `key` of `object` if the existing value is not equivalent
-     * using [`SameValueZero`](http://ecma-international.org/ecma-262/6.0/#sec-samevaluezero)
-     * for equality comparisons.
-     *
-     * @private
-     * @param {Object} object The object to modify.
-     * @param {string} key The key of the property to assign.
-     * @param {*} value The value to assign.
-     */
-    function assignValue(object, key, value) {
-      var objValue = object[key];
-      if (!(hasOwnProperty.call(object, key) && eq(objValue, value)) ||
-          (value === undefined && !(key in object))) {
-        object[key] = value;
-      }
+      window.RTCSessionDescription = mozRTCSessionDescription;
+      window.RTCIceCandidate = mozRTCIceCandidate;
     }
 
-    /**
-     * Gets the index at which the `key` is found in `array` of key-value pairs.
-     *
-     * @private
-     * @param {Array} array The array to search.
-     * @param {*} key The key to search for.
-     * @returns {number} Returns the index of the matched value, else `-1`.
-     */
-    function assocIndexOf(array, key) {
-      var length = array.length;
-      while (length--) {
-        if (eq(array[length][0], key)) {
-          return length;
+    // shim away need for obsolete RTCIceCandidate/RTCSessionDescription.
+    ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate']
+        .forEach(function(method) {
+          var nativeMethod = RTCPeerConnection.prototype[method];
+          RTCPeerConnection.prototype[method] = function() {
+            arguments[0] = new ((method === 'addIceCandidate') ?
+                RTCIceCandidate : RTCSessionDescription)(arguments[0]);
+            return nativeMethod.apply(this, arguments);
+          };
+        });
+
+    // support for addIceCandidate(null or undefined)
+    var nativeAddIceCandidate =
+        RTCPeerConnection.prototype.addIceCandidate;
+    RTCPeerConnection.prototype.addIceCandidate = function() {
+      if (!arguments[0]) {
+        if (arguments[1]) {
+          arguments[1].apply(null);
         }
+        return Promise.resolve();
       }
-      return -1;
-    }
+      return nativeAddIceCandidate.apply(this, arguments);
+    };
 
-    /**
-     * Aggregates elements of `collection` on `accumulator` with keys transformed
-     * by `iteratee` and values set by `setter`.
-     *
-     * @private
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Function} setter The function to set `accumulator` values.
-     * @param {Function} iteratee The iteratee to transform keys.
-     * @param {Object} accumulator The initial aggregated object.
-     * @returns {Function} Returns `accumulator`.
-     */
-    function baseAggregator(collection, setter, iteratee, accumulator) {
-      baseEach(collection, function(value, key, collection) {
-        setter(accumulator, value, iteratee(value), collection);
-      });
-      return accumulator;
-    }
+    if (browserDetails.version < 48) {
+      // shim getStats with maplike support
+      var makeMapStats = function(stats) {
+        var map = new Map();
+        Object.keys(stats).forEach(function(key) {
+          map.set(key, stats[key]);
+          map[key] = stats[key];
+        });
+        return map;
+      };
 
-    /**
-     * The base implementation of `_.assign` without support for multiple sources
-     * or `customizer` functions.
-     *
-     * @private
-     * @param {Object} object The destination object.
-     * @param {Object} source The source object.
-     * @returns {Object} Returns `object`.
-     */
-    function baseAssign(object, source) {
-      return object && copyObject(source, keys(source), object);
+      var nativeGetStats = RTCPeerConnection.prototype.getStats;
+      RTCPeerConnection.prototype.getStats = function(selector, onSucc, onErr) {
+        return nativeGetStats.apply(this, [selector || null])
+          .then(function(stats) {
+            return makeMapStats(stats);
+          })
+          .then(onSucc, onErr);
+      };
     }
+  }
+};
 
-    /**
-     * The base implementation of `_.at` without support for individual paths.
-     *
-     * @private
-     * @param {Object} object The object to iterate over.
-     * @param {string[]} paths The property paths of elements to pick.
-     * @returns {Array} Returns the picked elements.
-     */
-    function baseAt(object, paths) {
-      var index = -1,
-          isNil = object == null,
-          length = paths.length,
-          result = Array(length);
+// Expose public methods.
+module.exports = {
+  shimOnTrack: firefoxShim.shimOnTrack,
+  shimSourceObject: firefoxShim.shimSourceObject,
+  shimPeerConnection: firefoxShim.shimPeerConnection,
+  shimGetUserMedia: require('./getusermedia')
+};
 
-      while (++index < length) {
-        result[index] = isNil ? undefined : get(object, paths[index]);
-      }
-      return result;
-    }
+},{"../utils":15,"./getusermedia":13}],13:[function(require,module,exports){
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree.
+ */
+ /* eslint-env node */
+'use strict';
 
-    /**
-     * The base implementation of `_.clamp` which doesn't coerce arguments to numbers.
-     *
-     * @private
-     * @param {number} number The number to clamp.
-     * @param {number} [lower] The lower bound.
-     * @param {number} upper The upper bound.
-     * @returns {number} Returns the clamped number.
-     */
-    function baseClamp(number, lower, upper) {
-      if (number === number) {
-        if (upper !== undefined) {
-          number = number <= upper ? number : upper;
-        }
-        if (lower !== undefined) {
-          number = number >= lower ? number : lower;
-        }
-      }
-      return number;
-    }
+var logging = require('../utils').log;
+var browserDetails = require('../utils').browserDetails;
 
-    /**
-     * The base implementation of `_.clone` and `_.cloneDeep` which tracks
-     * traversed objects.
-     *
-     * @private
-     * @param {*} value The value to clone.
-     * @param {boolean} [isDeep] Specify a deep clone.
-     * @param {boolean} [isFull] Specify a clone including symbols.
-     * @param {Function} [customizer] The function to customize cloning.
-     * @param {string} [key] The key of `value`.
-     * @param {Object} [object] The parent object of `value`.
-     * @param {Object} [stack] Tracks traversed objects and their clone counterparts.
-     * @returns {*} Returns the cloned value.
-     */
-    function baseClone(value, isDeep, isFull, customizer, key, object, stack) {
-      var result;
-      if (customizer) {
-        result = object ? customizer(value, key, object, stack) : customizer(value);
-      }
-      if (result !== undefined) {
-        return result;
+// Expose public methods.
+module.exports = function() {
+  var shimError_ = function(e) {
+    return {
+      name: {
+        SecurityError: 'NotAllowedError',
+        PermissionDeniedError: 'NotAllowedError'
+      }[e.name] || e.name,
+      message: {
+        'The operation is insecure.': 'The request is not allowed by the ' +
+        'user agent or the platform in the current context.'
+      }[e.message] || e.message,
+      constraint: e.constraint,
+      toString: function() {
+        return this.name + (this.message && ': ') + this.message;
       }
-      if (!isObject(value)) {
-        return value;
+    };
+  };
+
+  // getUserMedia constraints shim.
+  var getUserMedia_ = function(constraints, onSuccess, onError) {
+    var constraintsToFF37_ = function(c) {
+      if (typeof c !== 'object' || c.require) {
+        return c;
       }
-      var isArr = isArray(value);
-      if (isArr) {
-        result = initCloneArray(value);
-        if (!isDeep) {
-          return copyArray(value, result);
+      var require = [];
+      Object.keys(c).forEach(function(key) {
+        if (key === 'require' || key === 'advanced' || key === 'mediaSource') {
+          return;
         }
-      } else {
-        var tag = getTag(value),
-            isFunc = tag == funcTag || tag == genTag;
-
-        if (isBuffer(value)) {
-          return cloneBuffer(value, isDeep);
+        var r = c[key] = (typeof c[key] === 'object') ?
+            c[key] : {ideal: c[key]};
+        if (r.min !== undefined ||
+            r.max !== undefined || r.exact !== undefined) {
+          require.push(key);
         }
-        if (tag == objectTag || tag == argsTag || (isFunc && !object)) {
-          if (isHostObject(value)) {
-            return object ? value : {};
+        if (r.exact !== undefined) {
+          if (typeof r.exact === 'number') {
+            r. min = r.max = r.exact;
+          } else {
+            c[key] = r.exact;
           }
-          result = initCloneObject(isFunc ? {} : value);
-          if (!isDeep) {
-            return copySymbols(value, baseAssign(result, value));
+          delete r.exact;
+        }
+        if (r.ideal !== undefined) {
+          c.advanced = c.advanced || [];
+          var oc = {};
+          if (typeof r.ideal === 'number') {
+            oc[key] = {min: r.ideal, max: r.ideal};
+          } else {
+            oc[key] = r.ideal;
           }
-        } else {
-          if (!cloneableTags[tag]) {
-            return object ? value : {};
+          c.advanced.push(oc);
+          delete r.ideal;
+          if (!Object.keys(r).length) {
+            delete c[key];
           }
-          result = initCloneByTag(value, tag, baseClone, isDeep);
         }
+      });
+      if (require.length) {
+        c.require = require;
       }
-      // Check for circular references and return its corresponding clone.
-      stack || (stack = new Stack);
-      var stacked = stack.get(value);
-      if (stacked) {
-        return stacked;
+      return c;
+    };
+    constraints = JSON.parse(JSON.stringify(constraints));
+    if (browserDetails.version < 38) {
+      logging('spec: ' + JSON.stringify(constraints));
+      if (constraints.audio) {
+        constraints.audio = constraintsToFF37_(constraints.audio);
       }
-      stack.set(value, result);
-
-      if (!isArr) {
-        var props = isFull ? getAllKeys(value) : keys(value);
+      if (constraints.video) {
+        constraints.video = constraintsToFF37_(constraints.video);
       }
-      // Recursively populate clone (susceptible to call stack limits).
-      arrayEach(props || value, function(subValue, key) {
-        if (props) {
-          key = subValue;
-          subValue = value[key];
-        }
-        assignValue(result, key, baseClone(subValue, isDeep, isFull, customizer, key, value, stack));
-      });
-      return result;
+      logging('ff37: ' + JSON.stringify(constraints));
     }
+    return navigator.mozGetUserMedia(constraints, onSuccess, function(e) {
+      onError(shimError_(e));
+    });
+  };
 
-    /**
-     * The base implementation of `_.conforms` which doesn't clone `source`.
-     *
-     * @private
-     * @param {Object} source The object of property predicates to conform to.
-     * @returns {Function} Returns the new spec function.
-     */
-    function baseConforms(source) {
-      var props = keys(source),
-          length = props.length;
+  // Returns the result of getUserMedia as a Promise.
+  var getUserMediaPromise_ = function(constraints) {
+    return new Promise(function(resolve, reject) {
+      getUserMedia_(constraints, resolve, reject);
+    });
+  };
 
-      return function(object) {
-        if (object == null) {
-          return !length;
-        }
-        var index = length;
-        while (index--) {
-          var key = props[index],
-              predicate = source[key],
-              value = object[key];
+  // Shim for mediaDevices on older versions.
+  if (!navigator.mediaDevices) {
+    navigator.mediaDevices = {getUserMedia: getUserMediaPromise_,
+      addEventListener: function() { },
+      removeEventListener: function() { }
+    };
+  }
+  navigator.mediaDevices.enumerateDevices =
+      navigator.mediaDevices.enumerateDevices || function() {
+        return new Promise(function(resolve) {
+          var infos = [
+            {kind: 'audioinput', deviceId: 'default', label: '', groupId: ''},
+            {kind: 'videoinput', deviceId: 'default', label: '', groupId: ''}
+          ];
+          resolve(infos);
+        });
+      };
 
-          if ((value === undefined &&
-              !(key in Object(object))) || !predicate(value)) {
-            return false;
-          }
+  if (browserDetails.version < 41) {
+    // Work around http://bugzil.la/1169665
+    var orgEnumerateDevices =
+        navigator.mediaDevices.enumerateDevices.bind(navigator.mediaDevices);
+    navigator.mediaDevices.enumerateDevices = function() {
+      return orgEnumerateDevices().then(undefined, function(e) {
+        if (e.name === 'NotFoundError') {
+          return [];
         }
-        return true;
-      };
+        throw e;
+      });
+    };
+  }
+  if (browserDetails.version < 49) {
+    var origGetUserMedia = navigator.mediaDevices.getUserMedia.
+        bind(navigator.mediaDevices);
+    navigator.mediaDevices.getUserMedia = function(c) {
+      return origGetUserMedia(c).then(function(stream) {
+        // Work around https://bugzil.la/802326
+        if (c.audio && !stream.getAudioTracks().length ||
+            c.video && !stream.getVideoTracks().length) {
+          stream.getTracks().forEach(function(track) {
+            track.stop();
+          });
+          throw new DOMException('The object can not be found here.',
+                                 'NotFoundError');
+        }
+        return stream;
+      }, function(e) {
+        return Promise.reject(shimError_(e));
+      });
+    };
+  }
+  navigator.getUserMedia = function(constraints, onSuccess, onError) {
+    if (browserDetails.version < 44) {
+      return getUserMedia_(constraints, onSuccess, onError);
     }
+    // Replace Firefox 44+'s deprecation warning with unprefixed version.
+    console.warn('navigator.getUserMedia has been replaced by ' +
+                 'navigator.mediaDevices.getUserMedia');
+    navigator.mediaDevices.getUserMedia(constraints).then(onSuccess, onError);
+  };
+};
 
-    /**
-     * The base implementation of `_.create` without support for assigning
-     * properties to the created object.
-     *
-     * @private
-     * @param {Object} prototype The object to inherit from.
-     * @returns {Object} Returns the new object.
-     */
-    function baseCreate(proto) {
-      return isObject(proto) ? objectCreate(proto) : {};
-    }
+},{"../utils":15}],14:[function(require,module,exports){
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree.
+ */
+'use strict';
+var safariShim = {
+  // TODO: DrAlex, should be here, double check against LayoutTests
+  // shimOnTrack: function() { },
 
-    /**
-     * The base implementation of `_.delay` and `_.defer` which accepts an array
-     * of `func` arguments.
-     *
-     * @private
-     * @param {Function} func The function to delay.
-     * @param {number} wait The number of milliseconds to delay invocation.
-     * @param {Object} args The arguments to provide to `func`.
-     * @returns {number} Returns the timer id.
-     */
-    function baseDelay(func, wait, args) {
-      if (typeof func != 'function') {
-        throw new TypeError(FUNC_ERROR_TEXT);
-      }
-      return setTimeout(function() { func.apply(undefined, args); }, wait);
-    }
+  // TODO: once the back-end for the mac port is done, add.
+  // TODO: check for webkitGTK+
+  // shimPeerConnection: function() { },
 
-    /**
-     * The base implementation of methods like `_.difference` without support
-     * for excluding multiple arrays or iteratee shorthands.
-     *
-     * @private
-     * @param {Array} array The array to inspect.
-     * @param {Array} values The values to exclude.
-     * @param {Function} [iteratee] The iteratee invoked per element.
-     * @param {Function} [comparator] The comparator invoked per element.
-     * @returns {Array} Returns the new array of filtered values.
-     */
-    function baseDifference(array, values, iteratee, comparator) {
-      var index = -1,
-          includes = arrayIncludes,
-          isCommon = true,
-          length = array.length,
-          result = [],
-          valuesLength = values.length;
+  shimGetUserMedia: function() {
+    navigator.getUserMedia = navigator.webkitGetUserMedia;
+  }
+};
 
-      if (!length) {
-        return result;
-      }
-      if (iteratee) {
-        values = arrayMap(values, baseUnary(iteratee));
-      }
-      if (comparator) {
-        includes = arrayIncludesWith;
-        isCommon = false;
-      }
-      else if (values.length >= LARGE_ARRAY_SIZE) {
-        includes = cacheHas;
-        isCommon = false;
-        values = new SetCache(values);
-      }
-      outer:
-      while (++index < length) {
-        var value = array[index],
-            computed = iteratee ? iteratee(value) : value;
+// Expose public methods.
+module.exports = {
+  shimGetUserMedia: safariShim.shimGetUserMedia
+  // TODO
+  // shimOnTrack: safariShim.shimOnTrack,
+  // shimPeerConnection: safariShim.shimPeerConnection
+};
 
-        value = (comparator || value !== 0) ? value : 0;
-        if (isCommon && computed === computed) {
-          var valuesIndex = valuesLength;
-          while (valuesIndex--) {
-            if (values[valuesIndex] === computed) {
-              continue outer;
-            }
-          }
-          result.push(value);
-        }
-        else if (!includes(values, computed, comparator)) {
-          result.push(value);
-        }
-      }
-      return result;
-    }
+},{}],15:[function(require,module,exports){
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree.
+ */
+ /* eslint-env node */
+'use strict';
 
-    /**
-     * The base implementation of `_.forEach` without support for iteratee shorthands.
-     *
-     * @private
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Function} iteratee The function invoked per iteration.
-     * @returns {Array|Object} Returns `collection`.
-     */
-    var baseEach = createBaseEach(baseForOwn);
+var logDisabled_ = true;
 
-    /**
-     * The base implementation of `_.forEachRight` without support for iteratee shorthands.
-     *
-     * @private
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Function} iteratee The function invoked per iteration.
-     * @returns {Array|Object} Returns `collection`.
-     */
-    var baseEachRight = createBaseEach(baseForOwnRight, true);
-
-    /**
-     * The base implementation of `_.every` without support for iteratee shorthands.
-     *
-     * @private
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Function} predicate The function invoked per iteration.
-     * @returns {boolean} Returns `true` if all elements pass the predicate check,
-     *  else `false`
-     */
-    function baseEvery(collection, predicate) {
-      var result = true;
-      baseEach(collection, function(value, index, collection) {
-        result = !!predicate(value, index, collection);
-        return result;
-      });
-      return result;
+// Utility methods.
+var utils = {
+  disableLog: function(bool) {
+    if (typeof bool !== 'boolean') {
+      return new Error('Argument type: ' + typeof bool +
+          '. Please use a boolean.');
     }
+    logDisabled_ = bool;
+    return (bool) ? 'adapter.js logging disabled' :
+        'adapter.js logging enabled';
+  },
 
-    /**
-     * The base implementation of methods like `_.max` and `_.min` which accepts a
-     * `comparator` to determine the extremum value.
-     *
-     * @private
-     * @param {Array} array The array to iterate over.
-     * @param {Function} iteratee The iteratee invoked per iteration.
-     * @param {Function} comparator The comparator used to compare values.
-     * @returns {*} Returns the extremum value.
-     */
-    function baseExtremum(array, iteratee, comparator) {
-      var index = -1,
-          length = array.length;
-
-      while (++index < length) {
-        var value = array[index],
-            current = iteratee(value);
-
-        if (current != null && (computed === undefined
-              ? (current === current && !isSymbol(current))
-              : comparator(current, computed)
-            )) {
-          var computed = current,
-              result = value;
-        }
+  log: function() {
+    if (typeof window === 'object') {
+      if (logDisabled_) {
+        return;
+      }
+      if (typeof console !== 'undefined' && typeof console.log === 'function') {
+        console.log.apply(console, arguments);
       }
-      return result;
     }
+  },
 
-    /**
-     * The base implementation of `_.fill` without an iteratee call guard.
-     *
-     * @private
-     * @param {Array} array The array to fill.
-     * @param {*} value The value to fill `array` with.
-     * @param {number} [start=0] The start position.
-     * @param {number} [end=array.length] The end position.
-     * @returns {Array} Returns `array`.
-     */
-    function baseFill(array, value, start, end) {
-      var length = array.length;
+  /**
+   * Extract browser version out of the provided user agent string.
+   *
+   * @param {!string} uastring userAgent string.
+   * @param {!string} expr Regular expression used as match criteria.
+   * @param {!number} pos position in the version string to be returned.
+   * @return {!number} browser version.
+   */
+  extractVersion: function(uastring, expr, pos) {
+    var match = uastring.match(expr);
+    return match && match.length >= pos && parseInt(match[pos], 10);
+  },
 
-      start = toInteger(start);
-      if (start < 0) {
-        start = -start > length ? 0 : (length + start);
-      }
-      end = (end === undefined || end > length) ? length : toInteger(end);
-      if (end < 0) {
-        end += length;
-      }
-      end = start > end ? 0 : toLength(end);
-      while (start < end) {
-        array[start++] = value;
-      }
-      return array;
-    }
+  /**
+   * Browser detector.
+   *
+   * @return {object} result containing browser and version
+   *     properties.
+   */
+  detectBrowser: function() {
+    // Returned result object.
+    var result = {};
+    result.browser = null;
+    result.version = null;
 
-    /**
-     * The base implementation of `_.filter` without support for iteratee shorthands.
-     *
-     * @private
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Function} predicate The function invoked per iteration.
-     * @returns {Array} Returns the new filtered array.
-     */
-    function baseFilter(collection, predicate) {
-      var result = [];
-      baseEach(collection, function(value, index, collection) {
-        if (predicate(value, index, collection)) {
-          result.push(value);
-        }
-      });
+    // Fail early if it's not a browser
+    if (typeof window === 'undefined' || !window.navigator) {
+      result.browser = 'Not a browser.';
       return result;
     }
 
-    /**
-     * The base implementation of `_.flatten` with support for restricting flattening.
-     *
-     * @private
-     * @param {Array} array The array to flatten.
-     * @param {number} depth The maximum recursion depth.
-     * @param {boolean} [predicate=isFlattenable] The function invoked per iteration.
-     * @param {boolean} [isStrict] Restrict to values that pass `predicate` checks.
-     * @param {Array} [result=[]] The initial result value.
-     * @returns {Array} Returns the new flattened array.
-     */
-    function baseFlatten(array, depth, predicate, isStrict, result) {
-      var index = -1,
-          length = array.length;
+    // Firefox.
+    if (navigator.mozGetUserMedia) {
+      result.browser = 'firefox';
+      result.version = this.extractVersion(navigator.userAgent,
+          /Firefox\/([0-9]+)\./, 1);
 
-      predicate || (predicate = isFlattenable);
-      result || (result = []);
+    // all webkit-based browsers
+    } else if (navigator.webkitGetUserMedia) {
+      // Chrome, Chromium, Webview, Opera, all use the chrome shim for now
+      if (window.webkitRTCPeerConnection) {
+        result.browser = 'chrome';
+        result.version = this.extractVersion(navigator.userAgent,
+          /Chrom(e|ium)\/([0-9]+)\./, 2);
 
-      while (++index < length) {
-        var value = array[index];
-        if (depth > 0 && predicate(value)) {
-          if (depth > 1) {
-            // Recursively flatten arrays (susceptible to call stack limits).
-            baseFlatten(value, depth - 1, predicate, isStrict, result);
-          } else {
-            arrayPush(result, value);
-          }
-        } else if (!isStrict) {
-          result[result.length] = value;
+      // Safari or unknown webkit-based
+      // for the time being Safari has support for MediaStreams but not webRTC
+      } else {
+        // Safari UA substrings of interest for reference:
+        // - webkit version:           AppleWebKit/602.1.25 (also used in Op,Cr)
+        // - safari UI version:        Version/9.0.3 (unique to Safari)
+        // - safari UI webkit version: Safari/601.4.4 (also used in Op,Cr)
+        //
+        // if the webkit version and safari UI webkit versions are equals,
+        // ... this is a stable version.
+        //
+        // only the internal webkit version is important today to know if
+        // media streams are supported
+        //
+        if (navigator.userAgent.match(/Version\/(\d+).(\d+)/)) {
+          result.browser = 'safari';
+          result.version = this.extractVersion(navigator.userAgent,
+            /AppleWebKit\/([0-9]+)\./, 1);
+
+        // unknown webkit-based browser
+        } else {
+          result.browser = 'Unsupported webkit-based browser ' +
+              'with GUM support but no WebRTC support.';
+          return result;
         }
       }
-      return result;
-    }
-
-    /**
-     * The base implementation of `baseForOwn` which iterates over `object`
-     * properties returned by `keysFunc` and invokes `iteratee` for each property.
-     * Iteratee functions may exit iteration early by explicitly returning `false`.
-     *
-     * @private
-     * @param {Object} object The object to iterate over.
-     * @param {Function} iteratee The function invoked per iteration.
-     * @param {Function} keysFunc The function to get the keys of `object`.
-     * @returns {Object} Returns `object`.
-     */
-    var baseFor = createBaseFor();
 
-    /**
-     * This function is like `baseFor` except that it iterates over properties
-     * in the opposite order.
-     *
-     * @private
-     * @param {Object} object The object to iterate over.
-     * @param {Function} iteratee The function invoked per iteration.
-     * @param {Function} keysFunc The function to get the keys of `object`.
-     * @returns {Object} Returns `object`.
-     */
-    var baseForRight = createBaseFor(true);
+    // Edge.
+    } else if (navigator.mediaDevices &&
+        navigator.userAgent.match(/Edge\/(\d+).(\d+)$/)) {
+      result.browser = 'edge';
+      result.version = this.extractVersion(navigator.userAgent,
+          /Edge\/(\d+).(\d+)$/, 2);
 
-    /**
-     * The base implementation of `_.forOwn` without support for iteratee shorthands.
-     *
-     * @private
-     * @param {Object} object The object to iterate over.
-     * @param {Function} iteratee The function invoked per iteration.
-     * @returns {Object} Returns `object`.
-     */
-    function baseForOwn(object, iteratee) {
-      return object && baseFor(object, iteratee, keys);
+    // Default fallthrough: not supported.
+    } else {
+      result.browser = 'Not a supported browser.';
+      return result;
     }
 
-    /**
-     * The base implementation of `_.forOwnRight` without support for iteratee shorthands.
-     *
-     * @private
-     * @param {Object} object The object to iterate over.
-     * @param {Function} iteratee The function invoked per iteration.
-     * @returns {Object} Returns `object`.
-     */
-    function baseForOwnRight(object, iteratee) {
-      return object && baseForRight(object, iteratee, keys);
-    }
+    return result;
+  }
+};
 
-    /**
-     * The base implementation of `_.functions` which creates an array of
-     * `object` function property names filtered from `props`.
-     *
-     * @private
-     * @param {Object} object The object to inspect.
-     * @param {Array} props The property names to filter.
-     * @returns {Array} Returns the function names.
-     */
-    function baseFunctions(object, props) {
-      return arrayFilter(props, function(key) {
-        return isFunction(object[key]);
-      });
-    }
+// Export.
+module.exports = {
+  log: utils.log,
+  disableLog: utils.disableLog,
+  browserDetails: utils.detectBrowser(),
+  extractVersion: utils.extractVersion
+};
 
-    /**
-     * The base implementation of `_.get` without support for default values.
-     *
-     * @private
-     * @param {Object} object The object to query.
-     * @param {Array|string} path The path of the property to get.
-     * @returns {*} Returns the resolved value.
-     */
-    function baseGet(object, path) {
-      path = isKey(path, object) ? [path] : castPath(path);
+},{}],16:[function(require,module,exports){
+(function (global){
+/**
+ * @license
+ * Lodash <https://lodash.com/>
+ * Copyright JS Foundation and other contributors <https://js.foundation/>
+ * Released under MIT license <https://lodash.com/license>
+ * Based on Underscore.js 1.8.3 <http://underscorejs.org/LICENSE>
+ * Copyright Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
+ */
+;(function() {
 
-      var index = 0,
-          length = path.length;
+  /** Used as a safe reference for `undefined` in pre-ES5 environments. */
+  var undefined;
 
-      while (object != null && index < length) {
-        object = object[toKey(path[index++])];
-      }
-      return (index && index == length) ? object : undefined;
-    }
+  /** Used as the semantic version number. */
+  var VERSION = '4.17.11';
 
-    /**
-     * The base implementation of `getAllKeys` and `getAllKeysIn` which uses
-     * `keysFunc` and `symbolsFunc` to get the enumerable property names and
-     * symbols of `object`.
-     *
-     * @private
-     * @param {Object} object The object to query.
-     * @param {Function} keysFunc The function to get the keys of `object`.
-     * @param {Function} symbolsFunc The function to get the symbols of `object`.
-     * @returns {Array} Returns the array of property names and symbols.
-     */
-    function baseGetAllKeys(object, keysFunc, symbolsFunc) {
-      var result = keysFunc(object);
-      return isArray(object) ? result : arrayPush(result, symbolsFunc(object));
-    }
+  /** Used as the size to enable large array optimizations. */
+  var LARGE_ARRAY_SIZE = 200;
 
-    /**
-     * The base implementation of `_.gt` which doesn't coerce arguments to numbers.
-     *
-     * @private
-     * @param {*} value The value to compare.
-     * @param {*} other The other value to compare.
-     * @returns {boolean} Returns `true` if `value` is greater than `other`,
-     *  else `false`.
-     */
-    function baseGt(value, other) {
-      return value > other;
-    }
+  /** Error message constants. */
+  var CORE_ERROR_TEXT = 'Unsupported core-js use. Try https://npms.io/search?q=ponyfill.',
+      FUNC_ERROR_TEXT = 'Expected a function';
 
-    /**
-     * The base implementation of `_.has` without support for deep paths.
-     *
-     * @private
-     * @param {Object} [object] The object to query.
-     * @param {Array|string} key The key to check.
-     * @returns {boolean} Returns `true` if `key` exists, else `false`.
-     */
-    function baseHas(object, key) {
-      // Avoid a bug in IE 10-11 where objects with a [[Prototype]] of `null`,
-      // that are composed entirely of index properties, return `false` for
-      // `hasOwnProperty` checks of them.
-      return object != null &&
-        (hasOwnProperty.call(object, key) ||
-          (typeof object == 'object' && key in object && getPrototype(object) === null));
-    }
+  /** Used to stand-in for `undefined` hash values. */
+  var HASH_UNDEFINED = '__lodash_hash_undefined__';
 
-    /**
-     * The base implementation of `_.hasIn` without support for deep paths.
-     *
-     * @private
-     * @param {Object} [object] The object to query.
-     * @param {Array|string} key The key to check.
-     * @returns {boolean} Returns `true` if `key` exists, else `false`.
-     */
-    function baseHasIn(object, key) {
-      return object != null && key in Object(object);
-    }
+  /** Used as the maximum memoize cache size. */
+  var MAX_MEMOIZE_SIZE = 500;
 
-    /**
-     * The base implementation of `_.inRange` which doesn't coerce arguments to numbers.
-     *
-     * @private
-     * @param {number} number The number to check.
-     * @param {number} start The start of the range.
-     * @param {number} end The end of the range.
-     * @returns {boolean} Returns `true` if `number` is in the range, else `false`.
-     */
-    function baseInRange(number, start, end) {
-      return number >= nativeMin(start, end) && number < nativeMax(start, end);
-    }
+  /** Used as the internal argument placeholder. */
+  var PLACEHOLDER = '__lodash_placeholder__';
 
-    /**
-     * The base implementation of methods like `_.intersection`, without support
-     * for iteratee shorthands, that accepts an array of arrays to inspect.
-     *
-     * @private
-     * @param {Array} arrays The arrays to inspect.
-     * @param {Function} [iteratee] The iteratee invoked per element.
-     * @param {Function} [comparator] The comparator invoked per element.
-     * @returns {Array} Returns the new array of shared values.
-     */
-    function baseIntersection(arrays, iteratee, comparator) {
-      var includes = comparator ? arrayIncludesWith : arrayIncludes,
-          length = arrays[0].length,
-          othLength = arrays.length,
-          othIndex = othLength,
-          caches = Array(othLength),
-          maxLength = Infinity,
-          result = [];
+  /** Used to compose bitmasks for cloning. */
+  var CLONE_DEEP_FLAG = 1,
+      CLONE_FLAT_FLAG = 2,
+      CLONE_SYMBOLS_FLAG = 4;
+
+  /** Used to compose bitmasks for value comparisons. */
+  var COMPARE_PARTIAL_FLAG = 1,
+      COMPARE_UNORDERED_FLAG = 2;
+
+  /** Used to compose bitmasks for function metadata. */
+  var WRAP_BIND_FLAG = 1,
+      WRAP_BIND_KEY_FLAG = 2,
+      WRAP_CURRY_BOUND_FLAG = 4,
+      WRAP_CURRY_FLAG = 8,
+      WRAP_CURRY_RIGHT_FLAG = 16,
+      WRAP_PARTIAL_FLAG = 32,
+      WRAP_PARTIAL_RIGHT_FLAG = 64,
+      WRAP_ARY_FLAG = 128,
+      WRAP_REARG_FLAG = 256,
+      WRAP_FLIP_FLAG = 512;
 
-      while (othIndex--) {
-        var array = arrays[othIndex];
-        if (othIndex && iteratee) {
-          array = arrayMap(array, baseUnary(iteratee));
-        }
-        maxLength = nativeMin(array.length, maxLength);
-        caches[othIndex] = !comparator && (iteratee || (length >= 120 && array.length >= 120))
-          ? new SetCache(othIndex && array)
-          : undefined;
-      }
-      array = arrays[0];
+  /** Used as default options for `_.truncate`. */
+  var DEFAULT_TRUNC_LENGTH = 30,
+      DEFAULT_TRUNC_OMISSION = '...';
 
-      var index = -1,
-          seen = caches[0];
+  /** Used to detect hot functions by number of calls within a span of milliseconds. */
+  var HOT_COUNT = 800,
+      HOT_SPAN = 16;
 
-      outer:
-      while (++index < length && result.length < maxLength) {
-        var value = array[index],
-            computed = iteratee ? iteratee(value) : value;
+  /** Used to indicate the type of lazy iteratees. */
+  var LAZY_FILTER_FLAG = 1,
+      LAZY_MAP_FLAG = 2,
+      LAZY_WHILE_FLAG = 3;
 
-        value = (comparator || value !== 0) ? value : 0;
-        if (!(seen
-              ? cacheHas(seen, computed)
-              : includes(result, computed, comparator)
-            )) {
-          othIndex = othLength;
-          while (--othIndex) {
-            var cache = caches[othIndex];
-            if (!(cache
-                  ? cacheHas(cache, computed)
-                  : includes(arrays[othIndex], computed, comparator))
-                ) {
-              continue outer;
-            }
-          }
-          if (seen) {
-            seen.push(computed);
-          }
-          result.push(value);
-        }
-      }
-      return result;
-    }
+  /** Used as references for various `Number` constants. */
+  var INFINITY = 1 / 0,
+      MAX_SAFE_INTEGER = 9007199254740991,
+      MAX_INTEGER = 1.7976931348623157e+308,
+      NAN = 0 / 0;
 
-    /**
-     * The base implementation of `_.invert` and `_.invertBy` which inverts
-     * `object` with values transformed by `iteratee` and set by `setter`.
-     *
-     * @private
-     * @param {Object} object The object to iterate over.
-     * @param {Function} setter The function to set `accumulator` values.
-     * @param {Function} iteratee The iteratee to transform values.
-     * @param {Object} accumulator The initial inverted object.
-     * @returns {Function} Returns `accumulator`.
-     */
-    function baseInverter(object, setter, iteratee, accumulator) {
-      baseForOwn(object, function(value, key, object) {
-        setter(accumulator, iteratee(value), key, object);
-      });
-      return accumulator;
-    }
+  /** Used as references for the maximum length and index of an array. */
+  var MAX_ARRAY_LENGTH = 4294967295,
+      MAX_ARRAY_INDEX = MAX_ARRAY_LENGTH - 1,
+      HALF_MAX_ARRAY_LENGTH = MAX_ARRAY_LENGTH >>> 1;
 
-    /**
-     * The base implementation of `_.invoke` without support for individual
-     * method arguments.
-     *
-     * @private
-     * @param {Object} object The object to query.
-     * @param {Array|string} path The path of the method to invoke.
-     * @param {Array} args The arguments to invoke the method with.
-     * @returns {*} Returns the result of the invoked method.
-     */
-    function baseInvoke(object, path, args) {
-      if (!isKey(path, object)) {
-        path = castPath(path);
-        object = parent(object, path);
-        path = last(path);
-      }
-      var func = object == null ? object : object[toKey(path)];
-      return func == null ? undefined : apply(func, object, args);
-    }
+  /** Used to associate wrap methods with their bit flags. */
+  var wrapFlags = [
+    ['ary', WRAP_ARY_FLAG],
+    ['bind', WRAP_BIND_FLAG],
+    ['bindKey', WRAP_BIND_KEY_FLAG],
+    ['curry', WRAP_CURRY_FLAG],
+    ['curryRight', WRAP_CURRY_RIGHT_FLAG],
+    ['flip', WRAP_FLIP_FLAG],
+    ['partial', WRAP_PARTIAL_FLAG],
+    ['partialRight', WRAP_PARTIAL_RIGHT_FLAG],
+    ['rearg', WRAP_REARG_FLAG]
+  ];
 
-    /**
-     * The base implementation of `_.isEqual` which supports partial comparisons
-     * and tracks traversed objects.
-     *
-     * @private
-     * @param {*} value The value to compare.
-     * @param {*} other The other value to compare.
-     * @param {Function} [customizer] The function to customize comparisons.
-     * @param {boolean} [bitmask] The bitmask of comparison flags.
-     *  The bitmask may be composed of the following flags:
-     *     1 - Unordered comparison
-     *     2 - Partial comparison
-     * @param {Object} [stack] Tracks traversed `value` and `other` objects.
-     * @returns {boolean} Returns `true` if the values are equivalent, else `false`.
-     */
-    function baseIsEqual(value, other, customizer, bitmask, stack) {
-      if (value === other) {
-        return true;
-      }
-      if (value == null || other == null || (!isObject(value) && !isObjectLike(other))) {
-        return value !== value && other !== other;
-      }
-      return baseIsEqualDeep(value, other, baseIsEqual, customizer, bitmask, stack);
-    }
+  /** `Object#toString` result references. */
+  var argsTag = '[object Arguments]',
+      arrayTag = '[object Array]',
+      asyncTag = '[object AsyncFunction]',
+      boolTag = '[object Boolean]',
+      dateTag = '[object Date]',
+      domExcTag = '[object DOMException]',
+      errorTag = '[object Error]',
+      funcTag = '[object Function]',
+      genTag = '[object GeneratorFunction]',
+      mapTag = '[object Map]',
+      numberTag = '[object Number]',
+      nullTag = '[object Null]',
+      objectTag = '[object Object]',
+      promiseTag = '[object Promise]',
+      proxyTag = '[object Proxy]',
+      regexpTag = '[object RegExp]',
+      setTag = '[object Set]',
+      stringTag = '[object String]',
+      symbolTag = '[object Symbol]',
+      undefinedTag = '[object Undefined]',
+      weakMapTag = '[object WeakMap]',
+      weakSetTag = '[object WeakSet]';
 
-    /**
-     * A specialized version of `baseIsEqual` for arrays and objects which performs
-     * deep comparisons and tracks traversed objects enabling objects with circular
-     * references to be compared.
-     *
-     * @private
-     * @param {Object} object The object to compare.
-     * @param {Object} other The other object to compare.
-     * @param {Function} equalFunc The function to determine equivalents of values.
-     * @param {Function} [customizer] The function to customize comparisons.
-     * @param {number} [bitmask] The bitmask of comparison flags. See `baseIsEqual`
-     *  for more details.
-     * @param {Object} [stack] Tracks traversed `object` and `other` objects.
-     * @returns {boolean} Returns `true` if the objects are equivalent, else `false`.
-     */
-    function baseIsEqualDeep(object, other, equalFunc, customizer, bitmask, stack) {
-      var objIsArr = isArray(object),
-          othIsArr = isArray(other),
-          objTag = arrayTag,
-          othTag = arrayTag;
-
-      if (!objIsArr) {
-        objTag = getTag(object);
-        objTag = objTag == argsTag ? objectTag : objTag;
-      }
-      if (!othIsArr) {
-        othTag = getTag(other);
-        othTag = othTag == argsTag ? objectTag : othTag;
-      }
-      var objIsObj = objTag == objectTag && !isHostObject(object),
-          othIsObj = othTag == objectTag && !isHostObject(other),
-          isSameTag = objTag == othTag;
+  var arrayBufferTag = '[object ArrayBuffer]',
+      dataViewTag = '[object DataView]',
+      float32Tag = '[object Float32Array]',
+      float64Tag = '[object Float64Array]',
+      int8Tag = '[object Int8Array]',
+      int16Tag = '[object Int16Array]',
+      int32Tag = '[object Int32Array]',
+      uint8Tag = '[object Uint8Array]',
+      uint8ClampedTag = '[object Uint8ClampedArray]',
+      uint16Tag = '[object Uint16Array]',
+      uint32Tag = '[object Uint32Array]';
 
-      if (isSameTag && !objIsObj) {
-        stack || (stack = new Stack);
-        return (objIsArr || isTypedArray(object))
-          ? equalArrays(object, other, equalFunc, customizer, bitmask, stack)
-          : equalByTag(object, other, objTag, equalFunc, customizer, bitmask, stack);
-      }
-      if (!(bitmask & PARTIAL_COMPARE_FLAG)) {
-        var objIsWrapped = objIsObj && hasOwnProperty.call(object, '__wrapped__'),
-            othIsWrapped = othIsObj && hasOwnProperty.call(other, '__wrapped__');
+  /** Used to match empty string literals in compiled template source. */
+  var reEmptyStringLeading = /\b__p \+= '';/g,
+      reEmptyStringMiddle = /\b(__p \+=) '' \+/g,
+      reEmptyStringTrailing = /(__e\(.*?\)|\b__t\)) \+\n'';/g;
 
-        if (objIsWrapped || othIsWrapped) {
-          var objUnwrapped = objIsWrapped ? object.value() : object,
-              othUnwrapped = othIsWrapped ? other.value() : other;
+  /** Used to match HTML entities and HTML characters. */
+  var reEscapedHtml = /&(?:amp|lt|gt|quot|#39);/g,
+      reUnescapedHtml = /[&<>"']/g,
+      reHasEscapedHtml = RegExp(reEscapedHtml.source),
+      reHasUnescapedHtml = RegExp(reUnescapedHtml.source);
 
-          stack || (stack = new Stack);
-          return equalFunc(objUnwrapped, othUnwrapped, customizer, bitmask, stack);
-        }
-      }
-      if (!isSameTag) {
-        return false;
-      }
-      stack || (stack = new Stack);
-      return equalObjects(object, other, equalFunc, customizer, bitmask, stack);
-    }
+  /** Used to match template delimiters. */
+  var reEscape = /<%-([\s\S]+?)%>/g,
+      reEvaluate = /<%([\s\S]+?)%>/g,
+      reInterpolate = /<%=([\s\S]+?)%>/g;
 
-    /**
-     * The base implementation of `_.isMatch` without support for iteratee shorthands.
-     *
-     * @private
-     * @param {Object} object The object to inspect.
-     * @param {Object} source The object of property values to match.
-     * @param {Array} matchData The property names, values, and compare flags to match.
-     * @param {Function} [customizer] The function to customize comparisons.
-     * @returns {boolean} Returns `true` if `object` is a match, else `false`.
-     */
-    function baseIsMatch(object, source, matchData, customizer) {
-      var index = matchData.length,
-          length = index,
-          noCustomizer = !customizer;
+  /** Used to match property names within property paths. */
+  var reIsDeepProp = /\.|\[(?:[^[\]]*|(["'])(?:(?!\1)[^\\]|\\.)*?\1)\]/,
+      reIsPlainProp = /^\w*$/,
+      rePropName = /[^.[\]]+|\[(?:(-?\d+(?:\.\d+)?)|(["'])((?:(?!\2)[^\\]|\\.)*?)\2)\]|(?=(?:\.|\[\])(?:\.|\[\]|$))/g;
 
-      if (object == null) {
-        return !length;
-      }
-      object = Object(object);
-      while (index--) {
-        var data = matchData[index];
-        if ((noCustomizer && data[2])
-              ? data[1] !== object[data[0]]
-              : !(data[0] in object)
-            ) {
-          return false;
-        }
-      }
-      while (++index < length) {
-        data = matchData[index];
-        var key = data[0],
-            objValue = object[key],
-            srcValue = data[1];
+  /**
+   * Used to match `RegExp`
+   * [syntax characters](http://ecma-international.org/ecma-262/7.0/#sec-patterns).
+   */
+  var reRegExpChar = /[\\^$.*+?()[\]{}|]/g,
+      reHasRegExpChar = RegExp(reRegExpChar.source);
 
-        if (noCustomizer && data[2]) {
-          if (objValue === undefined && !(key in object)) {
-            return false;
-          }
-        } else {
-          var stack = new Stack;
-          if (customizer) {
-            var result = customizer(objValue, srcValue, key, object, source, stack);
-          }
-          if (!(result === undefined
-                ? baseIsEqual(srcValue, objValue, customizer, UNORDERED_COMPARE_FLAG | PARTIAL_COMPARE_FLAG, stack)
-                : result
-              )) {
-            return false;
-          }
-        }
-      }
-      return true;
-    }
+  /** Used to match leading and trailing whitespace. */
+  var reTrim = /^\s+|\s+$/g,
+      reTrimStart = /^\s+/,
+      reTrimEnd = /\s+$/;
 
-    /**
-     * The base implementation of `_.isNative` without bad shim checks.
-     *
-     * @private
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is a native function,
-     *  else `false`.
-     */
-    function baseIsNative(value) {
-      if (!isObject(value) || isMasked(value)) {
-        return false;
-      }
-      var pattern = (isFunction(value) || isHostObject(value)) ? reIsNative : reIsHostCtor;
-      return pattern.test(toSource(value));
-    }
+  /** Used to match wrap detail comments. */
+  var reWrapComment = /\{(?:\n\/\* \[wrapped with .+\] \*\/)?\n?/,
+      reWrapDetails = /\{\n\/\* \[wrapped with (.+)\] \*/,
+      reSplitDetails = /,? & /;
 
-    /**
-     * The base implementation of `_.iteratee`.
-     *
-     * @private
-     * @param {*} [value=_.identity] The value to convert to an iteratee.
-     * @returns {Function} Returns the iteratee.
-     */
-    function baseIteratee(value) {
-      // Don't store the `typeof` result in a variable to avoid a JIT bug in Safari 9.
-      // See https://bugs.webkit.org/show_bug.cgi?id=156034 for more details.
-      if (typeof value == 'function') {
-        return value;
-      }
-      if (value == null) {
-        return identity;
-      }
-      if (typeof value == 'object') {
-        return isArray(value)
-          ? baseMatchesProperty(value[0], value[1])
-          : baseMatches(value);
-      }
-      return property(value);
-    }
+  /** Used to match words composed of alphanumeric characters. */
+  var reAsciiWord = /[^\x00-\x2f\x3a-\x40\x5b-\x60\x7b-\x7f]+/g;
 
-    /**
-     * The base implementation of `_.keys` which doesn't skip the constructor
-     * property of prototypes or treat sparse arrays as dense.
-     *
-     * @private
-     * @param {Object} object The object to query.
-     * @returns {Array} Returns the array of property names.
-     */
-    function baseKeys(object) {
-      return nativeKeys(Object(object));
-    }
+  /** Used to match backslashes in property paths. */
+  var reEscapeChar = /\\(\\)?/g;
 
-    /**
-     * The base implementation of `_.keysIn` which doesn't skip the constructor
-     * property of prototypes or treat sparse arrays as dense.
-     *
-     * @private
-     * @param {Object} object The object to query.
-     * @returns {Array} Returns the array of property names.
-     */
-    function baseKeysIn(object) {
-      object = object == null ? object : Object(object);
+  /**
+   * Used to match
+   * [ES template delimiters](http://ecma-international.org/ecma-262/7.0/#sec-template-literal-lexical-components).
+   */
+  var reEsTemplate = /\$\{([^\\}]*(?:\\.[^\\}]*)*)\}/g;
 
-      var result = [];
-      for (var key in object) {
-        result.push(key);
-      }
-      return result;
-    }
+  /** Used to match `RegExp` flags from their coerced string values. */
+  var reFlags = /\w*$/;
 
-    // Fallback for IE < 9 with es6-shim.
-    if (enumerate && !propertyIsEnumerable.call({ 'valueOf': 1 }, 'valueOf')) {
-      baseKeysIn = function(object) {
-        return iteratorToArray(enumerate(object));
-      };
-    }
+  /** Used to detect bad signed hexadecimal string values. */
+  var reIsBadHex = /^[-+]0x[0-9a-f]+$/i;
 
-    /**
-     * The base implementation of `_.lt` which doesn't coerce arguments to numbers.
-     *
-     * @private
-     * @param {*} value The value to compare.
-     * @param {*} other The other value to compare.
-     * @returns {boolean} Returns `true` if `value` is less than `other`,
-     *  else `false`.
-     */
-    function baseLt(value, other) {
-      return value < other;
-    }
+  /** Used to detect binary string values. */
+  var reIsBinary = /^0b[01]+$/i;
 
-    /**
-     * The base implementation of `_.map` without support for iteratee shorthands.
-     *
-     * @private
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Function} iteratee The function invoked per iteration.
-     * @returns {Array} Returns the new mapped array.
-     */
-    function baseMap(collection, iteratee) {
-      var index = -1,
-          result = isArrayLike(collection) ? Array(collection.length) : [];
+  /** Used to detect host constructors (Safari). */
+  var reIsHostCtor = /^\[object .+?Constructor\]$/;
 
-      baseEach(collection, function(value, key, collection) {
-        result[++index] = iteratee(value, key, collection);
-      });
-      return result;
-    }
+  /** Used to detect octal string values. */
+  var reIsOctal = /^0o[0-7]+$/i;
 
-    /**
-     * The base implementation of `_.matches` which doesn't clone `source`.
-     *
-     * @private
-     * @param {Object} source The object of property values to match.
-     * @returns {Function} Returns the new spec function.
-     */
-    function baseMatches(source) {
-      var matchData = getMatchData(source);
-      if (matchData.length == 1 && matchData[0][2]) {
-        return matchesStrictComparable(matchData[0][0], matchData[0][1]);
-      }
-      return function(object) {
-        return object === source || baseIsMatch(object, source, matchData);
-      };
-    }
+  /** Used to detect unsigned integer values. */
+  var reIsUint = /^(?:0|[1-9]\d*)$/;
 
-    /**
-     * The base implementation of `_.matchesProperty` which doesn't clone `srcValue`.
-     *
-     * @private
-     * @param {string} path The path of the property to get.
-     * @param {*} srcValue The value to match.
-     * @returns {Function} Returns the new spec function.
-     */
-    function baseMatchesProperty(path, srcValue) {
-      if (isKey(path) && isStrictComparable(srcValue)) {
-        return matchesStrictComparable(toKey(path), srcValue);
-      }
-      return function(object) {
-        var objValue = get(object, path);
-        return (objValue === undefined && objValue === srcValue)
-          ? hasIn(object, path)
-          : baseIsEqual(srcValue, objValue, undefined, UNORDERED_COMPARE_FLAG | PARTIAL_COMPARE_FLAG);
-      };
-    }
+  /** Used to match Latin Unicode letters (excluding mathematical operators). */
+  var reLatin = /[\xc0-\xd6\xd8-\xf6\xf8-\xff\u0100-\u017f]/g;
 
-    /**
-     * The base implementation of `_.merge` without support for multiple sources.
-     *
-     * @private
-     * @param {Object} object The destination object.
-     * @param {Object} source The source object.
-     * @param {number} srcIndex The index of `source`.
-     * @param {Function} [customizer] The function to customize merged values.
-     * @param {Object} [stack] Tracks traversed source values and their merged
-     *  counterparts.
-     */
-    function baseMerge(object, source, srcIndex, customizer, stack) {
-      if (object === source) {
-        return;
-      }
-      if (!(isArray(source) || isTypedArray(source))) {
-        var props = keysIn(source);
-      }
-      arrayEach(props || source, function(srcValue, key) {
-        if (props) {
-          key = srcValue;
-          srcValue = source[key];
-        }
-        if (isObject(srcValue)) {
-          stack || (stack = new Stack);
-          baseMergeDeep(object, source, key, srcIndex, baseMerge, customizer, stack);
-        }
-        else {
-          var newValue = customizer
-            ? customizer(object[key], srcValue, (key + ''), object, source, stack)
-            : undefined;
-
-          if (newValue === undefined) {
-            newValue = srcValue;
-          }
-          assignMergeValue(object, key, newValue);
-        }
-      });
-    }
+  /** Used to ensure capturing order of template delimiters. */
+  var reNoMatch = /($^)/;
 
-    /**
-     * A specialized version of `baseMerge` for arrays and objects which performs
-     * deep merges and tracks traversed objects enabling objects with circular
-     * references to be merged.
-     *
-     * @private
-     * @param {Object} object The destination object.
-     * @param {Object} source The source object.
-     * @param {string} key The key of the value to merge.
-     * @param {number} srcIndex The index of `source`.
-     * @param {Function} mergeFunc The function to merge values.
-     * @param {Function} [customizer] The function to customize assigned values.
-     * @param {Object} [stack] Tracks traversed source values and their merged
-     *  counterparts.
-     */
-    function baseMergeDeep(object, source, key, srcIndex, mergeFunc, customizer, stack) {
-      var objValue = object[key],
-          srcValue = source[key],
-          stacked = stack.get(srcValue);
+  /** Used to match unescaped characters in compiled string literals. */
+  var reUnescapedString = /['\n\r\u2028\u2029\\]/g;
 
-      if (stacked) {
-        assignMergeValue(object, key, stacked);
-        return;
-      }
-      var newValue = customizer
-        ? customizer(objValue, srcValue, (key + ''), object, source, stack)
-        : undefined;
+  /** Used to compose unicode character classes. */
+  var rsAstralRange = '\\ud800-\\udfff',
+      rsComboMarksRange = '\\u0300-\\u036f',
+      reComboHalfMarksRange = '\\ufe20-\\ufe2f',
+      rsComboSymbolsRange = '\\u20d0-\\u20ff',
+      rsComboRange = rsComboMarksRange + reComboHalfMarksRange + rsComboSymbolsRange,
+      rsDingbatRange = '\\u2700-\\u27bf',
+      rsLowerRange = 'a-z\\xdf-\\xf6\\xf8-\\xff',
+      rsMathOpRange = '\\xac\\xb1\\xd7\\xf7',
+      rsNonCharRange = '\\x00-\\x2f\\x3a-\\x40\\x5b-\\x60\\x7b-\\xbf',
+      rsPunctuationRange = '\\u2000-\\u206f',
+      rsSpaceRange = ' \\t\\x0b\\f\\xa0\\ufeff\\n\\r\\u2028\\u2029\\u1680\\u180e\\u2000\\u2001\\u2002\\u2003\\u2004\\u2005\\u2006\\u2007\\u2008\\u2009\\u200a\\u202f\\u205f\\u3000',
+      rsUpperRange = 'A-Z\\xc0-\\xd6\\xd8-\\xde',
+      rsVarRange = '\\ufe0e\\ufe0f',
+      rsBreakRange = rsMathOpRange + rsNonCharRange + rsPunctuationRange + rsSpaceRange;
 
-      var isCommon = newValue === undefined;
+  /** Used to compose unicode capture groups. */
+  var rsApos = "['\u2019]",
+      rsAstral = '[' + rsAstralRange + ']',
+      rsBreak = '[' + rsBreakRange + ']',
+      rsCombo = '[' + rsComboRange + ']',
+      rsDigits = '\\d+',
+      rsDingbat = '[' + rsDingbatRange + ']',
+      rsLower = '[' + rsLowerRange + ']',
+      rsMisc = '[^' + rsAstralRange + rsBreakRange + rsDigits + rsDingbatRange + rsLowerRange + rsUpperRange + ']',
+      rsFitz = '\\ud83c[\\udffb-\\udfff]',
+      rsModifier = '(?:' + rsCombo + '|' + rsFitz + ')',
+      rsNonAstral = '[^' + rsAstralRange + ']',
+      rsRegional = '(?:\\ud83c[\\udde6-\\uddff]){2}',
+      rsSurrPair = '[\\ud800-\\udbff][\\udc00-\\udfff]',
+      rsUpper = '[' + rsUpperRange + ']',
+      rsZWJ = '\\u200d';
 
-      if (isCommon) {
-        newValue = srcValue;
-        if (isArray(srcValue) || isTypedArray(srcValue)) {
-          if (isArray(objValue)) {
-            newValue = objValue;
-          }
-          else if (isArrayLikeObject(objValue)) {
-            newValue = copyArray(objValue);
-          }
-          else {
-            isCommon = false;
-            newValue = baseClone(srcValue, true);
-          }
-        }
-        else if (isPlainObject(srcValue) || isArguments(srcValue)) {
-          if (isArguments(objValue)) {
-            newValue = toPlainObject(objValue);
-          }
-          else if (!isObject(objValue) || (srcIndex && isFunction(objValue))) {
-            isCommon = false;
-            newValue = baseClone(srcValue, true);
-          }
-          else {
-            newValue = objValue;
-          }
-        }
-        else {
-          isCommon = false;
-        }
-      }
-      stack.set(srcValue, newValue);
+  /** Used to compose unicode regexes. */
+  var rsMiscLower = '(?:' + rsLower + '|' + rsMisc + ')',
+      rsMiscUpper = '(?:' + rsUpper + '|' + rsMisc + ')',
+      rsOptContrLower = '(?:' + rsApos + '(?:d|ll|m|re|s|t|ve))?',
+      rsOptContrUpper = '(?:' + rsApos + '(?:D|LL|M|RE|S|T|VE))?',
+      reOptMod = rsModifier + '?',
+      rsOptVar = '[' + rsVarRange + ']?',
+      rsOptJoin = '(?:' + rsZWJ + '(?:' + [rsNonAstral, rsRegional, rsSurrPair].join('|') + ')' + rsOptVar + reOptMod + ')*',
+      rsOrdLower = '\\d*(?:1st|2nd|3rd|(?![123])\\dth)(?=\\b|[A-Z_])',
+      rsOrdUpper = '\\d*(?:1ST|2ND|3RD|(?![123])\\dTH)(?=\\b|[a-z_])',
+      rsSeq = rsOptVar + reOptMod + rsOptJoin,
+      rsEmoji = '(?:' + [rsDingbat, rsRegional, rsSurrPair].join('|') + ')' + rsSeq,
+      rsSymbol = '(?:' + [rsNonAstral + rsCombo + '?', rsCombo, rsRegional, rsSurrPair, rsAstral].join('|') + ')';
 
-      if (isCommon) {
-        // Recursively merge objects and arrays (susceptible to call stack limits).
-        mergeFunc(newValue, srcValue, srcIndex, customizer, stack);
-      }
-      stack['delete'](srcValue);
-      assignMergeValue(object, key, newValue);
-    }
+  /** Used to match apostrophes. */
+  var reApos = RegExp(rsApos, 'g');
 
-    /**
-     * The base implementation of `_.nth` which doesn't coerce `n` to an integer.
-     *
-     * @private
-     * @param {Array} array The array to query.
-     * @param {number} n The index of the element to return.
-     * @returns {*} Returns the nth element of `array`.
-     */
-    function baseNth(array, n) {
-      var length = array.length;
-      if (!length) {
-        return;
-      }
-      n += n < 0 ? length : 0;
-      return isIndex(n, length) ? array[n] : undefined;
-    }
+  /**
+   * Used to match [combining diacritical marks](https://en.wikipedia.org/wiki/Combining_Diacritical_Marks) and
+   * [combining diacritical marks for symbols](https://en.wikipedia.org/wiki/Combining_Diacritical_Marks_for_Symbols).
+   */
+  var reComboMark = RegExp(rsCombo, 'g');
 
-    /**
-     * The base implementation of `_.orderBy` without param guards.
-     *
-     * @private
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Function[]|Object[]|string[]} iteratees The iteratees to sort by.
-     * @param {string[]} orders The sort orders of `iteratees`.
-     * @returns {Array} Returns the new sorted array.
-     */
-    function baseOrderBy(collection, iteratees, orders) {
-      var index = -1;
-      iteratees = arrayMap(iteratees.length ? iteratees : [identity], baseUnary(getIteratee()));
+  /** Used to match [string symbols](https://mathiasbynens.be/notes/javascript-unicode). */
+  var reUnicode = RegExp(rsFitz + '(?=' + rsFitz + ')|' + rsSymbol + rsSeq, 'g');
 
-      var result = baseMap(collection, function(value, key, collection) {
-        var criteria = arrayMap(iteratees, function(iteratee) {
-          return iteratee(value);
-        });
-        return { 'criteria': criteria, 'index': ++index, 'value': value };
-      });
+  /** Used to match complex or compound words. */
+  var reUnicodeWord = RegExp([
+    rsUpper + '?' + rsLower + '+' + rsOptContrLower + '(?=' + [rsBreak, rsUpper, '$'].join('|') + ')',
+    rsMiscUpper + '+' + rsOptContrUpper + '(?=' + [rsBreak, rsUpper + rsMiscLower, '$'].join('|') + ')',
+    rsUpper + '?' + rsMiscLower + '+' + rsOptContrLower,
+    rsUpper + '+' + rsOptContrUpper,
+    rsOrdUpper,
+    rsOrdLower,
+    rsDigits,
+    rsEmoji
+  ].join('|'), 'g');
 
-      return baseSortBy(result, function(object, other) {
-        return compareMultiple(object, other, orders);
-      });
-    }
+  /** Used to detect strings with [zero-width joiners or code points from the astral planes](http://eev.ee/blog/2015/09/12/dark-corners-of-unicode/). */
+  var reHasUnicode = RegExp('[' + rsZWJ + rsAstralRange  + rsComboRange + rsVarRange + ']');
 
-    /**
-     * The base implementation of `_.pick` without support for individual
-     * property identifiers.
-     *
-     * @private
-     * @param {Object} object The source object.
-     * @param {string[]} props The property identifiers to pick.
-     * @returns {Object} Returns the new object.
-     */
-    function basePick(object, props) {
-      object = Object(object);
-      return arrayReduce(props, function(result, key) {
-        if (key in object) {
-          result[key] = object[key];
-        }
-        return result;
-      }, {});
-    }
+  /** Used to detect strings that need a more robust regexp to match words. */
+  var reHasUnicodeWord = /[a-z][A-Z]|[A-Z]{2}[a-z]|[0-9][a-zA-Z]|[a-zA-Z][0-9]|[^a-zA-Z0-9 ]/;
 
-    /**
-     * The base implementation of  `_.pickBy` without support for iteratee shorthands.
-     *
-     * @private
-     * @param {Object} object The source object.
-     * @param {Function} predicate The function invoked per property.
-     * @returns {Object} Returns the new object.
-     */
-    function basePickBy(object, predicate) {
-      var index = -1,
-          props = getAllKeysIn(object),
-          length = props.length,
-          result = {};
+  /** Used to assign default `context` object properties. */
+  var contextProps = [
+    'Array', 'Buffer', 'DataView', 'Date', 'Error', 'Float32Array', 'Float64Array',
+    'Function', 'Int8Array', 'Int16Array', 'Int32Array', 'Map', 'Math', 'Object',
+    'Promise', 'RegExp', 'Set', 'String', 'Symbol', 'TypeError', 'Uint8Array',
+    'Uint8ClampedArray', 'Uint16Array', 'Uint32Array', 'WeakMap',
+    '_', 'clearTimeout', 'isFinite', 'parseInt', 'setTimeout'
+  ];
 
-      while (++index < length) {
-        var key = props[index],
-            value = object[key];
+  /** Used to make template sourceURLs easier to identify. */
+  var templateCounter = -1;
 
-        if (predicate(value, key)) {
-          result[key] = value;
-        }
-      }
-      return result;
-    }
+  /** Used to identify `toStringTag` values of typed arrays. */
+  var typedArrayTags = {};
+  typedArrayTags[float32Tag] = typedArrayTags[float64Tag] =
+  typedArrayTags[int8Tag] = typedArrayTags[int16Tag] =
+  typedArrayTags[int32Tag] = typedArrayTags[uint8Tag] =
+  typedArrayTags[uint8ClampedTag] = typedArrayTags[uint16Tag] =
+  typedArrayTags[uint32Tag] = true;
+  typedArrayTags[argsTag] = typedArrayTags[arrayTag] =
+  typedArrayTags[arrayBufferTag] = typedArrayTags[boolTag] =
+  typedArrayTags[dataViewTag] = typedArrayTags[dateTag] =
+  typedArrayTags[errorTag] = typedArrayTags[funcTag] =
+  typedArrayTags[mapTag] = typedArrayTags[numberTag] =
+  typedArrayTags[objectTag] = typedArrayTags[regexpTag] =
+  typedArrayTags[setTag] = typedArrayTags[stringTag] =
+  typedArrayTags[weakMapTag] = false;
 
-    /**
-     * The base implementation of `_.property` without support for deep paths.
-     *
-     * @private
-     * @param {string} key The key of the property to get.
-     * @returns {Function} Returns the new accessor function.
-     */
-    function baseProperty(key) {
-      return function(object) {
-        return object == null ? undefined : object[key];
-      };
-    }
+  /** Used to identify `toStringTag` values supported by `_.clone`. */
+  var cloneableTags = {};
+  cloneableTags[argsTag] = cloneableTags[arrayTag] =
+  cloneableTags[arrayBufferTag] = cloneableTags[dataViewTag] =
+  cloneableTags[boolTag] = cloneableTags[dateTag] =
+  cloneableTags[float32Tag] = cloneableTags[float64Tag] =
+  cloneableTags[int8Tag] = cloneableTags[int16Tag] =
+  cloneableTags[int32Tag] = cloneableTags[mapTag] =
+  cloneableTags[numberTag] = cloneableTags[objectTag] =
+  cloneableTags[regexpTag] = cloneableTags[setTag] =
+  cloneableTags[stringTag] = cloneableTags[symbolTag] =
+  cloneableTags[uint8Tag] = cloneableTags[uint8ClampedTag] =
+  cloneableTags[uint16Tag] = cloneableTags[uint32Tag] = true;
+  cloneableTags[errorTag] = cloneableTags[funcTag] =
+  cloneableTags[weakMapTag] = false;
 
-    /**
-     * A specialized version of `baseProperty` which supports deep paths.
-     *
-     * @private
-     * @param {Array|string} path The path of the property to get.
-     * @returns {Function} Returns the new accessor function.
-     */
-    function basePropertyDeep(path) {
-      return function(object) {
-        return baseGet(object, path);
-      };
-    }
-
-    /**
-     * The base implementation of `_.pullAllBy` without support for iteratee
-     * shorthands.
-     *
-     * @private
-     * @param {Array} array The array to modify.
-     * @param {Array} values The values to remove.
-     * @param {Function} [iteratee] The iteratee invoked per element.
-     * @param {Function} [comparator] The comparator invoked per element.
-     * @returns {Array} Returns `array`.
-     */
-    function basePullAll(array, values, iteratee, comparator) {
-      var indexOf = comparator ? baseIndexOfWith : baseIndexOf,
-          index = -1,
-          length = values.length,
-          seen = array;
+  /** Used to map Latin Unicode letters to basic Latin letters. */
+  var deburredLetters = {
+    // Latin-1 Supplement block.
+    '\xc0': 'A',  '\xc1': 'A', '\xc2': 'A', '\xc3': 'A', '\xc4': 'A', '\xc5': 'A',
+    '\xe0': 'a',  '\xe1': 'a', '\xe2': 'a', '\xe3': 'a', '\xe4': 'a', '\xe5': 'a',
+    '\xc7': 'C',  '\xe7': 'c',
+    '\xd0': 'D',  '\xf0': 'd',
+    '\xc8': 'E',  '\xc9': 'E', '\xca': 'E', '\xcb': 'E',
+    '\xe8': 'e',  '\xe9': 'e', '\xea': 'e', '\xeb': 'e',
+    '\xcc': 'I',  '\xcd': 'I', '\xce': 'I', '\xcf': 'I',
+    '\xec': 'i',  '\xed': 'i', '\xee': 'i', '\xef': 'i',
+    '\xd1': 'N',  '\xf1': 'n',
+    '\xd2': 'O',  '\xd3': 'O', '\xd4': 'O', '\xd5': 'O', '\xd6': 'O', '\xd8': 'O',
+    '\xf2': 'o',  '\xf3': 'o', '\xf4': 'o', '\xf5': 'o', '\xf6': 'o', '\xf8': 'o',
+    '\xd9': 'U',  '\xda': 'U', '\xdb': 'U', '\xdc': 'U',
+    '\xf9': 'u',  '\xfa': 'u', '\xfb': 'u', '\xfc': 'u',
+    '\xdd': 'Y',  '\xfd': 'y', '\xff': 'y',
+    '\xc6': 'Ae', '\xe6': 'ae',
+    '\xde': 'Th', '\xfe': 'th',
+    '\xdf': 'ss',
+    // Latin Extended-A block.
+    '\u0100': 'A',  '\u0102': 'A', '\u0104': 'A',
+    '\u0101': 'a',  '\u0103': 'a', '\u0105': 'a',
+    '\u0106': 'C',  '\u0108': 'C', '\u010a': 'C', '\u010c': 'C',
+    '\u0107': 'c',  '\u0109': 'c', '\u010b': 'c', '\u010d': 'c',
+    '\u010e': 'D',  '\u0110': 'D', '\u010f': 'd', '\u0111': 'd',
+    '\u0112': 'E',  '\u0114': 'E', '\u0116': 'E', '\u0118': 'E', '\u011a': 'E',
+    '\u0113': 'e',  '\u0115': 'e', '\u0117': 'e', '\u0119': 'e', '\u011b': 'e',
+    '\u011c': 'G',  '\u011e': 'G', '\u0120': 'G', '\u0122': 'G',
+    '\u011d': 'g',  '\u011f': 'g', '\u0121': 'g', '\u0123': 'g',
+    '\u0124': 'H',  '\u0126': 'H', '\u0125': 'h', '\u0127': 'h',
+    '\u0128': 'I',  '\u012a': 'I', '\u012c': 'I', '\u012e': 'I', '\u0130': 'I',
+    '\u0129': 'i',  '\u012b': 'i', '\u012d': 'i', '\u012f': 'i', '\u0131': 'i',
+    '\u0134': 'J',  '\u0135': 'j',
+    '\u0136': 'K',  '\u0137': 'k', '\u0138': 'k',
+    '\u0139': 'L',  '\u013b': 'L', '\u013d': 'L', '\u013f': 'L', '\u0141': 'L',
+    '\u013a': 'l',  '\u013c': 'l', '\u013e': 'l', '\u0140': 'l', '\u0142': 'l',
+    '\u0143': 'N',  '\u0145': 'N', '\u0147': 'N', '\u014a': 'N',
+    '\u0144': 'n',  '\u0146': 'n', '\u0148': 'n', '\u014b': 'n',
+    '\u014c': 'O',  '\u014e': 'O', '\u0150': 'O',
+    '\u014d': 'o',  '\u014f': 'o', '\u0151': 'o',
+    '\u0154': 'R',  '\u0156': 'R', '\u0158': 'R',
+    '\u0155': 'r',  '\u0157': 'r', '\u0159': 'r',
+    '\u015a': 'S',  '\u015c': 'S', '\u015e': 'S', '\u0160': 'S',
+    '\u015b': 's',  '\u015d': 's', '\u015f': 's', '\u0161': 's',
+    '\u0162': 'T',  '\u0164': 'T', '\u0166': 'T',
+    '\u0163': 't',  '\u0165': 't', '\u0167': 't',
+    '\u0168': 'U',  '\u016a': 'U', '\u016c': 'U', '\u016e': 'U', '\u0170': 'U', '\u0172': 'U',
+    '\u0169': 'u',  '\u016b': 'u', '\u016d': 'u', '\u016f': 'u', '\u0171': 'u', '\u0173': 'u',
+    '\u0174': 'W',  '\u0175': 'w',
+    '\u0176': 'Y',  '\u0177': 'y', '\u0178': 'Y',
+    '\u0179': 'Z',  '\u017b': 'Z', '\u017d': 'Z',
+    '\u017a': 'z',  '\u017c': 'z', '\u017e': 'z',
+    '\u0132': 'IJ', '\u0133': 'ij',
+    '\u0152': 'Oe', '\u0153': 'oe',
+    '\u0149': "'n", '\u017f': 's'
+  };
 
-      if (array === values) {
-        values = copyArray(values);
-      }
-      if (iteratee) {
-        seen = arrayMap(array, baseUnary(iteratee));
-      }
-      while (++index < length) {
-        var fromIndex = 0,
-            value = values[index],
-            computed = iteratee ? iteratee(value) : value;
+  /** Used to map characters to HTML entities. */
+  var htmlEscapes = {
+    '&': '&amp;',
+    '<': '&lt;',
+    '>': '&gt;',
+    '"': '&quot;',
+    "'": '&#39;'
+  };
 
-        while ((fromIndex = indexOf(seen, computed, fromIndex, comparator)) > -1) {
-          if (seen !== array) {
-            splice.call(seen, fromIndex, 1);
-          }
-          splice.call(array, fromIndex, 1);
-        }
-      }
-      return array;
-    }
+  /** Used to map HTML entities to characters. */
+  var htmlUnescapes = {
+    '&amp;': '&',
+    '&lt;': '<',
+    '&gt;': '>',
+    '&quot;': '"',
+    '&#39;': "'"
+  };
 
-    /**
-     * The base implementation of `_.pullAt` without support for individual
-     * indexes or capturing the removed elements.
-     *
-     * @private
-     * @param {Array} array The array to modify.
-     * @param {number[]} indexes The indexes of elements to remove.
-     * @returns {Array} Returns `array`.
-     */
-    function basePullAt(array, indexes) {
-      var length = array ? indexes.length : 0,
-          lastIndex = length - 1;
+  /** Used to escape characters for inclusion in compiled string literals. */
+  var stringEscapes = {
+    '\\': '\\',
+    "'": "'",
+    '\n': 'n',
+    '\r': 'r',
+    '\u2028': 'u2028',
+    '\u2029': 'u2029'
+  };
 
-      while (length--) {
-        var index = indexes[length];
-        if (length == lastIndex || index !== previous) {
-          var previous = index;
-          if (isIndex(index)) {
-            splice.call(array, index, 1);
-          }
-          else if (!isKey(index, array)) {
-            var path = castPath(index),
-                object = parent(array, path);
+  /** Built-in method references without a dependency on `root`. */
+  var freeParseFloat = parseFloat,
+      freeParseInt = parseInt;
 
-            if (object != null) {
-              delete object[toKey(last(path))];
-            }
-          }
-          else {
-            delete array[toKey(index)];
-          }
-        }
-      }
-      return array;
-    }
+  /** Detect free variable `global` from Node.js. */
+  var freeGlobal = typeof global == 'object' && global && global.Object === Object && global;
 
-    /**
-     * The base implementation of `_.random` without support for returning
-     * floating-point numbers.
-     *
-     * @private
-     * @param {number} lower The lower bound.
-     * @param {number} upper The upper bound.
-     * @returns {number} Returns the random number.
-     */
-    function baseRandom(lower, upper) {
-      return lower + nativeFloor(nativeRandom() * (upper - lower + 1));
-    }
+  /** Detect free variable `self`. */
+  var freeSelf = typeof self == 'object' && self && self.Object === Object && self;
 
-    /**
-     * The base implementation of `_.range` and `_.rangeRight` which doesn't
-     * coerce arguments to numbers.
-     *
-     * @private
-     * @param {number} start The start of the range.
-     * @param {number} end The end of the range.
-     * @param {number} step The value to increment or decrement by.
-     * @param {boolean} [fromRight] Specify iterating from right to left.
-     * @returns {Array} Returns the range of numbers.
-     */
-    function baseRange(start, end, step, fromRight) {
-      var index = -1,
-          length = nativeMax(nativeCeil((end - start) / (step || 1)), 0),
-          result = Array(length);
+  /** Used as a reference to the global object. */
+  var root = freeGlobal || freeSelf || Function('return this')();
 
-      while (length--) {
-        result[fromRight ? length : ++index] = start;
-        start += step;
-      }
-      return result;
-    }
+  /** Detect free variable `exports`. */
+  var freeExports = typeof exports == 'object' && exports && !exports.nodeType && exports;
 
-    /**
-     * The base implementation of `_.repeat` which doesn't coerce arguments.
-     *
-     * @private
-     * @param {string} string The string to repeat.
-     * @param {number} n The number of times to repeat the string.
-     * @returns {string} Returns the repeated string.
-     */
-    function baseRepeat(string, n) {
-      var result = '';
-      if (!string || n < 1 || n > MAX_SAFE_INTEGER) {
-        return result;
-      }
-      // Leverage the exponentiation by squaring algorithm for a faster repeat.
-      // See https://en.wikipedia.org/wiki/Exponentiation_by_squaring for more details.
-      do {
-        if (n % 2) {
-          result += string;
-        }
-        n = nativeFloor(n / 2);
-        if (n) {
-          string += string;
-        }
-      } while (n);
+  /** Detect free variable `module`. */
+  var freeModule = freeExports && typeof module == 'object' && module && !module.nodeType && module;
 
-      return result;
-    }
+  /** Detect the popular CommonJS extension `module.exports`. */
+  var moduleExports = freeModule && freeModule.exports === freeExports;
 
-    /**
-     * The base implementation of `_.set`.
-     *
-     * @private
-     * @param {Object} object The object to query.
-     * @param {Array|string} path The path of the property to set.
-     * @param {*} value The value to set.
-     * @param {Function} [customizer] The function to customize path creation.
-     * @returns {Object} Returns `object`.
-     */
-    function baseSet(object, path, value, customizer) {
-      path = isKey(path, object) ? [path] : castPath(path);
+  /** Detect free variable `process` from Node.js. */
+  var freeProcess = moduleExports && freeGlobal.process;
 
-      var index = -1,
-          length = path.length,
-          lastIndex = length - 1,
-          nested = object;
+  /** Used to access faster Node.js helpers. */
+  var nodeUtil = (function() {
+    try {
+      // Use `util.types` for Node.js 10+.
+      var types = freeModule && freeModule.require && freeModule.require('util').types;
 
-      while (nested != null && ++index < length) {
-        var key = toKey(path[index]);
-        if (isObject(nested)) {
-          var newValue = value;
-          if (index != lastIndex) {
-            var objValue = nested[key];
-            newValue = customizer ? customizer(objValue, key, nested) : undefined;
-            if (newValue === undefined) {
-              newValue = objValue == null
-                ? (isIndex(path[index + 1]) ? [] : {})
-                : objValue;
-            }
-          }
-          assignValue(nested, key, newValue);
-        }
-        nested = nested[key];
+      if (types) {
+        return types;
       }
-      return object;
-    }
 
-    /**
-     * The base implementation of `setData` without support for hot loop detection.
-     *
-     * @private
-     * @param {Function} func The function to associate metadata with.
-     * @param {*} data The metadata.
-     * @returns {Function} Returns `func`.
-     */
-    var baseSetData = !metaMap ? identity : function(func, data) {
-      metaMap.set(func, data);
-      return func;
-    };
+      // Legacy `process.binding('util')` for Node.js < 10.
+      return freeProcess && freeProcess.binding && freeProcess.binding('util');
+    } catch (e) {}
+  }());
 
-    /**
-     * The base implementation of `_.slice` without an iteratee call guard.
-     *
-     * @private
-     * @param {Array} array The array to slice.
-     * @param {number} [start=0] The start position.
-     * @param {number} [end=array.length] The end position.
-     * @returns {Array} Returns the slice of `array`.
-     */
-    function baseSlice(array, start, end) {
-      var index = -1,
-          length = array.length;
+  /* Node.js helper references. */
+  var nodeIsArrayBuffer = nodeUtil && nodeUtil.isArrayBuffer,
+      nodeIsDate = nodeUtil && nodeUtil.isDate,
+      nodeIsMap = nodeUtil && nodeUtil.isMap,
+      nodeIsRegExp = nodeUtil && nodeUtil.isRegExp,
+      nodeIsSet = nodeUtil && nodeUtil.isSet,
+      nodeIsTypedArray = nodeUtil && nodeUtil.isTypedArray;
 
-      if (start < 0) {
-        start = -start > length ? 0 : (length + start);
-      }
-      end = end > length ? length : end;
-      if (end < 0) {
-        end += length;
-      }
-      length = start > end ? 0 : ((end - start) >>> 0);
-      start >>>= 0;
+  /*--------------------------------------------------------------------------*/
 
-      var result = Array(length);
-      while (++index < length) {
-        result[index] = array[index + start];
-      }
-      return result;
+  /**
+   * A faster alternative to `Function#apply`, this function invokes `func`
+   * with the `this` binding of `thisArg` and the arguments of `args`.
+   *
+   * @private
+   * @param {Function} func The function to invoke.
+   * @param {*} thisArg The `this` binding of `func`.
+   * @param {Array} args The arguments to invoke `func` with.
+   * @returns {*} Returns the result of `func`.
+   */
+  function apply(func, thisArg, args) {
+    switch (args.length) {
+      case 0: return func.call(thisArg);
+      case 1: return func.call(thisArg, args[0]);
+      case 2: return func.call(thisArg, args[0], args[1]);
+      case 3: return func.call(thisArg, args[0], args[1], args[2]);
     }
+    return func.apply(thisArg, args);
+  }
 
-    /**
-     * The base implementation of `_.some` without support for iteratee shorthands.
-     *
-     * @private
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Function} predicate The function invoked per iteration.
-     * @returns {boolean} Returns `true` if any element passes the predicate check,
-     *  else `false`.
-     */
-    function baseSome(collection, predicate) {
-      var result;
+  /**
+   * A specialized version of `baseAggregator` for arrays.
+   *
+   * @private
+   * @param {Array} [array] The array to iterate over.
+   * @param {Function} setter The function to set `accumulator` values.
+   * @param {Function} iteratee The iteratee to transform keys.
+   * @param {Object} accumulator The initial aggregated object.
+   * @returns {Function} Returns `accumulator`.
+   */
+  function arrayAggregator(array, setter, iteratee, accumulator) {
+    var index = -1,
+        length = array == null ? 0 : array.length;
 
-      baseEach(collection, function(value, index, collection) {
-        result = predicate(value, index, collection);
-        return !result;
-      });
-      return !!result;
+    while (++index < length) {
+      var value = array[index];
+      setter(accumulator, value, iteratee(value), array);
     }
+    return accumulator;
+  }
 
-    /**
-     * The base implementation of `_.sortedIndex` and `_.sortedLastIndex` which
-     * performs a binary search of `array` to determine the index at which `value`
-     * should be inserted into `array` in order to maintain its sort order.
-     *
-     * @private
-     * @param {Array} array The sorted array to inspect.
-     * @param {*} value The value to evaluate.
-     * @param {boolean} [retHighest] Specify returning the highest qualified index.
-     * @returns {number} Returns the index at which `value` should be inserted
-     *  into `array`.
-     */
-    function baseSortedIndex(array, value, retHighest) {
-      var low = 0,
-          high = array ? array.length : low;
-
-      if (typeof value == 'number' && value === value && high <= HALF_MAX_ARRAY_LENGTH) {
-        while (low < high) {
-          var mid = (low + high) >>> 1,
-              computed = array[mid];
+  /**
+   * A specialized version of `_.forEach` for arrays without support for
+   * iteratee shorthands.
+   *
+   * @private
+   * @param {Array} [array] The array to iterate over.
+   * @param {Function} iteratee The function invoked per iteration.
+   * @returns {Array} Returns `array`.
+   */
+  function arrayEach(array, iteratee) {
+    var index = -1,
+        length = array == null ? 0 : array.length;
 
-          if (computed !== null && !isSymbol(computed) &&
-              (retHighest ? (computed <= value) : (computed < value))) {
-            low = mid + 1;
-          } else {
-            high = mid;
-          }
-        }
-        return high;
+    while (++index < length) {
+      if (iteratee(array[index], index, array) === false) {
+        break;
       }
-      return baseSortedIndexBy(array, value, identity, retHighest);
     }
+    return array;
+  }
 
-    /**
-     * The base implementation of `_.sortedIndexBy` and `_.sortedLastIndexBy`
-     * which invokes `iteratee` for `value` and each element of `array` to compute
-     * their sort ranking. The iteratee is invoked with one argument; (value).
-     *
-     * @private
-     * @param {Array} array The sorted array to inspect.
-     * @param {*} value The value to evaluate.
-     * @param {Function} iteratee The iteratee invoked per element.
-     * @param {boolean} [retHighest] Specify returning the highest qualified index.
-     * @returns {number} Returns the index at which `value` should be inserted
-     *  into `array`.
-     */
-    function baseSortedIndexBy(array, value, iteratee, retHighest) {
-      value = iteratee(value);
+  /**
+   * A specialized version of `_.forEachRight` for arrays without support for
+   * iteratee shorthands.
+   *
+   * @private
+   * @param {Array} [array] The array to iterate over.
+   * @param {Function} iteratee The function invoked per iteration.
+   * @returns {Array} Returns `array`.
+   */
+  function arrayEachRight(array, iteratee) {
+    var length = array == null ? 0 : array.length;
 
-      var low = 0,
-          high = array ? array.length : 0,
-          valIsNaN = value !== value,
-          valIsNull = value === null,
-          valIsSymbol = isSymbol(value),
-          valIsUndefined = value === undefined;
+    while (length--) {
+      if (iteratee(array[length], length, array) === false) {
+        break;
+      }
+    }
+    return array;
+  }
 
-      while (low < high) {
-        var mid = nativeFloor((low + high) / 2),
-            computed = iteratee(array[mid]),
-            othIsDefined = computed !== undefined,
-            othIsNull = computed === null,
-            othIsReflexive = computed === computed,
-            othIsSymbol = isSymbol(computed);
+  /**
+   * A specialized version of `_.every` for arrays without support for
+   * iteratee shorthands.
+   *
+   * @private
+   * @param {Array} [array] The array to iterate over.
+   * @param {Function} predicate The function invoked per iteration.
+   * @returns {boolean} Returns `true` if all elements pass the predicate check,
+   *  else `false`.
+   */
+  function arrayEvery(array, predicate) {
+    var index = -1,
+        length = array == null ? 0 : array.length;
 
-        if (valIsNaN) {
-          var setLow = retHighest || othIsReflexive;
-        } else if (valIsUndefined) {
-          setLow = othIsReflexive && (retHighest || othIsDefined);
-        } else if (valIsNull) {
-          setLow = othIsReflexive && othIsDefined && (retHighest || !othIsNull);
-        } else if (valIsSymbol) {
-          setLow = othIsReflexive && othIsDefined && !othIsNull && (retHighest || !othIsSymbol);
-        } else if (othIsNull || othIsSymbol) {
-          setLow = false;
-        } else {
-          setLow = retHighest ? (computed <= value) : (computed < value);
-        }
-        if (setLow) {
-          low = mid + 1;
-        } else {
-          high = mid;
-        }
+    while (++index < length) {
+      if (!predicate(array[index], index, array)) {
+        return false;
       }
-      return nativeMin(high, MAX_ARRAY_INDEX);
     }
+    return true;
+  }
 
-    /**
-     * The base implementation of `_.sortedUniq` and `_.sortedUniqBy` without
-     * support for iteratee shorthands.
-     *
-     * @private
-     * @param {Array} array The array to inspect.
-     * @param {Function} [iteratee] The iteratee invoked per element.
-     * @returns {Array} Returns the new duplicate free array.
-     */
-    function baseSortedUniq(array, iteratee) {
-      var index = -1,
-          length = array.length,
-          resIndex = 0,
-          result = [];
-
-      while (++index < length) {
-        var value = array[index],
-            computed = iteratee ? iteratee(value) : value;
+  /**
+   * A specialized version of `_.filter` for arrays without support for
+   * iteratee shorthands.
+   *
+   * @private
+   * @param {Array} [array] The array to iterate over.
+   * @param {Function} predicate The function invoked per iteration.
+   * @returns {Array} Returns the new filtered array.
+   */
+  function arrayFilter(array, predicate) {
+    var index = -1,
+        length = array == null ? 0 : array.length,
+        resIndex = 0,
+        result = [];
 
-        if (!index || !eq(computed, seen)) {
-          var seen = computed;
-          result[resIndex++] = value === 0 ? 0 : value;
-        }
+    while (++index < length) {
+      var value = array[index];
+      if (predicate(value, index, array)) {
+        result[resIndex++] = value;
       }
-      return result;
     }
+    return result;
+  }
 
-    /**
-     * The base implementation of `_.toNumber` which doesn't ensure correct
-     * conversions of binary, hexadecimal, or octal string values.
-     *
-     * @private
-     * @param {*} value The value to process.
-     * @returns {number} Returns the number.
-     */
-    function baseToNumber(value) {
-      if (typeof value == 'number') {
-        return value;
-      }
-      if (isSymbol(value)) {
-        return NAN;
+  /**
+   * A specialized version of `_.includes` for arrays without support for
+   * specifying an index to search from.
+   *
+   * @private
+   * @param {Array} [array] The array to inspect.
+   * @param {*} target The value to search for.
+   * @returns {boolean} Returns `true` if `target` is found, else `false`.
+   */
+  function arrayIncludes(array, value) {
+    var length = array == null ? 0 : array.length;
+    return !!length && baseIndexOf(array, value, 0) > -1;
+  }
+
+  /**
+   * This function is like `arrayIncludes` except that it accepts a comparator.
+   *
+   * @private
+   * @param {Array} [array] The array to inspect.
+   * @param {*} target The value to search for.
+   * @param {Function} comparator The comparator invoked per element.
+   * @returns {boolean} Returns `true` if `target` is found, else `false`.
+   */
+  function arrayIncludesWith(array, value, comparator) {
+    var index = -1,
+        length = array == null ? 0 : array.length;
+
+    while (++index < length) {
+      if (comparator(value, array[index])) {
+        return true;
       }
-      return +value;
     }
+    return false;
+  }
 
-    /**
-     * The base implementation of `_.toString` which doesn't convert nullish
-     * values to empty strings.
-     *
-     * @private
-     * @param {*} value The value to process.
-     * @returns {string} Returns the string.
-     */
-    function baseToString(value) {
-      // Exit early for strings to avoid a performance hit in some environments.
-      if (typeof value == 'string') {
-        return value;
-      }
-      if (isSymbol(value)) {
-        return symbolToString ? symbolToString.call(value) : '';
-      }
-      var result = (value + '');
-      return (result == '0' && (1 / value) == -INFINITY) ? '-0' : result;
-    }
+  /**
+   * A specialized version of `_.map` for arrays without support for iteratee
+   * shorthands.
+   *
+   * @private
+   * @param {Array} [array] The array to iterate over.
+   * @param {Function} iteratee The function invoked per iteration.
+   * @returns {Array} Returns the new mapped array.
+   */
+  function arrayMap(array, iteratee) {
+    var index = -1,
+        length = array == null ? 0 : array.length,
+        result = Array(length);
 
-    /**
-     * The base implementation of `_.uniqBy` without support for iteratee shorthands.
-     *
-     * @private
-     * @param {Array} array The array to inspect.
-     * @param {Function} [iteratee] The iteratee invoked per element.
-     * @param {Function} [comparator] The comparator invoked per element.
-     * @returns {Array} Returns the new duplicate free array.
-     */
-    function baseUniq(array, iteratee, comparator) {
-      var index = -1,
-          includes = arrayIncludes,
-          length = array.length,
-          isCommon = true,
-          result = [],
-          seen = result;
+    while (++index < length) {
+      result[index] = iteratee(array[index], index, array);
+    }
+    return result;
+  }
 
-      if (comparator) {
-        isCommon = false;
-        includes = arrayIncludesWith;
-      }
-      else if (length >= LARGE_ARRAY_SIZE) {
-        var set = iteratee ? null : createSet(array);
-        if (set) {
-          return setToArray(set);
-        }
-        isCommon = false;
-        includes = cacheHas;
-        seen = new SetCache;
-      }
-      else {
-        seen = iteratee ? [] : result;
-      }
-      outer:
-      while (++index < length) {
-        var value = array[index],
-            computed = iteratee ? iteratee(value) : value;
+  /**
+   * Appends the elements of `values` to `array`.
+   *
+   * @private
+   * @param {Array} array The array to modify.
+   * @param {Array} values The values to append.
+   * @returns {Array} Returns `array`.
+   */
+  function arrayPush(array, values) {
+    var index = -1,
+        length = values.length,
+        offset = array.length;
 
-        value = (comparator || value !== 0) ? value : 0;
-        if (isCommon && computed === computed) {
-          var seenIndex = seen.length;
-          while (seenIndex--) {
-            if (seen[seenIndex] === computed) {
-              continue outer;
-            }
-          }
-          if (iteratee) {
-            seen.push(computed);
-          }
-          result.push(value);
-        }
-        else if (!includes(seen, computed, comparator)) {
-          if (seen !== result) {
-            seen.push(computed);
-          }
-          result.push(value);
-        }
-      }
-      return result;
+    while (++index < length) {
+      array[offset + index] = values[index];
     }
+    return array;
+  }
 
-    /**
-     * The base implementation of `_.unset`.
-     *
-     * @private
-     * @param {Object} object The object to modify.
-     * @param {Array|string} path The path of the property to unset.
-     * @returns {boolean} Returns `true` if the property is deleted, else `false`.
-     */
-    function baseUnset(object, path) {
-      path = isKey(path, object) ? [path] : castPath(path);
-      object = parent(object, path);
+  /**
+   * A specialized version of `_.reduce` for arrays without support for
+   * iteratee shorthands.
+   *
+   * @private
+   * @param {Array} [array] The array to iterate over.
+   * @param {Function} iteratee The function invoked per iteration.
+   * @param {*} [accumulator] The initial value.
+   * @param {boolean} [initAccum] Specify using the first element of `array` as
+   *  the initial value.
+   * @returns {*} Returns the accumulated value.
+   */
+  function arrayReduce(array, iteratee, accumulator, initAccum) {
+    var index = -1,
+        length = array == null ? 0 : array.length;
 
-      var key = toKey(last(path));
-      return !(object != null && baseHas(object, key)) || delete object[key];
+    if (initAccum && length) {
+      accumulator = array[++index];
     }
-
-    /**
-     * The base implementation of `_.update`.
-     *
-     * @private
-     * @param {Object} object The object to query.
-     * @param {Array|string} path The path of the property to update.
-     * @param {Function} updater The function to produce the updated value.
-     * @param {Function} [customizer] The function to customize path creation.
-     * @returns {Object} Returns `object`.
-     */
-    function baseUpdate(object, path, updater, customizer) {
-      return baseSet(object, path, updater(baseGet(object, path)), customizer);
+    while (++index < length) {
+      accumulator = iteratee(accumulator, array[index], index, array);
     }
+    return accumulator;
+  }
 
-    /**
-     * The base implementation of methods like `_.dropWhile` and `_.takeWhile`
-     * without support for iteratee shorthands.
-     *
-     * @private
-     * @param {Array} array The array to query.
-     * @param {Function} predicate The function invoked per iteration.
-     * @param {boolean} [isDrop] Specify dropping elements instead of taking them.
-     * @param {boolean} [fromRight] Specify iterating from right to left.
-     * @returns {Array} Returns the slice of `array`.
-     */
-    function baseWhile(array, predicate, isDrop, fromRight) {
-      var length = array.length,
-          index = fromRight ? length : -1;
-
-      while ((fromRight ? index-- : ++index < length) &&
-        predicate(array[index], index, array)) {}
-
-      return isDrop
-        ? baseSlice(array, (fromRight ? 0 : index), (fromRight ? index + 1 : length))
-        : baseSlice(array, (fromRight ? index + 1 : 0), (fromRight ? length : index));
+  /**
+   * A specialized version of `_.reduceRight` for arrays without support for
+   * iteratee shorthands.
+   *
+   * @private
+   * @param {Array} [array] The array to iterate over.
+   * @param {Function} iteratee The function invoked per iteration.
+   * @param {*} [accumulator] The initial value.
+   * @param {boolean} [initAccum] Specify using the last element of `array` as
+   *  the initial value.
+   * @returns {*} Returns the accumulated value.
+   */
+  function arrayReduceRight(array, iteratee, accumulator, initAccum) {
+    var length = array == null ? 0 : array.length;
+    if (initAccum && length) {
+      accumulator = array[--length];
     }
-
-    /**
-     * The base implementation of `wrapperValue` which returns the result of
-     * performing a sequence of actions on the unwrapped `value`, where each
-     * successive action is supplied the return value of the previous.
-     *
-     * @private
-     * @param {*} value The unwrapped value.
-     * @param {Array} actions Actions to perform to resolve the unwrapped value.
-     * @returns {*} Returns the resolved value.
-     */
-    function baseWrapperValue(value, actions) {
-      var result = value;
-      if (result instanceof LazyWrapper) {
-        result = result.value();
-      }
-      return arrayReduce(actions, function(result, action) {
-        return action.func.apply(action.thisArg, arrayPush([result], action.args));
-      }, result);
+    while (length--) {
+      accumulator = iteratee(accumulator, array[length], length, array);
     }
+    return accumulator;
+  }
 
-    /**
-     * The base implementation of methods like `_.xor`, without support for
-     * iteratee shorthands, that accepts an array of arrays to inspect.
-     *
-     * @private
-     * @param {Array} arrays The arrays to inspect.
-     * @param {Function} [iteratee] The iteratee invoked per element.
-     * @param {Function} [comparator] The comparator invoked per element.
-     * @returns {Array} Returns the new array of values.
-     */
-    function baseXor(arrays, iteratee, comparator) {
-      var index = -1,
-          length = arrays.length;
+  /**
+   * A specialized version of `_.some` for arrays without support for iteratee
+   * shorthands.
+   *
+   * @private
+   * @param {Array} [array] The array to iterate over.
+   * @param {Function} predicate The function invoked per iteration.
+   * @returns {boolean} Returns `true` if any element passes the predicate check,
+   *  else `false`.
+   */
+  function arraySome(array, predicate) {
+    var index = -1,
+        length = array == null ? 0 : array.length;
 
-      while (++index < length) {
-        var result = result
-          ? arrayPush(
-              baseDifference(result, arrays[index], iteratee, comparator),
-              baseDifference(arrays[index], result, iteratee, comparator)
-            )
-          : arrays[index];
+    while (++index < length) {
+      if (predicate(array[index], index, array)) {
+        return true;
       }
-      return (result && result.length) ? baseUniq(result, iteratee, comparator) : [];
     }
+    return false;
+  }
 
-    /**
-     * This base implementation of `_.zipObject` which assigns values using `assignFunc`.
-     *
-     * @private
-     * @param {Array} props The property identifiers.
-     * @param {Array} values The property values.
-     * @param {Function} assignFunc The function to assign values.
-     * @returns {Object} Returns the new object.
-     */
-    function baseZipObject(props, values, assignFunc) {
-      var index = -1,
-          length = props.length,
-          valsLength = values.length,
-          result = {};
-
-      while (++index < length) {
-        var value = index < valsLength ? values[index] : undefined;
-        assignFunc(result, props[index], value);
-      }
-      return result;
-    }
+  /**
+   * Gets the size of an ASCII `string`.
+   *
+   * @private
+   * @param {string} string The string inspect.
+   * @returns {number} Returns the string size.
+   */
+  var asciiSize = baseProperty('length');
 
-    /**
-     * Casts `value` to an empty array if it's not an array like object.
-     *
-     * @private
-     * @param {*} value The value to inspect.
-     * @returns {Array|Object} Returns the cast array-like object.
-     */
-    function castArrayLikeObject(value) {
-      return isArrayLikeObject(value) ? value : [];
-    }
-
-    /**
-     * Casts `value` to `identity` if it's not a function.
-     *
-     * @private
-     * @param {*} value The value to inspect.
-     * @returns {Function} Returns cast function.
-     */
-    function castFunction(value) {
-      return typeof value == 'function' ? value : identity;
-    }
-
-    /**
-     * Casts `value` to a path array if it's not one.
-     *
-     * @private
-     * @param {*} value The value to inspect.
-     * @returns {Array} Returns the cast property path array.
-     */
-    function castPath(value) {
-      return isArray(value) ? value : stringToPath(value);
-    }
+  /**
+   * Converts an ASCII `string` to an array.
+   *
+   * @private
+   * @param {string} string The string to convert.
+   * @returns {Array} Returns the converted array.
+   */
+  function asciiToArray(string) {
+    return string.split('');
+  }
 
-    /**
-     * Casts `array` to a slice if it's needed.
-     *
-     * @private
-     * @param {Array} array The array to inspect.
-     * @param {number} start The start position.
-     * @param {number} [end=array.length] The end position.
-     * @returns {Array} Returns the cast slice.
-     */
-    function castSlice(array, start, end) {
-      var length = array.length;
-      end = end === undefined ? length : end;
-      return (!start && end >= length) ? array : baseSlice(array, start, end);
-    }
+  /**
+   * Splits an ASCII `string` into an array of its words.
+   *
+   * @private
+   * @param {string} The string to inspect.
+   * @returns {Array} Returns the words of `string`.
+   */
+  function asciiWords(string) {
+    return string.match(reAsciiWord) || [];
+  }
 
-    /**
-     * Creates a clone of  `buffer`.
-     *
-     * @private
-     * @param {Buffer} buffer The buffer to clone.
-     * @param {boolean} [isDeep] Specify a deep clone.
-     * @returns {Buffer} Returns the cloned buffer.
-     */
-    function cloneBuffer(buffer, isDeep) {
-      if (isDeep) {
-        return buffer.slice();
+  /**
+   * The base implementation of methods like `_.findKey` and `_.findLastKey`,
+   * without support for iteratee shorthands, which iterates over `collection`
+   * using `eachFunc`.
+   *
+   * @private
+   * @param {Array|Object} collection The collection to inspect.
+   * @param {Function} predicate The function invoked per iteration.
+   * @param {Function} eachFunc The function to iterate over `collection`.
+   * @returns {*} Returns the found element or its key, else `undefined`.
+   */
+  function baseFindKey(collection, predicate, eachFunc) {
+    var result;
+    eachFunc(collection, function(value, key, collection) {
+      if (predicate(value, key, collection)) {
+        result = key;
+        return false;
       }
-      var result = new buffer.constructor(buffer.length);
-      buffer.copy(result);
-      return result;
-    }
+    });
+    return result;
+  }
 
-    /**
-     * Creates a clone of `arrayBuffer`.
-     *
-     * @private
-     * @param {ArrayBuffer} arrayBuffer The array buffer to clone.
-     * @returns {ArrayBuffer} Returns the cloned array buffer.
-     */
-    function cloneArrayBuffer(arrayBuffer) {
-      var result = new arrayBuffer.constructor(arrayBuffer.byteLength);
-      new Uint8Array(result).set(new Uint8Array(arrayBuffer));
-      return result;
-    }
+  /**
+   * The base implementation of `_.findIndex` and `_.findLastIndex` without
+   * support for iteratee shorthands.
+   *
+   * @private
+   * @param {Array} array The array to inspect.
+   * @param {Function} predicate The function invoked per iteration.
+   * @param {number} fromIndex The index to search from.
+   * @param {boolean} [fromRight] Specify iterating from right to left.
+   * @returns {number} Returns the index of the matched value, else `-1`.
+   */
+  function baseFindIndex(array, predicate, fromIndex, fromRight) {
+    var length = array.length,
+        index = fromIndex + (fromRight ? 1 : -1);
 
-    /**
-     * Creates a clone of `dataView`.
-     *
-     * @private
-     * @param {Object} dataView The data view to clone.
-     * @param {boolean} [isDeep] Specify a deep clone.
-     * @returns {Object} Returns the cloned data view.
-     */
-    function cloneDataView(dataView, isDeep) {
-      var buffer = isDeep ? cloneArrayBuffer(dataView.buffer) : dataView.buffer;
-      return new dataView.constructor(buffer, dataView.byteOffset, dataView.byteLength);
+    while ((fromRight ? index-- : ++index < length)) {
+      if (predicate(array[index], index, array)) {
+        return index;
+      }
     }
+    return -1;
+  }
 
-    /**
-     * Creates a clone of `map`.
-     *
-     * @private
-     * @param {Object} map The map to clone.
-     * @param {Function} cloneFunc The function to clone values.
-     * @param {boolean} [isDeep] Specify a deep clone.
-     * @returns {Object} Returns the cloned map.
-     */
-    function cloneMap(map, isDeep, cloneFunc) {
-      var array = isDeep ? cloneFunc(mapToArray(map), true) : mapToArray(map);
-      return arrayReduce(array, addMapEntry, new map.constructor);
-    }
+  /**
+   * The base implementation of `_.indexOf` without `fromIndex` bounds checks.
+   *
+   * @private
+   * @param {Array} array The array to inspect.
+   * @param {*} value The value to search for.
+   * @param {number} fromIndex The index to search from.
+   * @returns {number} Returns the index of the matched value, else `-1`.
+   */
+  function baseIndexOf(array, value, fromIndex) {
+    return value === value
+      ? strictIndexOf(array, value, fromIndex)
+      : baseFindIndex(array, baseIsNaN, fromIndex);
+  }
 
-    /**
-     * Creates a clone of `regexp`.
-     *
-     * @private
-     * @param {Object} regexp The regexp to clone.
-     * @returns {Object} Returns the cloned regexp.
-     */
-    function cloneRegExp(regexp) {
-      var result = new regexp.constructor(regexp.source, reFlags.exec(regexp));
-      result.lastIndex = regexp.lastIndex;
-      return result;
-    }
+  /**
+   * This function is like `baseIndexOf` except that it accepts a comparator.
+   *
+   * @private
+   * @param {Array} array The array to inspect.
+   * @param {*} value The value to search for.
+   * @param {number} fromIndex The index to search from.
+   * @param {Function} comparator The comparator invoked per element.
+   * @returns {number} Returns the index of the matched value, else `-1`.
+   */
+  function baseIndexOfWith(array, value, fromIndex, comparator) {
+    var index = fromIndex - 1,
+        length = array.length;
 
-    /**
-     * Creates a clone of `set`.
-     *
-     * @private
-     * @param {Object} set The set to clone.
-     * @param {Function} cloneFunc The function to clone values.
-     * @param {boolean} [isDeep] Specify a deep clone.
-     * @returns {Object} Returns the cloned set.
-     */
-    function cloneSet(set, isDeep, cloneFunc) {
-      var array = isDeep ? cloneFunc(setToArray(set), true) : setToArray(set);
-      return arrayReduce(array, addSetEntry, new set.constructor);
+    while (++index < length) {
+      if (comparator(array[index], value)) {
+        return index;
+      }
     }
+    return -1;
+  }
 
-    /**
-     * Creates a clone of the `symbol` object.
-     *
-     * @private
-     * @param {Object} symbol The symbol object to clone.
-     * @returns {Object} Returns the cloned symbol object.
-     */
-    function cloneSymbol(symbol) {
-      return symbolValueOf ? Object(symbolValueOf.call(symbol)) : {};
-    }
+  /**
+   * The base implementation of `_.isNaN` without support for number objects.
+   *
+   * @private
+   * @param {*} value The value to check.
+   * @returns {boolean} Returns `true` if `value` is `NaN`, else `false`.
+   */
+  function baseIsNaN(value) {
+    return value !== value;
+  }
 
-    /**
-     * Creates a clone of `typedArray`.
-     *
-     * @private
-     * @param {Object} typedArray The typed array to clone.
-     * @param {boolean} [isDeep] Specify a deep clone.
-     * @returns {Object} Returns the cloned typed array.
-     */
-    function cloneTypedArray(typedArray, isDeep) {
-      var buffer = isDeep ? cloneArrayBuffer(typedArray.buffer) : typedArray.buffer;
-      return new typedArray.constructor(buffer, typedArray.byteOffset, typedArray.length);
-    }
+  /**
+   * The base implementation of `_.mean` and `_.meanBy` without support for
+   * iteratee shorthands.
+   *
+   * @private
+   * @param {Array} array The array to iterate over.
+   * @param {Function} iteratee The function invoked per iteration.
+   * @returns {number} Returns the mean.
+   */
+  function baseMean(array, iteratee) {
+    var length = array == null ? 0 : array.length;
+    return length ? (baseSum(array, iteratee) / length) : NAN;
+  }
 
-    /**
-     * Compares values to sort them in ascending order.
-     *
-     * @private
-     * @param {*} value The value to compare.
-     * @param {*} other The other value to compare.
-     * @returns {number} Returns the sort order indicator for `value`.
-     */
-    function compareAscending(value, other) {
-      if (value !== other) {
-        var valIsDefined = value !== undefined,
-            valIsNull = value === null,
-            valIsReflexive = value === value,
-            valIsSymbol = isSymbol(value);
+  /**
+   * The base implementation of `_.property` without support for deep paths.
+   *
+   * @private
+   * @param {string} key The key of the property to get.
+   * @returns {Function} Returns the new accessor function.
+   */
+  function baseProperty(key) {
+    return function(object) {
+      return object == null ? undefined : object[key];
+    };
+  }
 
-        var othIsDefined = other !== undefined,
-            othIsNull = other === null,
-            othIsReflexive = other === other,
-            othIsSymbol = isSymbol(other);
+  /**
+   * The base implementation of `_.propertyOf` without support for deep paths.
+   *
+   * @private
+   * @param {Object} object The object to query.
+   * @returns {Function} Returns the new accessor function.
+   */
+  function basePropertyOf(object) {
+    return function(key) {
+      return object == null ? undefined : object[key];
+    };
+  }
 
-        if ((!othIsNull && !othIsSymbol && !valIsSymbol && value > other) ||
-            (valIsSymbol && othIsDefined && othIsReflexive && !othIsNull && !othIsSymbol) ||
-            (valIsNull && othIsDefined && othIsReflexive) ||
-            (!valIsDefined && othIsReflexive) ||
-            !valIsReflexive) {
-          return 1;
-        }
-        if ((!valIsNull && !valIsSymbol && !othIsSymbol && value < other) ||
-            (othIsSymbol && valIsDefined && valIsReflexive && !valIsNull && !valIsSymbol) ||
-            (othIsNull && valIsDefined && valIsReflexive) ||
-            (!othIsDefined && valIsReflexive) ||
-            !othIsReflexive) {
-          return -1;
-        }
-      }
-      return 0;
-    }
-
-    /**
-     * Used by `_.orderBy` to compare multiple properties of a value to another
-     * and stable sort them.
-     *
-     * If `orders` is unspecified, all values are sorted in ascending order. Otherwise,
-     * specify an order of "desc" for descending or "asc" for ascending sort order
-     * of corresponding values.
-     *
-     * @private
-     * @param {Object} object The object to compare.
-     * @param {Object} other The other object to compare.
-     * @param {boolean[]|string[]} orders The order to sort by for each property.
-     * @returns {number} Returns the sort order indicator for `object`.
-     */
-    function compareMultiple(object, other, orders) {
-      var index = -1,
-          objCriteria = object.criteria,
-          othCriteria = other.criteria,
-          length = objCriteria.length,
-          ordersLength = orders.length;
-
-      while (++index < length) {
-        var result = compareAscending(objCriteria[index], othCriteria[index]);
-        if (result) {
-          if (index >= ordersLength) {
-            return result;
-          }
-          var order = orders[index];
-          return result * (order == 'desc' ? -1 : 1);
-        }
-      }
-      // Fixes an `Array#sort` bug in the JS engine embedded in Adobe applications
-      // that causes it, under certain circumstances, to provide the same value for
-      // `object` and `other`. See https://github.com/jashkenas/underscore/pull/1247
-      // for more details.
-      //
-      // This also ensures a stable sort in V8 and other engines.
-      // See https://bugs.chromium.org/p/v8/issues/detail?id=90 for more details.
-      return object.index - other.index;
-    }
+  /**
+   * The base implementation of `_.reduce` and `_.reduceRight`, without support
+   * for iteratee shorthands, which iterates over `collection` using `eachFunc`.
+   *
+   * @private
+   * @param {Array|Object} collection The collection to iterate over.
+   * @param {Function} iteratee The function invoked per iteration.
+   * @param {*} accumulator The initial value.
+   * @param {boolean} initAccum Specify using the first or last element of
+   *  `collection` as the initial value.
+   * @param {Function} eachFunc The function to iterate over `collection`.
+   * @returns {*} Returns the accumulated value.
+   */
+  function baseReduce(collection, iteratee, accumulator, initAccum, eachFunc) {
+    eachFunc(collection, function(value, index, collection) {
+      accumulator = initAccum
+        ? (initAccum = false, value)
+        : iteratee(accumulator, value, index, collection);
+    });
+    return accumulator;
+  }
 
-    /**
-     * Creates an array that is the composition of partially applied arguments,
-     * placeholders, and provided arguments into a single array of arguments.
-     *
-     * @private
-     * @param {Array} args The provided arguments.
-     * @param {Array} partials The arguments to prepend to those provided.
-     * @param {Array} holders The `partials` placeholder indexes.
-     * @params {boolean} [isCurried] Specify composing for a curried function.
-     * @returns {Array} Returns the new array of composed arguments.
-     */
-    function composeArgs(args, partials, holders, isCurried) {
-      var argsIndex = -1,
-          argsLength = args.length,
-          holdersLength = holders.length,
-          leftIndex = -1,
-          leftLength = partials.length,
-          rangeLength = nativeMax(argsLength - holdersLength, 0),
-          result = Array(leftLength + rangeLength),
-          isUncurried = !isCurried;
+  /**
+   * The base implementation of `_.sortBy` which uses `comparer` to define the
+   * sort order of `array` and replaces criteria objects with their corresponding
+   * values.
+   *
+   * @private
+   * @param {Array} array The array to sort.
+   * @param {Function} comparer The function to define sort order.
+   * @returns {Array} Returns `array`.
+   */
+  function baseSortBy(array, comparer) {
+    var length = array.length;
 
-      while (++leftIndex < leftLength) {
-        result[leftIndex] = partials[leftIndex];
-      }
-      while (++argsIndex < holdersLength) {
-        if (isUncurried || argsIndex < argsLength) {
-          result[holders[argsIndex]] = args[argsIndex];
-        }
-      }
-      while (rangeLength--) {
-        result[leftIndex++] = args[argsIndex++];
-      }
-      return result;
+    array.sort(comparer);
+    while (length--) {
+      array[length] = array[length].value;
     }
+    return array;
+  }
 
-    /**
-     * This function is like `composeArgs` except that the arguments composition
-     * is tailored for `_.partialRight`.
-     *
-     * @private
-     * @param {Array} args The provided arguments.
-     * @param {Array} partials The arguments to append to those provided.
-     * @param {Array} holders The `partials` placeholder indexes.
-     * @params {boolean} [isCurried] Specify composing for a curried function.
-     * @returns {Array} Returns the new array of composed arguments.
-     */
-    function composeArgsRight(args, partials, holders, isCurried) {
-      var argsIndex = -1,
-          argsLength = args.length,
-          holdersIndex = -1,
-          holdersLength = holders.length,
-          rightIndex = -1,
-          rightLength = partials.length,
-          rangeLength = nativeMax(argsLength - holdersLength, 0),
-          result = Array(rangeLength + rightLength),
-          isUncurried = !isCurried;
+  /**
+   * The base implementation of `_.sum` and `_.sumBy` without support for
+   * iteratee shorthands.
+   *
+   * @private
+   * @param {Array} array The array to iterate over.
+   * @param {Function} iteratee The function invoked per iteration.
+   * @returns {number} Returns the sum.
+   */
+  function baseSum(array, iteratee) {
+    var result,
+        index = -1,
+        length = array.length;
 
-      while (++argsIndex < rangeLength) {
-        result[argsIndex] = args[argsIndex];
-      }
-      var offset = argsIndex;
-      while (++rightIndex < rightLength) {
-        result[offset + rightIndex] = partials[rightIndex];
-      }
-      while (++holdersIndex < holdersLength) {
-        if (isUncurried || argsIndex < argsLength) {
-          result[offset + holders[holdersIndex]] = args[argsIndex++];
-        }
+    while (++index < length) {
+      var current = iteratee(array[index]);
+      if (current !== undefined) {
+        result = result === undefined ? current : (result + current);
       }
-      return result;
     }
+    return result;
+  }
 
-    /**
-     * Copies the values of `source` to `array`.
-     *
-     * @private
-     * @param {Array} source The array to copy values from.
-     * @param {Array} [array=[]] The array to copy values to.
-     * @returns {Array} Returns `array`.
-     */
-    function copyArray(source, array) {
-      var index = -1,
-          length = source.length;
+  /**
+   * The base implementation of `_.times` without support for iteratee shorthands
+   * or max array length checks.
+   *
+   * @private
+   * @param {number} n The number of times to invoke `iteratee`.
+   * @param {Function} iteratee The function invoked per iteration.
+   * @returns {Array} Returns the array of results.
+   */
+  function baseTimes(n, iteratee) {
+    var index = -1,
+        result = Array(n);
 
-      array || (array = Array(length));
-      while (++index < length) {
-        array[index] = source[index];
-      }
-      return array;
+    while (++index < n) {
+      result[index] = iteratee(index);
     }
+    return result;
+  }
 
-    /**
-     * Copies properties of `source` to `object`.
-     *
-     * @private
-     * @param {Object} source The object to copy properties from.
-     * @param {Array} props The property identifiers to copy.
-     * @param {Object} [object={}] The object to copy properties to.
-     * @param {Function} [customizer] The function to customize copied values.
-     * @returns {Object} Returns `object`.
-     */
-    function copyObject(source, props, object, customizer) {
-      object || (object = {});
-
-      var index = -1,
-          length = props.length;
+  /**
+   * The base implementation of `_.toPairs` and `_.toPairsIn` which creates an array
+   * of key-value pairs for `object` corresponding to the property names of `props`.
+   *
+   * @private
+   * @param {Object} object The object to query.
+   * @param {Array} props The property names to get values for.
+   * @returns {Object} Returns the key-value pairs.
+   */
+  function baseToPairs(object, props) {
+    return arrayMap(props, function(key) {
+      return [key, object[key]];
+    });
+  }
 
-      while (++index < length) {
-        var key = props[index];
+  /**
+   * The base implementation of `_.unary` without support for storing metadata.
+   *
+   * @private
+   * @param {Function} func The function to cap arguments for.
+   * @returns {Function} Returns the new capped function.
+   */
+  function baseUnary(func) {
+    return function(value) {
+      return func(value);
+    };
+  }
 
-        var newValue = customizer
-          ? customizer(object[key], source[key], key, object, source)
-          : source[key];
+  /**
+   * The base implementation of `_.values` and `_.valuesIn` which creates an
+   * array of `object` property values corresponding to the property names
+   * of `props`.
+   *
+   * @private
+   * @param {Object} object The object to query.
+   * @param {Array} props The property names to get values for.
+   * @returns {Object} Returns the array of property values.
+   */
+  function baseValues(object, props) {
+    return arrayMap(props, function(key) {
+      return object[key];
+    });
+  }
 
-        assignValue(object, key, newValue);
-      }
-      return object;
-    }
+  /**
+   * Checks if a `cache` value for `key` exists.
+   *
+   * @private
+   * @param {Object} cache The cache to query.
+   * @param {string} key The key of the entry to check.
+   * @returns {boolean} Returns `true` if an entry for `key` exists, else `false`.
+   */
+  function cacheHas(cache, key) {
+    return cache.has(key);
+  }
 
-    /**
-     * Copies own symbol properties of `source` to `object`.
-     *
-     * @private
-     * @param {Object} source The object to copy symbols from.
-     * @param {Object} [object={}] The object to copy symbols to.
-     * @returns {Object} Returns `object`.
-     */
-    function copySymbols(source, object) {
-      return copyObject(source, getSymbols(source), object);
-    }
+  /**
+   * Used by `_.trim` and `_.trimStart` to get the index of the first string symbol
+   * that is not found in the character symbols.
+   *
+   * @private
+   * @param {Array} strSymbols The string symbols to inspect.
+   * @param {Array} chrSymbols The character symbols to find.
+   * @returns {number} Returns the index of the first unmatched string symbol.
+   */
+  function charsStartIndex(strSymbols, chrSymbols) {
+    var index = -1,
+        length = strSymbols.length;
 
-    /**
-     * Creates a function like `_.groupBy`.
-     *
-     * @private
-     * @param {Function} setter The function to set accumulator values.
-     * @param {Function} [initializer] The accumulator object initializer.
-     * @returns {Function} Returns the new aggregator function.
-     */
-    function createAggregator(setter, initializer) {
-      return function(collection, iteratee) {
-        var func = isArray(collection) ? arrayAggregator : baseAggregator,
-            accumulator = initializer ? initializer() : {};
+    while (++index < length && baseIndexOf(chrSymbols, strSymbols[index], 0) > -1) {}
+    return index;
+  }
 
-        return func(collection, setter, getIteratee(iteratee), accumulator);
-      };
-    }
+  /**
+   * Used by `_.trim` and `_.trimEnd` to get the index of the last string symbol
+   * that is not found in the character symbols.
+   *
+   * @private
+   * @param {Array} strSymbols The string symbols to inspect.
+   * @param {Array} chrSymbols The character symbols to find.
+   * @returns {number} Returns the index of the last unmatched string symbol.
+   */
+  function charsEndIndex(strSymbols, chrSymbols) {
+    var index = strSymbols.length;
 
-    /**
-     * Creates a function like `_.assign`.
-     *
-     * @private
-     * @param {Function} assigner The function to assign values.
-     * @returns {Function} Returns the new assigner function.
-     */
-    function createAssigner(assigner) {
-      return rest(function(object, sources) {
-        var index = -1,
-            length = sources.length,
-            customizer = length > 1 ? sources[length - 1] : undefined,
-            guard = length > 2 ? sources[2] : undefined;
+    while (index-- && baseIndexOf(chrSymbols, strSymbols[index], 0) > -1) {}
+    return index;
+  }
 
-        customizer = (assigner.length > 3 && typeof customizer == 'function')
-          ? (length--, customizer)
-          : undefined;
+  /**
+   * Gets the number of `placeholder` occurrences in `array`.
+   *
+   * @private
+   * @param {Array} array The array to inspect.
+   * @param {*} placeholder The placeholder to search for.
+   * @returns {number} Returns the placeholder count.
+   */
+  function countHolders(array, placeholder) {
+    var length = array.length,
+        result = 0;
 
-        if (guard && isIterateeCall(sources[0], sources[1], guard)) {
-          customizer = length < 3 ? undefined : customizer;
-          length = 1;
-        }
-        object = Object(object);
-        while (++index < length) {
-          var source = sources[index];
-          if (source) {
-            assigner(object, source, index, customizer);
-          }
-        }
-        return object;
-      });
+    while (length--) {
+      if (array[length] === placeholder) {
+        ++result;
+      }
     }
+    return result;
+  }
 
-    /**
-     * Creates a `baseEach` or `baseEachRight` function.
-     *
-     * @private
-     * @param {Function} eachFunc The function to iterate over a collection.
-     * @param {boolean} [fromRight] Specify iterating from right to left.
-     * @returns {Function} Returns the new base function.
-     */
-    function createBaseEach(eachFunc, fromRight) {
-      return function(collection, iteratee) {
-        if (collection == null) {
-          return collection;
-        }
-        if (!isArrayLike(collection)) {
-          return eachFunc(collection, iteratee);
-        }
-        var length = collection.length,
-            index = fromRight ? length : -1,
-            iterable = Object(collection);
+  /**
+   * Used by `_.deburr` to convert Latin-1 Supplement and Latin Extended-A
+   * letters to basic Latin letters.
+   *
+   * @private
+   * @param {string} letter The matched letter to deburr.
+   * @returns {string} Returns the deburred letter.
+   */
+  var deburrLetter = basePropertyOf(deburredLetters);
 
-        while ((fromRight ? index-- : ++index < length)) {
-          if (iteratee(iterable[index], index, iterable) === false) {
-            break;
-          }
-        }
-        return collection;
-      };
-    }
+  /**
+   * Used by `_.escape` to convert characters to HTML entities.
+   *
+   * @private
+   * @param {string} chr The matched character to escape.
+   * @returns {string} Returns the escaped character.
+   */
+  var escapeHtmlChar = basePropertyOf(htmlEscapes);
 
-    /**
-     * Creates a base function for methods like `_.forIn` and `_.forOwn`.
-     *
-     * @private
-     * @param {boolean} [fromRight] Specify iterating from right to left.
-     * @returns {Function} Returns the new base function.
-     */
-    function createBaseFor(fromRight) {
-      return function(object, iteratee, keysFunc) {
-        var index = -1,
-            iterable = Object(object),
-            props = keysFunc(object),
-            length = props.length;
+  /**
+   * Used by `_.template` to escape characters for inclusion in compiled string literals.
+   *
+   * @private
+   * @param {string} chr The matched character to escape.
+   * @returns {string} Returns the escaped character.
+   */
+  function escapeStringChar(chr) {
+    return '\\' + stringEscapes[chr];
+  }
 
-        while (length--) {
-          var key = props[fromRight ? length : ++index];
-          if (iteratee(iterable[key], key, iterable) === false) {
-            break;
-          }
-        }
-        return object;
-      };
-    }
+  /**
+   * Gets the value at `key` of `object`.
+   *
+   * @private
+   * @param {Object} [object] The object to query.
+   * @param {string} key The key of the property to get.
+   * @returns {*} Returns the property value.
+   */
+  function getValue(object, key) {
+    return object == null ? undefined : object[key];
+  }
 
-    /**
-     * Creates a function that wraps `func` to invoke it with the optional `this`
-     * binding of `thisArg`.
-     *
-     * @private
-     * @param {Function} func The function to wrap.
-     * @param {number} bitmask The bitmask of wrapper flags. See `createWrapper`
-     *  for more details.
-     * @param {*} [thisArg] The `this` binding of `func`.
-     * @returns {Function} Returns the new wrapped function.
-     */
-    function createBaseWrapper(func, bitmask, thisArg) {
-      var isBind = bitmask & BIND_FLAG,
-          Ctor = createCtorWrapper(func);
+  /**
+   * Checks if `string` contains Unicode symbols.
+   *
+   * @private
+   * @param {string} string The string to inspect.
+   * @returns {boolean} Returns `true` if a symbol is found, else `false`.
+   */
+  function hasUnicode(string) {
+    return reHasUnicode.test(string);
+  }
 
-      function wrapper() {
-        var fn = (this && this !== root && this instanceof wrapper) ? Ctor : func;
-        return fn.apply(isBind ? thisArg : this, arguments);
-      }
-      return wrapper;
-    }
+  /**
+   * Checks if `string` contains a word composed of Unicode symbols.
+   *
+   * @private
+   * @param {string} string The string to inspect.
+   * @returns {boolean} Returns `true` if a word is found, else `false`.
+   */
+  function hasUnicodeWord(string) {
+    return reHasUnicodeWord.test(string);
+  }
 
-    /**
-     * Creates a function like `_.lowerFirst`.
-     *
-     * @private
-     * @param {string} methodName The name of the `String` case method to use.
-     * @returns {Function} Returns the new case function.
-     */
-    function createCaseFirst(methodName) {
-      return function(string) {
-        string = toString(string);
+  /**
+   * Converts `iterator` to an array.
+   *
+   * @private
+   * @param {Object} iterator The iterator to convert.
+   * @returns {Array} Returns the converted array.
+   */
+  function iteratorToArray(iterator) {
+    var data,
+        result = [];
 
-        var strSymbols = reHasComplexSymbol.test(string)
-          ? stringToArray(string)
-          : undefined;
+    while (!(data = iterator.next()).done) {
+      result.push(data.value);
+    }
+    return result;
+  }
 
-        var chr = strSymbols
-          ? strSymbols[0]
-          : string.charAt(0);
+  /**
+   * Converts `map` to its key-value pairs.
+   *
+   * @private
+   * @param {Object} map The map to convert.
+   * @returns {Array} Returns the key-value pairs.
+   */
+  function mapToArray(map) {
+    var index = -1,
+        result = Array(map.size);
 
-        var trailing = strSymbols
-          ? castSlice(strSymbols, 1).join('')
-          : string.slice(1);
+    map.forEach(function(value, key) {
+      result[++index] = [key, value];
+    });
+    return result;
+  }
 
-        return chr[methodName]() + trailing;
-      };
-    }
+  /**
+   * Creates a unary function that invokes `func` with its argument transformed.
+   *
+   * @private
+   * @param {Function} func The function to wrap.
+   * @param {Function} transform The argument transform.
+   * @returns {Function} Returns the new function.
+   */
+  function overArg(func, transform) {
+    return function(arg) {
+      return func(transform(arg));
+    };
+  }
 
-    /**
-     * Creates a function like `_.camelCase`.
-     *
-     * @private
-     * @param {Function} callback The function to combine each word.
-     * @returns {Function} Returns the new compounder function.
-     */
-    function createCompounder(callback) {
-      return function(string) {
-        return arrayReduce(words(deburr(string).replace(reApos, '')), callback, '');
-      };
+  /**
+   * Replaces all `placeholder` elements in `array` with an internal placeholder
+   * and returns an array of their indexes.
+   *
+   * @private
+   * @param {Array} array The array to modify.
+   * @param {*} placeholder The placeholder to replace.
+   * @returns {Array} Returns the new array of placeholder indexes.
+   */
+  function replaceHolders(array, placeholder) {
+    var index = -1,
+        length = array.length,
+        resIndex = 0,
+        result = [];
+
+    while (++index < length) {
+      var value = array[index];
+      if (value === placeholder || value === PLACEHOLDER) {
+        array[index] = PLACEHOLDER;
+        result[resIndex++] = index;
+      }
     }
+    return result;
+  }
 
-    /**
-     * Creates a function that produces an instance of `Ctor` regardless of
-     * whether it was invoked as part of a `new` expression or by `call` or `apply`.
-     *
-     * @private
-     * @param {Function} Ctor The constructor to wrap.
-     * @returns {Function} Returns the new wrapped function.
-     */
-    function createCtorWrapper(Ctor) {
-      return function() {
-        // Use a `switch` statement to work with class constructors. See
-        // http://ecma-international.org/ecma-262/6.0/#sec-ecmascript-function-objects-call-thisargument-argumentslist
-        // for more details.
-        var args = arguments;
-        switch (args.length) {
-          case 0: return new Ctor;
-          case 1: return new Ctor(args[0]);
-          case 2: return new Ctor(args[0], args[1]);
-          case 3: return new Ctor(args[0], args[1], args[2]);
-          case 4: return new Ctor(args[0], args[1], args[2], args[3]);
-          case 5: return new Ctor(args[0], args[1], args[2], args[3], args[4]);
-          case 6: return new Ctor(args[0], args[1], args[2], args[3], args[4], args[5]);
-          case 7: return new Ctor(args[0], args[1], args[2], args[3], args[4], args[5], args[6]);
-        }
-        var thisBinding = baseCreate(Ctor.prototype),
-            result = Ctor.apply(thisBinding, args);
+  /**
+   * Converts `set` to an array of its values.
+   *
+   * @private
+   * @param {Object} set The set to convert.
+   * @returns {Array} Returns the values.
+   */
+  function setToArray(set) {
+    var index = -1,
+        result = Array(set.size);
 
-        // Mimic the constructor's `return` behavior.
-        // See https://es5.github.io/#x13.2.2 for more details.
-        return isObject(result) ? result : thisBinding;
-      };
-    }
+    set.forEach(function(value) {
+      result[++index] = value;
+    });
+    return result;
+  }
 
-    /**
-     * Creates a function that wraps `func` to enable currying.
-     *
-     * @private
-     * @param {Function} func The function to wrap.
-     * @param {number} bitmask The bitmask of wrapper flags. See `createWrapper`
-     *  for more details.
-     * @param {number} arity The arity of `func`.
-     * @returns {Function} Returns the new wrapped function.
-     */
-    function createCurryWrapper(func, bitmask, arity) {
-      var Ctor = createCtorWrapper(func);
+  /**
+   * Converts `set` to its value-value pairs.
+   *
+   * @private
+   * @param {Object} set The set to convert.
+   * @returns {Array} Returns the value-value pairs.
+   */
+  function setToPairs(set) {
+    var index = -1,
+        result = Array(set.size);
 
-      function wrapper() {
-        var length = arguments.length,
-            args = Array(length),
-            index = length,
-            placeholder = getHolder(wrapper);
+    set.forEach(function(value) {
+      result[++index] = [value, value];
+    });
+    return result;
+  }
 
-        while (index--) {
-          args[index] = arguments[index];
-        }
-        var holders = (length < 3 && args[0] !== placeholder && args[length - 1] !== placeholder)
-          ? []
-          : replaceHolders(args, placeholder);
+  /**
+   * A specialized version of `_.indexOf` which performs strict equality
+   * comparisons of values, i.e. `===`.
+   *
+   * @private
+   * @param {Array} array The array to inspect.
+   * @param {*} value The value to search for.
+   * @param {number} fromIndex The index to search from.
+   * @returns {number} Returns the index of the matched value, else `-1`.
+   */
+  function strictIndexOf(array, value, fromIndex) {
+    var index = fromIndex - 1,
+        length = array.length;
 
-        length -= holders.length;
-        if (length < arity) {
-          return createRecurryWrapper(
-            func, bitmask, createHybridWrapper, wrapper.placeholder, undefined,
-            args, holders, undefined, undefined, arity - length);
-        }
-        var fn = (this && this !== root && this instanceof wrapper) ? Ctor : func;
-        return apply(fn, this, args);
+    while (++index < length) {
+      if (array[index] === value) {
+        return index;
       }
-      return wrapper;
     }
+    return -1;
+  }
 
-    /**
-     * Creates a `_.find` or `_.findLast` function.
-     *
-     * @private
-     * @param {Function} findIndexFunc The function to find the collection index.
-     * @returns {Function} Returns the new find function.
-     */
-    function createFind(findIndexFunc) {
-      return function(collection, predicate, fromIndex) {
-        var iterable = Object(collection);
-        predicate = getIteratee(predicate, 3);
-        if (!isArrayLike(collection)) {
-          var props = keys(collection);
-        }
-        var index = findIndexFunc(props || collection, function(value, key) {
-          if (props) {
-            key = value;
-            value = iterable[key];
-          }
-          return predicate(value, key, iterable);
-        }, fromIndex);
-        return index > -1 ? collection[props ? props[index] : index] : undefined;
-      };
+  /**
+   * A specialized version of `_.lastIndexOf` which performs strict equality
+   * comparisons of values, i.e. `===`.
+   *
+   * @private
+   * @param {Array} array The array to inspect.
+   * @param {*} value The value to search for.
+   * @param {number} fromIndex The index to search from.
+   * @returns {number} Returns the index of the matched value, else `-1`.
+   */
+  function strictLastIndexOf(array, value, fromIndex) {
+    var index = fromIndex + 1;
+    while (index--) {
+      if (array[index] === value) {
+        return index;
+      }
     }
+    return index;
+  }
 
-    /**
-     * Creates a `_.flow` or `_.flowRight` function.
-     *
-     * @private
-     * @param {boolean} [fromRight] Specify iterating from right to left.
-     * @returns {Function} Returns the new flow function.
-     */
-    function createFlow(fromRight) {
-      return rest(function(funcs) {
-        funcs = baseFlatten(funcs, 1);
-
-        var length = funcs.length,
-            index = length,
-            prereq = LodashWrapper.prototype.thru;
+  /**
+   * Gets the number of symbols in `string`.
+   *
+   * @private
+   * @param {string} string The string to inspect.
+   * @returns {number} Returns the string size.
+   */
+  function stringSize(string) {
+    return hasUnicode(string)
+      ? unicodeSize(string)
+      : asciiSize(string);
+  }
 
-        if (fromRight) {
-          funcs.reverse();
-        }
-        while (index--) {
-          var func = funcs[index];
-          if (typeof func != 'function') {
-            throw new TypeError(FUNC_ERROR_TEXT);
-          }
-          if (prereq && !wrapper && getFuncName(func) == 'wrapper') {
-            var wrapper = new LodashWrapper([], true);
-          }
-        }
-        index = wrapper ? index : length;
-        while (++index < length) {
-          func = funcs[index];
+  /**
+   * Converts `string` to an array.
+   *
+   * @private
+   * @param {string} string The string to convert.
+   * @returns {Array} Returns the converted array.
+   */
+  function stringToArray(string) {
+    return hasUnicode(string)
+      ? unicodeToArray(string)
+      : asciiToArray(string);
+  }
 
-          var funcName = getFuncName(func),
-              data = funcName == 'wrapper' ? getData(func) : undefined;
+  /**
+   * Used by `_.unescape` to convert HTML entities to characters.
+   *
+   * @private
+   * @param {string} chr The matched character to unescape.
+   * @returns {string} Returns the unescaped character.
+   */
+  var unescapeHtmlChar = basePropertyOf(htmlUnescapes);
 
-          if (data && isLaziable(data[0]) &&
-                data[1] == (ARY_FLAG | CURRY_FLAG | PARTIAL_FLAG | REARG_FLAG) &&
-                !data[4].length && data[9] == 1
-              ) {
-            wrapper = wrapper[getFuncName(data[0])].apply(wrapper, data[3]);
-          } else {
-            wrapper = (func.length == 1 && isLaziable(func))
-              ? wrapper[funcName]()
-              : wrapper.thru(func);
-          }
-        }
-        return function() {
-          var args = arguments,
-              value = args[0];
-
-          if (wrapper && args.length == 1 &&
-              isArray(value) && value.length >= LARGE_ARRAY_SIZE) {
-            return wrapper.plant(value).value();
-          }
-          var index = 0,
-              result = length ? funcs[index].apply(this, args) : value;
-
-          while (++index < length) {
-            result = funcs[index].call(this, result);
-          }
-          return result;
-        };
-      });
+  /**
+   * Gets the size of a Unicode `string`.
+   *
+   * @private
+   * @param {string} string The string inspect.
+   * @returns {number} Returns the string size.
+   */
+  function unicodeSize(string) {
+    var result = reUnicode.lastIndex = 0;
+    while (reUnicode.test(string)) {
+      ++result;
     }
+    return result;
+  }
 
-    /**
-     * Creates a function that wraps `func` to invoke it with optional `this`
-     * binding of `thisArg`, partial application, and currying.
-     *
-     * @private
-     * @param {Function|string} func The function or method name to wrap.
-     * @param {number} bitmask The bitmask of wrapper flags. See `createWrapper`
-     *  for more details.
-     * @param {*} [thisArg] The `this` binding of `func`.
-     * @param {Array} [partials] The arguments to prepend to those provided to
-     *  the new function.
-     * @param {Array} [holders] The `partials` placeholder indexes.
-     * @param {Array} [partialsRight] The arguments to append to those provided
-     *  to the new function.
-     * @param {Array} [holdersRight] The `partialsRight` placeholder indexes.
-     * @param {Array} [argPos] The argument positions of the new function.
-     * @param {number} [ary] The arity cap of `func`.
-     * @param {number} [arity] The arity of `func`.
-     * @returns {Function} Returns the new wrapped function.
-     */
-    function createHybridWrapper(func, bitmask, thisArg, partials, holders, partialsRight, holdersRight, argPos, ary, arity) {
-      var isAry = bitmask & ARY_FLAG,
-          isBind = bitmask & BIND_FLAG,
-          isBindKey = bitmask & BIND_KEY_FLAG,
-          isCurried = bitmask & (CURRY_FLAG | CURRY_RIGHT_FLAG),
-          isFlip = bitmask & FLIP_FLAG,
-          Ctor = isBindKey ? undefined : createCtorWrapper(func);
+  /**
+   * Converts a Unicode `string` to an array.
+   *
+   * @private
+   * @param {string} string The string to convert.
+   * @returns {Array} Returns the converted array.
+   */
+  function unicodeToArray(string) {
+    return string.match(reUnicode) || [];
+  }
 
-      function wrapper() {
-        var length = arguments.length,
-            args = Array(length),
-            index = length;
+  /**
+   * Splits a Unicode `string` into an array of its words.
+   *
+   * @private
+   * @param {string} The string to inspect.
+   * @returns {Array} Returns the words of `string`.
+   */
+  function unicodeWords(string) {
+    return string.match(reUnicodeWord) || [];
+  }
 
-        while (index--) {
-          args[index] = arguments[index];
-        }
-        if (isCurried) {
-          var placeholder = getHolder(wrapper),
-              holdersCount = countHolders(args, placeholder);
-        }
-        if (partials) {
-          args = composeArgs(args, partials, holders, isCurried);
-        }
-        if (partialsRight) {
-          args = composeArgsRight(args, partialsRight, holdersRight, isCurried);
-        }
-        length -= holdersCount;
-        if (isCurried && length < arity) {
-          var newHolders = replaceHolders(args, placeholder);
-          return createRecurryWrapper(
-            func, bitmask, createHybridWrapper, wrapper.placeholder, thisArg,
-            args, newHolders, argPos, ary, arity - length
-          );
-        }
-        var thisBinding = isBind ? thisArg : this,
-            fn = isBindKey ? thisBinding[func] : func;
+  /*--------------------------------------------------------------------------*/
 
-        length = args.length;
-        if (argPos) {
-          args = reorder(args, argPos);
-        } else if (isFlip && length > 1) {
-          args.reverse();
-        }
-        if (isAry && ary < length) {
-          args.length = ary;
-        }
-        if (this && this !== root && this instanceof wrapper) {
-          fn = Ctor || createCtorWrapper(fn);
-        }
-        return fn.apply(thisBinding, args);
-      }
-      return wrapper;
-    }
+  /**
+   * Create a new pristine `lodash` function using the `context` object.
+   *
+   * @static
+   * @memberOf _
+   * @since 1.1.0
+   * @category Util
+   * @param {Object} [context=root] The context object.
+   * @returns {Function} Returns a new `lodash` function.
+   * @example
+   *
+   * _.mixin({ 'foo': _.constant('foo') });
+   *
+   * var lodash = _.runInContext();
+   * lodash.mixin({ 'bar': lodash.constant('bar') });
+   *
+   * _.isFunction(_.foo);
+   * // => true
+   * _.isFunction(_.bar);
+   * // => false
+   *
+   * lodash.isFunction(lodash.foo);
+   * // => false
+   * lodash.isFunction(lodash.bar);
+   * // => true
+   *
+   * // Create a suped-up `defer` in Node.js.
+   * var defer = _.runInContext({ 'setTimeout': setImmediate }).defer;
+   */
+  var runInContext = (function runInContext(context) {
+    context = context == null ? root : _.defaults(root.Object(), context, _.pick(root, contextProps));
 
-    /**
-     * Creates a function like `_.invertBy`.
-     *
-     * @private
-     * @param {Function} setter The function to set accumulator values.
-     * @param {Function} toIteratee The function to resolve iteratees.
-     * @returns {Function} Returns the new inverter function.
-     */
-    function createInverter(setter, toIteratee) {
-      return function(object, iteratee) {
-        return baseInverter(object, setter, toIteratee(iteratee), {});
-      };
-    }
+    /** Built-in constructor references. */
+    var Array = context.Array,
+        Date = context.Date,
+        Error = context.Error,
+        Function = context.Function,
+        Math = context.Math,
+        Object = context.Object,
+        RegExp = context.RegExp,
+        String = context.String,
+        TypeError = context.TypeError;
 
-    /**
-     * Creates a function that performs a mathematical operation on two values.
-     *
-     * @private
-     * @param {Function} operator The function to perform the operation.
-     * @returns {Function} Returns the new mathematical operation function.
-     */
-    function createMathOperation(operator) {
-      return function(value, other) {
-        var result;
-        if (value === undefined && other === undefined) {
-          return 0;
-        }
-        if (value !== undefined) {
-          result = value;
-        }
-        if (other !== undefined) {
-          if (result === undefined) {
-            return other;
-          }
-          if (typeof value == 'string' || typeof other == 'string') {
-            value = baseToString(value);
-            other = baseToString(other);
-          } else {
-            value = baseToNumber(value);
-            other = baseToNumber(other);
-          }
-          result = operator(value, other);
-        }
-        return result;
-      };
-    }
+    /** Used for built-in method references. */
+    var arrayProto = Array.prototype,
+        funcProto = Function.prototype,
+        objectProto = Object.prototype;
 
-    /**
-     * Creates a function like `_.over`.
-     *
-     * @private
-     * @param {Function} arrayFunc The function to iterate over iteratees.
-     * @returns {Function} Returns the new over function.
-     */
-    function createOver(arrayFunc) {
-      return rest(function(iteratees) {
-        iteratees = (iteratees.length == 1 && isArray(iteratees[0]))
-          ? arrayMap(iteratees[0], baseUnary(getIteratee()))
-          : arrayMap(baseFlatten(iteratees, 1, isFlattenableIteratee), baseUnary(getIteratee()));
+    /** Used to detect overreaching core-js shims. */
+    var coreJsData = context['__core-js_shared__'];
 
-        return rest(function(args) {
-          var thisArg = this;
-          return arrayFunc(iteratees, function(iteratee) {
-            return apply(iteratee, thisArg, args);
-          });
-        });
-      });
-    }
+    /** Used to resolve the decompiled source of functions. */
+    var funcToString = funcProto.toString;
 
-    /**
-     * Creates the padding for `string` based on `length`. The `chars` string
-     * is truncated if the number of characters exceeds `length`.
-     *
-     * @private
-     * @param {number} length The padding length.
-     * @param {string} [chars=' '] The string used as padding.
-     * @returns {string} Returns the padding for `string`.
-     */
-    function createPadding(length, chars) {
-      chars = chars === undefined ? ' ' : baseToString(chars);
+    /** Used to check objects for own properties. */
+    var hasOwnProperty = objectProto.hasOwnProperty;
 
-      var charsLength = chars.length;
-      if (charsLength < 2) {
-        return charsLength ? baseRepeat(chars, length) : chars;
-      }
-      var result = baseRepeat(chars, nativeCeil(length / stringSize(chars)));
-      return reHasComplexSymbol.test(chars)
-        ? castSlice(stringToArray(result), 0, length).join('')
-        : result.slice(0, length);
-    }
+    /** Used to generate unique IDs. */
+    var idCounter = 0;
+
+    /** Used to detect methods masquerading as native. */
+    var maskSrcKey = (function() {
+      var uid = /[^.]+$/.exec(coreJsData && coreJsData.keys && coreJsData.keys.IE_PROTO || '');
+      return uid ? ('Symbol(src)_1.' + uid) : '';
+    }());
 
     /**
-     * Creates a function that wraps `func` to invoke it with the `this` binding
-     * of `thisArg` and `partials` prepended to the arguments it receives.
-     *
-     * @private
-     * @param {Function} func The function to wrap.
-     * @param {number} bitmask The bitmask of wrapper flags. See `createWrapper`
-     *  for more details.
-     * @param {*} thisArg The `this` binding of `func`.
-     * @param {Array} partials The arguments to prepend to those provided to
-     *  the new function.
-     * @returns {Function} Returns the new wrapped function.
+     * Used to resolve the
+     * [`toStringTag`](http://ecma-international.org/ecma-262/7.0/#sec-object.prototype.tostring)
+     * of values.
      */
-    function createPartialWrapper(func, bitmask, thisArg, partials) {
-      var isBind = bitmask & BIND_FLAG,
-          Ctor = createCtorWrapper(func);
+    var nativeObjectToString = objectProto.toString;
 
-      function wrapper() {
-        var argsIndex = -1,
-            argsLength = arguments.length,
-            leftIndex = -1,
-            leftLength = partials.length,
-            args = Array(leftLength + argsLength),
-            fn = (this && this !== root && this instanceof wrapper) ? Ctor : func;
+    /** Used to infer the `Object` constructor. */
+    var objectCtorString = funcToString.call(Object);
 
-        while (++leftIndex < leftLength) {
-          args[leftIndex] = partials[leftIndex];
-        }
-        while (argsLength--) {
-          args[leftIndex++] = arguments[++argsIndex];
-        }
-        return apply(fn, isBind ? thisArg : this, args);
-      }
-      return wrapper;
-    }
+    /** Used to restore the original `_` reference in `_.noConflict`. */
+    var oldDash = root._;
 
-    /**
-     * Creates a `_.range` or `_.rangeRight` function.
+    /** Used to detect if a method is native. */
+    var reIsNative = RegExp('^' +
+      funcToString.call(hasOwnProperty).replace(reRegExpChar, '\\$&')
+      .replace(/hasOwnProperty|(function).*?(?=\\\()| for .+?(?=\\\])/g, '$1.*?') + '$'
+    );
+
+    /** Built-in value references. */
+    var Buffer = moduleExports ? context.Buffer : undefined,
+        Symbol = context.Symbol,
+        Uint8Array = context.Uint8Array,
+        allocUnsafe = Buffer ? Buffer.allocUnsafe : undefined,
+        getPrototype = overArg(Object.getPrototypeOf, Object),
+        objectCreate = Object.create,
+        propertyIsEnumerable = objectProto.propertyIsEnumerable,
+        splice = arrayProto.splice,
+        spreadableSymbol = Symbol ? Symbol.isConcatSpreadable : undefined,
+        symIterator = Symbol ? Symbol.iterator : undefined,
+        symToStringTag = Symbol ? Symbol.toStringTag : undefined;
+
+    var defineProperty = (function() {
+      try {
+        var func = getNative(Object, 'defineProperty');
+        func({}, '', {});
+        return func;
+      } catch (e) {}
+    }());
+
+    /** Mocked built-ins. */
+    var ctxClearTimeout = context.clearTimeout !== root.clearTimeout && context.clearTimeout,
+        ctxNow = Date && Date.now !== root.Date.now && Date.now,
+        ctxSetTimeout = context.setTimeout !== root.setTimeout && context.setTimeout;
+
+    /* Built-in method references for those with the same name as other `lodash` methods. */
+    var nativeCeil = Math.ceil,
+        nativeFloor = Math.floor,
+        nativeGetSymbols = Object.getOwnPropertySymbols,
+        nativeIsBuffer = Buffer ? Buffer.isBuffer : undefined,
+        nativeIsFinite = context.isFinite,
+        nativeJoin = arrayProto.join,
+        nativeKeys = overArg(Object.keys, Object),
+        nativeMax = Math.max,
+        nativeMin = Math.min,
+        nativeNow = Date.now,
+        nativeParseInt = context.parseInt,
+        nativeRandom = Math.random,
+        nativeReverse = arrayProto.reverse;
+
+    /* Built-in method references that are verified to be native. */
+    var DataView = getNative(context, 'DataView'),
+        Map = getNative(context, 'Map'),
+        Promise = getNative(context, 'Promise'),
+        Set = getNative(context, 'Set'),
+        WeakMap = getNative(context, 'WeakMap'),
+        nativeCreate = getNative(Object, 'create');
+
+    /** Used to store function metadata. */
+    var metaMap = WeakMap && new WeakMap;
+
+    /** Used to lookup unminified function names. */
+    var realNames = {};
+
+    /** Used to detect maps, sets, and weakmaps. */
+    var dataViewCtorString = toSource(DataView),
+        mapCtorString = toSource(Map),
+        promiseCtorString = toSource(Promise),
+        setCtorString = toSource(Set),
+        weakMapCtorString = toSource(WeakMap);
+
+    /** Used to convert symbols to primitives and strings. */
+    var symbolProto = Symbol ? Symbol.prototype : undefined,
+        symbolValueOf = symbolProto ? symbolProto.valueOf : undefined,
+        symbolToString = symbolProto ? symbolProto.toString : undefined;
+
+    /*------------------------------------------------------------------------*/
+
+    /**
+     * Creates a `lodash` object which wraps `value` to enable implicit method
+     * chain sequences. Methods that operate on and return arrays, collections,
+     * and functions can be chained together. Methods that retrieve a single value
+     * or may return a primitive value will automatically end the chain sequence
+     * and return the unwrapped value. Otherwise, the value must be unwrapped
+     * with `_#value`.
      *
-     * @private
-     * @param {boolean} [fromRight] Specify iterating from right to left.
-     * @returns {Function} Returns the new range function.
+     * Explicit chain sequences, which must be unwrapped with `_#value`, may be
+     * enabled using `_.chain`.
+     *
+     * The execution of chained methods is lazy, that is, it's deferred until
+     * `_#value` is implicitly or explicitly called.
+     *
+     * Lazy evaluation allows several methods to support shortcut fusion.
+     * Shortcut fusion is an optimization to merge iteratee calls; this avoids
+     * the creation of intermediate arrays and can greatly reduce the number of
+     * iteratee executions. Sections of a chain sequence qualify for shortcut
+     * fusion if the section is applied to an array and iteratees accept only
+     * one argument. The heuristic for whether a section qualifies for shortcut
+     * fusion is subject to change.
+     *
+     * Chaining is supported in custom builds as long as the `_#value` method is
+     * directly or indirectly included in the build.
+     *
+     * In addition to lodash methods, wrappers have `Array` and `String` methods.
+     *
+     * The wrapper `Array` methods are:
+     * `concat`, `join`, `pop`, `push`, `shift`, `sort`, `splice`, and `unshift`
+     *
+     * The wrapper `String` methods are:
+     * `replace` and `split`
+     *
+     * The wrapper methods that support shortcut fusion are:
+     * `at`, `compact`, `drop`, `dropRight`, `dropWhile`, `filter`, `find`,
+     * `findLast`, `head`, `initial`, `last`, `map`, `reject`, `reverse`, `slice`,
+     * `tail`, `take`, `takeRight`, `takeRightWhile`, `takeWhile`, and `toArray`
+     *
+     * The chainable wrapper methods are:
+     * `after`, `ary`, `assign`, `assignIn`, `assignInWith`, `assignWith`, `at`,
+     * `before`, `bind`, `bindAll`, `bindKey`, `castArray`, `chain`, `chunk`,
+     * `commit`, `compact`, `concat`, `conforms`, `constant`, `countBy`, `create`,
+     * `curry`, `debounce`, `defaults`, `defaultsDeep`, `defer`, `delay`,
+     * `difference`, `differenceBy`, `differenceWith`, `drop`, `dropRight`,
+     * `dropRightWhile`, `dropWhile`, `extend`, `extendWith`, `fill`, `filter`,
+     * `flatMap`, `flatMapDeep`, `flatMapDepth`, `flatten`, `flattenDeep`,
+     * `flattenDepth`, `flip`, `flow`, `flowRight`, `fromPairs`, `functions`,
+     * `functionsIn`, `groupBy`, `initial`, `intersection`, `intersectionBy`,
+     * `intersectionWith`, `invert`, `invertBy`, `invokeMap`, `iteratee`, `keyBy`,
+     * `keys`, `keysIn`, `map`, `mapKeys`, `mapValues`, `matches`, `matchesProperty`,
+     * `memoize`, `merge`, `mergeWith`, `method`, `methodOf`, `mixin`, `negate`,
+     * `nthArg`, `omit`, `omitBy`, `once`, `orderBy`, `over`, `overArgs`,
+     * `overEvery`, `overSome`, `partial`, `partialRight`, `partition`, `pick`,
+     * `pickBy`, `plant`, `property`, `propertyOf`, `pull`, `pullAll`, `pullAllBy`,
+     * `pullAllWith`, `pullAt`, `push`, `range`, `rangeRight`, `rearg`, `reject`,
+     * `remove`, `rest`, `reverse`, `sampleSize`, `set`, `setWith`, `shuffle`,
+     * `slice`, `sort`, `sortBy`, `splice`, `spread`, `tail`, `take`, `takeRight`,
+     * `takeRightWhile`, `takeWhile`, `tap`, `throttle`, `thru`, `toArray`,
+     * `toPairs`, `toPairsIn`, `toPath`, `toPlainObject`, `transform`, `unary`,
+     * `union`, `unionBy`, `unionWith`, `uniq`, `uniqBy`, `uniqWith`, `unset`,
+     * `unshift`, `unzip`, `unzipWith`, `update`, `updateWith`, `values`,
+     * `valuesIn`, `without`, `wrap`, `xor`, `xorBy`, `xorWith`, `zip`,
+     * `zipObject`, `zipObjectDeep`, and `zipWith`
+     *
+     * The wrapper methods that are **not** chainable by default are:
+     * `add`, `attempt`, `camelCase`, `capitalize`, `ceil`, `clamp`, `clone`,
+     * `cloneDeep`, `cloneDeepWith`, `cloneWith`, `conformsTo`, `deburr`,
+     * `defaultTo`, `divide`, `each`, `eachRight`, `endsWith`, `eq`, `escape`,
+     * `escapeRegExp`, `every`, `find`, `findIndex`, `findKey`, `findLast`,
+     * `findLastIndex`, `findLastKey`, `first`, `floor`, `forEach`, `forEachRight`,
+     * `forIn`, `forInRight`, `forOwn`, `forOwnRight`, `get`, `gt`, `gte`, `has`,
+     * `hasIn`, `head`, `identity`, `includes`, `indexOf`, `inRange`, `invoke`,
+     * `isArguments`, `isArray`, `isArrayBuffer`, `isArrayLike`, `isArrayLikeObject`,
+     * `isBoolean`, `isBuffer`, `isDate`, `isElement`, `isEmpty`, `isEqual`,
+     * `isEqualWith`, `isError`, `isFinite`, `isFunction`, `isInteger`, `isLength`,
+     * `isMap`, `isMatch`, `isMatchWith`, `isNaN`, `isNative`, `isNil`, `isNull`,
+     * `isNumber`, `isObject`, `isObjectLike`, `isPlainObject`, `isRegExp`,
+     * `isSafeInteger`, `isSet`, `isString`, `isUndefined`, `isTypedArray`,
+     * `isWeakMap`, `isWeakSet`, `join`, `kebabCase`, `last`, `lastIndexOf`,
+     * `lowerCase`, `lowerFirst`, `lt`, `lte`, `max`, `maxBy`, `mean`, `meanBy`,
+     * `min`, `minBy`, `multiply`, `noConflict`, `noop`, `now`, `nth`, `pad`,
+     * `padEnd`, `padStart`, `parseInt`, `pop`, `random`, `reduce`, `reduceRight`,
+     * `repeat`, `result`, `round`, `runInContext`, `sample`, `shift`, `size`,
+     * `snakeCase`, `some`, `sortedIndex`, `sortedIndexBy`, `sortedLastIndex`,
+     * `sortedLastIndexBy`, `startCase`, `startsWith`, `stubArray`, `stubFalse`,
+     * `stubObject`, `stubString`, `stubTrue`, `subtract`, `sum`, `sumBy`,
+     * `template`, `times`, `toFinite`, `toInteger`, `toJSON`, `toLength`,
+     * `toLower`, `toNumber`, `toSafeInteger`, `toString`, `toUpper`, `trim`,
+     * `trimEnd`, `trimStart`, `truncate`, `unescape`, `uniqueId`, `upperCase`,
+     * `upperFirst`, `value`, and `words`
+     *
+     * @name _
+     * @constructor
+     * @category Seq
+     * @param {*} value The value to wrap in a `lodash` instance.
+     * @returns {Object} Returns the new `lodash` wrapper instance.
+     * @example
+     *
+     * function square(n) {
+     *   return n * n;
+     * }
+     *
+     * var wrapped = _([1, 2, 3]);
+     *
+     * // Returns an unwrapped value.
+     * wrapped.reduce(_.add);
+     * // => 6
+     *
+     * // Returns a wrapped value.
+     * var squares = wrapped.map(square);
+     *
+     * _.isArray(squares);
+     * // => false
+     *
+     * _.isArray(squares.value());
+     * // => true
      */
-    function createRange(fromRight) {
-      return function(start, end, step) {
-        if (step && typeof step != 'number' && isIterateeCall(start, end, step)) {
-          end = step = undefined;
+    function lodash(value) {
+      if (isObjectLike(value) && !isArray(value) && !(value instanceof LazyWrapper)) {
+        if (value instanceof LodashWrapper) {
+          return value;
         }
-        // Ensure the sign of `-0` is preserved.
-        start = toNumber(start);
-        start = start === start ? start : 0;
-        if (end === undefined) {
-          end = start;
-          start = 0;
-        } else {
-          end = toNumber(end) || 0;
+        if (hasOwnProperty.call(value, '__wrapped__')) {
+          return wrapperClone(value);
         }
-        step = step === undefined ? (start < end ? 1 : -1) : (toNumber(step) || 0);
-        return baseRange(start, end, step, fromRight);
-      };
+      }
+      return new LodashWrapper(value);
     }
 
     /**
-     * Creates a function that performs a relational operation on two values.
+     * The base implementation of `_.create` without support for assigning
+     * properties to the created object.
      *
      * @private
-     * @param {Function} operator The function to perform the operation.
-     * @returns {Function} Returns the new relational operation function.
+     * @param {Object} proto The object to inherit from.
+     * @returns {Object} Returns the new object.
      */
-    function createRelationalOperation(operator) {
-      return function(value, other) {
-        if (!(typeof value == 'string' && typeof other == 'string')) {
-          value = toNumber(value);
-          other = toNumber(other);
+    var baseCreate = (function() {
+      function object() {}
+      return function(proto) {
+        if (!isObject(proto)) {
+          return {};
         }
-        return operator(value, other);
+        if (objectCreate) {
+          return objectCreate(proto);
+        }
+        object.prototype = proto;
+        var result = new object;
+        object.prototype = undefined;
+        return result;
       };
-    }
+    }());
 
     /**
-     * Creates a function that wraps `func` to continue currying.
+     * The function whose prototype chain sequence wrappers inherit from.
      *
      * @private
-     * @param {Function} func The function to wrap.
-     * @param {number} bitmask The bitmask of wrapper flags. See `createWrapper`
-     *  for more details.
-     * @param {Function} wrapFunc The function to create the `func` wrapper.
-     * @param {*} placeholder The placeholder value.
-     * @param {*} [thisArg] The `this` binding of `func`.
-     * @param {Array} [partials] The arguments to prepend to those provided to
-     *  the new function.
-     * @param {Array} [holders] The `partials` placeholder indexes.
-     * @param {Array} [argPos] The argument positions of the new function.
-     * @param {number} [ary] The arity cap of `func`.
-     * @param {number} [arity] The arity of `func`.
-     * @returns {Function} Returns the new wrapped function.
      */
-    function createRecurryWrapper(func, bitmask, wrapFunc, placeholder, thisArg, partials, holders, argPos, ary, arity) {
-      var isCurry = bitmask & CURRY_FLAG,
-          newHolders = isCurry ? holders : undefined,
-          newHoldersRight = isCurry ? undefined : holders,
-          newPartials = isCurry ? partials : undefined,
-          newPartialsRight = isCurry ? undefined : partials;
-
-      bitmask |= (isCurry ? PARTIAL_FLAG : PARTIAL_RIGHT_FLAG);
-      bitmask &= ~(isCurry ? PARTIAL_RIGHT_FLAG : PARTIAL_FLAG);
-
-      if (!(bitmask & CURRY_BOUND_FLAG)) {
-        bitmask &= ~(BIND_FLAG | BIND_KEY_FLAG);
-      }
-      var newData = [
-        func, bitmask, thisArg, newPartials, newHolders, newPartialsRight,
-        newHoldersRight, argPos, ary, arity
-      ];
-
-      var result = wrapFunc.apply(undefined, newData);
-      if (isLaziable(func)) {
-        setData(result, newData);
-      }
-      result.placeholder = placeholder;
-      return result;
+    function baseLodash() {
+      // No operation performed.
     }
 
     /**
-     * Creates a function like `_.round`.
+     * The base constructor for creating `lodash` wrapper objects.
      *
      * @private
-     * @param {string} methodName The name of the `Math` method to use when rounding.
-     * @returns {Function} Returns the new round function.
+     * @param {*} value The value to wrap.
+     * @param {boolean} [chainAll] Enable explicit method chain sequences.
      */
-    function createRound(methodName) {
-      var func = Math[methodName];
-      return function(number, precision) {
-        number = toNumber(number);
-        precision = nativeMin(toInteger(precision), 292);
-        if (precision) {
-          // Shift with exponential notation to avoid floating-point issues.
-          // See [MDN](https://mdn.io/round#Examples) for more details.
-          var pair = (toString(number) + 'e').split('e'),
-              value = func(pair[0] + 'e' + (+pair[1] + precision));
+    function LodashWrapper(value, chainAll) {
+      this.__wrapped__ = value;
+      this.__actions__ = [];
+      this.__chain__ = !!chainAll;
+      this.__index__ = 0;
+      this.__values__ = undefined;
+    }
 
-          pair = (toString(value) + 'e').split('e');
-          return +(pair[0] + 'e' + (+pair[1] - precision));
-        }
-        return func(number);
-      };
-    }
+    /**
+     * By default, the template delimiters used by lodash are like those in
+     * embedded Ruby (ERB) as well as ES2015 template strings. Change the
+     * following template settings to use alternative delimiters.
+     *
+     * @static
+     * @memberOf _
+     * @type {Object}
+     */
+    lodash.templateSettings = {
+
+      /**
+       * Used to detect `data` property values to be HTML-escaped.
+       *
+       * @memberOf _.templateSettings
+       * @type {RegExp}
+       */
+      'escape': reEscape,
+
+      /**
+       * Used to detect code to be evaluated.
+       *
+       * @memberOf _.templateSettings
+       * @type {RegExp}
+       */
+      'evaluate': reEvaluate,
+
+      /**
+       * Used to detect `data` property values to inject.
+       *
+       * @memberOf _.templateSettings
+       * @type {RegExp}
+       */
+      'interpolate': reInterpolate,
+
+      /**
+       * Used to reference the data object in the template text.
+       *
+       * @memberOf _.templateSettings
+       * @type {string}
+       */
+      'variable': '',
+
+      /**
+       * Used to import variables into the compiled template.
+       *
+       * @memberOf _.templateSettings
+       * @type {Object}
+       */
+      'imports': {
+
+        /**
+         * A reference to the `lodash` function.
+         *
+         * @memberOf _.templateSettings.imports
+         * @type {Function}
+         */
+        '_': lodash
+      }
+    };
+
+    // Ensure wrappers are instances of `baseLodash`.
+    lodash.prototype = baseLodash.prototype;
+    lodash.prototype.constructor = lodash;
+
+    LodashWrapper.prototype = baseCreate(baseLodash.prototype);
+    LodashWrapper.prototype.constructor = LodashWrapper;
+
+    /*------------------------------------------------------------------------*/
 
     /**
-     * Creates a set of `values`.
+     * Creates a lazy wrapper object which wraps `value` to enable lazy evaluation.
      *
      * @private
-     * @param {Array} values The values to add to the set.
-     * @returns {Object} Returns the new set.
+     * @constructor
+     * @param {*} value The value to wrap.
      */
-    var createSet = !(Set && (1 / setToArray(new Set([,-0]))[1]) == INFINITY) ? noop : function(values) {
-      return new Set(values);
-    };
+    function LazyWrapper(value) {
+      this.__wrapped__ = value;
+      this.__actions__ = [];
+      this.__dir__ = 1;
+      this.__filtered__ = false;
+      this.__iteratees__ = [];
+      this.__takeCount__ = MAX_ARRAY_LENGTH;
+      this.__views__ = [];
+    }
 
     /**
-     * Creates a `_.toPairs` or `_.toPairsIn` function.
+     * Creates a clone of the lazy wrapper object.
      *
      * @private
-     * @param {Function} keysFunc The function to get the keys of a given object.
-     * @returns {Function} Returns the new pairs function.
+     * @name clone
+     * @memberOf LazyWrapper
+     * @returns {Object} Returns the cloned `LazyWrapper` object.
      */
-    function createToPairs(keysFunc) {
-      return function(object) {
-        var tag = getTag(object);
-        if (tag == mapTag) {
-          return mapToArray(object);
-        }
-        if (tag == setTag) {
-          return setToPairs(object);
-        }
-        return baseToPairs(object, keysFunc(object));
-      };
+    function lazyClone() {
+      var result = new LazyWrapper(this.__wrapped__);
+      result.__actions__ = copyArray(this.__actions__);
+      result.__dir__ = this.__dir__;
+      result.__filtered__ = this.__filtered__;
+      result.__iteratees__ = copyArray(this.__iteratees__);
+      result.__takeCount__ = this.__takeCount__;
+      result.__views__ = copyArray(this.__views__);
+      return result;
     }
 
     /**
-     * Creates a function that either curries or invokes `func` with optional
-     * `this` binding and partially applied arguments.
+     * Reverses the direction of lazy iteration.
      *
      * @private
-     * @param {Function|string} func The function or method name to wrap.
-     * @param {number} bitmask The bitmask of wrapper flags.
-     *  The bitmask may be composed of the following flags:
-     *     1 - `_.bind`
-     *     2 - `_.bindKey`
-     *     4 - `_.curry` or `_.curryRight` of a bound function
-     *     8 - `_.curry`
-     *    16 - `_.curryRight`
-     *    32 - `_.partial`
-     *    64 - `_.partialRight`
-     *   128 - `_.rearg`
-     *   256 - `_.ary`
-     *   512 - `_.flip`
-     * @param {*} [thisArg] The `this` binding of `func`.
-     * @param {Array} [partials] The arguments to be partially applied.
-     * @param {Array} [holders] The `partials` placeholder indexes.
-     * @param {Array} [argPos] The argument positions of the new function.
-     * @param {number} [ary] The arity cap of `func`.
-     * @param {number} [arity] The arity of `func`.
-     * @returns {Function} Returns the new wrapped function.
+     * @name reverse
+     * @memberOf LazyWrapper
+     * @returns {Object} Returns the new reversed `LazyWrapper` object.
      */
-    function createWrapper(func, bitmask, thisArg, partials, holders, argPos, ary, arity) {
-      var isBindKey = bitmask & BIND_KEY_FLAG;
-      if (!isBindKey && typeof func != 'function') {
-        throw new TypeError(FUNC_ERROR_TEXT);
-      }
-      var length = partials ? partials.length : 0;
-      if (!length) {
-        bitmask &= ~(PARTIAL_FLAG | PARTIAL_RIGHT_FLAG);
-        partials = holders = undefined;
+    function lazyReverse() {
+      if (this.__filtered__) {
+        var result = new LazyWrapper(this);
+        result.__dir__ = -1;
+        result.__filtered__ = true;
+      } else {
+        result = this.clone();
+        result.__dir__ *= -1;
       }
-      ary = ary === undefined ? ary : nativeMax(toInteger(ary), 0);
-      arity = arity === undefined ? arity : toInteger(arity);
-      length -= holders ? holders.length : 0;
+      return result;
+    }
 
-      if (bitmask & PARTIAL_RIGHT_FLAG) {
-        var partialsRight = partials,
-            holdersRight = holders;
+    /**
+     * Extracts the unwrapped value from its lazy wrapper.
+     *
+     * @private
+     * @name value
+     * @memberOf LazyWrapper
+     * @returns {*} Returns the unwrapped value.
+     */
+    function lazyValue() {
+      var array = this.__wrapped__.value(),
+          dir = this.__dir__,
+          isArr = isArray(array),
+          isRight = dir < 0,
+          arrLength = isArr ? array.length : 0,
+          view = getView(0, arrLength, this.__views__),
+          start = view.start,
+          end = view.end,
+          length = end - start,
+          index = isRight ? end : (start - 1),
+          iteratees = this.__iteratees__,
+          iterLength = iteratees.length,
+          resIndex = 0,
+          takeCount = nativeMin(length, this.__takeCount__);
 
-        partials = holders = undefined;
+      if (!isArr || (!isRight && arrLength == length && takeCount == length)) {
+        return baseWrapperValue(array, this.__actions__);
       }
-      var data = isBindKey ? undefined : getData(func);
+      var result = [];
 
-      var newData = [
-        func, bitmask, thisArg, partials, holders, partialsRight, holdersRight,
-        argPos, ary, arity
-      ];
+      outer:
+      while (length-- && resIndex < takeCount) {
+        index += dir;
 
-      if (data) {
-        mergeData(newData, data);
-      }
-      func = newData[0];
-      bitmask = newData[1];
-      thisArg = newData[2];
-      partials = newData[3];
-      holders = newData[4];
-      arity = newData[9] = newData[9] == null
-        ? (isBindKey ? 0 : func.length)
-        : nativeMax(newData[9] - length, 0);
+        var iterIndex = -1,
+            value = array[index];
 
-      if (!arity && bitmask & (CURRY_FLAG | CURRY_RIGHT_FLAG)) {
-        bitmask &= ~(CURRY_FLAG | CURRY_RIGHT_FLAG);
-      }
-      if (!bitmask || bitmask == BIND_FLAG) {
-        var result = createBaseWrapper(func, bitmask, thisArg);
-      } else if (bitmask == CURRY_FLAG || bitmask == CURRY_RIGHT_FLAG) {
-        result = createCurryWrapper(func, bitmask, arity);
-      } else if ((bitmask == PARTIAL_FLAG || bitmask == (BIND_FLAG | PARTIAL_FLAG)) && !holders.length) {
-        result = createPartialWrapper(func, bitmask, thisArg, partials);
-      } else {
-        result = createHybridWrapper.apply(undefined, newData);
+        while (++iterIndex < iterLength) {
+          var data = iteratees[iterIndex],
+              iteratee = data.iteratee,
+              type = data.type,
+              computed = iteratee(value);
+
+          if (type == LAZY_MAP_FLAG) {
+            value = computed;
+          } else if (!computed) {
+            if (type == LAZY_FILTER_FLAG) {
+              continue outer;
+            } else {
+              break outer;
+            }
+          }
+        }
+        result[resIndex++] = value;
       }
-      var setter = data ? baseSetData : setData;
-      return setter(result, newData);
+      return result;
     }
 
+    // Ensure `LazyWrapper` is an instance of `baseLodash`.
+    LazyWrapper.prototype = baseCreate(baseLodash.prototype);
+    LazyWrapper.prototype.constructor = LazyWrapper;
+
+    /*------------------------------------------------------------------------*/
+
     /**
-     * A specialized version of `baseIsEqualDeep` for arrays with support for
-     * partial deep comparisons.
+     * Creates a hash object.
      *
      * @private
-     * @param {Array} array The array to compare.
-     * @param {Array} other The other array to compare.
-     * @param {Function} equalFunc The function to determine equivalents of values.
-     * @param {Function} customizer The function to customize comparisons.
-     * @param {number} bitmask The bitmask of comparison flags. See `baseIsEqual`
-     *  for more details.
-     * @param {Object} stack Tracks traversed `array` and `other` objects.
-     * @returns {boolean} Returns `true` if the arrays are equivalent, else `false`.
+     * @constructor
+     * @param {Array} [entries] The key-value pairs to cache.
      */
-    function equalArrays(array, other, equalFunc, customizer, bitmask, stack) {
-      var isPartial = bitmask & PARTIAL_COMPARE_FLAG,
-          arrLength = array.length,
-          othLength = other.length;
-
-      if (arrLength != othLength && !(isPartial && othLength > arrLength)) {
-        return false;
-      }
-      // Assume cyclic values are equal.
-      var stacked = stack.get(array);
-      if (stacked) {
-        return stacked == other;
-      }
+    function Hash(entries) {
       var index = -1,
-          result = true,
-          seen = (bitmask & UNORDERED_COMPARE_FLAG) ? new SetCache : undefined;
+          length = entries == null ? 0 : entries.length;
 
-      stack.set(array, other);
-
-      // Ignore non-index properties.
-      while (++index < arrLength) {
-        var arrValue = array[index],
-            othValue = other[index];
-
-        if (customizer) {
-          var compared = isPartial
-            ? customizer(othValue, arrValue, index, other, array, stack)
-            : customizer(arrValue, othValue, index, array, other, stack);
-        }
-        if (compared !== undefined) {
-          if (compared) {
-            continue;
-          }
-          result = false;
-          break;
-        }
-        // Recursively compare arrays (susceptible to call stack limits).
-        if (seen) {
-          if (!arraySome(other, function(othValue, othIndex) {
-                if (!seen.has(othIndex) &&
-                    (arrValue === othValue || equalFunc(arrValue, othValue, customizer, bitmask, stack))) {
-                  return seen.add(othIndex);
-                }
-              })) {
-            result = false;
-            break;
-          }
-        } else if (!(
-              arrValue === othValue ||
-                equalFunc(arrValue, othValue, customizer, bitmask, stack)
-            )) {
-          result = false;
-          break;
-        }
-      }
-      stack['delete'](array);
-      return result;
-    }
+      this.clear();
+      while (++index < length) {
+        var entry = entries[index];
+        this.set(entry[0], entry[1]);
+      }
+    }
 
     /**
-     * A specialized version of `baseIsEqualDeep` for comparing objects of
-     * the same `toStringTag`.
-     *
-     * **Note:** This function only supports comparing values with tags of
-     * `Boolean`, `Date`, `Error`, `Number`, `RegExp`, or `String`.
+     * Removes all key-value entries from the hash.
      *
      * @private
-     * @param {Object} object The object to compare.
-     * @param {Object} other The other object to compare.
-     * @param {string} tag The `toStringTag` of the objects to compare.
-     * @param {Function} equalFunc The function to determine equivalents of values.
-     * @param {Function} customizer The function to customize comparisons.
-     * @param {number} bitmask The bitmask of comparison flags. See `baseIsEqual`
-     *  for more details.
-     * @param {Object} stack Tracks traversed `object` and `other` objects.
-     * @returns {boolean} Returns `true` if the objects are equivalent, else `false`.
+     * @name clear
+     * @memberOf Hash
      */
-    function equalByTag(object, other, tag, equalFunc, customizer, bitmask, stack) {
-      switch (tag) {
-        case dataViewTag:
-          if ((object.byteLength != other.byteLength) ||
-              (object.byteOffset != other.byteOffset)) {
-            return false;
-          }
-          object = object.buffer;
-          other = other.buffer;
-
-        case arrayBufferTag:
-          if ((object.byteLength != other.byteLength) ||
-              !equalFunc(new Uint8Array(object), new Uint8Array(other))) {
-            return false;
-          }
-          return true;
-
-        case boolTag:
-        case dateTag:
-          // Coerce dates and booleans to numbers, dates to milliseconds and
-          // booleans to `1` or `0` treating invalid dates coerced to `NaN` as
-          // not equal.
-          return +object == +other;
-
-        case errorTag:
-          return object.name == other.name && object.message == other.message;
-
-        case numberTag:
-          // Treat `NaN` vs. `NaN` as equal.
-          return (object != +object) ? other != +other : object == +other;
-
-        case regexpTag:
-        case stringTag:
-          // Coerce regexes to strings and treat strings, primitives and objects,
-          // as equal. See http://www.ecma-international.org/ecma-262/6.0/#sec-regexp.prototype.tostring
-          // for more details.
-          return object == (other + '');
-
-        case mapTag:
-          var convert = mapToArray;
-
-        case setTag:
-          var isPartial = bitmask & PARTIAL_COMPARE_FLAG;
-          convert || (convert = setToArray);
-
-          if (object.size != other.size && !isPartial) {
-            return false;
-          }
-          // Assume cyclic values are equal.
-          var stacked = stack.get(object);
-          if (stacked) {
-            return stacked == other;
-          }
-          bitmask |= UNORDERED_COMPARE_FLAG;
-          stack.set(object, other);
-
-          // Recursively compare objects (susceptible to call stack limits).
-          return equalArrays(convert(object), convert(other), equalFunc, customizer, bitmask, stack);
-
-        case symbolTag:
-          if (symbolValueOf) {
-            return symbolValueOf.call(object) == symbolValueOf.call(other);
-          }
-      }
-      return false;
+    function hashClear() {
+      this.__data__ = nativeCreate ? nativeCreate(null) : {};
+      this.size = 0;
     }
 
     /**
-     * A specialized version of `baseIsEqualDeep` for objects with support for
-     * partial deep comparisons.
+     * Removes `key` and its value from the hash.
      *
      * @private
-     * @param {Object} object The object to compare.
-     * @param {Object} other The other object to compare.
-     * @param {Function} equalFunc The function to determine equivalents of values.
-     * @param {Function} customizer The function to customize comparisons.
-     * @param {number} bitmask The bitmask of comparison flags. See `baseIsEqual`
-     *  for more details.
-     * @param {Object} stack Tracks traversed `object` and `other` objects.
-     * @returns {boolean} Returns `true` if the objects are equivalent, else `false`.
+     * @name delete
+     * @memberOf Hash
+     * @param {Object} hash The hash to modify.
+     * @param {string} key The key of the value to remove.
+     * @returns {boolean} Returns `true` if the entry was removed, else `false`.
      */
-    function equalObjects(object, other, equalFunc, customizer, bitmask, stack) {
-      var isPartial = bitmask & PARTIAL_COMPARE_FLAG,
-          objProps = keys(object),
-          objLength = objProps.length,
-          othProps = keys(other),
-          othLength = othProps.length;
-
-      if (objLength != othLength && !isPartial) {
-        return false;
-      }
-      var index = objLength;
-      while (index--) {
-        var key = objProps[index];
-        if (!(isPartial ? key in other : baseHas(other, key))) {
-          return false;
-        }
-      }
-      // Assume cyclic values are equal.
-      var stacked = stack.get(object);
-      if (stacked) {
-        return stacked == other;
-      }
-      var result = true;
-      stack.set(object, other);
-
-      var skipCtor = isPartial;
-      while (++index < objLength) {
-        key = objProps[index];
-        var objValue = object[key],
-            othValue = other[key];
-
-        if (customizer) {
-          var compared = isPartial
-            ? customizer(othValue, objValue, key, other, object, stack)
-            : customizer(objValue, othValue, key, object, other, stack);
-        }
-        // Recursively compare objects (susceptible to call stack limits).
-        if (!(compared === undefined
-              ? (objValue === othValue || equalFunc(objValue, othValue, customizer, bitmask, stack))
-              : compared
-            )) {
-          result = false;
-          break;
-        }
-        skipCtor || (skipCtor = key == 'constructor');
-      }
-      if (result && !skipCtor) {
-        var objCtor = object.constructor,
-            othCtor = other.constructor;
-
-        // Non `Object` object instances with different constructors are not equal.
-        if (objCtor != othCtor &&
-            ('constructor' in object && 'constructor' in other) &&
-            !(typeof objCtor == 'function' && objCtor instanceof objCtor &&
-              typeof othCtor == 'function' && othCtor instanceof othCtor)) {
-          result = false;
-        }
-      }
-      stack['delete'](object);
+    function hashDelete(key) {
+      var result = this.has(key) && delete this.__data__[key];
+      this.size -= result ? 1 : 0;
       return result;
     }
 
     /**
-     * Creates an array of own enumerable property names and symbols of `object`.
+     * Gets the hash value for `key`.
      *
      * @private
-     * @param {Object} object The object to query.
-     * @returns {Array} Returns the array of property names and symbols.
+     * @name get
+     * @memberOf Hash
+     * @param {string} key The key of the value to get.
+     * @returns {*} Returns the entry value.
      */
-    function getAllKeys(object) {
-      return baseGetAllKeys(object, keys, getSymbols);
+    function hashGet(key) {
+      var data = this.__data__;
+      if (nativeCreate) {
+        var result = data[key];
+        return result === HASH_UNDEFINED ? undefined : result;
+      }
+      return hasOwnProperty.call(data, key) ? data[key] : undefined;
     }
 
     /**
-     * Creates an array of own and inherited enumerable property names and
-     * symbols of `object`.
+     * Checks if a hash value for `key` exists.
      *
      * @private
-     * @param {Object} object The object to query.
-     * @returns {Array} Returns the array of property names and symbols.
+     * @name has
+     * @memberOf Hash
+     * @param {string} key The key of the entry to check.
+     * @returns {boolean} Returns `true` if an entry for `key` exists, else `false`.
      */
-    function getAllKeysIn(object) {
-      return baseGetAllKeys(object, keysIn, getSymbolsIn);
+    function hashHas(key) {
+      var data = this.__data__;
+      return nativeCreate ? (data[key] !== undefined) : hasOwnProperty.call(data, key);
     }
 
     /**
-     * Gets metadata for `func`.
+     * Sets the hash `key` to `value`.
      *
      * @private
-     * @param {Function} func The function to query.
-     * @returns {*} Returns the metadata for `func`.
+     * @name set
+     * @memberOf Hash
+     * @param {string} key The key of the value to set.
+     * @param {*} value The value to set.
+     * @returns {Object} Returns the hash instance.
      */
-    var getData = !metaMap ? noop : function(func) {
-      return metaMap.get(func);
-    };
+    function hashSet(key, value) {
+      var data = this.__data__;
+      this.size += this.has(key) ? 0 : 1;
+      data[key] = (nativeCreate && value === undefined) ? HASH_UNDEFINED : value;
+      return this;
+    }
+
+    // Add methods to `Hash`.
+    Hash.prototype.clear = hashClear;
+    Hash.prototype['delete'] = hashDelete;
+    Hash.prototype.get = hashGet;
+    Hash.prototype.has = hashHas;
+    Hash.prototype.set = hashSet;
+
+    /*------------------------------------------------------------------------*/
 
     /**
-     * Gets the name of `func`.
+     * Creates an list cache object.
      *
      * @private
-     * @param {Function} func The function to query.
-     * @returns {string} Returns the function name.
+     * @constructor
+     * @param {Array} [entries] The key-value pairs to cache.
      */
-    function getFuncName(func) {
-      var result = (func.name + ''),
-          array = realNames[result],
-          length = hasOwnProperty.call(realNames, result) ? array.length : 0;
+    function ListCache(entries) {
+      var index = -1,
+          length = entries == null ? 0 : entries.length;
 
-      while (length--) {
-        var data = array[length],
-            otherFunc = data.func;
-        if (otherFunc == null || otherFunc == func) {
-          return data.name;
-        }
+      this.clear();
+      while (++index < length) {
+        var entry = entries[index];
+        this.set(entry[0], entry[1]);
       }
-      return result;
     }
 
     /**
-     * Gets the argument placeholder value for `func`.
+     * Removes all key-value entries from the list cache.
      *
      * @private
-     * @param {Function} func The function to inspect.
-     * @returns {*} Returns the placeholder value.
+     * @name clear
+     * @memberOf ListCache
      */
-    function getHolder(func) {
-      var object = hasOwnProperty.call(lodash, 'placeholder') ? lodash : func;
-      return object.placeholder;
+    function listCacheClear() {
+      this.__data__ = [];
+      this.size = 0;
     }
 
     /**
-     * Gets the appropriate "iteratee" function. If `_.iteratee` is customized,
-     * this function returns the custom method, otherwise it returns `baseIteratee`.
-     * If arguments are provided, the chosen function is invoked with them and
-     * its result is returned.
+     * Removes `key` and its value from the list cache.
      *
      * @private
-     * @param {*} [value] The value to convert to an iteratee.
-     * @param {number} [arity] The arity of the created iteratee.
-     * @returns {Function} Returns the chosen function or its result.
+     * @name delete
+     * @memberOf ListCache
+     * @param {string} key The key of the value to remove.
+     * @returns {boolean} Returns `true` if the entry was removed, else `false`.
      */
-    function getIteratee() {
-      var result = lodash.iteratee || iteratee;
-      result = result === iteratee ? baseIteratee : result;
-      return arguments.length ? result(arguments[0], arguments[1]) : result;
+    function listCacheDelete(key) {
+      var data = this.__data__,
+          index = assocIndexOf(data, key);
+
+      if (index < 0) {
+        return false;
+      }
+      var lastIndex = data.length - 1;
+      if (index == lastIndex) {
+        data.pop();
+      } else {
+        splice.call(data, index, 1);
+      }
+      --this.size;
+      return true;
     }
 
     /**
-     * Gets the "length" property value of `object`.
-     *
-     * **Note:** This function is used to avoid a
-     * [JIT bug](https://bugs.webkit.org/show_bug.cgi?id=142792) that affects
-     * Safari on at least iOS 8.1-8.3 ARM64.
+     * Gets the list cache value for `key`.
      *
      * @private
-     * @param {Object} object The object to query.
-     * @returns {*} Returns the "length" value.
+     * @name get
+     * @memberOf ListCache
+     * @param {string} key The key of the value to get.
+     * @returns {*} Returns the entry value.
      */
-    var getLength = baseProperty('length');
+    function listCacheGet(key) {
+      var data = this.__data__,
+          index = assocIndexOf(data, key);
+
+      return index < 0 ? undefined : data[index][1];
+    }
 
     /**
-     * Gets the data for `map`.
+     * Checks if a list cache value for `key` exists.
      *
      * @private
-     * @param {Object} map The map to query.
-     * @param {string} key The reference key.
-     * @returns {*} Returns the map data.
+     * @name has
+     * @memberOf ListCache
+     * @param {string} key The key of the entry to check.
+     * @returns {boolean} Returns `true` if an entry for `key` exists, else `false`.
      */
-    function getMapData(map, key) {
-      var data = map.__data__;
-      return isKeyable(key)
-        ? data[typeof key == 'string' ? 'string' : 'hash']
-        : data.map;
+    function listCacheHas(key) {
+      return assocIndexOf(this.__data__, key) > -1;
     }
 
     /**
-     * Gets the property names, values, and compare flags of `object`.
+     * Sets the list cache `key` to `value`.
      *
      * @private
-     * @param {Object} object The object to query.
-     * @returns {Array} Returns the match data of `object`.
+     * @name set
+     * @memberOf ListCache
+     * @param {string} key The key of the value to set.
+     * @param {*} value The value to set.
+     * @returns {Object} Returns the list cache instance.
      */
-    function getMatchData(object) {
-      var result = keys(object),
-          length = result.length;
-
-      while (length--) {
-        var key = result[length],
-            value = object[key];
+    function listCacheSet(key, value) {
+      var data = this.__data__,
+          index = assocIndexOf(data, key);
 
-        result[length] = [key, value, isStrictComparable(value)];
+      if (index < 0) {
+        ++this.size;
+        data.push([key, value]);
+      } else {
+        data[index][1] = value;
       }
-      return result;
+      return this;
     }
 
+    // Add methods to `ListCache`.
+    ListCache.prototype.clear = listCacheClear;
+    ListCache.prototype['delete'] = listCacheDelete;
+    ListCache.prototype.get = listCacheGet;
+    ListCache.prototype.has = listCacheHas;
+    ListCache.prototype.set = listCacheSet;
+
+    /*------------------------------------------------------------------------*/
+
     /**
-     * Gets the native function at `key` of `object`.
+     * Creates a map cache object to store key-value pairs.
      *
      * @private
-     * @param {Object} object The object to query.
-     * @param {string} key The key of the method to get.
-     * @returns {*} Returns the function if it's native, else `undefined`.
+     * @constructor
+     * @param {Array} [entries] The key-value pairs to cache.
      */
-    function getNative(object, key) {
-      var value = getValue(object, key);
-      return baseIsNative(value) ? value : undefined;
+    function MapCache(entries) {
+      var index = -1,
+          length = entries == null ? 0 : entries.length;
+
+      this.clear();
+      while (++index < length) {
+        var entry = entries[index];
+        this.set(entry[0], entry[1]);
+      }
     }
 
     /**
-     * Gets the `[[Prototype]]` of `value`.
+     * Removes all key-value entries from the map.
      *
      * @private
-     * @param {*} value The value to query.
-     * @returns {null|Object} Returns the `[[Prototype]]`.
+     * @name clear
+     * @memberOf MapCache
      */
-    function getPrototype(value) {
-      return nativeGetPrototype(Object(value));
+    function mapCacheClear() {
+      this.size = 0;
+      this.__data__ = {
+        'hash': new Hash,
+        'map': new (Map || ListCache),
+        'string': new Hash
+      };
     }
 
     /**
-     * Creates an array of the own enumerable symbol properties of `object`.
+     * Removes `key` and its value from the map.
      *
      * @private
-     * @param {Object} object The object to query.
-     * @returns {Array} Returns the array of symbols.
+     * @name delete
+     * @memberOf MapCache
+     * @param {string} key The key of the value to remove.
+     * @returns {boolean} Returns `true` if the entry was removed, else `false`.
      */
-    function getSymbols(object) {
-      // Coerce `object` to an object to avoid non-object errors in V8.
-      // See https://bugs.chromium.org/p/v8/issues/detail?id=3443 for more details.
-      return getOwnPropertySymbols(Object(object));
-    }
-
-    // Fallback for IE < 11.
-    if (!getOwnPropertySymbols) {
-      getSymbols = stubArray;
+    function mapCacheDelete(key) {
+      var result = getMapData(this, key)['delete'](key);
+      this.size -= result ? 1 : 0;
+      return result;
     }
 
     /**
-     * Creates an array of the own and inherited enumerable symbol properties
-     * of `object`.
+     * Gets the map value for `key`.
      *
      * @private
-     * @param {Object} object The object to query.
-     * @returns {Array} Returns the array of symbols.
+     * @name get
+     * @memberOf MapCache
+     * @param {string} key The key of the value to get.
+     * @returns {*} Returns the entry value.
      */
-    var getSymbolsIn = !getOwnPropertySymbols ? getSymbols : function(object) {
-      var result = [];
-      while (object) {
-        arrayPush(result, getSymbols(object));
-        object = getPrototype(object);
-      }
-      return result;
-    };
+    function mapCacheGet(key) {
+      return getMapData(this, key).get(key);
+    }
 
     /**
-     * Gets the `toStringTag` of `value`.
+     * Checks if a map value for `key` exists.
      *
      * @private
-     * @param {*} value The value to query.
-     * @returns {string} Returns the `toStringTag`.
+     * @name has
+     * @memberOf MapCache
+     * @param {string} key The key of the entry to check.
+     * @returns {boolean} Returns `true` if an entry for `key` exists, else `false`.
      */
-    function getTag(value) {
-      return objectToString.call(value);
-    }
-
-    // Fallback for data views, maps, sets, and weak maps in IE 11,
-    // for data views in Edge, and promises in Node.js.
-    if ((DataView && getTag(new DataView(new ArrayBuffer(1))) != dataViewTag) ||
-        (Map && getTag(new Map) != mapTag) ||
-        (Promise && getTag(Promise.resolve()) != promiseTag) ||
-        (Set && getTag(new Set) != setTag) ||
-        (WeakMap && getTag(new WeakMap) != weakMapTag)) {
-      getTag = function(value) {
-        var result = objectToString.call(value),
-            Ctor = result == objectTag ? value.constructor : undefined,
-            ctorString = Ctor ? toSource(Ctor) : undefined;
-
-        if (ctorString) {
-          switch (ctorString) {
-            case dataViewCtorString: return dataViewTag;
-            case mapCtorString: return mapTag;
-            case promiseCtorString: return promiseTag;
-            case setCtorString: return setTag;
-            case weakMapCtorString: return weakMapTag;
-          }
-        }
-        return result;
-      };
+    function mapCacheHas(key) {
+      return getMapData(this, key).has(key);
     }
 
     /**
-     * Gets the view, applying any `transforms` to the `start` and `end` positions.
+     * Sets the map `key` to `value`.
      *
      * @private
-     * @param {number} start The start of the view.
-     * @param {number} end The end of the view.
-     * @param {Array} transforms The transformations to apply to the view.
-     * @returns {Object} Returns an object containing the `start` and `end`
-     *  positions of the view.
+     * @name set
+     * @memberOf MapCache
+     * @param {string} key The key of the value to set.
+     * @param {*} value The value to set.
+     * @returns {Object} Returns the map cache instance.
      */
-    function getView(start, end, transforms) {
-      var index = -1,
-          length = transforms.length;
-
-      while (++index < length) {
-        var data = transforms[index],
-            size = data.size;
+    function mapCacheSet(key, value) {
+      var data = getMapData(this, key),
+          size = data.size;
 
-        switch (data.type) {
-          case 'drop':      start += size; break;
-          case 'dropRight': end -= size; break;
-          case 'take':      end = nativeMin(end, start + size); break;
-          case 'takeRight': start = nativeMax(start, end - size); break;
-        }
-      }
-      return { 'start': start, 'end': end };
+      data.set(key, value);
+      this.size += data.size == size ? 0 : 1;
+      return this;
     }
 
+    // Add methods to `MapCache`.
+    MapCache.prototype.clear = mapCacheClear;
+    MapCache.prototype['delete'] = mapCacheDelete;
+    MapCache.prototype.get = mapCacheGet;
+    MapCache.prototype.has = mapCacheHas;
+    MapCache.prototype.set = mapCacheSet;
+
+    /*------------------------------------------------------------------------*/
+
     /**
-     * Checks if `path` exists on `object`.
+     *
+     * Creates an array cache object to store unique values.
      *
      * @private
-     * @param {Object} object The object to query.
-     * @param {Array|string} path The path to check.
-     * @param {Function} hasFunc The function to check properties.
-     * @returns {boolean} Returns `true` if `path` exists, else `false`.
+     * @constructor
+     * @param {Array} [values] The values to cache.
      */
-    function hasPath(object, path, hasFunc) {
-      path = isKey(path, object) ? [path] : castPath(path);
-
-      var result,
-          index = -1,
-          length = path.length;
+    function SetCache(values) {
+      var index = -1,
+          length = values == null ? 0 : values.length;
 
+      this.__data__ = new MapCache;
       while (++index < length) {
-        var key = toKey(path[index]);
-        if (!(result = object != null && hasFunc(object, key))) {
-          break;
-        }
-        object = object[key];
-      }
-      if (result) {
-        return result;
+        this.add(values[index]);
       }
-      var length = object ? object.length : 0;
-      return !!length && isLength(length) && isIndex(key, length) &&
-        (isArray(object) || isString(object) || isArguments(object));
     }
 
     /**
-     * Initializes an array clone.
+     * Adds `value` to the array cache.
      *
      * @private
-     * @param {Array} array The array to clone.
-     * @returns {Array} Returns the initialized clone.
-     */
-    function initCloneArray(array) {
-      var length = array.length,
-          result = array.constructor(length);
-
-      // Add properties assigned by `RegExp#exec`.
-      if (length && typeof array[0] == 'string' && hasOwnProperty.call(array, 'index')) {
-        result.index = array.index;
-        result.input = array.input;
-      }
-      return result;
+     * @name add
+     * @memberOf SetCache
+     * @alias push
+     * @param {*} value The value to cache.
+     * @returns {Object} Returns the cache instance.
+     */
+    function setCacheAdd(value) {
+      this.__data__.set(value, HASH_UNDEFINED);
+      return this;
     }
 
     /**
-     * Initializes an object clone.
+     * Checks if `value` is in the array cache.
      *
      * @private
-     * @param {Object} object The object to clone.
-     * @returns {Object} Returns the initialized clone.
+     * @name has
+     * @memberOf SetCache
+     * @param {*} value The value to search for.
+     * @returns {number} Returns `true` if `value` is found, else `false`.
      */
-    function initCloneObject(object) {
-      return (typeof object.constructor == 'function' && !isPrototype(object))
-        ? baseCreate(getPrototype(object))
-        : {};
+    function setCacheHas(value) {
+      return this.__data__.has(value);
     }
 
+    // Add methods to `SetCache`.
+    SetCache.prototype.add = SetCache.prototype.push = setCacheAdd;
+    SetCache.prototype.has = setCacheHas;
+
+    /*------------------------------------------------------------------------*/
+
     /**
-     * Initializes an object clone based on its `toStringTag`.
-     *
-     * **Note:** This function only supports cloning values with tags of
-     * `Boolean`, `Date`, `Error`, `Number`, `RegExp`, or `String`.
+     * Creates a stack cache object to store key-value pairs.
      *
      * @private
-     * @param {Object} object The object to clone.
-     * @param {string} tag The `toStringTag` of the object to clone.
-     * @param {Function} cloneFunc The function to clone values.
-     * @param {boolean} [isDeep] Specify a deep clone.
-     * @returns {Object} Returns the initialized clone.
+     * @constructor
+     * @param {Array} [entries] The key-value pairs to cache.
      */
-    function initCloneByTag(object, tag, cloneFunc, isDeep) {
-      var Ctor = object.constructor;
-      switch (tag) {
-        case arrayBufferTag:
-          return cloneArrayBuffer(object);
-
-        case boolTag:
-        case dateTag:
-          return new Ctor(+object);
-
-        case dataViewTag:
-          return cloneDataView(object, isDeep);
-
-        case float32Tag: case float64Tag:
-        case int8Tag: case int16Tag: case int32Tag:
-        case uint8Tag: case uint8ClampedTag: case uint16Tag: case uint32Tag:
-          return cloneTypedArray(object, isDeep);
-
-        case mapTag:
-          return cloneMap(object, isDeep, cloneFunc);
-
-        case numberTag:
-        case stringTag:
-          return new Ctor(object);
-
-        case regexpTag:
-          return cloneRegExp(object);
-
-        case setTag:
-          return cloneSet(object, isDeep, cloneFunc);
-
-        case symbolTag:
-          return cloneSymbol(object);
-      }
+    function Stack(entries) {
+      var data = this.__data__ = new ListCache(entries);
+      this.size = data.size;
     }
 
     /**
-     * Creates an array of index keys for `object` values of arrays,
-     * `arguments` objects, and strings, otherwise `null` is returned.
+     * Removes all key-value entries from the stack.
      *
      * @private
-     * @param {Object} object The object to query.
-     * @returns {Array|null} Returns index keys, else `null`.
+     * @name clear
+     * @memberOf Stack
      */
-    function indexKeys(object) {
-      var length = object ? object.length : undefined;
-      if (isLength(length) &&
-          (isArray(object) || isString(object) || isArguments(object))) {
-        return baseTimes(length, String);
-      }
-      return null;
+    function stackClear() {
+      this.__data__ = new ListCache;
+      this.size = 0;
     }
 
     /**
-     * Checks if `value` is a flattenable `arguments` object or array.
+     * Removes `key` and its value from the stack.
      *
      * @private
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is flattenable, else `false`.
+     * @name delete
+     * @memberOf Stack
+     * @param {string} key The key of the value to remove.
+     * @returns {boolean} Returns `true` if the entry was removed, else `false`.
      */
-    function isFlattenable(value) {
-      return isArray(value) || isArguments(value);
+    function stackDelete(key) {
+      var data = this.__data__,
+          result = data['delete'](key);
+
+      this.size = data.size;
+      return result;
     }
 
     /**
-     * Checks if `value` is a flattenable array and not a `_.matchesProperty`
-     * iteratee shorthand.
+     * Gets the stack value for `key`.
      *
      * @private
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is flattenable, else `false`.
+     * @name get
+     * @memberOf Stack
+     * @param {string} key The key of the value to get.
+     * @returns {*} Returns the entry value.
      */
-    function isFlattenableIteratee(value) {
-      return isArray(value) && !(value.length == 2 && !isFunction(value[0]));
+    function stackGet(key) {
+      return this.__data__.get(key);
     }
 
     /**
-     * Checks if `value` is a valid array-like index.
+     * Checks if a stack value for `key` exists.
      *
      * @private
-     * @param {*} value The value to check.
-     * @param {number} [length=MAX_SAFE_INTEGER] The upper bounds of a valid index.
-     * @returns {boolean} Returns `true` if `value` is a valid index, else `false`.
+     * @name has
+     * @memberOf Stack
+     * @param {string} key The key of the entry to check.
+     * @returns {boolean} Returns `true` if an entry for `key` exists, else `false`.
      */
-    function isIndex(value, length) {
-      length = length == null ? MAX_SAFE_INTEGER : length;
-      return !!length &&
-        (typeof value == 'number' || reIsUint.test(value)) &&
-        (value > -1 && value % 1 == 0 && value < length);
+    function stackHas(key) {
+      return this.__data__.has(key);
     }
 
     /**
-     * Checks if the given arguments are from an iteratee call.
+     * Sets the stack `key` to `value`.
      *
      * @private
-     * @param {*} value The potential iteratee value argument.
-     * @param {*} index The potential iteratee index or key argument.
-     * @param {*} object The potential iteratee object argument.
-     * @returns {boolean} Returns `true` if the arguments are from an iteratee call,
-     *  else `false`.
+     * @name set
+     * @memberOf Stack
+     * @param {string} key The key of the value to set.
+     * @param {*} value The value to set.
+     * @returns {Object} Returns the stack cache instance.
      */
-    function isIterateeCall(value, index, object) {
-      if (!isObject(object)) {
-        return false;
-      }
-      var type = typeof index;
-      if (type == 'number'
-            ? (isArrayLike(object) && isIndex(index, object.length))
-            : (type == 'string' && index in object)
-          ) {
-        return eq(object[index], value);
+    function stackSet(key, value) {
+      var data = this.__data__;
+      if (data instanceof ListCache) {
+        var pairs = data.__data__;
+        if (!Map || (pairs.length < LARGE_ARRAY_SIZE - 1)) {
+          pairs.push([key, value]);
+          this.size = ++data.size;
+          return this;
+        }
+        data = this.__data__ = new MapCache(pairs);
       }
-      return false;
+      data.set(key, value);
+      this.size = data.size;
+      return this;
     }
 
+    // Add methods to `Stack`.
+    Stack.prototype.clear = stackClear;
+    Stack.prototype['delete'] = stackDelete;
+    Stack.prototype.get = stackGet;
+    Stack.prototype.has = stackHas;
+    Stack.prototype.set = stackSet;
+
+    /*------------------------------------------------------------------------*/
+
     /**
-     * Checks if `value` is a property name and not a property path.
+     * Creates an array of the enumerable property names of the array-like `value`.
      *
      * @private
-     * @param {*} value The value to check.
-     * @param {Object} [object] The object to query keys on.
-     * @returns {boolean} Returns `true` if `value` is a property name, else `false`.
+     * @param {*} value The value to query.
+     * @param {boolean} inherited Specify returning inherited property names.
+     * @returns {Array} Returns the array of property names.
      */
-    function isKey(value, object) {
-      if (isArray(value)) {
-        return false;
-      }
-      var type = typeof value;
-      if (type == 'number' || type == 'symbol' || type == 'boolean' ||
-          value == null || isSymbol(value)) {
-        return true;
+    function arrayLikeKeys(value, inherited) {
+      var isArr = isArray(value),
+          isArg = !isArr && isArguments(value),
+          isBuff = !isArr && !isArg && isBuffer(value),
+          isType = !isArr && !isArg && !isBuff && isTypedArray(value),
+          skipIndexes = isArr || isArg || isBuff || isType,
+          result = skipIndexes ? baseTimes(value.length, String) : [],
+          length = result.length;
+
+      for (var key in value) {
+        if ((inherited || hasOwnProperty.call(value, key)) &&
+            !(skipIndexes && (
+               // Safari 9 has enumerable `arguments.length` in strict mode.
+               key == 'length' ||
+               // Node.js 0.10 has enumerable non-index properties on buffers.
+               (isBuff && (key == 'offset' || key == 'parent')) ||
+               // PhantomJS 2 has enumerable non-index properties on typed arrays.
+               (isType && (key == 'buffer' || key == 'byteLength' || key == 'byteOffset')) ||
+               // Skip index properties.
+               isIndex(key, length)
+            ))) {
+          result.push(key);
+        }
       }
-      return reIsPlainProp.test(value) || !reIsDeepProp.test(value) ||
-        (object != null && value in Object(object));
+      return result;
     }
 
     /**
-     * Checks if `value` is suitable for use as unique object key.
+     * A specialized version of `_.sample` for arrays.
      *
      * @private
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is suitable, else `false`.
+     * @param {Array} array The array to sample.
+     * @returns {*} Returns the random element.
      */
-    function isKeyable(value) {
-      var type = typeof value;
-      return (type == 'string' || type == 'number' || type == 'symbol' || type == 'boolean')
-        ? (value !== '__proto__')
-        : (value === null);
+    function arraySample(array) {
+      var length = array.length;
+      return length ? array[baseRandom(0, length - 1)] : undefined;
     }
 
     /**
-     * Checks if `func` has a lazy counterpart.
+     * A specialized version of `_.sampleSize` for arrays.
      *
      * @private
-     * @param {Function} func The function to check.
-     * @returns {boolean} Returns `true` if `func` has a lazy counterpart,
-     *  else `false`.
+     * @param {Array} array The array to sample.
+     * @param {number} n The number of elements to sample.
+     * @returns {Array} Returns the random elements.
      */
-    function isLaziable(func) {
-      var funcName = getFuncName(func),
-          other = lodash[funcName];
-
-      if (typeof other != 'function' || !(funcName in LazyWrapper.prototype)) {
-        return false;
-      }
-      if (func === other) {
-        return true;
-      }
-      var data = getData(other);
-      return !!data && func === data[0];
+    function arraySampleSize(array, n) {
+      return shuffleSelf(copyArray(array), baseClamp(n, 0, array.length));
     }
 
     /**
-     * Checks if `func` has its source masked.
+     * A specialized version of `_.shuffle` for arrays.
      *
      * @private
-     * @param {Function} func The function to check.
-     * @returns {boolean} Returns `true` if `func` is masked, else `false`.
+     * @param {Array} array The array to shuffle.
+     * @returns {Array} Returns the new shuffled array.
      */
-    function isMasked(func) {
-      return !!maskSrcKey && (maskSrcKey in func);
+    function arrayShuffle(array) {
+      return shuffleSelf(copyArray(array));
     }
 
     /**
-     * Checks if `func` is capable of being masked.
+     * This function is like `assignValue` except that it doesn't assign
+     * `undefined` values.
      *
      * @private
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `func` is maskable, else `false`.
+     * @param {Object} object The object to modify.
+     * @param {string} key The key of the property to assign.
+     * @param {*} value The value to assign.
      */
-    var isMaskable = coreJsData ? isFunction : stubFalse;
+    function assignMergeValue(object, key, value) {
+      if ((value !== undefined && !eq(object[key], value)) ||
+          (value === undefined && !(key in object))) {
+        baseAssignValue(object, key, value);
+      }
+    }
 
     /**
-     * Checks if `value` is likely a prototype object.
+     * Assigns `value` to `key` of `object` if the existing value is not equivalent
+     * using [`SameValueZero`](http://ecma-international.org/ecma-262/7.0/#sec-samevaluezero)
+     * for equality comparisons.
      *
      * @private
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is a prototype, else `false`.
+     * @param {Object} object The object to modify.
+     * @param {string} key The key of the property to assign.
+     * @param {*} value The value to assign.
      */
-    function isPrototype(value) {
-      var Ctor = value && value.constructor,
-          proto = (typeof Ctor == 'function' && Ctor.prototype) || objectProto;
-
-      return value === proto;
+    function assignValue(object, key, value) {
+      var objValue = object[key];
+      if (!(hasOwnProperty.call(object, key) && eq(objValue, value)) ||
+          (value === undefined && !(key in object))) {
+        baseAssignValue(object, key, value);
+      }
     }
 
     /**
-     * Checks if `value` is suitable for strict equality comparisons, i.e. `===`.
+     * Gets the index at which the `key` is found in `array` of key-value pairs.
      *
      * @private
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` if suitable for strict
-     *  equality comparisons, else `false`.
+     * @param {Array} array The array to inspect.
+     * @param {*} key The key to search for.
+     * @returns {number} Returns the index of the matched value, else `-1`.
      */
-    function isStrictComparable(value) {
-      return value === value && !isObject(value);
+    function assocIndexOf(array, key) {
+      var length = array.length;
+      while (length--) {
+        if (eq(array[length][0], key)) {
+          return length;
+        }
+      }
+      return -1;
     }
 
     /**
-     * A specialized version of `matchesProperty` for source values suitable
-     * for strict equality comparisons, i.e. `===`.
+     * Aggregates elements of `collection` on `accumulator` with keys transformed
+     * by `iteratee` and values set by `setter`.
      *
      * @private
-     * @param {string} key The key of the property to get.
-     * @param {*} srcValue The value to match.
-     * @returns {Function} Returns the new spec function.
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} setter The function to set `accumulator` values.
+     * @param {Function} iteratee The iteratee to transform keys.
+     * @param {Object} accumulator The initial aggregated object.
+     * @returns {Function} Returns `accumulator`.
      */
-    function matchesStrictComparable(key, srcValue) {
-      return function(object) {
-        if (object == null) {
-          return false;
-        }
-        return object[key] === srcValue &&
-          (srcValue !== undefined || (key in Object(object)));
-      };
+    function baseAggregator(collection, setter, iteratee, accumulator) {
+      baseEach(collection, function(value, key, collection) {
+        setter(accumulator, value, iteratee(value), collection);
+      });
+      return accumulator;
     }
 
     /**
-     * Merges the function metadata of `source` into `data`.
-     *
-     * Merging metadata reduces the number of wrappers used to invoke a function.
-     * This is possible because methods like `_.bind`, `_.curry`, and `_.partial`
-     * may be applied regardless of execution order. Methods like `_.ary` and
-     * `_.rearg` modify function arguments, making the order in which they are
-     * executed important, preventing the merging of metadata. However, we make
-     * an exception for a safe combined case where curried functions have `_.ary`
-     * and or `_.rearg` applied.
+     * The base implementation of `_.assign` without support for multiple sources
+     * or `customizer` functions.
      *
      * @private
-     * @param {Array} data The destination metadata.
-     * @param {Array} source The source metadata.
-     * @returns {Array} Returns `data`.
+     * @param {Object} object The destination object.
+     * @param {Object} source The source object.
+     * @returns {Object} Returns `object`.
      */
-    function mergeData(data, source) {
-      var bitmask = data[1],
-          srcBitmask = source[1],
-          newBitmask = bitmask | srcBitmask,
-          isCommon = newBitmask < (BIND_FLAG | BIND_KEY_FLAG | ARY_FLAG);
-
-      var isCombo =
-        ((srcBitmask == ARY_FLAG) && (bitmask == CURRY_FLAG)) ||
-        ((srcBitmask == ARY_FLAG) && (bitmask == REARG_FLAG) && (data[7].length <= source[8])) ||
-        ((srcBitmask == (ARY_FLAG | REARG_FLAG)) && (source[7].length <= source[8]) && (bitmask == CURRY_FLAG));
-
-      // Exit early if metadata can't be merged.
-      if (!(isCommon || isCombo)) {
-        return data;
-      }
-      // Use source `thisArg` if available.
-      if (srcBitmask & BIND_FLAG) {
-        data[2] = source[2];
-        // Set when currying a bound function.
-        newBitmask |= bitmask & BIND_FLAG ? 0 : CURRY_BOUND_FLAG;
-      }
-      // Compose partial arguments.
-      var value = source[3];
-      if (value) {
-        var partials = data[3];
-        data[3] = partials ? composeArgs(partials, value, source[4]) : value;
-        data[4] = partials ? replaceHolders(data[3], PLACEHOLDER) : source[4];
-      }
-      // Compose partial right arguments.
-      value = source[5];
-      if (value) {
-        partials = data[5];
-        data[5] = partials ? composeArgsRight(partials, value, source[6]) : value;
-        data[6] = partials ? replaceHolders(data[5], PLACEHOLDER) : source[6];
-      }
-      // Use source `argPos` if available.
-      value = source[7];
-      if (value) {
-        data[7] = value;
-      }
-      // Use source `ary` if it's smaller.
-      if (srcBitmask & ARY_FLAG) {
-        data[8] = data[8] == null ? source[8] : nativeMin(data[8], source[8]);
-      }
-      // Use source `arity` if one is not provided.
-      if (data[9] == null) {
-        data[9] = source[9];
-      }
-      // Use source `func` and merge bitmasks.
-      data[0] = source[0];
-      data[1] = newBitmask;
-
-      return data;
+    function baseAssign(object, source) {
+      return object && copyObject(source, keys(source), object);
     }
 
     /**
-     * Used by `_.defaultsDeep` to customize its `_.merge` use.
+     * The base implementation of `_.assignIn` without support for multiple sources
+     * or `customizer` functions.
      *
      * @private
-     * @param {*} objValue The destination value.
-     * @param {*} srcValue The source value.
-     * @param {string} key The key of the property to merge.
-     * @param {Object} object The parent object of `objValue`.
-     * @param {Object} source The parent object of `srcValue`.
-     * @param {Object} [stack] Tracks traversed source values and their merged
-     *  counterparts.
-     * @returns {*} Returns the value to assign.
+     * @param {Object} object The destination object.
+     * @param {Object} source The source object.
+     * @returns {Object} Returns `object`.
      */
-    function mergeDefaults(objValue, srcValue, key, object, source, stack) {
-      if (isObject(objValue) && isObject(srcValue)) {
-        baseMerge(objValue, srcValue, undefined, mergeDefaults, stack.set(srcValue, objValue));
-      }
-      return objValue;
+    function baseAssignIn(object, source) {
+      return object && copyObject(source, keysIn(source), object);
     }
 
     /**
-     * Gets the parent value at `path` of `object`.
+     * The base implementation of `assignValue` and `assignMergeValue` without
+     * value checks.
      *
      * @private
-     * @param {Object} object The object to query.
-     * @param {Array} path The path to get the parent value of.
-     * @returns {*} Returns the parent value.
+     * @param {Object} object The object to modify.
+     * @param {string} key The key of the property to assign.
+     * @param {*} value The value to assign.
      */
-    function parent(object, path) {
-      return path.length == 1 ? object : baseGet(object, baseSlice(path, 0, -1));
+    function baseAssignValue(object, key, value) {
+      if (key == '__proto__' && defineProperty) {
+        defineProperty(object, key, {
+          'configurable': true,
+          'enumerable': true,
+          'value': value,
+          'writable': true
+        });
+      } else {
+        object[key] = value;
+      }
     }
 
     /**
-     * Reorder `array` according to the specified indexes where the element at
-     * the first index is assigned as the first element, the element at
-     * the second index is assigned as the second element, and so on.
+     * The base implementation of `_.at` without support for individual paths.
      *
      * @private
-     * @param {Array} array The array to reorder.
-     * @param {Array} indexes The arranged array indexes.
-     * @returns {Array} Returns `array`.
+     * @param {Object} object The object to iterate over.
+     * @param {string[]} paths The property paths to pick.
+     * @returns {Array} Returns the picked elements.
      */
-    function reorder(array, indexes) {
-      var arrLength = array.length,
-          length = nativeMin(indexes.length, arrLength),
-          oldArray = copyArray(array);
+    function baseAt(object, paths) {
+      var index = -1,
+          length = paths.length,
+          result = Array(length),
+          skip = object == null;
 
-      while (length--) {
-        var index = indexes[length];
-        array[length] = isIndex(index, arrLength) ? oldArray[index] : undefined;
+      while (++index < length) {
+        result[index] = skip ? undefined : get(object, paths[index]);
       }
-      return array;
+      return result;
     }
 
     /**
-     * Sets metadata for `func`.
+     * The base implementation of `_.clamp` which doesn't coerce arguments.
      *
-     * **Note:** If this function becomes hot, i.e. is invoked a lot in a short
-     * period of time, it will trip its breaker and transition to an identity
-     * function to avoid garbage collection pauses in V8. See
-     * [V8 issue 2070](https://bugs.chromium.org/p/v8/issues/detail?id=2070)
-     * for more details.
+     * @private
+     * @param {number} number The number to clamp.
+     * @param {number} [lower] The lower bound.
+     * @param {number} upper The upper bound.
+     * @returns {number} Returns the clamped number.
+     */
+    function baseClamp(number, lower, upper) {
+      if (number === number) {
+        if (upper !== undefined) {
+          number = number <= upper ? number : upper;
+        }
+        if (lower !== undefined) {
+          number = number >= lower ? number : lower;
+        }
+      }
+      return number;
+    }
+
+    /**
+     * The base implementation of `_.clone` and `_.cloneDeep` which tracks
+     * traversed objects.
      *
      * @private
-     * @param {Function} func The function to associate metadata with.
-     * @param {*} data The metadata.
-     * @returns {Function} Returns `func`.
+     * @param {*} value The value to clone.
+     * @param {boolean} bitmask The bitmask flags.
+     *  1 - Deep clone
+     *  2 - Flatten inherited properties
+     *  4 - Clone symbols
+     * @param {Function} [customizer] The function to customize cloning.
+     * @param {string} [key] The key of `value`.
+     * @param {Object} [object] The parent object of `value`.
+     * @param {Object} [stack] Tracks traversed objects and their clone counterparts.
+     * @returns {*} Returns the cloned value.
      */
-    var setData = (function() {
-      var count = 0,
-          lastCalled = 0;
+    function baseClone(value, bitmask, customizer, key, object, stack) {
+      var result,
+          isDeep = bitmask & CLONE_DEEP_FLAG,
+          isFlat = bitmask & CLONE_FLAT_FLAG,
+          isFull = bitmask & CLONE_SYMBOLS_FLAG;
 
-      return function(key, value) {
-        var stamp = now(),
-            remaining = HOT_SPAN - (stamp - lastCalled);
+      if (customizer) {
+        result = object ? customizer(value, key, object, stack) : customizer(value);
+      }
+      if (result !== undefined) {
+        return result;
+      }
+      if (!isObject(value)) {
+        return value;
+      }
+      var isArr = isArray(value);
+      if (isArr) {
+        result = initCloneArray(value);
+        if (!isDeep) {
+          return copyArray(value, result);
+        }
+      } else {
+        var tag = getTag(value),
+            isFunc = tag == funcTag || tag == genTag;
 
-        lastCalled = stamp;
-        if (remaining > 0) {
-          if (++count >= HOT_COUNT) {
-            return key;
+        if (isBuffer(value)) {
+          return cloneBuffer(value, isDeep);
+        }
+        if (tag == objectTag || tag == argsTag || (isFunc && !object)) {
+          result = (isFlat || isFunc) ? {} : initCloneObject(value);
+          if (!isDeep) {
+            return isFlat
+              ? copySymbolsIn(value, baseAssignIn(result, value))
+              : copySymbols(value, baseAssign(result, value));
           }
         } else {
-          count = 0;
+          if (!cloneableTags[tag]) {
+            return object ? value : {};
+          }
+          result = initCloneByTag(value, tag, isDeep);
         }
-        return baseSetData(key, value);
-      };
-    }());
+      }
+      // Check for circular references and return its corresponding clone.
+      stack || (stack = new Stack);
+      var stacked = stack.get(value);
+      if (stacked) {
+        return stacked;
+      }
+      stack.set(value, result);
 
-    /**
-     * Converts `string` to a property path array.
-     *
-     * @private
-     * @param {string} string The string to convert.
-     * @returns {Array} Returns the property path array.
-     */
-    var stringToPath = memoize(function(string) {
-      var result = [];
-      toString(string).replace(rePropName, function(match, number, quote, string) {
-        result.push(quote ? string.replace(reEscapeChar, '$1') : (number || match));
+      if (isSet(value)) {
+        value.forEach(function(subValue) {
+          result.add(baseClone(subValue, bitmask, customizer, subValue, value, stack));
+        });
+
+        return result;
+      }
+
+      if (isMap(value)) {
+        value.forEach(function(subValue, key) {
+          result.set(key, baseClone(subValue, bitmask, customizer, key, value, stack));
+        });
+
+        return result;
+      }
+
+      var keysFunc = isFull
+        ? (isFlat ? getAllKeysIn : getAllKeys)
+        : (isFlat ? keysIn : keys);
+
+      var props = isArr ? undefined : keysFunc(value);
+      arrayEach(props || value, function(subValue, key) {
+        if (props) {
+          key = subValue;
+          subValue = value[key];
+        }
+        // Recursively populate clone (susceptible to call stack limits).
+        assignValue(result, key, baseClone(subValue, bitmask, customizer, key, value, stack));
       });
       return result;
-    });
+    }
 
     /**
-     * Converts `value` to a string key if it's not a string or symbol.
+     * The base implementation of `_.conforms` which doesn't clone `source`.
      *
      * @private
-     * @param {*} value The value to inspect.
-     * @returns {string|symbol} Returns the key.
+     * @param {Object} source The object of property predicates to conform to.
+     * @returns {Function} Returns the new spec function.
      */
-    function toKey(value) {
-      if (typeof value == 'string' || isSymbol(value)) {
-        return value;
-      }
-      var result = (value + '');
-      return (result == '0' && (1 / value) == -INFINITY) ? '-0' : result;
+    function baseConforms(source) {
+      var props = keys(source);
+      return function(object) {
+        return baseConformsTo(object, source, props);
+      };
     }
 
     /**
-     * Converts `func` to its source code.
+     * The base implementation of `_.conformsTo` which accepts `props` to check.
      *
      * @private
-     * @param {Function} func The function to process.
-     * @returns {string} Returns the source code.
+     * @param {Object} object The object to inspect.
+     * @param {Object} source The object of property predicates to conform to.
+     * @returns {boolean} Returns `true` if `object` conforms, else `false`.
      */
-    function toSource(func) {
-      if (func != null) {
-        try {
-          return funcToString.call(func);
-        } catch (e) {}
-        try {
-          return (func + '');
-        } catch (e) {}
+    function baseConformsTo(object, source, props) {
+      var length = props.length;
+      if (object == null) {
+        return !length;
       }
-      return '';
+      object = Object(object);
+      while (length--) {
+        var key = props[length],
+            predicate = source[key],
+            value = object[key];
+
+        if ((value === undefined && !(key in object)) || !predicate(value)) {
+          return false;
+        }
+      }
+      return true;
     }
 
     /**
-     * Creates a clone of `wrapper`.
+     * The base implementation of `_.delay` and `_.defer` which accepts `args`
+     * to provide to `func`.
      *
      * @private
-     * @param {Object} wrapper The wrapper to clone.
-     * @returns {Object} Returns the cloned wrapper.
+     * @param {Function} func The function to delay.
+     * @param {number} wait The number of milliseconds to delay invocation.
+     * @param {Array} args The arguments to provide to `func`.
+     * @returns {number|Object} Returns the timer id or timeout object.
      */
-    function wrapperClone(wrapper) {
-      if (wrapper instanceof LazyWrapper) {
-        return wrapper.clone();
+    function baseDelay(func, wait, args) {
+      if (typeof func != 'function') {
+        throw new TypeError(FUNC_ERROR_TEXT);
       }
-      var result = new LodashWrapper(wrapper.__wrapped__, wrapper.__chain__);
-      result.__actions__ = copyArray(wrapper.__actions__);
-      result.__index__  = wrapper.__index__;
-      result.__values__ = wrapper.__values__;
-      return result;
+      return setTimeout(function() { func.apply(undefined, args); }, wait);
     }
 
-    /*------------------------------------------------------------------------*/
-
     /**
-     * Creates an array of elements split into groups the length of `size`.
-     * If `array` can't be split evenly, the final chunk will be the remaining
-     * elements.
-     *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Array
-     * @param {Array} array The array to process.
-     * @param {number} [size=1] The length of each chunk
-     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
-     * @returns {Array} Returns the new array of chunks.
-     * @example
-     *
-     * _.chunk(['a', 'b', 'c', 'd'], 2);
-     * // => [['a', 'b'], ['c', 'd']]
+     * The base implementation of methods like `_.difference` without support
+     * for excluding multiple arrays or iteratee shorthands.
      *
-     * _.chunk(['a', 'b', 'c', 'd'], 3);
-     * // => [['a', 'b', 'c'], ['d']]
+     * @private
+     * @param {Array} array The array to inspect.
+     * @param {Array} values The values to exclude.
+     * @param {Function} [iteratee] The iteratee invoked per element.
+     * @param {Function} [comparator] The comparator invoked per element.
+     * @returns {Array} Returns the new array of filtered values.
      */
-    function chunk(array, size, guard) {
-      if ((guard ? isIterateeCall(array, size, guard) : size === undefined)) {
-        size = 1;
-      } else {
-        size = nativeMax(toInteger(size), 0);
+    function baseDifference(array, values, iteratee, comparator) {
+      var index = -1,
+          includes = arrayIncludes,
+          isCommon = true,
+          length = array.length,
+          result = [],
+          valuesLength = values.length;
+
+      if (!length) {
+        return result;
       }
-      var length = array ? array.length : 0;
-      if (!length || size < 1) {
-        return [];
+      if (iteratee) {
+        values = arrayMap(values, baseUnary(iteratee));
       }
-      var index = 0,
-          resIndex = 0,
-          result = Array(nativeCeil(length / size));
+      if (comparator) {
+        includes = arrayIncludesWith;
+        isCommon = false;
+      }
+      else if (values.length >= LARGE_ARRAY_SIZE) {
+        includes = cacheHas;
+        isCommon = false;
+        values = new SetCache(values);
+      }
+      outer:
+      while (++index < length) {
+        var value = array[index],
+            computed = iteratee == null ? value : iteratee(value);
 
-      while (index < length) {
-        result[resIndex++] = baseSlice(array, index, (index += size));
+        value = (comparator || value !== 0) ? value : 0;
+        if (isCommon && computed === computed) {
+          var valuesIndex = valuesLength;
+          while (valuesIndex--) {
+            if (values[valuesIndex] === computed) {
+              continue outer;
+            }
+          }
+          result.push(value);
+        }
+        else if (!includes(values, computed, comparator)) {
+          result.push(value);
+        }
       }
       return result;
     }
 
     /**
-     * Creates an array with all falsey values removed. The values `false`, `null`,
-     * `0`, `""`, `undefined`, and `NaN` are falsey.
+     * The base implementation of `_.forEach` without support for iteratee shorthands.
      *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Array
-     * @param {Array} array The array to compact.
-     * @returns {Array} Returns the new array of filtered values.
-     * @example
+     * @private
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} iteratee The function invoked per iteration.
+     * @returns {Array|Object} Returns `collection`.
+     */
+    var baseEach = createBaseEach(baseForOwn);
+
+    /**
+     * The base implementation of `_.forEachRight` without support for iteratee shorthands.
      *
-     * _.compact([0, 1, false, 2, '', 3]);
-     * // => [1, 2, 3]
+     * @private
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} iteratee The function invoked per iteration.
+     * @returns {Array|Object} Returns `collection`.
      */
-    function compact(array) {
+    var baseEachRight = createBaseEach(baseForOwnRight, true);
+
+    /**
+     * The base implementation of `_.every` without support for iteratee shorthands.
+     *
+     * @private
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} predicate The function invoked per iteration.
+     * @returns {boolean} Returns `true` if all elements pass the predicate check,
+     *  else `false`
+     */
+    function baseEvery(collection, predicate) {
+      var result = true;
+      baseEach(collection, function(value, index, collection) {
+        result = !!predicate(value, index, collection);
+        return result;
+      });
+      return result;
+    }
+
+    /**
+     * The base implementation of methods like `_.max` and `_.min` which accepts a
+     * `comparator` to determine the extremum value.
+     *
+     * @private
+     * @param {Array} array The array to iterate over.
+     * @param {Function} iteratee The iteratee invoked per iteration.
+     * @param {Function} comparator The comparator used to compare values.
+     * @returns {*} Returns the extremum value.
+     */
+    function baseExtremum(array, iteratee, comparator) {
       var index = -1,
-          length = array ? array.length : 0,
-          resIndex = 0,
-          result = [];
+          length = array.length;
 
       while (++index < length) {
-        var value = array[index];
-        if (value) {
-          result[resIndex++] = value;
+        var value = array[index],
+            current = iteratee(value);
+
+        if (current != null && (computed === undefined
+              ? (current === current && !isSymbol(current))
+              : comparator(current, computed)
+            )) {
+          var computed = current,
+              result = value;
         }
       }
       return result;
     }
 
     /**
-     * Creates a new array concatenating `array` with any additional arrays
-     * and/or values.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {Array} array The array to concatenate.
-     * @param {...*} [values] The values to concatenate.
-     * @returns {Array} Returns the new concatenated array.
-     * @example
-     *
-     * var array = [1];
-     * var other = _.concat(array, 2, [3], [[4]]);
-     *
-     * console.log(other);
-     * // => [1, 2, 3, [4]]
+     * The base implementation of `_.fill` without an iteratee call guard.
      *
-     * console.log(array);
-     * // => [1]
+     * @private
+     * @param {Array} array The array to fill.
+     * @param {*} value The value to fill `array` with.
+     * @param {number} [start=0] The start position.
+     * @param {number} [end=array.length] The end position.
+     * @returns {Array} Returns `array`.
      */
-    function concat() {
-      var length = arguments.length,
-          args = Array(length ? length - 1 : 0),
-          array = arguments[0],
-          index = length;
+    function baseFill(array, value, start, end) {
+      var length = array.length;
 
-      while (index--) {
-        args[index - 1] = arguments[index];
+      start = toInteger(start);
+      if (start < 0) {
+        start = -start > length ? 0 : (length + start);
       }
-      return length
-        ? arrayPush(isArray(array) ? copyArray(array) : [array], baseFlatten(args, 1))
-        : [];
+      end = (end === undefined || end > length) ? length : toInteger(end);
+      if (end < 0) {
+        end += length;
+      }
+      end = start > end ? 0 : toLength(end);
+      while (start < end) {
+        array[start++] = value;
+      }
+      return array;
     }
 
     /**
-     * Creates an array of unique `array` values not included in the other given
-     * arrays using [`SameValueZero`](http://ecma-international.org/ecma-262/6.0/#sec-samevaluezero)
-     * for equality comparisons. The order of result values is determined by the
-     * order they occur in the first array.
+     * The base implementation of `_.filter` without support for iteratee shorthands.
      *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Array
-     * @param {Array} array The array to inspect.
-     * @param {...Array} [values] The values to exclude.
-     * @returns {Array} Returns the new array of filtered values.
-     * @see _.without, _.xor
-     * @example
-     *
-     * _.difference([2, 1], [2, 3]);
-     * // => [1]
+     * @private
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} predicate The function invoked per iteration.
+     * @returns {Array} Returns the new filtered array.
      */
-    var difference = rest(function(array, values) {
-      return isArrayLikeObject(array)
-        ? baseDifference(array, baseFlatten(values, 1, isArrayLikeObject, true))
-        : [];
-    });
+    function baseFilter(collection, predicate) {
+      var result = [];
+      baseEach(collection, function(value, index, collection) {
+        if (predicate(value, index, collection)) {
+          result.push(value);
+        }
+      });
+      return result;
+    }
 
     /**
-     * This method is like `_.difference` except that it accepts `iteratee` which
-     * is invoked for each element of `array` and `values` to generate the criterion
-     * by which they're compared. Result values are chosen from the first array.
-     * The iteratee is invoked with one argument: (value).
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {Array} array The array to inspect.
-     * @param {...Array} [values] The values to exclude.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The iteratee invoked per element.
-     * @returns {Array} Returns the new array of filtered values.
-     * @example
-     *
-     * _.differenceBy([2.1, 1.2], [2.3, 3.4], Math.floor);
-     * // => [1.2]
+     * The base implementation of `_.flatten` with support for restricting flattening.
      *
-     * // The `_.property` iteratee shorthand.
-     * _.differenceBy([{ 'x': 2 }, { 'x': 1 }], [{ 'x': 1 }], 'x');
-     * // => [{ 'x': 2 }]
+     * @private
+     * @param {Array} array The array to flatten.
+     * @param {number} depth The maximum recursion depth.
+     * @param {boolean} [predicate=isFlattenable] The function invoked per iteration.
+     * @param {boolean} [isStrict] Restrict to values that pass `predicate` checks.
+     * @param {Array} [result=[]] The initial result value.
+     * @returns {Array} Returns the new flattened array.
      */
-    var differenceBy = rest(function(array, values) {
-      var iteratee = last(values);
-      if (isArrayLikeObject(iteratee)) {
-        iteratee = undefined;
+    function baseFlatten(array, depth, predicate, isStrict, result) {
+      var index = -1,
+          length = array.length;
+
+      predicate || (predicate = isFlattenable);
+      result || (result = []);
+
+      while (++index < length) {
+        var value = array[index];
+        if (depth > 0 && predicate(value)) {
+          if (depth > 1) {
+            // Recursively flatten arrays (susceptible to call stack limits).
+            baseFlatten(value, depth - 1, predicate, isStrict, result);
+          } else {
+            arrayPush(result, value);
+          }
+        } else if (!isStrict) {
+          result[result.length] = value;
+        }
       }
-      return isArrayLikeObject(array)
-        ? baseDifference(array, baseFlatten(values, 1, isArrayLikeObject, true), getIteratee(iteratee))
-        : [];
-    });
+      return result;
+    }
 
     /**
-     * This method is like `_.difference` except that it accepts `comparator`
-     * which is invoked to compare elements of `array` to `values`. Result values
-     * are chosen from the first array. The comparator is invoked with two arguments:
-     * (arrVal, othVal).
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {Array} array The array to inspect.
-     * @param {...Array} [values] The values to exclude.
-     * @param {Function} [comparator] The comparator invoked per element.
-     * @returns {Array} Returns the new array of filtered values.
-     * @example
-     *
-     * var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }];
+     * The base implementation of `baseForOwn` which iterates over `object`
+     * properties returned by `keysFunc` and invokes `iteratee` for each property.
+     * Iteratee functions may exit iteration early by explicitly returning `false`.
      *
-     * _.differenceWith(objects, [{ 'x': 1, 'y': 2 }], _.isEqual);
-     * // => [{ 'x': 2, 'y': 1 }]
+     * @private
+     * @param {Object} object The object to iterate over.
+     * @param {Function} iteratee The function invoked per iteration.
+     * @param {Function} keysFunc The function to get the keys of `object`.
+     * @returns {Object} Returns `object`.
      */
-    var differenceWith = rest(function(array, values) {
-      var comparator = last(values);
-      if (isArrayLikeObject(comparator)) {
-        comparator = undefined;
-      }
-      return isArrayLikeObject(array)
-        ? baseDifference(array, baseFlatten(values, 1, isArrayLikeObject, true), undefined, comparator)
-        : [];
-    });
+    var baseFor = createBaseFor();
 
     /**
-     * Creates a slice of `array` with `n` elements dropped from the beginning.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.5.0
-     * @category Array
-     * @param {Array} array The array to query.
-     * @param {number} [n=1] The number of elements to drop.
-     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
-     * @returns {Array} Returns the slice of `array`.
-     * @example
-     *
-     * _.drop([1, 2, 3]);
-     * // => [2, 3]
-     *
-     * _.drop([1, 2, 3], 2);
-     * // => [3]
+     * This function is like `baseFor` except that it iterates over properties
+     * in the opposite order.
      *
-     * _.drop([1, 2, 3], 5);
-     * // => []
+     * @private
+     * @param {Object} object The object to iterate over.
+     * @param {Function} iteratee The function invoked per iteration.
+     * @param {Function} keysFunc The function to get the keys of `object`.
+     * @returns {Object} Returns `object`.
+     */
+    var baseForRight = createBaseFor(true);
+
+    /**
+     * The base implementation of `_.forOwn` without support for iteratee shorthands.
      *
-     * _.drop([1, 2, 3], 0);
-     * // => [1, 2, 3]
+     * @private
+     * @param {Object} object The object to iterate over.
+     * @param {Function} iteratee The function invoked per iteration.
+     * @returns {Object} Returns `object`.
      */
-    function drop(array, n, guard) {
-      var length = array ? array.length : 0;
-      if (!length) {
-        return [];
-      }
-      n = (guard || n === undefined) ? 1 : toInteger(n);
-      return baseSlice(array, n < 0 ? 0 : n, length);
+    function baseForOwn(object, iteratee) {
+      return object && baseFor(object, iteratee, keys);
     }
 
     /**
-     * Creates a slice of `array` with `n` elements dropped from the end.
-     *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Array
-     * @param {Array} array The array to query.
-     * @param {number} [n=1] The number of elements to drop.
-     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
-     * @returns {Array} Returns the slice of `array`.
-     * @example
-     *
-     * _.dropRight([1, 2, 3]);
-     * // => [1, 2]
-     *
-     * _.dropRight([1, 2, 3], 2);
-     * // => [1]
-     *
-     * _.dropRight([1, 2, 3], 5);
-     * // => []
+     * The base implementation of `_.forOwnRight` without support for iteratee shorthands.
      *
-     * _.dropRight([1, 2, 3], 0);
-     * // => [1, 2, 3]
+     * @private
+     * @param {Object} object The object to iterate over.
+     * @param {Function} iteratee The function invoked per iteration.
+     * @returns {Object} Returns `object`.
      */
-    function dropRight(array, n, guard) {
-      var length = array ? array.length : 0;
-      if (!length) {
-        return [];
-      }
-      n = (guard || n === undefined) ? 1 : toInteger(n);
-      n = length - n;
-      return baseSlice(array, 0, n < 0 ? 0 : n);
+    function baseForOwnRight(object, iteratee) {
+      return object && baseForRight(object, iteratee, keys);
     }
 
     /**
-     * Creates a slice of `array` excluding elements dropped from the end.
-     * Elements are dropped until `predicate` returns falsey. The predicate is
-     * invoked with three arguments: (value, index, array).
-     *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Array
-     * @param {Array} array The array to query.
-     * @param {Array|Function|Object|string} [predicate=_.identity]
-     *  The function invoked per iteration.
-     * @returns {Array} Returns the slice of `array`.
-     * @example
-     *
-     * var users = [
-     *   { 'user': 'barney',  'active': true },
-     *   { 'user': 'fred',    'active': false },
-     *   { 'user': 'pebbles', 'active': false }
-     * ];
-     *
-     * _.dropRightWhile(users, function(o) { return !o.active; });
-     * // => objects for ['barney']
-     *
-     * // The `_.matches` iteratee shorthand.
-     * _.dropRightWhile(users, { 'user': 'pebbles', 'active': false });
-     * // => objects for ['barney', 'fred']
+     * The base implementation of `_.functions` which creates an array of
+     * `object` function property names filtered from `props`.
      *
-     * // The `_.matchesProperty` iteratee shorthand.
-     * _.dropRightWhile(users, ['active', false]);
-     * // => objects for ['barney']
+     * @private
+     * @param {Object} object The object to inspect.
+     * @param {Array} props The property names to filter.
+     * @returns {Array} Returns the function names.
+     */
+    function baseFunctions(object, props) {
+      return arrayFilter(props, function(key) {
+        return isFunction(object[key]);
+      });
+    }
+
+    /**
+     * The base implementation of `_.get` without support for default values.
      *
-     * // The `_.property` iteratee shorthand.
-     * _.dropRightWhile(users, 'active');
-     * // => objects for ['barney', 'fred', 'pebbles']
+     * @private
+     * @param {Object} object The object to query.
+     * @param {Array|string} path The path of the property to get.
+     * @returns {*} Returns the resolved value.
      */
-    function dropRightWhile(array, predicate) {
-      return (array && array.length)
-        ? baseWhile(array, getIteratee(predicate, 3), true, true)
-        : [];
+    function baseGet(object, path) {
+      path = castPath(path, object);
+
+      var index = 0,
+          length = path.length;
+
+      while (object != null && index < length) {
+        object = object[toKey(path[index++])];
+      }
+      return (index && index == length) ? object : undefined;
     }
 
     /**
-     * Creates a slice of `array` excluding elements dropped from the beginning.
-     * Elements are dropped until `predicate` returns falsey. The predicate is
-     * invoked with three arguments: (value, index, array).
+     * The base implementation of `getAllKeys` and `getAllKeysIn` which uses
+     * `keysFunc` and `symbolsFunc` to get the enumerable property names and
+     * symbols of `object`.
      *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Array
-     * @param {Array} array The array to query.
-     * @param {Array|Function|Object|string} [predicate=_.identity]
-     *  The function invoked per iteration.
-     * @returns {Array} Returns the slice of `array`.
-     * @example
-     *
-     * var users = [
-     *   { 'user': 'barney',  'active': false },
-     *   { 'user': 'fred',    'active': false },
-     *   { 'user': 'pebbles', 'active': true }
-     * ];
-     *
-     * _.dropWhile(users, function(o) { return !o.active; });
-     * // => objects for ['pebbles']
-     *
-     * // The `_.matches` iteratee shorthand.
-     * _.dropWhile(users, { 'user': 'barney', 'active': false });
-     * // => objects for ['fred', 'pebbles']
-     *
-     * // The `_.matchesProperty` iteratee shorthand.
-     * _.dropWhile(users, ['active', false]);
-     * // => objects for ['pebbles']
-     *
-     * // The `_.property` iteratee shorthand.
-     * _.dropWhile(users, 'active');
-     * // => objects for ['barney', 'fred', 'pebbles']
+     * @private
+     * @param {Object} object The object to query.
+     * @param {Function} keysFunc The function to get the keys of `object`.
+     * @param {Function} symbolsFunc The function to get the symbols of `object`.
+     * @returns {Array} Returns the array of property names and symbols.
      */
-    function dropWhile(array, predicate) {
-      return (array && array.length)
-        ? baseWhile(array, getIteratee(predicate, 3), true)
-        : [];
+    function baseGetAllKeys(object, keysFunc, symbolsFunc) {
+      var result = keysFunc(object);
+      return isArray(object) ? result : arrayPush(result, symbolsFunc(object));
     }
 
     /**
-     * Fills elements of `array` with `value` from `start` up to, but not
-     * including, `end`.
-     *
-     * **Note:** This method mutates `array`.
-     *
-     * @static
-     * @memberOf _
-     * @since 3.2.0
-     * @category Array
-     * @param {Array} array The array to fill.
-     * @param {*} value The value to fill `array` with.
-     * @param {number} [start=0] The start position.
-     * @param {number} [end=array.length] The end position.
-     * @returns {Array} Returns `array`.
-     * @example
-     *
-     * var array = [1, 2, 3];
-     *
-     * _.fill(array, 'a');
-     * console.log(array);
-     * // => ['a', 'a', 'a']
-     *
-     * _.fill(Array(3), 2);
-     * // => [2, 2, 2]
+     * The base implementation of `getTag` without fallbacks for buggy environments.
      *
-     * _.fill([4, 6, 8, 10], '*', 1, 3);
-     * // => [4, '*', '*', 10]
+     * @private
+     * @param {*} value The value to query.
+     * @returns {string} Returns the `toStringTag`.
      */
-    function fill(array, value, start, end) {
-      var length = array ? array.length : 0;
-      if (!length) {
-        return [];
-      }
-      if (start && typeof start != 'number' && isIterateeCall(array, value, start)) {
-        start = 0;
-        end = length;
+    function baseGetTag(value) {
+      if (value == null) {
+        return value === undefined ? undefinedTag : nullTag;
       }
-      return baseFill(array, value, start, end);
+      return (symToStringTag && symToStringTag in Object(value))
+        ? getRawTag(value)
+        : objectToString(value);
     }
 
     /**
-     * This method is like `_.find` except that it returns the index of the first
-     * element `predicate` returns truthy for instead of the element itself.
-     *
-     * @static
-     * @memberOf _
-     * @since 1.1.0
-     * @category Array
-     * @param {Array} array The array to search.
-     * @param {Array|Function|Object|string} [predicate=_.identity]
-     *  The function invoked per iteration.
-     * @param {number} [fromIndex=0] The index to search from.
-     * @returns {number} Returns the index of the found element, else `-1`.
-     * @example
-     *
-     * var users = [
-     *   { 'user': 'barney',  'active': false },
-     *   { 'user': 'fred',    'active': false },
-     *   { 'user': 'pebbles', 'active': true }
-     * ];
-     *
-     * _.findIndex(users, function(o) { return o.user == 'barney'; });
-     * // => 0
-     *
-     * // The `_.matches` iteratee shorthand.
-     * _.findIndex(users, { 'user': 'fred', 'active': false });
-     * // => 1
-     *
-     * // The `_.matchesProperty` iteratee shorthand.
-     * _.findIndex(users, ['active', false]);
-     * // => 0
+     * The base implementation of `_.gt` which doesn't coerce arguments.
      *
-     * // The `_.property` iteratee shorthand.
-     * _.findIndex(users, 'active');
-     * // => 2
+     * @private
+     * @param {*} value The value to compare.
+     * @param {*} other The other value to compare.
+     * @returns {boolean} Returns `true` if `value` is greater than `other`,
+     *  else `false`.
      */
-    function findIndex(array, predicate, fromIndex) {
-      var length = array ? array.length : 0;
-      if (!length) {
-        return -1;
-      }
-      var index = fromIndex == null ? 0 : toInteger(fromIndex);
-      if (index < 0) {
-        index = nativeMax(length + index, 0);
-      }
-      return baseFindIndex(array, getIteratee(predicate, 3), index);
+    function baseGt(value, other) {
+      return value > other;
     }
 
     /**
-     * This method is like `_.findIndex` except that it iterates over elements
-     * of `collection` from right to left.
-     *
-     * @static
-     * @memberOf _
-     * @since 2.0.0
-     * @category Array
-     * @param {Array} array The array to search.
-     * @param {Array|Function|Object|string} [predicate=_.identity]
-     *  The function invoked per iteration.
-     * @param {number} [fromIndex=array.length-1] The index to search from.
-     * @returns {number} Returns the index of the found element, else `-1`.
-     * @example
-     *
-     * var users = [
-     *   { 'user': 'barney',  'active': true },
-     *   { 'user': 'fred',    'active': false },
-     *   { 'user': 'pebbles', 'active': false }
-     * ];
-     *
-     * _.findLastIndex(users, function(o) { return o.user == 'pebbles'; });
-     * // => 2
-     *
-     * // The `_.matches` iteratee shorthand.
-     * _.findLastIndex(users, { 'user': 'barney', 'active': true });
-     * // => 0
-     *
-     * // The `_.matchesProperty` iteratee shorthand.
-     * _.findLastIndex(users, ['active', false]);
-     * // => 2
+     * The base implementation of `_.has` without support for deep paths.
      *
-     * // The `_.property` iteratee shorthand.
-     * _.findLastIndex(users, 'active');
-     * // => 0
+     * @private
+     * @param {Object} [object] The object to query.
+     * @param {Array|string} key The key to check.
+     * @returns {boolean} Returns `true` if `key` exists, else `false`.
      */
-    function findLastIndex(array, predicate, fromIndex) {
-      var length = array ? array.length : 0;
-      if (!length) {
-        return -1;
-      }
-      var index = length - 1;
-      if (fromIndex !== undefined) {
-        index = toInteger(fromIndex);
-        index = fromIndex < 0
-          ? nativeMax(length + index, 0)
-          : nativeMin(index, length - 1);
-      }
-      return baseFindIndex(array, getIteratee(predicate, 3), index, true);
+    function baseHas(object, key) {
+      return object != null && hasOwnProperty.call(object, key);
     }
 
     /**
-     * Flattens `array` a single level deep.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Array
-     * @param {Array} array The array to flatten.
-     * @returns {Array} Returns the new flattened array.
-     * @example
+     * The base implementation of `_.hasIn` without support for deep paths.
      *
-     * _.flatten([1, [2, [3, [4]], 5]]);
-     * // => [1, 2, [3, [4]], 5]
+     * @private
+     * @param {Object} [object] The object to query.
+     * @param {Array|string} key The key to check.
+     * @returns {boolean} Returns `true` if `key` exists, else `false`.
      */
-    function flatten(array) {
-      var length = array ? array.length : 0;
-      return length ? baseFlatten(array, 1) : [];
+    function baseHasIn(object, key) {
+      return object != null && key in Object(object);
     }
 
     /**
-     * Recursively flattens `array`.
-     *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Array
-     * @param {Array} array The array to flatten.
-     * @returns {Array} Returns the new flattened array.
-     * @example
+     * The base implementation of `_.inRange` which doesn't coerce arguments.
      *
-     * _.flattenDeep([1, [2, [3, [4]], 5]]);
-     * // => [1, 2, 3, 4, 5]
+     * @private
+     * @param {number} number The number to check.
+     * @param {number} start The start of the range.
+     * @param {number} end The end of the range.
+     * @returns {boolean} Returns `true` if `number` is in the range, else `false`.
      */
-    function flattenDeep(array) {
-      var length = array ? array.length : 0;
-      return length ? baseFlatten(array, INFINITY) : [];
+    function baseInRange(number, start, end) {
+      return number >= nativeMin(start, end) && number < nativeMax(start, end);
     }
 
     /**
-     * Recursively flatten `array` up to `depth` times.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.4.0
-     * @category Array
-     * @param {Array} array The array to flatten.
-     * @param {number} [depth=1] The maximum recursion depth.
-     * @returns {Array} Returns the new flattened array.
-     * @example
-     *
-     * var array = [1, [2, [3, [4]], 5]];
-     *
-     * _.flattenDepth(array, 1);
-     * // => [1, 2, [3, [4]], 5]
+     * The base implementation of methods like `_.intersection`, without support
+     * for iteratee shorthands, that accepts an array of arrays to inspect.
      *
-     * _.flattenDepth(array, 2);
-     * // => [1, 2, 3, [4], 5]
+     * @private
+     * @param {Array} arrays The arrays to inspect.
+     * @param {Function} [iteratee] The iteratee invoked per element.
+     * @param {Function} [comparator] The comparator invoked per element.
+     * @returns {Array} Returns the new array of shared values.
      */
-    function flattenDepth(array, depth) {
-      var length = array ? array.length : 0;
-      if (!length) {
-        return [];
-      }
-      depth = depth === undefined ? 1 : toInteger(depth);
-      return baseFlatten(array, depth);
-    }
+    function baseIntersection(arrays, iteratee, comparator) {
+      var includes = comparator ? arrayIncludesWith : arrayIncludes,
+          length = arrays[0].length,
+          othLength = arrays.length,
+          othIndex = othLength,
+          caches = Array(othLength),
+          maxLength = Infinity,
+          result = [];
+
+      while (othIndex--) {
+        var array = arrays[othIndex];
+        if (othIndex && iteratee) {
+          array = arrayMap(array, baseUnary(iteratee));
+        }
+        maxLength = nativeMin(array.length, maxLength);
+        caches[othIndex] = !comparator && (iteratee || (length >= 120 && array.length >= 120))
+          ? new SetCache(othIndex && array)
+          : undefined;
+      }
+      array = arrays[0];
 
-    /**
-     * The inverse of `_.toPairs`; this method returns an object composed
-     * from key-value `pairs`.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {Array} pairs The key-value pairs.
-     * @returns {Object} Returns the new object.
-     * @example
-     *
-     * _.fromPairs([['fred', 30], ['barney', 40]]);
-     * // => { 'fred': 30, 'barney': 40 }
-     */
-    function fromPairs(pairs) {
       var index = -1,
-          length = pairs ? pairs.length : 0,
-          result = {};
+          seen = caches[0];
 
-      while (++index < length) {
-        var pair = pairs[index];
-        result[pair[0]] = pair[1];
+      outer:
+      while (++index < length && result.length < maxLength) {
+        var value = array[index],
+            computed = iteratee ? iteratee(value) : value;
+
+        value = (comparator || value !== 0) ? value : 0;
+        if (!(seen
+              ? cacheHas(seen, computed)
+              : includes(result, computed, comparator)
+            )) {
+          othIndex = othLength;
+          while (--othIndex) {
+            var cache = caches[othIndex];
+            if (!(cache
+                  ? cacheHas(cache, computed)
+                  : includes(arrays[othIndex], computed, comparator))
+                ) {
+              continue outer;
+            }
+          }
+          if (seen) {
+            seen.push(computed);
+          }
+          result.push(value);
+        }
       }
       return result;
     }
 
     /**
-     * Gets the first element of `array`.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @alias first
-     * @category Array
-     * @param {Array} array The array to query.
-     * @returns {*} Returns the first element of `array`.
-     * @example
-     *
-     * _.head([1, 2, 3]);
-     * // => 1
+     * The base implementation of `_.invert` and `_.invertBy` which inverts
+     * `object` with values transformed by `iteratee` and set by `setter`.
      *
-     * _.head([]);
-     * // => undefined
+     * @private
+     * @param {Object} object The object to iterate over.
+     * @param {Function} setter The function to set `accumulator` values.
+     * @param {Function} iteratee The iteratee to transform values.
+     * @param {Object} accumulator The initial inverted object.
+     * @returns {Function} Returns `accumulator`.
      */
-    function head(array) {
-      return (array && array.length) ? array[0] : undefined;
+    function baseInverter(object, setter, iteratee, accumulator) {
+      baseForOwn(object, function(value, key, object) {
+        setter(accumulator, iteratee(value), key, object);
+      });
+      return accumulator;
     }
 
     /**
-     * Gets the index at which the first occurrence of `value` is found in `array`
-     * using [`SameValueZero`](http://ecma-international.org/ecma-262/6.0/#sec-samevaluezero)
-     * for equality comparisons. If `fromIndex` is negative, it's used as the
-     * offset from the end of `array`.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Array
-     * @param {Array} array The array to search.
-     * @param {*} value The value to search for.
-     * @param {number} [fromIndex=0] The index to search from.
-     * @returns {number} Returns the index of the matched value, else `-1`.
-     * @example
-     *
-     * _.indexOf([1, 2, 1, 2], 2);
-     * // => 1
+     * The base implementation of `_.invoke` without support for individual
+     * method arguments.
      *
-     * // Search from the `fromIndex`.
-     * _.indexOf([1, 2, 1, 2], 2, 2);
-     * // => 3
+     * @private
+     * @param {Object} object The object to query.
+     * @param {Array|string} path The path of the method to invoke.
+     * @param {Array} args The arguments to invoke the method with.
+     * @returns {*} Returns the result of the invoked method.
      */
-    function indexOf(array, value, fromIndex) {
-      var length = array ? array.length : 0;
-      if (!length) {
-        return -1;
-      }
-      var index = fromIndex == null ? 0 : toInteger(fromIndex);
-      if (index < 0) {
-        index = nativeMax(length + index, 0);
-      }
-      return baseIndexOf(array, value, index);
+    function baseInvoke(object, path, args) {
+      path = castPath(path, object);
+      object = parent(object, path);
+      var func = object == null ? object : object[toKey(last(path))];
+      return func == null ? undefined : apply(func, object, args);
     }
 
     /**
-     * Gets all but the last element of `array`.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Array
-     * @param {Array} array The array to query.
-     * @returns {Array} Returns the slice of `array`.
-     * @example
+     * The base implementation of `_.isArguments`.
      *
-     * _.initial([1, 2, 3]);
-     * // => [1, 2]
+     * @private
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is an `arguments` object,
      */
-    function initial(array) {
-      return dropRight(array, 1);
+    function baseIsArguments(value) {
+      return isObjectLike(value) && baseGetTag(value) == argsTag;
     }
 
     /**
-     * Creates an array of unique values that are included in all given arrays
-     * using [`SameValueZero`](http://ecma-international.org/ecma-262/6.0/#sec-samevaluezero)
-     * for equality comparisons. The order of result values is determined by the
-     * order they occur in the first array.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Array
-     * @param {...Array} [arrays] The arrays to inspect.
-     * @returns {Array} Returns the new array of intersecting values.
-     * @example
+     * The base implementation of `_.isArrayBuffer` without Node.js optimizations.
      *
-     * _.intersection([2, 1], [2, 3]);
-     * // => [2]
+     * @private
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is an array buffer, else `false`.
      */
-    var intersection = rest(function(arrays) {
-      var mapped = arrayMap(arrays, castArrayLikeObject);
-      return (mapped.length && mapped[0] === arrays[0])
-        ? baseIntersection(mapped)
-        : [];
-    });
+    function baseIsArrayBuffer(value) {
+      return isObjectLike(value) && baseGetTag(value) == arrayBufferTag;
+    }
 
     /**
-     * This method is like `_.intersection` except that it accepts `iteratee`
-     * which is invoked for each element of each `arrays` to generate the criterion
-     * by which they're compared. Result values are chosen from the first array.
-     * The iteratee is invoked with one argument: (value).
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {...Array} [arrays] The arrays to inspect.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The iteratee invoked per element.
-     * @returns {Array} Returns the new array of intersecting values.
-     * @example
-     *
-     * _.intersectionBy([2.1, 1.2], [2.3, 3.4], Math.floor);
-     * // => [2.1]
+     * The base implementation of `_.isDate` without Node.js optimizations.
      *
-     * // The `_.property` iteratee shorthand.
-     * _.intersectionBy([{ 'x': 1 }], [{ 'x': 2 }, { 'x': 1 }], 'x');
-     * // => [{ 'x': 1 }]
+     * @private
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a date object, else `false`.
      */
-    var intersectionBy = rest(function(arrays) {
-      var iteratee = last(arrays),
-          mapped = arrayMap(arrays, castArrayLikeObject);
-
-      if (iteratee === last(mapped)) {
-        iteratee = undefined;
-      } else {
-        mapped.pop();
-      }
-      return (mapped.length && mapped[0] === arrays[0])
-        ? baseIntersection(mapped, getIteratee(iteratee))
-        : [];
-    });
+    function baseIsDate(value) {
+      return isObjectLike(value) && baseGetTag(value) == dateTag;
+    }
 
     /**
-     * This method is like `_.intersection` except that it accepts `comparator`
-     * which is invoked to compare elements of `arrays`. Result values are chosen
-     * from the first array. The comparator is invoked with two arguments:
-     * (arrVal, othVal).
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {...Array} [arrays] The arrays to inspect.
-     * @param {Function} [comparator] The comparator invoked per element.
-     * @returns {Array} Returns the new array of intersecting values.
-     * @example
-     *
-     * var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }];
-     * var others = [{ 'x': 1, 'y': 1 }, { 'x': 1, 'y': 2 }];
+     * The base implementation of `_.isEqual` which supports partial comparisons
+     * and tracks traversed objects.
      *
-     * _.intersectionWith(objects, others, _.isEqual);
-     * // => [{ 'x': 1, 'y': 2 }]
+     * @private
+     * @param {*} value The value to compare.
+     * @param {*} other The other value to compare.
+     * @param {boolean} bitmask The bitmask flags.
+     *  1 - Unordered comparison
+     *  2 - Partial comparison
+     * @param {Function} [customizer] The function to customize comparisons.
+     * @param {Object} [stack] Tracks traversed `value` and `other` objects.
+     * @returns {boolean} Returns `true` if the values are equivalent, else `false`.
      */
-    var intersectionWith = rest(function(arrays) {
-      var comparator = last(arrays),
-          mapped = arrayMap(arrays, castArrayLikeObject);
-
-      if (comparator === last(mapped)) {
-        comparator = undefined;
-      } else {
-        mapped.pop();
+    function baseIsEqual(value, other, bitmask, customizer, stack) {
+      if (value === other) {
+        return true;
       }
-      return (mapped.length && mapped[0] === arrays[0])
-        ? baseIntersection(mapped, undefined, comparator)
-        : [];
-    });
+      if (value == null || other == null || (!isObjectLike(value) && !isObjectLike(other))) {
+        return value !== value && other !== other;
+      }
+      return baseIsEqualDeep(value, other, bitmask, customizer, baseIsEqual, stack);
+    }
 
     /**
-     * Converts all elements in `array` into a string separated by `separator`.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {Array} array The array to convert.
-     * @param {string} [separator=','] The element separator.
-     * @returns {string} Returns the joined string.
-     * @example
+     * A specialized version of `baseIsEqual` for arrays and objects which performs
+     * deep comparisons and tracks traversed objects enabling objects with circular
+     * references to be compared.
      *
-     * _.join(['a', 'b', 'c'], '~');
-     * // => 'a~b~c'
+     * @private
+     * @param {Object} object The object to compare.
+     * @param {Object} other The other object to compare.
+     * @param {number} bitmask The bitmask flags. See `baseIsEqual` for more details.
+     * @param {Function} customizer The function to customize comparisons.
+     * @param {Function} equalFunc The function to determine equivalents of values.
+     * @param {Object} [stack] Tracks traversed `object` and `other` objects.
+     * @returns {boolean} Returns `true` if the objects are equivalent, else `false`.
      */
-    function join(array, separator) {
-      return array ? nativeJoin.call(array, separator) : '';
-    }
+    function baseIsEqualDeep(object, other, bitmask, customizer, equalFunc, stack) {
+      var objIsArr = isArray(object),
+          othIsArr = isArray(other),
+          objTag = objIsArr ? arrayTag : getTag(object),
+          othTag = othIsArr ? arrayTag : getTag(other);
 
-    /**
-     * Gets the last element of `array`.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Array
-     * @param {Array} array The array to query.
-     * @returns {*} Returns the last element of `array`.
-     * @example
+      objTag = objTag == argsTag ? objectTag : objTag;
+      othTag = othTag == argsTag ? objectTag : othTag;
+
+      var objIsObj = objTag == objectTag,
+          othIsObj = othTag == objectTag,
+          isSameTag = objTag == othTag;
+
+      if (isSameTag && isBuffer(object)) {
+        if (!isBuffer(other)) {
+          return false;
+        }
+        objIsArr = true;
+        objIsObj = false;
+      }
+      if (isSameTag && !objIsObj) {
+        stack || (stack = new Stack);
+        return (objIsArr || isTypedArray(object))
+          ? equalArrays(object, other, bitmask, customizer, equalFunc, stack)
+          : equalByTag(object, other, objTag, bitmask, customizer, equalFunc, stack);
+      }
+      if (!(bitmask & COMPARE_PARTIAL_FLAG)) {
+        var objIsWrapped = objIsObj && hasOwnProperty.call(object, '__wrapped__'),
+            othIsWrapped = othIsObj && hasOwnProperty.call(other, '__wrapped__');
+
+        if (objIsWrapped || othIsWrapped) {
+          var objUnwrapped = objIsWrapped ? object.value() : object,
+              othUnwrapped = othIsWrapped ? other.value() : other;
+
+          stack || (stack = new Stack);
+          return equalFunc(objUnwrapped, othUnwrapped, bitmask, customizer, stack);
+        }
+      }
+      if (!isSameTag) {
+        return false;
+      }
+      stack || (stack = new Stack);
+      return equalObjects(object, other, bitmask, customizer, equalFunc, stack);
+    }
+
+    /**
+     * The base implementation of `_.isMap` without Node.js optimizations.
      *
-     * _.last([1, 2, 3]);
-     * // => 3
+     * @private
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a map, else `false`.
      */
-    function last(array) {
-      var length = array ? array.length : 0;
-      return length ? array[length - 1] : undefined;
+    function baseIsMap(value) {
+      return isObjectLike(value) && getTag(value) == mapTag;
     }
 
     /**
-     * This method is like `_.indexOf` except that it iterates over elements of
-     * `array` from right to left.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Array
-     * @param {Array} array The array to search.
-     * @param {*} value The value to search for.
-     * @param {number} [fromIndex=array.length-1] The index to search from.
-     * @returns {number} Returns the index of the matched value, else `-1`.
-     * @example
-     *
-     * _.lastIndexOf([1, 2, 1, 2], 2);
-     * // => 3
+     * The base implementation of `_.isMatch` without support for iteratee shorthands.
      *
-     * // Search from the `fromIndex`.
-     * _.lastIndexOf([1, 2, 1, 2], 2, 2);
-     * // => 1
+     * @private
+     * @param {Object} object The object to inspect.
+     * @param {Object} source The object of property values to match.
+     * @param {Array} matchData The property names, values, and compare flags to match.
+     * @param {Function} [customizer] The function to customize comparisons.
+     * @returns {boolean} Returns `true` if `object` is a match, else `false`.
      */
-    function lastIndexOf(array, value, fromIndex) {
-      var length = array ? array.length : 0;
-      if (!length) {
-        return -1;
-      }
-      var index = length;
-      if (fromIndex !== undefined) {
-        index = toInteger(fromIndex);
-        index = (
-          index < 0
-            ? nativeMax(length + index, 0)
-            : nativeMin(index, length - 1)
-        ) + 1;
-      }
-      if (value !== value) {
-        return indexOfNaN(array, index - 1, true);
+    function baseIsMatch(object, source, matchData, customizer) {
+      var index = matchData.length,
+          length = index,
+          noCustomizer = !customizer;
+
+      if (object == null) {
+        return !length;
       }
+      object = Object(object);
       while (index--) {
-        if (array[index] === value) {
-          return index;
+        var data = matchData[index];
+        if ((noCustomizer && data[2])
+              ? data[1] !== object[data[0]]
+              : !(data[0] in object)
+            ) {
+          return false;
         }
       }
-      return -1;
+      while (++index < length) {
+        data = matchData[index];
+        var key = data[0],
+            objValue = object[key],
+            srcValue = data[1];
+
+        if (noCustomizer && data[2]) {
+          if (objValue === undefined && !(key in object)) {
+            return false;
+          }
+        } else {
+          var stack = new Stack;
+          if (customizer) {
+            var result = customizer(objValue, srcValue, key, object, source, stack);
+          }
+          if (!(result === undefined
+                ? baseIsEqual(srcValue, objValue, COMPARE_PARTIAL_FLAG | COMPARE_UNORDERED_FLAG, customizer, stack)
+                : result
+              )) {
+            return false;
+          }
+        }
+      }
+      return true;
     }
 
     /**
-     * Gets the element at index `n` of `array`. If `n` is negative, the nth
-     * element from the end is returned.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.11.0
-     * @category Array
-     * @param {Array} array The array to query.
-     * @param {number} [n=0] The index of the element to return.
-     * @returns {*} Returns the nth element of `array`.
-     * @example
-     *
-     * var array = ['a', 'b', 'c', 'd'];
-     *
-     * _.nth(array, 1);
-     * // => 'b'
+     * The base implementation of `_.isNative` without bad shim checks.
      *
-     * _.nth(array, -2);
-     * // => 'c';
+     * @private
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a native function,
+     *  else `false`.
      */
-    function nth(array, n) {
-      return (array && array.length) ? baseNth(array, toInteger(n)) : undefined;
+    function baseIsNative(value) {
+      if (!isObject(value) || isMasked(value)) {
+        return false;
+      }
+      var pattern = isFunction(value) ? reIsNative : reIsHostCtor;
+      return pattern.test(toSource(value));
     }
 
     /**
-     * Removes all given values from `array` using
-     * [`SameValueZero`](http://ecma-international.org/ecma-262/6.0/#sec-samevaluezero)
-     * for equality comparisons.
-     *
-     * **Note:** Unlike `_.without`, this method mutates `array`. Use `_.remove`
-     * to remove elements from an array by predicate.
-     *
-     * @static
-     * @memberOf _
-     * @since 2.0.0
-     * @category Array
-     * @param {Array} array The array to modify.
-     * @param {...*} [values] The values to remove.
-     * @returns {Array} Returns `array`.
-     * @example
-     *
-     * var array = ['a', 'b', 'c', 'a', 'b', 'c'];
+     * The base implementation of `_.isRegExp` without Node.js optimizations.
      *
-     * _.pull(array, 'a', 'c');
-     * console.log(array);
-     * // => ['b', 'b']
+     * @private
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a regexp, else `false`.
      */
-    var pull = rest(pullAll);
+    function baseIsRegExp(value) {
+      return isObjectLike(value) && baseGetTag(value) == regexpTag;
+    }
 
     /**
-     * This method is like `_.pull` except that it accepts an array of values to remove.
-     *
-     * **Note:** Unlike `_.difference`, this method mutates `array`.
+     * The base implementation of `_.isSet` without Node.js optimizations.
      *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {Array} array The array to modify.
-     * @param {Array} values The values to remove.
-     * @returns {Array} Returns `array`.
-     * @example
-     *
-     * var array = ['a', 'b', 'c', 'a', 'b', 'c'];
-     *
-     * _.pullAll(array, ['a', 'c']);
-     * console.log(array);
-     * // => ['b', 'b']
+     * @private
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a set, else `false`.
      */
-    function pullAll(array, values) {
-      return (array && array.length && values && values.length)
-        ? basePullAll(array, values)
-        : array;
+    function baseIsSet(value) {
+      return isObjectLike(value) && getTag(value) == setTag;
     }
 
     /**
-     * This method is like `_.pullAll` except that it accepts `iteratee` which is
-     * invoked for each element of `array` and `values` to generate the criterion
-     * by which they're compared. The iteratee is invoked with one argument: (value).
-     *
-     * **Note:** Unlike `_.differenceBy`, this method mutates `array`.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {Array} array The array to modify.
-     * @param {Array} values The values to remove.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The iteratee invoked per element.
-     * @returns {Array} Returns `array`.
-     * @example
-     *
-     * var array = [{ 'x': 1 }, { 'x': 2 }, { 'x': 3 }, { 'x': 1 }];
+     * The base implementation of `_.isTypedArray` without Node.js optimizations.
      *
-     * _.pullAllBy(array, [{ 'x': 1 }, { 'x': 3 }], 'x');
-     * console.log(array);
-     * // => [{ 'x': 2 }]
+     * @private
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a typed array, else `false`.
      */
-    function pullAllBy(array, values, iteratee) {
-      return (array && array.length && values && values.length)
-        ? basePullAll(array, values, getIteratee(iteratee))
-        : array;
+    function baseIsTypedArray(value) {
+      return isObjectLike(value) &&
+        isLength(value.length) && !!typedArrayTags[baseGetTag(value)];
     }
 
     /**
-     * This method is like `_.pullAll` except that it accepts `comparator` which
-     * is invoked to compare elements of `array` to `values`. The comparator is
-     * invoked with two arguments: (arrVal, othVal).
-     *
-     * **Note:** Unlike `_.differenceWith`, this method mutates `array`.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.6.0
-     * @category Array
-     * @param {Array} array The array to modify.
-     * @param {Array} values The values to remove.
-     * @param {Function} [comparator] The comparator invoked per element.
-     * @returns {Array} Returns `array`.
-     * @example
-     *
-     * var array = [{ 'x': 1, 'y': 2 }, { 'x': 3, 'y': 4 }, { 'x': 5, 'y': 6 }];
+     * The base implementation of `_.iteratee`.
      *
-     * _.pullAllWith(array, [{ 'x': 3, 'y': 4 }], _.isEqual);
-     * console.log(array);
-     * // => [{ 'x': 1, 'y': 2 }, { 'x': 5, 'y': 6 }]
+     * @private
+     * @param {*} [value=_.identity] The value to convert to an iteratee.
+     * @returns {Function} Returns the iteratee.
      */
-    function pullAllWith(array, values, comparator) {
-      return (array && array.length && values && values.length)
-        ? basePullAll(array, values, undefined, comparator)
-        : array;
+    function baseIteratee(value) {
+      // Don't store the `typeof` result in a variable to avoid a JIT bug in Safari 9.
+      // See https://bugs.webkit.org/show_bug.cgi?id=156034 for more details.
+      if (typeof value == 'function') {
+        return value;
+      }
+      if (value == null) {
+        return identity;
+      }
+      if (typeof value == 'object') {
+        return isArray(value)
+          ? baseMatchesProperty(value[0], value[1])
+          : baseMatches(value);
+      }
+      return property(value);
     }
 
     /**
-     * Removes elements from `array` corresponding to `indexes` and returns an
-     * array of removed elements.
-     *
-     * **Note:** Unlike `_.at`, this method mutates `array`.
+     * The base implementation of `_.keys` which doesn't treat sparse arrays as dense.
      *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Array
-     * @param {Array} array The array to modify.
-     * @param {...(number|number[])} [indexes] The indexes of elements to remove.
-     * @returns {Array} Returns the new array of removed elements.
-     * @example
-     *
-     * var array = ['a', 'b', 'c', 'd'];
-     * var pulled = _.pullAt(array, [1, 3]);
-     *
-     * console.log(array);
-     * // => ['a', 'c']
-     *
-     * console.log(pulled);
-     * // => ['b', 'd']
+     * @private
+     * @param {Object} object The object to query.
+     * @returns {Array} Returns the array of property names.
      */
-    var pullAt = rest(function(array, indexes) {
-      indexes = baseFlatten(indexes, 1);
-
-      var length = array ? array.length : 0,
-          result = baseAt(array, indexes);
-
-      basePullAt(array, arrayMap(indexes, function(index) {
-        return isIndex(index, length) ? +index : index;
-      }).sort(compareAscending));
-
+    function baseKeys(object) {
+      if (!isPrototype(object)) {
+        return nativeKeys(object);
+      }
+      var result = [];
+      for (var key in Object(object)) {
+        if (hasOwnProperty.call(object, key) && key != 'constructor') {
+          result.push(key);
+        }
+      }
       return result;
-    });
+    }
 
     /**
-     * Removes all elements from `array` that `predicate` returns truthy for
-     * and returns an array of the removed elements. The predicate is invoked
-     * with three arguments: (value, index, array).
-     *
-     * **Note:** Unlike `_.filter`, this method mutates `array`. Use `_.pull`
-     * to pull elements from an array by value.
-     *
-     * @static
-     * @memberOf _
-     * @since 2.0.0
-     * @category Array
-     * @param {Array} array The array to modify.
-     * @param {Array|Function|Object|string} [predicate=_.identity]
-     *  The function invoked per iteration.
-     * @returns {Array} Returns the new array of removed elements.
-     * @example
-     *
-     * var array = [1, 2, 3, 4];
-     * var evens = _.remove(array, function(n) {
-     *   return n % 2 == 0;
-     * });
-     *
-     * console.log(array);
-     * // => [1, 3]
+     * The base implementation of `_.keysIn` which doesn't treat sparse arrays as dense.
      *
-     * console.log(evens);
-     * // => [2, 4]
+     * @private
+     * @param {Object} object The object to query.
+     * @returns {Array} Returns the array of property names.
      */
-    function remove(array, predicate) {
-      var result = [];
-      if (!(array && array.length)) {
-        return result;
+    function baseKeysIn(object) {
+      if (!isObject(object)) {
+        return nativeKeysIn(object);
       }
-      var index = -1,
-          indexes = [],
-          length = array.length;
+      var isProto = isPrototype(object),
+          result = [];
 
-      predicate = getIteratee(predicate, 3);
-      while (++index < length) {
-        var value = array[index];
-        if (predicate(value, index, array)) {
-          result.push(value);
-          indexes.push(index);
+      for (var key in object) {
+        if (!(key == 'constructor' && (isProto || !hasOwnProperty.call(object, key)))) {
+          result.push(key);
         }
       }
-      basePullAt(array, indexes);
       return result;
     }
 
     /**
-     * Reverses `array` so that the first element becomes the last, the second
-     * element becomes the second to last, and so on.
-     *
-     * **Note:** This method mutates `array` and is based on
-     * [`Array#reverse`](https://mdn.io/Array/reverse).
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {Array} array The array to modify.
-     * @returns {Array} Returns `array`.
-     * @example
-     *
-     * var array = [1, 2, 3];
-     *
-     * _.reverse(array);
-     * // => [3, 2, 1]
+     * The base implementation of `_.lt` which doesn't coerce arguments.
      *
-     * console.log(array);
-     * // => [3, 2, 1]
+     * @private
+     * @param {*} value The value to compare.
+     * @param {*} other The other value to compare.
+     * @returns {boolean} Returns `true` if `value` is less than `other`,
+     *  else `false`.
      */
-    function reverse(array) {
-      return array ? nativeReverse.call(array) : array;
+    function baseLt(value, other) {
+      return value < other;
     }
 
     /**
-     * Creates a slice of `array` from `start` up to, but not including, `end`.
-     *
-     * **Note:** This method is used instead of
-     * [`Array#slice`](https://mdn.io/Array/slice) to ensure dense arrays are
-     * returned.
+     * The base implementation of `_.map` without support for iteratee shorthands.
      *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Array
-     * @param {Array} array The array to slice.
-     * @param {number} [start=0] The start position.
-     * @param {number} [end=array.length] The end position.
-     * @returns {Array} Returns the slice of `array`.
+     * @private
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} iteratee The function invoked per iteration.
+     * @returns {Array} Returns the new mapped array.
      */
-    function slice(array, start, end) {
-      var length = array ? array.length : 0;
-      if (!length) {
-        return [];
-      }
-      if (end && typeof end != 'number' && isIterateeCall(array, start, end)) {
-        start = 0;
-        end = length;
-      }
-      else {
-        start = start == null ? 0 : toInteger(start);
-        end = end === undefined ? length : toInteger(end);
-      }
-      return baseSlice(array, start, end);
+    function baseMap(collection, iteratee) {
+      var index = -1,
+          result = isArrayLike(collection) ? Array(collection.length) : [];
+
+      baseEach(collection, function(value, key, collection) {
+        result[++index] = iteratee(value, key, collection);
+      });
+      return result;
     }
 
     /**
-     * Uses a binary search to determine the lowest index at which `value`
-     * should be inserted into `array` in order to maintain its sort order.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Array
-     * @param {Array} array The sorted array to inspect.
-     * @param {*} value The value to evaluate.
-     * @returns {number} Returns the index at which `value` should be inserted
-     *  into `array`.
-     * @example
+     * The base implementation of `_.matches` which doesn't clone `source`.
      *
-     * _.sortedIndex([30, 50], 40);
-     * // => 1
+     * @private
+     * @param {Object} source The object of property values to match.
+     * @returns {Function} Returns the new spec function.
      */
-    function sortedIndex(array, value) {
-      return baseSortedIndex(array, value);
+    function baseMatches(source) {
+      var matchData = getMatchData(source);
+      if (matchData.length == 1 && matchData[0][2]) {
+        return matchesStrictComparable(matchData[0][0], matchData[0][1]);
+      }
+      return function(object) {
+        return object === source || baseIsMatch(object, source, matchData);
+      };
     }
 
     /**
-     * This method is like `_.sortedIndex` except that it accepts `iteratee`
-     * which is invoked for `value` and each element of `array` to compute their
-     * sort ranking. The iteratee is invoked with one argument: (value).
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {Array} array The sorted array to inspect.
-     * @param {*} value The value to evaluate.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The iteratee invoked per element.
-     * @returns {number} Returns the index at which `value` should be inserted
-     *  into `array`.
-     * @example
-     *
-     * var objects = [{ 'x': 4 }, { 'x': 5 }];
-     *
-     * _.sortedIndexBy(objects, { 'x': 4 }, function(o) { return o.x; });
-     * // => 0
+     * The base implementation of `_.matchesProperty` which doesn't clone `srcValue`.
      *
-     * // The `_.property` iteratee shorthand.
-     * _.sortedIndexBy(objects, { 'x': 4 }, 'x');
-     * // => 0
+     * @private
+     * @param {string} path The path of the property to get.
+     * @param {*} srcValue The value to match.
+     * @returns {Function} Returns the new spec function.
      */
-    function sortedIndexBy(array, value, iteratee) {
-      return baseSortedIndexBy(array, value, getIteratee(iteratee));
+    function baseMatchesProperty(path, srcValue) {
+      if (isKey(path) && isStrictComparable(srcValue)) {
+        return matchesStrictComparable(toKey(path), srcValue);
+      }
+      return function(object) {
+        var objValue = get(object, path);
+        return (objValue === undefined && objValue === srcValue)
+          ? hasIn(object, path)
+          : baseIsEqual(srcValue, objValue, COMPARE_PARTIAL_FLAG | COMPARE_UNORDERED_FLAG);
+      };
     }
 
     /**
-     * This method is like `_.indexOf` except that it performs a binary
-     * search on a sorted `array`.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {Array} array The array to search.
-     * @param {*} value The value to search for.
-     * @returns {number} Returns the index of the matched value, else `-1`.
-     * @example
+     * The base implementation of `_.merge` without support for multiple sources.
      *
-     * _.sortedIndexOf([4, 5, 5, 5, 6], 5);
-     * // => 1
+     * @private
+     * @param {Object} object The destination object.
+     * @param {Object} source The source object.
+     * @param {number} srcIndex The index of `source`.
+     * @param {Function} [customizer] The function to customize merged values.
+     * @param {Object} [stack] Tracks traversed source values and their merged
+     *  counterparts.
      */
-    function sortedIndexOf(array, value) {
-      var length = array ? array.length : 0;
-      if (length) {
-        var index = baseSortedIndex(array, value);
-        if (index < length && eq(array[index], value)) {
-          return index;
-        }
+    function baseMerge(object, source, srcIndex, customizer, stack) {
+      if (object === source) {
+        return;
       }
-      return -1;
+      baseFor(source, function(srcValue, key) {
+        if (isObject(srcValue)) {
+          stack || (stack = new Stack);
+          baseMergeDeep(object, source, key, srcIndex, baseMerge, customizer, stack);
+        }
+        else {
+          var newValue = customizer
+            ? customizer(safeGet(object, key), srcValue, (key + ''), object, source, stack)
+            : undefined;
+
+          if (newValue === undefined) {
+            newValue = srcValue;
+          }
+          assignMergeValue(object, key, newValue);
+        }
+      }, keysIn);
     }
 
     /**
-     * This method is like `_.sortedIndex` except that it returns the highest
-     * index at which `value` should be inserted into `array` in order to
-     * maintain its sort order.
-     *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Array
-     * @param {Array} array The sorted array to inspect.
-     * @param {*} value The value to evaluate.
-     * @returns {number} Returns the index at which `value` should be inserted
-     *  into `array`.
-     * @example
+     * A specialized version of `baseMerge` for arrays and objects which performs
+     * deep merges and tracks traversed objects enabling objects with circular
+     * references to be merged.
      *
-     * _.sortedLastIndex([4, 5, 5, 5, 6], 5);
-     * // => 4
+     * @private
+     * @param {Object} object The destination object.
+     * @param {Object} source The source object.
+     * @param {string} key The key of the value to merge.
+     * @param {number} srcIndex The index of `source`.
+     * @param {Function} mergeFunc The function to merge values.
+     * @param {Function} [customizer] The function to customize assigned values.
+     * @param {Object} [stack] Tracks traversed source values and their merged
+     *  counterparts.
      */
-    function sortedLastIndex(array, value) {
-      return baseSortedIndex(array, value, true);
-    }
+    function baseMergeDeep(object, source, key, srcIndex, mergeFunc, customizer, stack) {
+      var objValue = safeGet(object, key),
+          srcValue = safeGet(source, key),
+          stacked = stack.get(srcValue);
 
-    /**
-     * This method is like `_.sortedLastIndex` except that it accepts `iteratee`
-     * which is invoked for `value` and each element of `array` to compute their
-     * sort ranking. The iteratee is invoked with one argument: (value).
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {Array} array The sorted array to inspect.
-     * @param {*} value The value to evaluate.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The iteratee invoked per element.
-     * @returns {number} Returns the index at which `value` should be inserted
-     *  into `array`.
-     * @example
-     *
-     * var objects = [{ 'x': 4 }, { 'x': 5 }];
-     *
-     * _.sortedLastIndexBy(objects, { 'x': 4 }, function(o) { return o.x; });
-     * // => 1
-     *
-     * // The `_.property` iteratee shorthand.
-     * _.sortedLastIndexBy(objects, { 'x': 4 }, 'x');
-     * // => 1
-     */
-    function sortedLastIndexBy(array, value, iteratee) {
-      return baseSortedIndexBy(array, value, getIteratee(iteratee), true);
+      if (stacked) {
+        assignMergeValue(object, key, stacked);
+        return;
+      }
+      var newValue = customizer
+        ? customizer(objValue, srcValue, (key + ''), object, source, stack)
+        : undefined;
+
+      var isCommon = newValue === undefined;
+
+      if (isCommon) {
+        var isArr = isArray(srcValue),
+            isBuff = !isArr && isBuffer(srcValue),
+            isTyped = !isArr && !isBuff && isTypedArray(srcValue);
+
+        newValue = srcValue;
+        if (isArr || isBuff || isTyped) {
+          if (isArray(objValue)) {
+            newValue = objValue;
+          }
+          else if (isArrayLikeObject(objValue)) {
+            newValue = copyArray(objValue);
+          }
+          else if (isBuff) {
+            isCommon = false;
+            newValue = cloneBuffer(srcValue, true);
+          }
+          else if (isTyped) {
+            isCommon = false;
+            newValue = cloneTypedArray(srcValue, true);
+          }
+          else {
+            newValue = [];
+          }
+        }
+        else if (isPlainObject(srcValue) || isArguments(srcValue)) {
+          newValue = objValue;
+          if (isArguments(objValue)) {
+            newValue = toPlainObject(objValue);
+          }
+          else if (!isObject(objValue) || isFunction(objValue)) {
+            newValue = initCloneObject(srcValue);
+          }
+        }
+        else {
+          isCommon = false;
+        }
+      }
+      if (isCommon) {
+        // Recursively merge objects and arrays (susceptible to call stack limits).
+        stack.set(srcValue, newValue);
+        mergeFunc(newValue, srcValue, srcIndex, customizer, stack);
+        stack['delete'](srcValue);
+      }
+      assignMergeValue(object, key, newValue);
     }
 
     /**
-     * This method is like `_.lastIndexOf` except that it performs a binary
-     * search on a sorted `array`.
+     * The base implementation of `_.nth` which doesn't coerce arguments.
      *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {Array} array The array to search.
-     * @param {*} value The value to search for.
-     * @returns {number} Returns the index of the matched value, else `-1`.
-     * @example
-     *
-     * _.sortedLastIndexOf([4, 5, 5, 5, 6], 5);
-     * // => 3
+     * @private
+     * @param {Array} array The array to query.
+     * @param {number} n The index of the element to return.
+     * @returns {*} Returns the nth element of `array`.
      */
-    function sortedLastIndexOf(array, value) {
-      var length = array ? array.length : 0;
-      if (length) {
-        var index = baseSortedIndex(array, value, true) - 1;
-        if (eq(array[index], value)) {
-          return index;
-        }
+    function baseNth(array, n) {
+      var length = array.length;
+      if (!length) {
+        return;
       }
-      return -1;
+      n += n < 0 ? length : 0;
+      return isIndex(n, length) ? array[n] : undefined;
     }
 
     /**
-     * This method is like `_.uniq` except that it's designed and optimized
-     * for sorted arrays.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {Array} array The array to inspect.
-     * @returns {Array} Returns the new duplicate free array.
-     * @example
+     * The base implementation of `_.orderBy` without param guards.
      *
-     * _.sortedUniq([1, 1, 2]);
-     * // => [1, 2]
+     * @private
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function[]|Object[]|string[]} iteratees The iteratees to sort by.
+     * @param {string[]} orders The sort orders of `iteratees`.
+     * @returns {Array} Returns the new sorted array.
      */
-    function sortedUniq(array) {
-      return (array && array.length)
-        ? baseSortedUniq(array)
-        : [];
+    function baseOrderBy(collection, iteratees, orders) {
+      var index = -1;
+      iteratees = arrayMap(iteratees.length ? iteratees : [identity], baseUnary(getIteratee()));
+
+      var result = baseMap(collection, function(value, key, collection) {
+        var criteria = arrayMap(iteratees, function(iteratee) {
+          return iteratee(value);
+        });
+        return { 'criteria': criteria, 'index': ++index, 'value': value };
+      });
+
+      return baseSortBy(result, function(object, other) {
+        return compareMultiple(object, other, orders);
+      });
     }
 
     /**
-     * This method is like `_.uniqBy` except that it's designed and optimized
-     * for sorted arrays.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {Array} array The array to inspect.
-     * @param {Function} [iteratee] The iteratee invoked per element.
-     * @returns {Array} Returns the new duplicate free array.
-     * @example
+     * The base implementation of `_.pick` without support for individual
+     * property identifiers.
      *
-     * _.sortedUniqBy([1.1, 1.2, 2.3, 2.4], Math.floor);
-     * // => [1.1, 2.3]
+     * @private
+     * @param {Object} object The source object.
+     * @param {string[]} paths The property paths to pick.
+     * @returns {Object} Returns the new object.
      */
-    function sortedUniqBy(array, iteratee) {
-      return (array && array.length)
-        ? baseSortedUniq(array, getIteratee(iteratee))
-        : [];
+    function basePick(object, paths) {
+      return basePickBy(object, paths, function(value, path) {
+        return hasIn(object, path);
+      });
     }
 
     /**
-     * Gets all but the first element of `array`.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {Array} array The array to query.
-     * @returns {Array} Returns the slice of `array`.
-     * @example
+     * The base implementation of  `_.pickBy` without support for iteratee shorthands.
      *
-     * _.tail([1, 2, 3]);
-     * // => [2, 3]
+     * @private
+     * @param {Object} object The source object.
+     * @param {string[]} paths The property paths to pick.
+     * @param {Function} predicate The function invoked per property.
+     * @returns {Object} Returns the new object.
      */
-    function tail(array) {
-      return drop(array, 1);
+    function basePickBy(object, paths, predicate) {
+      var index = -1,
+          length = paths.length,
+          result = {};
+
+      while (++index < length) {
+        var path = paths[index],
+            value = baseGet(object, path);
+
+        if (predicate(value, path)) {
+          baseSet(result, castPath(path, object), value);
+        }
+      }
+      return result;
     }
 
     /**
-     * Creates a slice of `array` with `n` elements taken from the beginning.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Array
-     * @param {Array} array The array to query.
-     * @param {number} [n=1] The number of elements to take.
-     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
-     * @returns {Array} Returns the slice of `array`.
-     * @example
-     *
-     * _.take([1, 2, 3]);
-     * // => [1]
-     *
-     * _.take([1, 2, 3], 2);
-     * // => [1, 2]
-     *
-     * _.take([1, 2, 3], 5);
-     * // => [1, 2, 3]
+     * A specialized version of `baseProperty` which supports deep paths.
      *
-     * _.take([1, 2, 3], 0);
-     * // => []
+     * @private
+     * @param {Array|string} path The path of the property to get.
+     * @returns {Function} Returns the new accessor function.
      */
-    function take(array, n, guard) {
-      if (!(array && array.length)) {
-        return [];
-      }
-      n = (guard || n === undefined) ? 1 : toInteger(n);
-      return baseSlice(array, 0, n < 0 ? 0 : n);
+    function basePropertyDeep(path) {
+      return function(object) {
+        return baseGet(object, path);
+      };
     }
 
     /**
-     * Creates a slice of `array` with `n` elements taken from the end.
-     *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Array
-     * @param {Array} array The array to query.
-     * @param {number} [n=1] The number of elements to take.
-     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
-     * @returns {Array} Returns the slice of `array`.
-     * @example
+     * The base implementation of `_.pullAllBy` without support for iteratee
+     * shorthands.
      *
-     * _.takeRight([1, 2, 3]);
-     * // => [3]
-     *
-     * _.takeRight([1, 2, 3], 2);
-     * // => [2, 3]
-     *
-     * _.takeRight([1, 2, 3], 5);
-     * // => [1, 2, 3]
-     *
-     * _.takeRight([1, 2, 3], 0);
-     * // => []
+     * @private
+     * @param {Array} array The array to modify.
+     * @param {Array} values The values to remove.
+     * @param {Function} [iteratee] The iteratee invoked per element.
+     * @param {Function} [comparator] The comparator invoked per element.
+     * @returns {Array} Returns `array`.
      */
-    function takeRight(array, n, guard) {
-      var length = array ? array.length : 0;
-      if (!length) {
-        return [];
+    function basePullAll(array, values, iteratee, comparator) {
+      var indexOf = comparator ? baseIndexOfWith : baseIndexOf,
+          index = -1,
+          length = values.length,
+          seen = array;
+
+      if (array === values) {
+        values = copyArray(values);
       }
-      n = (guard || n === undefined) ? 1 : toInteger(n);
-      n = length - n;
-      return baseSlice(array, n < 0 ? 0 : n, length);
+      if (iteratee) {
+        seen = arrayMap(array, baseUnary(iteratee));
+      }
+      while (++index < length) {
+        var fromIndex = 0,
+            value = values[index],
+            computed = iteratee ? iteratee(value) : value;
+
+        while ((fromIndex = indexOf(seen, computed, fromIndex, comparator)) > -1) {
+          if (seen !== array) {
+            splice.call(seen, fromIndex, 1);
+          }
+          splice.call(array, fromIndex, 1);
+        }
+      }
+      return array;
     }
 
     /**
-     * Creates a slice of `array` with elements taken from the end. Elements are
-     * taken until `predicate` returns falsey. The predicate is invoked with
-     * three arguments: (value, index, array).
-     *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Array
-     * @param {Array} array The array to query.
-     * @param {Array|Function|Object|string} [predicate=_.identity]
-     *  The function invoked per iteration.
-     * @returns {Array} Returns the slice of `array`.
-     * @example
-     *
-     * var users = [
-     *   { 'user': 'barney',  'active': true },
-     *   { 'user': 'fred',    'active': false },
-     *   { 'user': 'pebbles', 'active': false }
-     * ];
-     *
-     * _.takeRightWhile(users, function(o) { return !o.active; });
-     * // => objects for ['fred', 'pebbles']
-     *
-     * // The `_.matches` iteratee shorthand.
-     * _.takeRightWhile(users, { 'user': 'pebbles', 'active': false });
-     * // => objects for ['pebbles']
-     *
-     * // The `_.matchesProperty` iteratee shorthand.
-     * _.takeRightWhile(users, ['active', false]);
-     * // => objects for ['fred', 'pebbles']
+     * The base implementation of `_.pullAt` without support for individual
+     * indexes or capturing the removed elements.
      *
-     * // The `_.property` iteratee shorthand.
-     * _.takeRightWhile(users, 'active');
-     * // => []
+     * @private
+     * @param {Array} array The array to modify.
+     * @param {number[]} indexes The indexes of elements to remove.
+     * @returns {Array} Returns `array`.
      */
-    function takeRightWhile(array, predicate) {
-      return (array && array.length)
-        ? baseWhile(array, getIteratee(predicate, 3), false, true)
-        : [];
+    function basePullAt(array, indexes) {
+      var length = array ? indexes.length : 0,
+          lastIndex = length - 1;
+
+      while (length--) {
+        var index = indexes[length];
+        if (length == lastIndex || index !== previous) {
+          var previous = index;
+          if (isIndex(index)) {
+            splice.call(array, index, 1);
+          } else {
+            baseUnset(array, index);
+          }
+        }
+      }
+      return array;
     }
 
     /**
-     * Creates a slice of `array` with elements taken from the beginning. Elements
-     * are taken until `predicate` returns falsey. The predicate is invoked with
-     * three arguments: (value, index, array).
-     *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Array
-     * @param {Array} array The array to query.
-     * @param {Array|Function|Object|string} [predicate=_.identity]
-     *  The function invoked per iteration.
-     * @returns {Array} Returns the slice of `array`.
-     * @example
-     *
-     * var users = [
-     *   { 'user': 'barney',  'active': false },
-     *   { 'user': 'fred',    'active': false},
-     *   { 'user': 'pebbles', 'active': true }
-     * ];
-     *
-     * _.takeWhile(users, function(o) { return !o.active; });
-     * // => objects for ['barney', 'fred']
-     *
-     * // The `_.matches` iteratee shorthand.
-     * _.takeWhile(users, { 'user': 'barney', 'active': false });
-     * // => objects for ['barney']
-     *
-     * // The `_.matchesProperty` iteratee shorthand.
-     * _.takeWhile(users, ['active', false]);
-     * // => objects for ['barney', 'fred']
+     * The base implementation of `_.random` without support for returning
+     * floating-point numbers.
      *
-     * // The `_.property` iteratee shorthand.
-     * _.takeWhile(users, 'active');
-     * // => []
+     * @private
+     * @param {number} lower The lower bound.
+     * @param {number} upper The upper bound.
+     * @returns {number} Returns the random number.
      */
-    function takeWhile(array, predicate) {
-      return (array && array.length)
-        ? baseWhile(array, getIteratee(predicate, 3))
-        : [];
+    function baseRandom(lower, upper) {
+      return lower + nativeFloor(nativeRandom() * (upper - lower + 1));
     }
 
     /**
-     * Creates an array of unique values, in order, from all given arrays using
-     * [`SameValueZero`](http://ecma-international.org/ecma-262/6.0/#sec-samevaluezero)
-     * for equality comparisons.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Array
-     * @param {...Array} [arrays] The arrays to inspect.
-     * @returns {Array} Returns the new array of combined values.
-     * @example
+     * The base implementation of `_.range` and `_.rangeRight` which doesn't
+     * coerce arguments.
      *
-     * _.union([2], [1, 2]);
-     * // => [2, 1]
+     * @private
+     * @param {number} start The start of the range.
+     * @param {number} end The end of the range.
+     * @param {number} step The value to increment or decrement by.
+     * @param {boolean} [fromRight] Specify iterating from right to left.
+     * @returns {Array} Returns the range of numbers.
      */
-    var union = rest(function(arrays) {
-      return baseUniq(baseFlatten(arrays, 1, isArrayLikeObject, true));
-    });
+    function baseRange(start, end, step, fromRight) {
+      var index = -1,
+          length = nativeMax(nativeCeil((end - start) / (step || 1)), 0),
+          result = Array(length);
+
+      while (length--) {
+        result[fromRight ? length : ++index] = start;
+        start += step;
+      }
+      return result;
+    }
 
     /**
-     * This method is like `_.union` except that it accepts `iteratee` which is
-     * invoked for each element of each `arrays` to generate the criterion by
-     * which uniqueness is computed. The iteratee is invoked with one argument:
-     * (value).
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {...Array} [arrays] The arrays to inspect.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The iteratee invoked per element.
-     * @returns {Array} Returns the new array of combined values.
-     * @example
-     *
-     * _.unionBy([2.1], [1.2, 2.3], Math.floor);
-     * // => [2.1, 1.2]
+     * The base implementation of `_.repeat` which doesn't coerce arguments.
      *
-     * // The `_.property` iteratee shorthand.
-     * _.unionBy([{ 'x': 1 }], [{ 'x': 2 }, { 'x': 1 }], 'x');
-     * // => [{ 'x': 1 }, { 'x': 2 }]
+     * @private
+     * @param {string} string The string to repeat.
+     * @param {number} n The number of times to repeat the string.
+     * @returns {string} Returns the repeated string.
      */
-    var unionBy = rest(function(arrays) {
-      var iteratee = last(arrays);
-      if (isArrayLikeObject(iteratee)) {
-        iteratee = undefined;
+    function baseRepeat(string, n) {
+      var result = '';
+      if (!string || n < 1 || n > MAX_SAFE_INTEGER) {
+        return result;
       }
-      return baseUniq(baseFlatten(arrays, 1, isArrayLikeObject, true), getIteratee(iteratee));
-    });
+      // Leverage the exponentiation by squaring algorithm for a faster repeat.
+      // See https://en.wikipedia.org/wiki/Exponentiation_by_squaring for more details.
+      do {
+        if (n % 2) {
+          result += string;
+        }
+        n = nativeFloor(n / 2);
+        if (n) {
+          string += string;
+        }
+      } while (n);
+
+      return result;
+    }
 
     /**
-     * This method is like `_.union` except that it accepts `comparator` which
-     * is invoked to compare elements of `arrays`. The comparator is invoked
-     * with two arguments: (arrVal, othVal).
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {...Array} [arrays] The arrays to inspect.
-     * @param {Function} [comparator] The comparator invoked per element.
-     * @returns {Array} Returns the new array of combined values.
-     * @example
+     * The base implementation of `_.rest` which doesn't validate or coerce arguments.
      *
-     * var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }];
-     * var others = [{ 'x': 1, 'y': 1 }, { 'x': 1, 'y': 2 }];
+     * @private
+     * @param {Function} func The function to apply a rest parameter to.
+     * @param {number} [start=func.length-1] The start position of the rest parameter.
+     * @returns {Function} Returns the new function.
+     */
+    function baseRest(func, start) {
+      return setToString(overRest(func, start, identity), func + '');
+    }
+
+    /**
+     * The base implementation of `_.sample`.
      *
-     * _.unionWith(objects, others, _.isEqual);
-     * // => [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }, { 'x': 1, 'y': 1 }]
+     * @private
+     * @param {Array|Object} collection The collection to sample.
+     * @returns {*} Returns the random element.
      */
-    var unionWith = rest(function(arrays) {
-      var comparator = last(arrays);
-      if (isArrayLikeObject(comparator)) {
-        comparator = undefined;
-      }
-      return baseUniq(baseFlatten(arrays, 1, isArrayLikeObject, true), undefined, comparator);
-    });
+    function baseSample(collection) {
+      return arraySample(values(collection));
+    }
 
     /**
-     * Creates a duplicate-free version of an array, using
-     * [`SameValueZero`](http://ecma-international.org/ecma-262/6.0/#sec-samevaluezero)
-     * for equality comparisons, in which only the first occurrence of each
-     * element is kept.
+     * The base implementation of `_.sampleSize` without param guards.
      *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Array
-     * @param {Array} array The array to inspect.
-     * @returns {Array} Returns the new duplicate free array.
-     * @example
-     *
-     * _.uniq([2, 1, 2]);
-     * // => [2, 1]
+     * @private
+     * @param {Array|Object} collection The collection to sample.
+     * @param {number} n The number of elements to sample.
+     * @returns {Array} Returns the random elements.
      */
-    function uniq(array) {
-      return (array && array.length)
-        ? baseUniq(array)
-        : [];
+    function baseSampleSize(collection, n) {
+      var array = values(collection);
+      return shuffleSelf(array, baseClamp(n, 0, array.length));
     }
 
     /**
-     * This method is like `_.uniq` except that it accepts `iteratee` which is
-     * invoked for each element in `array` to generate the criterion by which
-     * uniqueness is computed. The iteratee is invoked with one argument: (value).
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {Array} array The array to inspect.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The iteratee invoked per element.
-     * @returns {Array} Returns the new duplicate free array.
-     * @example
-     *
-     * _.uniqBy([2.1, 1.2, 2.3], Math.floor);
-     * // => [2.1, 1.2]
+     * The base implementation of `_.set`.
      *
-     * // The `_.property` iteratee shorthand.
-     * _.uniqBy([{ 'x': 1 }, { 'x': 2 }, { 'x': 1 }], 'x');
-     * // => [{ 'x': 1 }, { 'x': 2 }]
+     * @private
+     * @param {Object} object The object to modify.
+     * @param {Array|string} path The path of the property to set.
+     * @param {*} value The value to set.
+     * @param {Function} [customizer] The function to customize path creation.
+     * @returns {Object} Returns `object`.
      */
-    function uniqBy(array, iteratee) {
-      return (array && array.length)
-        ? baseUniq(array, getIteratee(iteratee))
-        : [];
+    function baseSet(object, path, value, customizer) {
+      if (!isObject(object)) {
+        return object;
+      }
+      path = castPath(path, object);
+
+      var index = -1,
+          length = path.length,
+          lastIndex = length - 1,
+          nested = object;
+
+      while (nested != null && ++index < length) {
+        var key = toKey(path[index]),
+            newValue = value;
+
+        if (index != lastIndex) {
+          var objValue = nested[key];
+          newValue = customizer ? customizer(objValue, key, nested) : undefined;
+          if (newValue === undefined) {
+            newValue = isObject(objValue)
+              ? objValue
+              : (isIndex(path[index + 1]) ? [] : {});
+          }
+        }
+        assignValue(nested, key, newValue);
+        nested = nested[key];
+      }
+      return object;
     }
 
     /**
-     * This method is like `_.uniq` except that it accepts `comparator` which
-     * is invoked to compare elements of `array`. The comparator is invoked with
-     * two arguments: (arrVal, othVal).
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {Array} array The array to inspect.
-     * @param {Function} [comparator] The comparator invoked per element.
-     * @returns {Array} Returns the new duplicate free array.
-     * @example
-     *
-     * var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }, { 'x': 1, 'y': 2 }];
+     * The base implementation of `setData` without support for hot loop shorting.
      *
-     * _.uniqWith(objects, _.isEqual);
-     * // => [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }]
+     * @private
+     * @param {Function} func The function to associate metadata with.
+     * @param {*} data The metadata.
+     * @returns {Function} Returns `func`.
      */
-    function uniqWith(array, comparator) {
-      return (array && array.length)
-        ? baseUniq(array, undefined, comparator)
-        : [];
-    }
+    var baseSetData = !metaMap ? identity : function(func, data) {
+      metaMap.set(func, data);
+      return func;
+    };
 
     /**
-     * This method is like `_.zip` except that it accepts an array of grouped
-     * elements and creates an array regrouping the elements to their pre-zip
-     * configuration.
-     *
-     * @static
-     * @memberOf _
-     * @since 1.2.0
-     * @category Array
-     * @param {Array} array The array of grouped elements to process.
-     * @returns {Array} Returns the new array of regrouped elements.
-     * @example
+     * The base implementation of `setToString` without support for hot loop shorting.
      *
-     * var zipped = _.zip(['fred', 'barney'], [30, 40], [true, false]);
-     * // => [['fred', 30, true], ['barney', 40, false]]
-     *
-     * _.unzip(zipped);
-     * // => [['fred', 'barney'], [30, 40], [true, false]]
+     * @private
+     * @param {Function} func The function to modify.
+     * @param {Function} string The `toString` result.
+     * @returns {Function} Returns `func`.
      */
-    function unzip(array) {
-      if (!(array && array.length)) {
-        return [];
-      }
-      var length = 0;
-      array = arrayFilter(array, function(group) {
-        if (isArrayLikeObject(group)) {
-          length = nativeMax(group.length, length);
-          return true;
-        }
-      });
-      return baseTimes(length, function(index) {
-        return arrayMap(array, baseProperty(index));
+    var baseSetToString = !defineProperty ? identity : function(func, string) {
+      return defineProperty(func, 'toString', {
+        'configurable': true,
+        'enumerable': false,
+        'value': constant(string),
+        'writable': true
       });
-    }
+    };
 
     /**
-     * This method is like `_.unzip` except that it accepts `iteratee` to specify
-     * how regrouped values should be combined. The iteratee is invoked with the
-     * elements of each group: (...group).
-     *
-     * @static
-     * @memberOf _
-     * @since 3.8.0
-     * @category Array
-     * @param {Array} array The array of grouped elements to process.
-     * @param {Function} [iteratee=_.identity] The function to combine
-     *  regrouped values.
-     * @returns {Array} Returns the new array of regrouped elements.
-     * @example
+     * The base implementation of `_.shuffle`.
      *
-     * var zipped = _.zip([1, 2], [10, 20], [100, 200]);
-     * // => [[1, 10, 100], [2, 20, 200]]
+     * @private
+     * @param {Array|Object} collection The collection to shuffle.
+     * @returns {Array} Returns the new shuffled array.
+     */
+    function baseShuffle(collection) {
+      return shuffleSelf(values(collection));
+    }
+
+    /**
+     * The base implementation of `_.slice` without an iteratee call guard.
      *
-     * _.unzipWith(zipped, _.add);
-     * // => [3, 30, 300]
+     * @private
+     * @param {Array} array The array to slice.
+     * @param {number} [start=0] The start position.
+     * @param {number} [end=array.length] The end position.
+     * @returns {Array} Returns the slice of `array`.
      */
-    function unzipWith(array, iteratee) {
-      if (!(array && array.length)) {
-        return [];
+    function baseSlice(array, start, end) {
+      var index = -1,
+          length = array.length;
+
+      if (start < 0) {
+        start = -start > length ? 0 : (length + start);
       }
-      var result = unzip(array);
-      if (iteratee == null) {
-        return result;
+      end = end > length ? length : end;
+      if (end < 0) {
+        end += length;
       }
-      return arrayMap(result, function(group) {
-        return apply(iteratee, undefined, group);
-      });
+      length = start > end ? 0 : ((end - start) >>> 0);
+      start >>>= 0;
+
+      var result = Array(length);
+      while (++index < length) {
+        result[index] = array[index + start];
+      }
+      return result;
     }
 
     /**
-     * Creates an array excluding all given values using
-     * [`SameValueZero`](http://ecma-international.org/ecma-262/6.0/#sec-samevaluezero)
-     * for equality comparisons.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Array
-     * @param {Array} array The array to inspect.
-     * @param {...*} [values] The values to exclude.
-     * @returns {Array} Returns the new array of filtered values.
-     * @see _.difference, _.xor
-     * @example
+     * The base implementation of `_.some` without support for iteratee shorthands.
      *
-     * _.without([2, 1, 2, 3], 1, 2);
-     * // => [3]
+     * @private
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} predicate The function invoked per iteration.
+     * @returns {boolean} Returns `true` if any element passes the predicate check,
+     *  else `false`.
      */
-    var without = rest(function(array, values) {
-      return isArrayLikeObject(array)
-        ? baseDifference(array, values)
-        : [];
-    });
+    function baseSome(collection, predicate) {
+      var result;
+
+      baseEach(collection, function(value, index, collection) {
+        result = predicate(value, index, collection);
+        return !result;
+      });
+      return !!result;
+    }
 
     /**
-     * Creates an array of unique values that is the
-     * [symmetric difference](https://en.wikipedia.org/wiki/Symmetric_difference)
-     * of the given arrays. The order of result values is determined by the order
-     * they occur in the arrays.
-     *
-     * @static
-     * @memberOf _
-     * @since 2.4.0
-     * @category Array
-     * @param {...Array} [arrays] The arrays to inspect.
-     * @returns {Array} Returns the new array of filtered values.
-     * @see _.difference, _.without
-     * @example
+     * The base implementation of `_.sortedIndex` and `_.sortedLastIndex` which
+     * performs a binary search of `array` to determine the index at which `value`
+     * should be inserted into `array` in order to maintain its sort order.
      *
-     * _.xor([2, 1], [2, 3]);
-     * // => [1, 3]
+     * @private
+     * @param {Array} array The sorted array to inspect.
+     * @param {*} value The value to evaluate.
+     * @param {boolean} [retHighest] Specify returning the highest qualified index.
+     * @returns {number} Returns the index at which `value` should be inserted
+     *  into `array`.
      */
-    var xor = rest(function(arrays) {
-      return baseXor(arrayFilter(arrays, isArrayLikeObject));
-    });
+    function baseSortedIndex(array, value, retHighest) {
+      var low = 0,
+          high = array == null ? low : array.length;
+
+      if (typeof value == 'number' && value === value && high <= HALF_MAX_ARRAY_LENGTH) {
+        while (low < high) {
+          var mid = (low + high) >>> 1,
+              computed = array[mid];
+
+          if (computed !== null && !isSymbol(computed) &&
+              (retHighest ? (computed <= value) : (computed < value))) {
+            low = mid + 1;
+          } else {
+            high = mid;
+          }
+        }
+        return high;
+      }
+      return baseSortedIndexBy(array, value, identity, retHighest);
+    }
 
     /**
-     * This method is like `_.xor` except that it accepts `iteratee` which is
-     * invoked for each element of each `arrays` to generate the criterion by
-     * which by which they're compared. The iteratee is invoked with one argument:
-     * (value).
+     * The base implementation of `_.sortedIndexBy` and `_.sortedLastIndexBy`
+     * which invokes `iteratee` for `value` and each element of `array` to compute
+     * their sort ranking. The iteratee is invoked with one argument; (value).
      *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {...Array} [arrays] The arrays to inspect.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The iteratee invoked per element.
-     * @returns {Array} Returns the new array of filtered values.
-     * @example
-     *
-     * _.xorBy([2.1, 1.2], [2.3, 3.4], Math.floor);
-     * // => [1.2, 3.4]
-     *
-     * // The `_.property` iteratee shorthand.
-     * _.xorBy([{ 'x': 1 }], [{ 'x': 2 }, { 'x': 1 }], 'x');
-     * // => [{ 'x': 2 }]
+     * @private
+     * @param {Array} array The sorted array to inspect.
+     * @param {*} value The value to evaluate.
+     * @param {Function} iteratee The iteratee invoked per element.
+     * @param {boolean} [retHighest] Specify returning the highest qualified index.
+     * @returns {number} Returns the index at which `value` should be inserted
+     *  into `array`.
      */
-    var xorBy = rest(function(arrays) {
-      var iteratee = last(arrays);
-      if (isArrayLikeObject(iteratee)) {
-        iteratee = undefined;
+    function baseSortedIndexBy(array, value, iteratee, retHighest) {
+      value = iteratee(value);
+
+      var low = 0,
+          high = array == null ? 0 : array.length,
+          valIsNaN = value !== value,
+          valIsNull = value === null,
+          valIsSymbol = isSymbol(value),
+          valIsUndefined = value === undefined;
+
+      while (low < high) {
+        var mid = nativeFloor((low + high) / 2),
+            computed = iteratee(array[mid]),
+            othIsDefined = computed !== undefined,
+            othIsNull = computed === null,
+            othIsReflexive = computed === computed,
+            othIsSymbol = isSymbol(computed);
+
+        if (valIsNaN) {
+          var setLow = retHighest || othIsReflexive;
+        } else if (valIsUndefined) {
+          setLow = othIsReflexive && (retHighest || othIsDefined);
+        } else if (valIsNull) {
+          setLow = othIsReflexive && othIsDefined && (retHighest || !othIsNull);
+        } else if (valIsSymbol) {
+          setLow = othIsReflexive && othIsDefined && !othIsNull && (retHighest || !othIsSymbol);
+        } else if (othIsNull || othIsSymbol) {
+          setLow = false;
+        } else {
+          setLow = retHighest ? (computed <= value) : (computed < value);
+        }
+        if (setLow) {
+          low = mid + 1;
+        } else {
+          high = mid;
+        }
       }
-      return baseXor(arrayFilter(arrays, isArrayLikeObject), getIteratee(iteratee));
-    });
+      return nativeMin(high, MAX_ARRAY_INDEX);
+    }
 
     /**
-     * This method is like `_.xor` except that it accepts `comparator` which is
-     * invoked to compare elements of `arrays`. The comparator is invoked with
-     * two arguments: (arrVal, othVal).
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Array
-     * @param {...Array} [arrays] The arrays to inspect.
-     * @param {Function} [comparator] The comparator invoked per element.
-     * @returns {Array} Returns the new array of filtered values.
-     * @example
-     *
-     * var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }];
-     * var others = [{ 'x': 1, 'y': 1 }, { 'x': 1, 'y': 2 }];
+     * The base implementation of `_.sortedUniq` and `_.sortedUniqBy` without
+     * support for iteratee shorthands.
      *
-     * _.xorWith(objects, others, _.isEqual);
-     * // => [{ 'x': 2, 'y': 1 }, { 'x': 1, 'y': 1 }]
+     * @private
+     * @param {Array} array The array to inspect.
+     * @param {Function} [iteratee] The iteratee invoked per element.
+     * @returns {Array} Returns the new duplicate free array.
      */
-    var xorWith = rest(function(arrays) {
-      var comparator = last(arrays);
-      if (isArrayLikeObject(comparator)) {
-        comparator = undefined;
+    function baseSortedUniq(array, iteratee) {
+      var index = -1,
+          length = array.length,
+          resIndex = 0,
+          result = [];
+
+      while (++index < length) {
+        var value = array[index],
+            computed = iteratee ? iteratee(value) : value;
+
+        if (!index || !eq(computed, seen)) {
+          var seen = computed;
+          result[resIndex++] = value === 0 ? 0 : value;
+        }
       }
-      return baseXor(arrayFilter(arrays, isArrayLikeObject), undefined, comparator);
-    });
+      return result;
+    }
 
     /**
-     * Creates an array of grouped elements, the first of which contains the
-     * first elements of the given arrays, the second of which contains the
-     * second elements of the given arrays, and so on.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Array
-     * @param {...Array} [arrays] The arrays to process.
-     * @returns {Array} Returns the new array of grouped elements.
-     * @example
+     * The base implementation of `_.toNumber` which doesn't ensure correct
+     * conversions of binary, hexadecimal, or octal string values.
      *
-     * _.zip(['fred', 'barney'], [30, 40], [true, false]);
-     * // => [['fred', 30, true], ['barney', 40, false]]
+     * @private
+     * @param {*} value The value to process.
+     * @returns {number} Returns the number.
      */
-    var zip = rest(unzip);
+    function baseToNumber(value) {
+      if (typeof value == 'number') {
+        return value;
+      }
+      if (isSymbol(value)) {
+        return NAN;
+      }
+      return +value;
+    }
 
     /**
-     * This method is like `_.fromPairs` except that it accepts two arrays,
-     * one of property identifiers and one of corresponding values.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.4.0
-     * @category Array
-     * @param {Array} [props=[]] The property identifiers.
-     * @param {Array} [values=[]] The property values.
-     * @returns {Object} Returns the new object.
-     * @example
+     * The base implementation of `_.toString` which doesn't convert nullish
+     * values to empty strings.
      *
-     * _.zipObject(['a', 'b'], [1, 2]);
-     * // => { 'a': 1, 'b': 2 }
+     * @private
+     * @param {*} value The value to process.
+     * @returns {string} Returns the string.
      */
-    function zipObject(props, values) {
-      return baseZipObject(props || [], values || [], assignValue);
+    function baseToString(value) {
+      // Exit early for strings to avoid a performance hit in some environments.
+      if (typeof value == 'string') {
+        return value;
+      }
+      if (isArray(value)) {
+        // Recursively convert values (susceptible to call stack limits).
+        return arrayMap(value, baseToString) + '';
+      }
+      if (isSymbol(value)) {
+        return symbolToString ? symbolToString.call(value) : '';
+      }
+      var result = (value + '');
+      return (result == '0' && (1 / value) == -INFINITY) ? '-0' : result;
     }
 
     /**
-     * This method is like `_.zipObject` except that it supports property paths.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.1.0
-     * @category Array
-     * @param {Array} [props=[]] The property identifiers.
-     * @param {Array} [values=[]] The property values.
-     * @returns {Object} Returns the new object.
-     * @example
+     * The base implementation of `_.uniqBy` without support for iteratee shorthands.
      *
-     * _.zipObjectDeep(['a.b[0].c', 'a.b[1].d'], [1, 2]);
-     * // => { 'a': { 'b': [{ 'c': 1 }, { 'd': 2 }] } }
+     * @private
+     * @param {Array} array The array to inspect.
+     * @param {Function} [iteratee] The iteratee invoked per element.
+     * @param {Function} [comparator] The comparator invoked per element.
+     * @returns {Array} Returns the new duplicate free array.
      */
-    function zipObjectDeep(props, values) {
-      return baseZipObject(props || [], values || [], baseSet);
+    function baseUniq(array, iteratee, comparator) {
+      var index = -1,
+          includes = arrayIncludes,
+          length = array.length,
+          isCommon = true,
+          result = [],
+          seen = result;
+
+      if (comparator) {
+        isCommon = false;
+        includes = arrayIncludesWith;
+      }
+      else if (length >= LARGE_ARRAY_SIZE) {
+        var set = iteratee ? null : createSet(array);
+        if (set) {
+          return setToArray(set);
+        }
+        isCommon = false;
+        includes = cacheHas;
+        seen = new SetCache;
+      }
+      else {
+        seen = iteratee ? [] : result;
+      }
+      outer:
+      while (++index < length) {
+        var value = array[index],
+            computed = iteratee ? iteratee(value) : value;
+
+        value = (comparator || value !== 0) ? value : 0;
+        if (isCommon && computed === computed) {
+          var seenIndex = seen.length;
+          while (seenIndex--) {
+            if (seen[seenIndex] === computed) {
+              continue outer;
+            }
+          }
+          if (iteratee) {
+            seen.push(computed);
+          }
+          result.push(value);
+        }
+        else if (!includes(seen, computed, comparator)) {
+          if (seen !== result) {
+            seen.push(computed);
+          }
+          result.push(value);
+        }
+      }
+      return result;
     }
 
     /**
-     * This method is like `_.zip` except that it accepts `iteratee` to specify
-     * how grouped values should be combined. The iteratee is invoked with the
-     * elements of each group: (...group).
-     *
-     * @static
-     * @memberOf _
-     * @since 3.8.0
-     * @category Array
-     * @param {...Array} [arrays] The arrays to process.
-     * @param {Function} [iteratee=_.identity] The function to combine grouped values.
-     * @returns {Array} Returns the new array of grouped elements.
-     * @example
+     * The base implementation of `_.unset`.
      *
-     * _.zipWith([1, 2], [10, 20], [100, 200], function(a, b, c) {
-     *   return a + b + c;
-     * });
-     * // => [111, 222]
+     * @private
+     * @param {Object} object The object to modify.
+     * @param {Array|string} path The property path to unset.
+     * @returns {boolean} Returns `true` if the property is deleted, else `false`.
      */
-    var zipWith = rest(function(arrays) {
-      var length = arrays.length,
-          iteratee = length > 1 ? arrays[length - 1] : undefined;
-
-      iteratee = typeof iteratee == 'function' ? (arrays.pop(), iteratee) : undefined;
-      return unzipWith(arrays, iteratee);
-    });
-
-    /*------------------------------------------------------------------------*/
+    function baseUnset(object, path) {
+      path = castPath(path, object);
+      object = parent(object, path);
+      return object == null || delete object[toKey(last(path))];
+    }
 
     /**
-     * Creates a `lodash` wrapper instance that wraps `value` with explicit method
-     * chain sequences enabled. The result of such sequences must be unwrapped
-     * with `_#value`.
-     *
-     * @static
-     * @memberOf _
-     * @since 1.3.0
-     * @category Seq
-     * @param {*} value The value to wrap.
-     * @returns {Object} Returns the new `lodash` wrapper instance.
-     * @example
-     *
-     * var users = [
-     *   { 'user': 'barney',  'age': 36 },
-     *   { 'user': 'fred',    'age': 40 },
-     *   { 'user': 'pebbles', 'age': 1 }
-     * ];
+     * The base implementation of `_.update`.
      *
-     * var youngest = _
-     *   .chain(users)
-     *   .sortBy('age')
-     *   .map(function(o) {
-     *     return o.user + ' is ' + o.age;
-     *   })
-     *   .head()
-     *   .value();
-     * // => 'pebbles is 1'
+     * @private
+     * @param {Object} object The object to modify.
+     * @param {Array|string} path The path of the property to update.
+     * @param {Function} updater The function to produce the updated value.
+     * @param {Function} [customizer] The function to customize path creation.
+     * @returns {Object} Returns `object`.
      */
-    function chain(value) {
-      var result = lodash(value);
-      result.__chain__ = true;
-      return result;
+    function baseUpdate(object, path, updater, customizer) {
+      return baseSet(object, path, updater(baseGet(object, path)), customizer);
     }
 
     /**
-     * This method invokes `interceptor` and returns `value`. The interceptor
-     * is invoked with one argument; (value). The purpose of this method is to
-     * "tap into" a method chain sequence in order to modify intermediate results.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Seq
-     * @param {*} value The value to provide to `interceptor`.
-     * @param {Function} interceptor The function to invoke.
-     * @returns {*} Returns `value`.
-     * @example
+     * The base implementation of methods like `_.dropWhile` and `_.takeWhile`
+     * without support for iteratee shorthands.
      *
-     * _([1, 2, 3])
-     *  .tap(function(array) {
-     *    // Mutate input array.
-     *    array.pop();
-     *  })
-     *  .reverse()
-     *  .value();
-     * // => [2, 1]
+     * @private
+     * @param {Array} array The array to query.
+     * @param {Function} predicate The function invoked per iteration.
+     * @param {boolean} [isDrop] Specify dropping elements instead of taking them.
+     * @param {boolean} [fromRight] Specify iterating from right to left.
+     * @returns {Array} Returns the slice of `array`.
      */
-    function tap(value, interceptor) {
-      interceptor(value);
-      return value;
+    function baseWhile(array, predicate, isDrop, fromRight) {
+      var length = array.length,
+          index = fromRight ? length : -1;
+
+      while ((fromRight ? index-- : ++index < length) &&
+        predicate(array[index], index, array)) {}
+
+      return isDrop
+        ? baseSlice(array, (fromRight ? 0 : index), (fromRight ? index + 1 : length))
+        : baseSlice(array, (fromRight ? index + 1 : 0), (fromRight ? length : index));
     }
 
     /**
-     * This method is like `_.tap` except that it returns the result of `interceptor`.
-     * The purpose of this method is to "pass thru" values replacing intermediate
-     * results in a method chain sequence.
-     *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Seq
-     * @param {*} value The value to provide to `interceptor`.
-     * @param {Function} interceptor The function to invoke.
-     * @returns {*} Returns the result of `interceptor`.
-     * @example
+     * The base implementation of `wrapperValue` which returns the result of
+     * performing a sequence of actions on the unwrapped `value`, where each
+     * successive action is supplied the return value of the previous.
      *
-     * _('  abc  ')
-     *  .chain()
-     *  .trim()
-     *  .thru(function(value) {
-     *    return [value];
-     *  })
-     *  .value();
-     * // => ['abc']
+     * @private
+     * @param {*} value The unwrapped value.
+     * @param {Array} actions Actions to perform to resolve the unwrapped value.
+     * @returns {*} Returns the resolved value.
      */
-    function thru(value, interceptor) {
-      return interceptor(value);
+    function baseWrapperValue(value, actions) {
+      var result = value;
+      if (result instanceof LazyWrapper) {
+        result = result.value();
+      }
+      return arrayReduce(actions, function(result, action) {
+        return action.func.apply(action.thisArg, arrayPush([result], action.args));
+      }, result);
     }
 
     /**
-     * This method is the wrapper version of `_.at`.
-     *
-     * @name at
-     * @memberOf _
-     * @since 1.0.0
-     * @category Seq
-     * @param {...(string|string[])} [paths] The property paths of elements to pick.
-     * @returns {Object} Returns the new `lodash` wrapper instance.
-     * @example
-     *
-     * var object = { 'a': [{ 'b': { 'c': 3 } }, 4] };
+     * The base implementation of methods like `_.xor`, without support for
+     * iteratee shorthands, that accepts an array of arrays to inspect.
      *
-     * _(object).at(['a[0].b.c', 'a[1]']).value();
-     * // => [3, 4]
+     * @private
+     * @param {Array} arrays The arrays to inspect.
+     * @param {Function} [iteratee] The iteratee invoked per element.
+     * @param {Function} [comparator] The comparator invoked per element.
+     * @returns {Array} Returns the new array of values.
      */
-    var wrapperAt = rest(function(paths) {
-      paths = baseFlatten(paths, 1);
-      var length = paths.length,
-          start = length ? paths[0] : 0,
-          value = this.__wrapped__,
-          interceptor = function(object) { return baseAt(object, paths); };
-
-      if (length > 1 || this.__actions__.length ||
-          !(value instanceof LazyWrapper) || !isIndex(start)) {
-        return this.thru(interceptor);
+    function baseXor(arrays, iteratee, comparator) {
+      var length = arrays.length;
+      if (length < 2) {
+        return length ? baseUniq(arrays[0]) : [];
       }
-      value = value.slice(start, +start + (length ? 1 : 0));
-      value.__actions__.push({
-        'func': thru,
-        'args': [interceptor],
-        'thisArg': undefined
-      });
-      return new LodashWrapper(value, this.__chain__).thru(function(array) {
-        if (length && !array.length) {
-          array.push(undefined);
+      var index = -1,
+          result = Array(length);
+
+      while (++index < length) {
+        var array = arrays[index],
+            othIndex = -1;
+
+        while (++othIndex < length) {
+          if (othIndex != index) {
+            result[index] = baseDifference(result[index] || array, arrays[othIndex], iteratee, comparator);
+          }
         }
-        return array;
-      });
-    });
+      }
+      return baseUniq(baseFlatten(result, 1), iteratee, comparator);
+    }
 
     /**
-     * Creates a `lodash` wrapper instance with explicit method chain sequences enabled.
-     *
-     * @name chain
-     * @memberOf _
-     * @since 0.1.0
-     * @category Seq
-     * @returns {Object} Returns the new `lodash` wrapper instance.
-     * @example
-     *
-     * var users = [
-     *   { 'user': 'barney', 'age': 36 },
-     *   { 'user': 'fred',   'age': 40 }
-     * ];
-     *
-     * // A sequence without explicit chaining.
-     * _(users).head();
-     * // => { 'user': 'barney', 'age': 36 }
+     * This base implementation of `_.zipObject` which assigns values using `assignFunc`.
      *
-     * // A sequence with explicit chaining.
-     * _(users)
-     *   .chain()
-     *   .head()
-     *   .pick('user')
-     *   .value();
-     * // => { 'user': 'barney' }
+     * @private
+     * @param {Array} props The property identifiers.
+     * @param {Array} values The property values.
+     * @param {Function} assignFunc The function to assign values.
+     * @returns {Object} Returns the new object.
      */
-    function wrapperChain() {
-      return chain(this);
+    function baseZipObject(props, values, assignFunc) {
+      var index = -1,
+          length = props.length,
+          valsLength = values.length,
+          result = {};
+
+      while (++index < length) {
+        var value = index < valsLength ? values[index] : undefined;
+        assignFunc(result, props[index], value);
+      }
+      return result;
     }
 
     /**
-     * Executes the chain sequence and returns the wrapped result.
-     *
-     * @name commit
-     * @memberOf _
-     * @since 3.2.0
-     * @category Seq
-     * @returns {Object} Returns the new `lodash` wrapper instance.
-     * @example
-     *
-     * var array = [1, 2];
-     * var wrapped = _(array).push(3);
-     *
-     * console.log(array);
-     * // => [1, 2]
-     *
-     * wrapped = wrapped.commit();
-     * console.log(array);
-     * // => [1, 2, 3]
+     * Casts `value` to an empty array if it's not an array like object.
      *
-     * wrapped.last();
-     * // => 3
+     * @private
+     * @param {*} value The value to inspect.
+     * @returns {Array|Object} Returns the cast array-like object.
+     */
+    function castArrayLikeObject(value) {
+      return isArrayLikeObject(value) ? value : [];
+    }
+
+    /**
+     * Casts `value` to `identity` if it's not a function.
      *
-     * console.log(array);
-     * // => [1, 2, 3]
+     * @private
+     * @param {*} value The value to inspect.
+     * @returns {Function} Returns cast function.
      */
-    function wrapperCommit() {
-      return new LodashWrapper(this.value(), this.__chain__);
+    function castFunction(value) {
+      return typeof value == 'function' ? value : identity;
     }
 
     /**
-     * Gets the next value on a wrapped object following the
-     * [iterator protocol](https://mdn.io/iteration_protocols#iterator).
+     * Casts `value` to a path array if it's not one.
      *
-     * @name next
-     * @memberOf _
-     * @since 4.0.0
-     * @category Seq
-     * @returns {Object} Returns the next iterator value.
-     * @example
-     *
-     * var wrapped = _([1, 2]);
-     *
-     * wrapped.next();
-     * // => { 'done': false, 'value': 1 }
-     *
-     * wrapped.next();
-     * // => { 'done': false, 'value': 2 }
-     *
-     * wrapped.next();
-     * // => { 'done': true, 'value': undefined }
+     * @private
+     * @param {*} value The value to inspect.
+     * @param {Object} [object] The object to query keys on.
+     * @returns {Array} Returns the cast property path array.
      */
-    function wrapperNext() {
-      if (this.__values__ === undefined) {
-        this.__values__ = toArray(this.value());
+    function castPath(value, object) {
+      if (isArray(value)) {
+        return value;
       }
-      var done = this.__index__ >= this.__values__.length,
-          value = done ? undefined : this.__values__[this.__index__++];
-
-      return { 'done': done, 'value': value };
+      return isKey(value, object) ? [value] : stringToPath(toString(value));
     }
 
     /**
-     * Enables the wrapper to be iterable.
-     *
-     * @name Symbol.iterator
-     * @memberOf _
-     * @since 4.0.0
-     * @category Seq
-     * @returns {Object} Returns the wrapper object.
-     * @example
-     *
-     * var wrapped = _([1, 2]);
+     * A `baseRest` alias which can be replaced with `identity` by module
+     * replacement plugins.
      *
-     * wrapped[Symbol.iterator]() === wrapped;
-     * // => true
+     * @private
+     * @type {Function}
+     * @param {Function} func The function to apply a rest parameter to.
+     * @returns {Function} Returns the new function.
+     */
+    var castRest = baseRest;
+
+    /**
+     * Casts `array` to a slice if it's needed.
      *
-     * Array.from(wrapped);
-     * // => [1, 2]
+     * @private
+     * @param {Array} array The array to inspect.
+     * @param {number} start The start position.
+     * @param {number} [end=array.length] The end position.
+     * @returns {Array} Returns the cast slice.
      */
-    function wrapperToIterator() {
-      return this;
+    function castSlice(array, start, end) {
+      var length = array.length;
+      end = end === undefined ? length : end;
+      return (!start && end >= length) ? array : baseSlice(array, start, end);
     }
 
     /**
-     * Creates a clone of the chain sequence planting `value` as the wrapped value.
-     *
-     * @name plant
-     * @memberOf _
-     * @since 3.2.0
-     * @category Seq
-     * @param {*} value The value to plant.
-     * @returns {Object} Returns the new `lodash` wrapper instance.
-     * @example
-     *
-     * function square(n) {
-     *   return n * n;
-     * }
-     *
-     * var wrapped = _([1, 2]).map(square);
-     * var other = wrapped.plant([3, 4]);
-     *
-     * other.value();
-     * // => [9, 16]
+     * A simple wrapper around the global [`clearTimeout`](https://mdn.io/clearTimeout).
      *
-     * wrapped.value();
-     * // => [1, 4]
+     * @private
+     * @param {number|Object} id The timer id or timeout object of the timer to clear.
      */
-    function wrapperPlant(value) {
-      var result,
-          parent = this;
+    var clearTimeout = ctxClearTimeout || function(id) {
+      return root.clearTimeout(id);
+    };
 
-      while (parent instanceof baseLodash) {
-        var clone = wrapperClone(parent);
-        clone.__index__ = 0;
-        clone.__values__ = undefined;
-        if (result) {
-          previous.__wrapped__ = clone;
-        } else {
-          result = clone;
-        }
-        var previous = clone;
-        parent = parent.__wrapped__;
+    /**
+     * Creates a clone of  `buffer`.
+     *
+     * @private
+     * @param {Buffer} buffer The buffer to clone.
+     * @param {boolean} [isDeep] Specify a deep clone.
+     * @returns {Buffer} Returns the cloned buffer.
+     */
+    function cloneBuffer(buffer, isDeep) {
+      if (isDeep) {
+        return buffer.slice();
       }
-      previous.__wrapped__ = value;
+      var length = buffer.length,
+          result = allocUnsafe ? allocUnsafe(length) : new buffer.constructor(length);
+
+      buffer.copy(result);
       return result;
     }
 
     /**
-     * This method is the wrapper version of `_.reverse`.
-     *
-     * **Note:** This method mutates the wrapped array.
-     *
-     * @name reverse
-     * @memberOf _
-     * @since 0.1.0
-     * @category Seq
-     * @returns {Object} Returns the new `lodash` wrapper instance.
-     * @example
-     *
-     * var array = [1, 2, 3];
-     *
-     * _(array).reverse().value()
-     * // => [3, 2, 1]
+     * Creates a clone of `arrayBuffer`.
      *
-     * console.log(array);
-     * // => [3, 2, 1]
+     * @private
+     * @param {ArrayBuffer} arrayBuffer The array buffer to clone.
+     * @returns {ArrayBuffer} Returns the cloned array buffer.
      */
-    function wrapperReverse() {
-      var value = this.__wrapped__;
-      if (value instanceof LazyWrapper) {
-        var wrapped = value;
-        if (this.__actions__.length) {
-          wrapped = new LazyWrapper(this);
-        }
-        wrapped = wrapped.reverse();
-        wrapped.__actions__.push({
-          'func': thru,
-          'args': [reverse],
-          'thisArg': undefined
-        });
-        return new LodashWrapper(wrapped, this.__chain__);
-      }
-      return this.thru(reverse);
+    function cloneArrayBuffer(arrayBuffer) {
+      var result = new arrayBuffer.constructor(arrayBuffer.byteLength);
+      new Uint8Array(result).set(new Uint8Array(arrayBuffer));
+      return result;
     }
 
     /**
-     * Executes the chain sequence to resolve the unwrapped value.
-     *
-     * @name value
-     * @memberOf _
-     * @since 0.1.0
-     * @alias toJSON, valueOf
-     * @category Seq
-     * @returns {*} Returns the resolved unwrapped value.
-     * @example
+     * Creates a clone of `dataView`.
      *
-     * _([1, 2, 3]).value();
-     * // => [1, 2, 3]
+     * @private
+     * @param {Object} dataView The data view to clone.
+     * @param {boolean} [isDeep] Specify a deep clone.
+     * @returns {Object} Returns the cloned data view.
      */
-    function wrapperValue() {
-      return baseWrapperValue(this.__wrapped__, this.__actions__);
+    function cloneDataView(dataView, isDeep) {
+      var buffer = isDeep ? cloneArrayBuffer(dataView.buffer) : dataView.buffer;
+      return new dataView.constructor(buffer, dataView.byteOffset, dataView.byteLength);
     }
 
-    /*------------------------------------------------------------------------*/
-
     /**
-     * Creates an object composed of keys generated from the results of running
-     * each element of `collection` thru `iteratee`. The corresponding value of
-     * each key is the number of times the key was returned by `iteratee`. The
-     * iteratee is invoked with one argument: (value).
-     *
-     * @static
-     * @memberOf _
-     * @since 0.5.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The iteratee to transform keys.
-     * @returns {Object} Returns the composed aggregate object.
-     * @example
-     *
-     * _.countBy([6.1, 4.2, 6.3], Math.floor);
-     * // => { '4': 1, '6': 2 }
+     * Creates a clone of `regexp`.
      *
-     * // The `_.property` iteratee shorthand.
-     * _.countBy(['one', 'two', 'three'], 'length');
-     * // => { '3': 2, '5': 1 }
+     * @private
+     * @param {Object} regexp The regexp to clone.
+     * @returns {Object} Returns the cloned regexp.
      */
-    var countBy = createAggregator(function(result, value, key) {
-      hasOwnProperty.call(result, key) ? ++result[key] : (result[key] = 1);
-    });
+    function cloneRegExp(regexp) {
+      var result = new regexp.constructor(regexp.source, reFlags.exec(regexp));
+      result.lastIndex = regexp.lastIndex;
+      return result;
+    }
 
     /**
-     * Checks if `predicate` returns truthy for **all** elements of `collection`.
-     * Iteration is stopped once `predicate` returns falsey. The predicate is
-     * invoked with three arguments: (value, index|key, collection).
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Array|Function|Object|string} [predicate=_.identity]
-     *  The function invoked per iteration.
-     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
-     * @returns {boolean} Returns `true` if all elements pass the predicate check,
-     *  else `false`.
-     * @example
-     *
-     * _.every([true, 1, null, 'yes'], Boolean);
-     * // => false
-     *
-     * var users = [
-     *   { 'user': 'barney', 'age': 36, 'active': false },
-     *   { 'user': 'fred',   'age': 40, 'active': false }
-     * ];
-     *
-     * // The `_.matches` iteratee shorthand.
-     * _.every(users, { 'user': 'barney', 'active': false });
-     * // => false
-     *
-     * // The `_.matchesProperty` iteratee shorthand.
-     * _.every(users, ['active', false]);
-     * // => true
+     * Creates a clone of the `symbol` object.
      *
-     * // The `_.property` iteratee shorthand.
-     * _.every(users, 'active');
-     * // => false
+     * @private
+     * @param {Object} symbol The symbol object to clone.
+     * @returns {Object} Returns the cloned symbol object.
      */
-    function every(collection, predicate, guard) {
-      var func = isArray(collection) ? arrayEvery : baseEvery;
-      if (guard && isIterateeCall(collection, predicate, guard)) {
-        predicate = undefined;
-      }
-      return func(collection, getIteratee(predicate, 3));
+    function cloneSymbol(symbol) {
+      return symbolValueOf ? Object(symbolValueOf.call(symbol)) : {};
     }
 
     /**
-     * Iterates over elements of `collection`, returning an array of all elements
-     * `predicate` returns truthy for. The predicate is invoked with three
-     * arguments: (value, index|key, collection).
+     * Creates a clone of `typedArray`.
      *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Array|Function|Object|string} [predicate=_.identity]
-     *  The function invoked per iteration.
-     * @returns {Array} Returns the new filtered array.
-     * @see _.reject
-     * @example
-     *
-     * var users = [
-     *   { 'user': 'barney', 'age': 36, 'active': true },
-     *   { 'user': 'fred',   'age': 40, 'active': false }
-     * ];
-     *
-     * _.filter(users, function(o) { return !o.active; });
-     * // => objects for ['fred']
-     *
-     * // The `_.matches` iteratee shorthand.
-     * _.filter(users, { 'age': 36, 'active': true });
-     * // => objects for ['barney']
-     *
-     * // The `_.matchesProperty` iteratee shorthand.
-     * _.filter(users, ['active', false]);
-     * // => objects for ['fred']
-     *
-     * // The `_.property` iteratee shorthand.
-     * _.filter(users, 'active');
-     * // => objects for ['barney']
+     * @private
+     * @param {Object} typedArray The typed array to clone.
+     * @param {boolean} [isDeep] Specify a deep clone.
+     * @returns {Object} Returns the cloned typed array.
      */
-    function filter(collection, predicate) {
-      var func = isArray(collection) ? arrayFilter : baseFilter;
-      return func(collection, getIteratee(predicate, 3));
+    function cloneTypedArray(typedArray, isDeep) {
+      var buffer = isDeep ? cloneArrayBuffer(typedArray.buffer) : typedArray.buffer;
+      return new typedArray.constructor(buffer, typedArray.byteOffset, typedArray.length);
     }
 
     /**
-     * Iterates over elements of `collection`, returning the first element
-     * `predicate` returns truthy for. The predicate is invoked with three
-     * arguments: (value, index|key, collection).
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to search.
-     * @param {Array|Function|Object|string} [predicate=_.identity]
-     *  The function invoked per iteration.
-     * @param {number} [fromIndex=0] The index to search from.
-     * @returns {*} Returns the matched element, else `undefined`.
-     * @example
-     *
-     * var users = [
-     *   { 'user': 'barney',  'age': 36, 'active': true },
-     *   { 'user': 'fred',    'age': 40, 'active': false },
-     *   { 'user': 'pebbles', 'age': 1,  'active': true }
-     * ];
-     *
-     * _.find(users, function(o) { return o.age < 40; });
-     * // => object for 'barney'
-     *
-     * // The `_.matches` iteratee shorthand.
-     * _.find(users, { 'age': 1, 'active': true });
-     * // => object for 'pebbles'
-     *
-     * // The `_.matchesProperty` iteratee shorthand.
-     * _.find(users, ['active', false]);
-     * // => object for 'fred'
+     * Compares values to sort them in ascending order.
      *
-     * // The `_.property` iteratee shorthand.
-     * _.find(users, 'active');
-     * // => object for 'barney'
+     * @private
+     * @param {*} value The value to compare.
+     * @param {*} other The other value to compare.
+     * @returns {number} Returns the sort order indicator for `value`.
      */
-    var find = createFind(findIndex);
+    function compareAscending(value, other) {
+      if (value !== other) {
+        var valIsDefined = value !== undefined,
+            valIsNull = value === null,
+            valIsReflexive = value === value,
+            valIsSymbol = isSymbol(value);
+
+        var othIsDefined = other !== undefined,
+            othIsNull = other === null,
+            othIsReflexive = other === other,
+            othIsSymbol = isSymbol(other);
+
+        if ((!othIsNull && !othIsSymbol && !valIsSymbol && value > other) ||
+            (valIsSymbol && othIsDefined && othIsReflexive && !othIsNull && !othIsSymbol) ||
+            (valIsNull && othIsDefined && othIsReflexive) ||
+            (!valIsDefined && othIsReflexive) ||
+            !valIsReflexive) {
+          return 1;
+        }
+        if ((!valIsNull && !valIsSymbol && !othIsSymbol && value < other) ||
+            (othIsSymbol && valIsDefined && valIsReflexive && !valIsNull && !valIsSymbol) ||
+            (othIsNull && valIsDefined && valIsReflexive) ||
+            (!othIsDefined && valIsReflexive) ||
+            !othIsReflexive) {
+          return -1;
+        }
+      }
+      return 0;
+    }
 
     /**
-     * This method is like `_.find` except that it iterates over elements of
-     * `collection` from right to left.
+     * Used by `_.orderBy` to compare multiple properties of a value to another
+     * and stable sort them.
      *
-     * @static
-     * @memberOf _
-     * @since 2.0.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to search.
-     * @param {Array|Function|Object|string} [predicate=_.identity]
-     *  The function invoked per iteration.
-     * @param {number} [fromIndex=collection.length-1] The index to search from.
-     * @returns {*} Returns the matched element, else `undefined`.
-     * @example
+     * If `orders` is unspecified, all values are sorted in ascending order. Otherwise,
+     * specify an order of "desc" for descending or "asc" for ascending sort order
+     * of corresponding values.
      *
-     * _.findLast([1, 2, 3, 4], function(n) {
-     *   return n % 2 == 1;
-     * });
-     * // => 3
+     * @private
+     * @param {Object} object The object to compare.
+     * @param {Object} other The other object to compare.
+     * @param {boolean[]|string[]} orders The order to sort by for each property.
+     * @returns {number} Returns the sort order indicator for `object`.
      */
-    var findLast = createFind(findLastIndex);
+    function compareMultiple(object, other, orders) {
+      var index = -1,
+          objCriteria = object.criteria,
+          othCriteria = other.criteria,
+          length = objCriteria.length,
+          ordersLength = orders.length;
+
+      while (++index < length) {
+        var result = compareAscending(objCriteria[index], othCriteria[index]);
+        if (result) {
+          if (index >= ordersLength) {
+            return result;
+          }
+          var order = orders[index];
+          return result * (order == 'desc' ? -1 : 1);
+        }
+      }
+      // Fixes an `Array#sort` bug in the JS engine embedded in Adobe applications
+      // that causes it, under certain circumstances, to provide the same value for
+      // `object` and `other`. See https://github.com/jashkenas/underscore/pull/1247
+      // for more details.
+      //
+      // This also ensures a stable sort in V8 and other engines.
+      // See https://bugs.chromium.org/p/v8/issues/detail?id=90 for more details.
+      return object.index - other.index;
+    }
 
     /**
-     * Creates a flattened array of values by running each element in `collection`
-     * thru `iteratee` and flattening the mapped results. The iteratee is invoked
-     * with three arguments: (value, index|key, collection).
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The function invoked per iteration.
-     * @returns {Array} Returns the new flattened array.
-     * @example
-     *
-     * function duplicate(n) {
-     *   return [n, n];
-     * }
+     * Creates an array that is the composition of partially applied arguments,
+     * placeholders, and provided arguments into a single array of arguments.
      *
-     * _.flatMap([1, 2], duplicate);
-     * // => [1, 1, 2, 2]
+     * @private
+     * @param {Array} args The provided arguments.
+     * @param {Array} partials The arguments to prepend to those provided.
+     * @param {Array} holders The `partials` placeholder indexes.
+     * @params {boolean} [isCurried] Specify composing for a curried function.
+     * @returns {Array} Returns the new array of composed arguments.
      */
-    function flatMap(collection, iteratee) {
-      return baseFlatten(map(collection, iteratee), 1);
+    function composeArgs(args, partials, holders, isCurried) {
+      var argsIndex = -1,
+          argsLength = args.length,
+          holdersLength = holders.length,
+          leftIndex = -1,
+          leftLength = partials.length,
+          rangeLength = nativeMax(argsLength - holdersLength, 0),
+          result = Array(leftLength + rangeLength),
+          isUncurried = !isCurried;
+
+      while (++leftIndex < leftLength) {
+        result[leftIndex] = partials[leftIndex];
+      }
+      while (++argsIndex < holdersLength) {
+        if (isUncurried || argsIndex < argsLength) {
+          result[holders[argsIndex]] = args[argsIndex];
+        }
+      }
+      while (rangeLength--) {
+        result[leftIndex++] = args[argsIndex++];
+      }
+      return result;
     }
 
     /**
-     * This method is like `_.flatMap` except that it recursively flattens the
-     * mapped results.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.7.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The function invoked per iteration.
-     * @returns {Array} Returns the new flattened array.
-     * @example
-     *
-     * function duplicate(n) {
-     *   return [[[n, n]]];
-     * }
+     * This function is like `composeArgs` except that the arguments composition
+     * is tailored for `_.partialRight`.
      *
-     * _.flatMapDeep([1, 2], duplicate);
-     * // => [1, 1, 2, 2]
+     * @private
+     * @param {Array} args The provided arguments.
+     * @param {Array} partials The arguments to append to those provided.
+     * @param {Array} holders The `partials` placeholder indexes.
+     * @params {boolean} [isCurried] Specify composing for a curried function.
+     * @returns {Array} Returns the new array of composed arguments.
      */
-    function flatMapDeep(collection, iteratee) {
-      return baseFlatten(map(collection, iteratee), INFINITY);
+    function composeArgsRight(args, partials, holders, isCurried) {
+      var argsIndex = -1,
+          argsLength = args.length,
+          holdersIndex = -1,
+          holdersLength = holders.length,
+          rightIndex = -1,
+          rightLength = partials.length,
+          rangeLength = nativeMax(argsLength - holdersLength, 0),
+          result = Array(rangeLength + rightLength),
+          isUncurried = !isCurried;
+
+      while (++argsIndex < rangeLength) {
+        result[argsIndex] = args[argsIndex];
+      }
+      var offset = argsIndex;
+      while (++rightIndex < rightLength) {
+        result[offset + rightIndex] = partials[rightIndex];
+      }
+      while (++holdersIndex < holdersLength) {
+        if (isUncurried || argsIndex < argsLength) {
+          result[offset + holders[holdersIndex]] = args[argsIndex++];
+        }
+      }
+      return result;
     }
 
     /**
-     * This method is like `_.flatMap` except that it recursively flattens the
-     * mapped results up to `depth` times.
+     * Copies the values of `source` to `array`.
      *
-     * @static
-     * @memberOf _
-     * @since 4.7.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The function invoked per iteration.
-     * @param {number} [depth=1] The maximum recursion depth.
-     * @returns {Array} Returns the new flattened array.
-     * @example
-     *
-     * function duplicate(n) {
-     *   return [[[n, n]]];
-     * }
-     *
-     * _.flatMapDepth([1, 2], duplicate, 2);
-     * // => [[1, 1], [2, 2]]
+     * @private
+     * @param {Array} source The array to copy values from.
+     * @param {Array} [array=[]] The array to copy values to.
+     * @returns {Array} Returns `array`.
      */
-    function flatMapDepth(collection, iteratee, depth) {
-      depth = depth === undefined ? 1 : toInteger(depth);
-      return baseFlatten(map(collection, iteratee), depth);
+    function copyArray(source, array) {
+      var index = -1,
+          length = source.length;
+
+      array || (array = Array(length));
+      while (++index < length) {
+        array[index] = source[index];
+      }
+      return array;
     }
 
     /**
-     * Iterates over elements of `collection` and invokes `iteratee` for each element.
-     * The iteratee is invoked with three arguments: (value, index|key, collection).
-     * Iteratee functions may exit iteration early by explicitly returning `false`.
-     *
-     * **Note:** As with other "Collections" methods, objects with a "length"
-     * property are iterated like arrays. To avoid this behavior use `_.forIn`
-     * or `_.forOwn` for object iteration.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @alias each
-     * @category Collection
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
-     * @returns {Array|Object} Returns `collection`.
-     * @see _.forEachRight
-     * @example
-     *
-     * _([1, 2]).forEach(function(value) {
-     *   console.log(value);
-     * });
-     * // => Logs `1` then `2`.
+     * Copies properties of `source` to `object`.
      *
-     * _.forEach({ 'a': 1, 'b': 2 }, function(value, key) {
-     *   console.log(key);
-     * });
-     * // => Logs 'a' then 'b' (iteration order is not guaranteed).
+     * @private
+     * @param {Object} source The object to copy properties from.
+     * @param {Array} props The property identifiers to copy.
+     * @param {Object} [object={}] The object to copy properties to.
+     * @param {Function} [customizer] The function to customize copied values.
+     * @returns {Object} Returns `object`.
      */
-    function forEach(collection, iteratee) {
-      var func = isArray(collection) ? arrayEach : baseEach;
-      return func(collection, getIteratee(iteratee, 3));
+    function copyObject(source, props, object, customizer) {
+      var isNew = !object;
+      object || (object = {});
+
+      var index = -1,
+          length = props.length;
+
+      while (++index < length) {
+        var key = props[index];
+
+        var newValue = customizer
+          ? customizer(object[key], source[key], key, object, source)
+          : undefined;
+
+        if (newValue === undefined) {
+          newValue = source[key];
+        }
+        if (isNew) {
+          baseAssignValue(object, key, newValue);
+        } else {
+          assignValue(object, key, newValue);
+        }
+      }
+      return object;
     }
 
     /**
-     * This method is like `_.forEach` except that it iterates over elements of
-     * `collection` from right to left.
-     *
-     * @static
-     * @memberOf _
-     * @since 2.0.0
-     * @alias eachRight
-     * @category Collection
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
-     * @returns {Array|Object} Returns `collection`.
-     * @see _.forEach
-     * @example
+     * Copies own symbols of `source` to `object`.
      *
-     * _.forEachRight([1, 2], function(value) {
-     *   console.log(value);
-     * });
-     * // => Logs `2` then `1`.
+     * @private
+     * @param {Object} source The object to copy symbols from.
+     * @param {Object} [object={}] The object to copy symbols to.
+     * @returns {Object} Returns `object`.
      */
-    function forEachRight(collection, iteratee) {
-      var func = isArray(collection) ? arrayEachRight : baseEachRight;
-      return func(collection, getIteratee(iteratee, 3));
+    function copySymbols(source, object) {
+      return copyObject(source, getSymbols(source), object);
     }
 
     /**
-     * Creates an object composed of keys generated from the results of running
-     * each element of `collection` thru `iteratee`. The order of grouped values
-     * is determined by the order they occur in `collection`. The corresponding
-     * value of each key is an array of elements responsible for generating the
-     * key. The iteratee is invoked with one argument: (value).
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The iteratee to transform keys.
-     * @returns {Object} Returns the composed aggregate object.
-     * @example
-     *
-     * _.groupBy([6.1, 4.2, 6.3], Math.floor);
-     * // => { '4': [4.2], '6': [6.1, 6.3] }
+     * Copies own and inherited symbols of `source` to `object`.
      *
-     * // The `_.property` iteratee shorthand.
-     * _.groupBy(['one', 'two', 'three'], 'length');
-     * // => { '3': ['one', 'two'], '5': ['three'] }
+     * @private
+     * @param {Object} source The object to copy symbols from.
+     * @param {Object} [object={}] The object to copy symbols to.
+     * @returns {Object} Returns `object`.
      */
-    var groupBy = createAggregator(function(result, value, key) {
-      if (hasOwnProperty.call(result, key)) {
-        result[key].push(value);
-      } else {
-        result[key] = [value];
-      }
-    });
+    function copySymbolsIn(source, object) {
+      return copyObject(source, getSymbolsIn(source), object);
+    }
 
     /**
-     * Checks if `value` is in `collection`. If `collection` is a string, it's
-     * checked for a substring of `value`, otherwise
-     * [`SameValueZero`](http://ecma-international.org/ecma-262/6.0/#sec-samevaluezero)
-     * is used for equality comparisons. If `fromIndex` is negative, it's used as
-     * the offset from the end of `collection`.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Collection
-     * @param {Array|Object|string} collection The collection to search.
-     * @param {*} value The value to search for.
-     * @param {number} [fromIndex=0] The index to search from.
-     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.reduce`.
-     * @returns {boolean} Returns `true` if `value` is found, else `false`.
-     * @example
-     *
-     * _.includes([1, 2, 3], 1);
-     * // => true
-     *
-     * _.includes([1, 2, 3], 1, 2);
-     * // => false
-     *
-     * _.includes({ 'user': 'fred', 'age': 40 }, 'fred');
-     * // => true
+     * Creates a function like `_.groupBy`.
      *
-     * _.includes('pebbles', 'eb');
-     * // => true
+     * @private
+     * @param {Function} setter The function to set accumulator values.
+     * @param {Function} [initializer] The accumulator object initializer.
+     * @returns {Function} Returns the new aggregator function.
      */
-    function includes(collection, value, fromIndex, guard) {
-      collection = isArrayLike(collection) ? collection : values(collection);
-      fromIndex = (fromIndex && !guard) ? toInteger(fromIndex) : 0;
+    function createAggregator(setter, initializer) {
+      return function(collection, iteratee) {
+        var func = isArray(collection) ? arrayAggregator : baseAggregator,
+            accumulator = initializer ? initializer() : {};
 
-      var length = collection.length;
-      if (fromIndex < 0) {
-        fromIndex = nativeMax(length + fromIndex, 0);
-      }
-      return isString(collection)
-        ? (fromIndex <= length && collection.indexOf(value, fromIndex) > -1)
-        : (!!length && baseIndexOf(collection, value, fromIndex) > -1);
+        return func(collection, setter, getIteratee(iteratee, 2), accumulator);
+      };
     }
 
     /**
-     * Invokes the method at `path` of each element in `collection`, returning
-     * an array of the results of each invoked method. Any additional arguments
-     * are provided to each invoked method. If `methodName` is a function, it's
-     * invoked for and `this` bound to, each element in `collection`.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Array|Function|string} path The path of the method to invoke or
-     *  the function invoked per iteration.
-     * @param {...*} [args] The arguments to invoke each method with.
-     * @returns {Array} Returns the array of results.
-     * @example
-     *
-     * _.invokeMap([[5, 1, 7], [3, 2, 1]], 'sort');
-     * // => [[1, 5, 7], [1, 2, 3]]
+     * Creates a function like `_.assign`.
      *
-     * _.invokeMap([123, 456], String.prototype.split, '');
-     * // => [['1', '2', '3'], ['4', '5', '6']]
+     * @private
+     * @param {Function} assigner The function to assign values.
+     * @returns {Function} Returns the new assigner function.
      */
-    var invokeMap = rest(function(collection, path, args) {
-      var index = -1,
-          isFunc = typeof path == 'function',
-          isProp = isKey(path),
-          result = isArrayLike(collection) ? Array(collection.length) : [];
+    function createAssigner(assigner) {
+      return baseRest(function(object, sources) {
+        var index = -1,
+            length = sources.length,
+            customizer = length > 1 ? sources[length - 1] : undefined,
+            guard = length > 2 ? sources[2] : undefined;
 
-      baseEach(collection, function(value) {
-        var func = isFunc ? path : ((isProp && value != null) ? value[path] : undefined);
-        result[++index] = func ? apply(func, value, args) : baseInvoke(value, path, args);
+        customizer = (assigner.length > 3 && typeof customizer == 'function')
+          ? (length--, customizer)
+          : undefined;
+
+        if (guard && isIterateeCall(sources[0], sources[1], guard)) {
+          customizer = length < 3 ? undefined : customizer;
+          length = 1;
+        }
+        object = Object(object);
+        while (++index < length) {
+          var source = sources[index];
+          if (source) {
+            assigner(object, source, index, customizer);
+          }
+        }
+        return object;
       });
-      return result;
-    });
+    }
 
     /**
-     * Creates an object composed of keys generated from the results of running
-     * each element of `collection` thru `iteratee`. The corresponding value of
-     * each key is the last element responsible for generating the key. The
-     * iteratee is invoked with one argument: (value).
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The iteratee to transform keys.
-     * @returns {Object} Returns the composed aggregate object.
-     * @example
-     *
-     * var array = [
-     *   { 'dir': 'left', 'code': 97 },
-     *   { 'dir': 'right', 'code': 100 }
-     * ];
-     *
-     * _.keyBy(array, function(o) {
-     *   return String.fromCharCode(o.code);
-     * });
-     * // => { 'a': { 'dir': 'left', 'code': 97 }, 'd': { 'dir': 'right', 'code': 100 } }
+     * Creates a `baseEach` or `baseEachRight` function.
      *
-     * _.keyBy(array, 'dir');
-     * // => { 'left': { 'dir': 'left', 'code': 97 }, 'right': { 'dir': 'right', 'code': 100 } }
+     * @private
+     * @param {Function} eachFunc The function to iterate over a collection.
+     * @param {boolean} [fromRight] Specify iterating from right to left.
+     * @returns {Function} Returns the new base function.
      */
-    var keyBy = createAggregator(function(result, value, key) {
-      result[key] = value;
-    });
+    function createBaseEach(eachFunc, fromRight) {
+      return function(collection, iteratee) {
+        if (collection == null) {
+          return collection;
+        }
+        if (!isArrayLike(collection)) {
+          return eachFunc(collection, iteratee);
+        }
+        var length = collection.length,
+            index = fromRight ? length : -1,
+            iterable = Object(collection);
+
+        while ((fromRight ? index-- : ++index < length)) {
+          if (iteratee(iterable[index], index, iterable) === false) {
+            break;
+          }
+        }
+        return collection;
+      };
+    }
 
     /**
-     * Creates an array of values by running each element in `collection` thru
-     * `iteratee`. The iteratee is invoked with three arguments:
-     * (value, index|key, collection).
-     *
-     * Many lodash methods are guarded to work as iteratees for methods like
-     * `_.every`, `_.filter`, `_.map`, `_.mapValues`, `_.reject`, and `_.some`.
-     *
-     * The guarded methods are:
-     * `ary`, `chunk`, `curry`, `curryRight`, `drop`, `dropRight`, `every`,
-     * `fill`, `invert`, `parseInt`, `random`, `range`, `rangeRight`, `repeat`,
-     * `sampleSize`, `slice`, `some`, `sortBy`, `split`, `take`, `takeRight`,
-     * `template`, `trim`, `trimEnd`, `trimStart`, and `words`
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The function invoked per iteration.
-     * @returns {Array} Returns the new mapped array.
-     * @example
-     *
-     * function square(n) {
-     *   return n * n;
-     * }
-     *
-     * _.map([4, 8], square);
-     * // => [16, 64]
-     *
-     * _.map({ 'a': 4, 'b': 8 }, square);
-     * // => [16, 64] (iteration order is not guaranteed)
-     *
-     * var users = [
-     *   { 'user': 'barney' },
-     *   { 'user': 'fred' }
-     * ];
+     * Creates a base function for methods like `_.forIn` and `_.forOwn`.
      *
-     * // The `_.property` iteratee shorthand.
-     * _.map(users, 'user');
-     * // => ['barney', 'fred']
+     * @private
+     * @param {boolean} [fromRight] Specify iterating from right to left.
+     * @returns {Function} Returns the new base function.
      */
-    function map(collection, iteratee) {
-      var func = isArray(collection) ? arrayMap : baseMap;
-      return func(collection, getIteratee(iteratee, 3));
+    function createBaseFor(fromRight) {
+      return function(object, iteratee, keysFunc) {
+        var index = -1,
+            iterable = Object(object),
+            props = keysFunc(object),
+            length = props.length;
+
+        while (length--) {
+          var key = props[fromRight ? length : ++index];
+          if (iteratee(iterable[key], key, iterable) === false) {
+            break;
+          }
+        }
+        return object;
+      };
     }
 
     /**
-     * This method is like `_.sortBy` except that it allows specifying the sort
-     * orders of the iteratees to sort by. If `orders` is unspecified, all values
-     * are sorted in ascending order. Otherwise, specify an order of "desc" for
-     * descending or "asc" for ascending sort order of corresponding values.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Array[]|Function[]|Object[]|string[]} [iteratees=[_.identity]]
-     *  The iteratees to sort by.
-     * @param {string[]} [orders] The sort orders of `iteratees`.
-     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.reduce`.
-     * @returns {Array} Returns the new sorted array.
-     * @example
-     *
-     * var users = [
-     *   { 'user': 'fred',   'age': 48 },
-     *   { 'user': 'barney', 'age': 34 },
-     *   { 'user': 'fred',   'age': 40 },
-     *   { 'user': 'barney', 'age': 36 }
-     * ];
+     * Creates a function that wraps `func` to invoke it with the optional `this`
+     * binding of `thisArg`.
      *
-     * // Sort by `user` in ascending order and by `age` in descending order.
-     * _.orderBy(users, ['user', 'age'], ['asc', 'desc']);
-     * // => objects for [['barney', 36], ['barney', 34], ['fred', 48], ['fred', 40]]
+     * @private
+     * @param {Function} func The function to wrap.
+     * @param {number} bitmask The bitmask flags. See `createWrap` for more details.
+     * @param {*} [thisArg] The `this` binding of `func`.
+     * @returns {Function} Returns the new wrapped function.
      */
-    function orderBy(collection, iteratees, orders, guard) {
-      if (collection == null) {
-        return [];
-      }
-      if (!isArray(iteratees)) {
-        iteratees = iteratees == null ? [] : [iteratees];
-      }
-      orders = guard ? undefined : orders;
-      if (!isArray(orders)) {
-        orders = orders == null ? [] : [orders];
+    function createBind(func, bitmask, thisArg) {
+      var isBind = bitmask & WRAP_BIND_FLAG,
+          Ctor = createCtor(func);
+
+      function wrapper() {
+        var fn = (this && this !== root && this instanceof wrapper) ? Ctor : func;
+        return fn.apply(isBind ? thisArg : this, arguments);
       }
-      return baseOrderBy(collection, iteratees, orders);
+      return wrapper;
     }
 
     /**
-     * Creates an array of elements split into two groups, the first of which
-     * contains elements `predicate` returns truthy for, the second of which
-     * contains elements `predicate` returns falsey for. The predicate is
-     * invoked with one argument: (value).
-     *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Array|Function|Object|string} [predicate=_.identity]
-     *  The function invoked per iteration.
-     * @returns {Array} Returns the array of grouped elements.
-     * @example
-     *
-     * var users = [
-     *   { 'user': 'barney',  'age': 36, 'active': false },
-     *   { 'user': 'fred',    'age': 40, 'active': true },
-     *   { 'user': 'pebbles', 'age': 1,  'active': false }
-     * ];
-     *
-     * _.partition(users, function(o) { return o.active; });
-     * // => objects for [['fred'], ['barney', 'pebbles']]
-     *
-     * // The `_.matches` iteratee shorthand.
-     * _.partition(users, { 'age': 1, 'active': false });
-     * // => objects for [['pebbles'], ['barney', 'fred']]
-     *
-     * // The `_.matchesProperty` iteratee shorthand.
-     * _.partition(users, ['active', false]);
-     * // => objects for [['barney', 'pebbles'], ['fred']]
+     * Creates a function like `_.lowerFirst`.
      *
-     * // The `_.property` iteratee shorthand.
-     * _.partition(users, 'active');
-     * // => objects for [['fred'], ['barney', 'pebbles']]
+     * @private
+     * @param {string} methodName The name of the `String` case method to use.
+     * @returns {Function} Returns the new case function.
      */
-    var partition = createAggregator(function(result, value, key) {
-      result[key ? 0 : 1].push(value);
-    }, function() { return [[], []]; });
+    function createCaseFirst(methodName) {
+      return function(string) {
+        string = toString(string);
+
+        var strSymbols = hasUnicode(string)
+          ? stringToArray(string)
+          : undefined;
+
+        var chr = strSymbols
+          ? strSymbols[0]
+          : string.charAt(0);
+
+        var trailing = strSymbols
+          ? castSlice(strSymbols, 1).join('')
+          : string.slice(1);
+
+        return chr[methodName]() + trailing;
+      };
+    }
 
     /**
-     * Reduces `collection` to a value which is the accumulated result of running
-     * each element in `collection` thru `iteratee`, where each successive
-     * invocation is supplied the return value of the previous. If `accumulator`
-     * is not given, the first element of `collection` is used as the initial
-     * value. The iteratee is invoked with four arguments:
-     * (accumulator, value, index|key, collection).
-     *
-     * Many lodash methods are guarded to work as iteratees for methods like
-     * `_.reduce`, `_.reduceRight`, and `_.transform`.
-     *
-     * The guarded methods are:
-     * `assign`, `defaults`, `defaultsDeep`, `includes`, `merge`, `orderBy`,
-     * and `sortBy`
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
-     * @param {*} [accumulator] The initial value.
-     * @returns {*} Returns the accumulated value.
-     * @see _.reduceRight
-     * @example
-     *
-     * _.reduce([1, 2], function(sum, n) {
-     *   return sum + n;
-     * }, 0);
-     * // => 3
+     * Creates a function like `_.camelCase`.
      *
-     * _.reduce({ 'a': 1, 'b': 2, 'c': 1 }, function(result, value, key) {
-     *   (result[value] || (result[value] = [])).push(key);
-     *   return result;
-     * }, {});
-     * // => { '1': ['a', 'c'], '2': ['b'] } (iteration order is not guaranteed)
+     * @private
+     * @param {Function} callback The function to combine each word.
+     * @returns {Function} Returns the new compounder function.
      */
-    function reduce(collection, iteratee, accumulator) {
-      var func = isArray(collection) ? arrayReduce : baseReduce,
-          initAccum = arguments.length < 3;
-
-      return func(collection, getIteratee(iteratee, 4), accumulator, initAccum, baseEach);
+    function createCompounder(callback) {
+      return function(string) {
+        return arrayReduce(words(deburr(string).replace(reApos, '')), callback, '');
+      };
     }
 
     /**
-     * This method is like `_.reduce` except that it iterates over elements of
-     * `collection` from right to left.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
-     * @param {*} [accumulator] The initial value.
-     * @returns {*} Returns the accumulated value.
-     * @see _.reduce
-     * @example
-     *
-     * var array = [[0, 1], [2, 3], [4, 5]];
+     * Creates a function that produces an instance of `Ctor` regardless of
+     * whether it was invoked as part of a `new` expression or by `call` or `apply`.
      *
-     * _.reduceRight(array, function(flattened, other) {
-     *   return flattened.concat(other);
-     * }, []);
-     * // => [4, 5, 2, 3, 0, 1]
+     * @private
+     * @param {Function} Ctor The constructor to wrap.
+     * @returns {Function} Returns the new wrapped function.
      */
-    function reduceRight(collection, iteratee, accumulator) {
-      var func = isArray(collection) ? arrayReduceRight : baseReduce,
-          initAccum = arguments.length < 3;
-
-      return func(collection, getIteratee(iteratee, 4), accumulator, initAccum, baseEachRight);
-    }
+    function createCtor(Ctor) {
+      return function() {
+        // Use a `switch` statement to work with class constructors. See
+        // http://ecma-international.org/ecma-262/7.0/#sec-ecmascript-function-objects-call-thisargument-argumentslist
+        // for more details.
+        var args = arguments;
+        switch (args.length) {
+          case 0: return new Ctor;
+          case 1: return new Ctor(args[0]);
+          case 2: return new Ctor(args[0], args[1]);
+          case 3: return new Ctor(args[0], args[1], args[2]);
+          case 4: return new Ctor(args[0], args[1], args[2], args[3]);
+          case 5: return new Ctor(args[0], args[1], args[2], args[3], args[4]);
+          case 6: return new Ctor(args[0], args[1], args[2], args[3], args[4], args[5]);
+          case 7: return new Ctor(args[0], args[1], args[2], args[3], args[4], args[5], args[6]);
+        }
+        var thisBinding = baseCreate(Ctor.prototype),
+            result = Ctor.apply(thisBinding, args);
 
-    /**
-     * The opposite of `_.filter`; this method returns the elements of `collection`
-     * that `predicate` does **not** return truthy for.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Array|Function|Object|string} [predicate=_.identity]
-     *  The function invoked per iteration.
-     * @returns {Array} Returns the new filtered array.
-     * @see _.filter
-     * @example
-     *
-     * var users = [
-     *   { 'user': 'barney', 'age': 36, 'active': false },
-     *   { 'user': 'fred',   'age': 40, 'active': true }
-     * ];
-     *
-     * _.reject(users, function(o) { return !o.active; });
-     * // => objects for ['fred']
-     *
-     * // The `_.matches` iteratee shorthand.
-     * _.reject(users, { 'age': 40, 'active': true });
-     * // => objects for ['barney']
-     *
-     * // The `_.matchesProperty` iteratee shorthand.
-     * _.reject(users, ['active', false]);
-     * // => objects for ['fred']
-     *
-     * // The `_.property` iteratee shorthand.
-     * _.reject(users, 'active');
-     * // => objects for ['barney']
-     */
-    function reject(collection, predicate) {
-      var func = isArray(collection) ? arrayFilter : baseFilter;
-      predicate = getIteratee(predicate, 3);
-      return func(collection, function(value, index, collection) {
-        return !predicate(value, index, collection);
-      });
+        // Mimic the constructor's `return` behavior.
+        // See https://es5.github.io/#x13.2.2 for more details.
+        return isObject(result) ? result : thisBinding;
+      };
     }
 
     /**
-     * Gets a random element from `collection`.
-     *
-     * @static
-     * @memberOf _
-     * @since 2.0.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to sample.
-     * @returns {*} Returns the random element.
-     * @example
+     * Creates a function that wraps `func` to enable currying.
      *
-     * _.sample([1, 2, 3, 4]);
-     * // => 2
+     * @private
+     * @param {Function} func The function to wrap.
+     * @param {number} bitmask The bitmask flags. See `createWrap` for more details.
+     * @param {number} arity The arity of `func`.
+     * @returns {Function} Returns the new wrapped function.
      */
-    function sample(collection) {
-      var array = isArrayLike(collection) ? collection : values(collection),
-          length = array.length;
+    function createCurry(func, bitmask, arity) {
+      var Ctor = createCtor(func);
 
-      return length > 0 ? array[baseRandom(0, length - 1)] : undefined;
-    }
-
-    /**
-     * Gets `n` random elements at unique keys from `collection` up to the
-     * size of `collection`.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to sample.
-     * @param {number} [n=1] The number of elements to sample.
-     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
-     * @returns {Array} Returns the random elements.
-     * @example
-     *
-     * _.sampleSize([1, 2, 3], 2);
-     * // => [3, 1]
-     *
-     * _.sampleSize([1, 2, 3], 4);
-     * // => [2, 3, 1]
-     */
-    function sampleSize(collection, n, guard) {
-      var index = -1,
-          result = toArray(collection),
-          length = result.length,
-          lastIndex = length - 1;
+      function wrapper() {
+        var length = arguments.length,
+            args = Array(length),
+            index = length,
+            placeholder = getHolder(wrapper);
 
-      if ((guard ? isIterateeCall(collection, n, guard) : n === undefined)) {
-        n = 1;
-      } else {
-        n = baseClamp(toInteger(n), 0, length);
-      }
-      while (++index < n) {
-        var rand = baseRandom(index, lastIndex),
-            value = result[rand];
+        while (index--) {
+          args[index] = arguments[index];
+        }
+        var holders = (length < 3 && args[0] !== placeholder && args[length - 1] !== placeholder)
+          ? []
+          : replaceHolders(args, placeholder);
 
-        result[rand] = result[index];
-        result[index] = value;
+        length -= holders.length;
+        if (length < arity) {
+          return createRecurry(
+            func, bitmask, createHybrid, wrapper.placeholder, undefined,
+            args, holders, undefined, undefined, arity - length);
+        }
+        var fn = (this && this !== root && this instanceof wrapper) ? Ctor : func;
+        return apply(fn, this, args);
       }
-      result.length = n;
-      return result;
+      return wrapper;
     }
 
     /**
-     * Creates an array of shuffled values, using a version of the
-     * [Fisher-Yates shuffle](https://en.wikipedia.org/wiki/Fisher-Yates_shuffle).
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to shuffle.
-     * @returns {Array} Returns the new shuffled array.
-     * @example
+     * Creates a `_.find` or `_.findLast` function.
      *
-     * _.shuffle([1, 2, 3, 4]);
-     * // => [4, 1, 3, 2]
+     * @private
+     * @param {Function} findIndexFunc The function to find the collection index.
+     * @returns {Function} Returns the new find function.
      */
-    function shuffle(collection) {
-      return sampleSize(collection, MAX_ARRAY_LENGTH);
+    function createFind(findIndexFunc) {
+      return function(collection, predicate, fromIndex) {
+        var iterable = Object(collection);
+        if (!isArrayLike(collection)) {
+          var iteratee = getIteratee(predicate, 3);
+          collection = keys(collection);
+          predicate = function(key) { return iteratee(iterable[key], key, iterable); };
+        }
+        var index = findIndexFunc(collection, predicate, fromIndex);
+        return index > -1 ? iterable[iteratee ? collection[index] : index] : undefined;
+      };
     }
 
     /**
-     * Gets the size of `collection` by returning its length for array-like
-     * values or the number of own enumerable string keyed properties for objects.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to inspect.
-     * @returns {number} Returns the collection size.
-     * @example
-     *
-     * _.size([1, 2, 3]);
-     * // => 3
-     *
-     * _.size({ 'a': 1, 'b': 2 });
-     * // => 2
+     * Creates a `_.flow` or `_.flowRight` function.
      *
-     * _.size('pebbles');
-     * // => 7
+     * @private
+     * @param {boolean} [fromRight] Specify iterating from right to left.
+     * @returns {Function} Returns the new flow function.
      */
-    function size(collection) {
-      if (collection == null) {
-        return 0;
-      }
-      if (isArrayLike(collection)) {
-        var result = collection.length;
-        return (result && isString(collection)) ? stringSize(collection) : result;
-      }
-      if (isObjectLike(collection)) {
-        var tag = getTag(collection);
-        if (tag == mapTag || tag == setTag) {
-          return collection.size;
+    function createFlow(fromRight) {
+      return flatRest(function(funcs) {
+        var length = funcs.length,
+            index = length,
+            prereq = LodashWrapper.prototype.thru;
+
+        if (fromRight) {
+          funcs.reverse();
         }
-      }
-      return keys(collection).length;
+        while (index--) {
+          var func = funcs[index];
+          if (typeof func != 'function') {
+            throw new TypeError(FUNC_ERROR_TEXT);
+          }
+          if (prereq && !wrapper && getFuncName(func) == 'wrapper') {
+            var wrapper = new LodashWrapper([], true);
+          }
+        }
+        index = wrapper ? index : length;
+        while (++index < length) {
+          func = funcs[index];
+
+          var funcName = getFuncName(func),
+              data = funcName == 'wrapper' ? getData(func) : undefined;
+
+          if (data && isLaziable(data[0]) &&
+                data[1] == (WRAP_ARY_FLAG | WRAP_CURRY_FLAG | WRAP_PARTIAL_FLAG | WRAP_REARG_FLAG) &&
+                !data[4].length && data[9] == 1
+              ) {
+            wrapper = wrapper[getFuncName(data[0])].apply(wrapper, data[3]);
+          } else {
+            wrapper = (func.length == 1 && isLaziable(func))
+              ? wrapper[funcName]()
+              : wrapper.thru(func);
+          }
+        }
+        return function() {
+          var args = arguments,
+              value = args[0];
+
+          if (wrapper && args.length == 1 && isArray(value)) {
+            return wrapper.plant(value).value();
+          }
+          var index = 0,
+              result = length ? funcs[index].apply(this, args) : value;
+
+          while (++index < length) {
+            result = funcs[index].call(this, result);
+          }
+          return result;
+        };
+      });
     }
 
     /**
-     * Checks if `predicate` returns truthy for **any** element of `collection`.
-     * Iteration is stopped once `predicate` returns truthy. The predicate is
-     * invoked with three arguments: (value, index|key, collection).
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {Array|Function|Object|string} [predicate=_.identity]
-     *  The function invoked per iteration.
-     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
-     * @returns {boolean} Returns `true` if any element passes the predicate check,
-     *  else `false`.
-     * @example
-     *
-     * _.some([null, 0, 'yes', false], Boolean);
-     * // => true
+     * Creates a function that wraps `func` to invoke it with optional `this`
+     * binding of `thisArg`, partial application, and currying.
      *
-     * var users = [
-     *   { 'user': 'barney', 'active': true },
-     *   { 'user': 'fred',   'active': false }
-     * ];
-     *
-     * // The `_.matches` iteratee shorthand.
-     * _.some(users, { 'user': 'barney', 'active': false });
-     * // => false
-     *
-     * // The `_.matchesProperty` iteratee shorthand.
-     * _.some(users, ['active', false]);
-     * // => true
-     *
-     * // The `_.property` iteratee shorthand.
-     * _.some(users, 'active');
-     * // => true
+     * @private
+     * @param {Function|string} func The function or method name to wrap.
+     * @param {number} bitmask The bitmask flags. See `createWrap` for more details.
+     * @param {*} [thisArg] The `this` binding of `func`.
+     * @param {Array} [partials] The arguments to prepend to those provided to
+     *  the new function.
+     * @param {Array} [holders] The `partials` placeholder indexes.
+     * @param {Array} [partialsRight] The arguments to append to those provided
+     *  to the new function.
+     * @param {Array} [holdersRight] The `partialsRight` placeholder indexes.
+     * @param {Array} [argPos] The argument positions of the new function.
+     * @param {number} [ary] The arity cap of `func`.
+     * @param {number} [arity] The arity of `func`.
+     * @returns {Function} Returns the new wrapped function.
      */
-    function some(collection, predicate, guard) {
-      var func = isArray(collection) ? arraySome : baseSome;
-      if (guard && isIterateeCall(collection, predicate, guard)) {
-        predicate = undefined;
-      }
-      return func(collection, getIteratee(predicate, 3));
-    }
+    function createHybrid(func, bitmask, thisArg, partials, holders, partialsRight, holdersRight, argPos, ary, arity) {
+      var isAry = bitmask & WRAP_ARY_FLAG,
+          isBind = bitmask & WRAP_BIND_FLAG,
+          isBindKey = bitmask & WRAP_BIND_KEY_FLAG,
+          isCurried = bitmask & (WRAP_CURRY_FLAG | WRAP_CURRY_RIGHT_FLAG),
+          isFlip = bitmask & WRAP_FLIP_FLAG,
+          Ctor = isBindKey ? undefined : createCtor(func);
 
-    /**
-     * Creates an array of elements, sorted in ascending order by the results of
-     * running each element in a collection thru each iteratee. This method
-     * performs a stable sort, that is, it preserves the original sort order of
-     * equal elements. The iteratees are invoked with one argument: (value).
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Collection
-     * @param {Array|Object} collection The collection to iterate over.
-     * @param {...(Array|Array[]|Function|Function[]|Object|Object[]|string|string[])}
-     *  [iteratees=[_.identity]] The iteratees to sort by.
-     * @returns {Array} Returns the new sorted array.
-     * @example
-     *
-     * var users = [
-     *   { 'user': 'fred',   'age': 48 },
-     *   { 'user': 'barney', 'age': 36 },
-     *   { 'user': 'fred',   'age': 40 },
-     *   { 'user': 'barney', 'age': 34 }
-     * ];
-     *
-     * _.sortBy(users, function(o) { return o.user; });
-     * // => objects for [['barney', 36], ['barney', 34], ['fred', 48], ['fred', 40]]
-     *
-     * _.sortBy(users, ['user', 'age']);
-     * // => objects for [['barney', 34], ['barney', 36], ['fred', 40], ['fred', 48]]
-     *
-     * _.sortBy(users, 'user', function(o) {
-     *   return Math.floor(o.age / 10);
-     * });
-     * // => objects for [['barney', 36], ['barney', 34], ['fred', 48], ['fred', 40]]
-     */
-    var sortBy = rest(function(collection, iteratees) {
-      if (collection == null) {
-        return [];
-      }
-      var length = iteratees.length;
-      if (length > 1 && isIterateeCall(collection, iteratees[0], iteratees[1])) {
-        iteratees = [];
-      } else if (length > 2 && isIterateeCall(iteratees[0], iteratees[1], iteratees[2])) {
-        iteratees = [iteratees[0]];
-      }
-      iteratees = (iteratees.length == 1 && isArray(iteratees[0]))
-        ? iteratees[0]
-        : baseFlatten(iteratees, 1, isFlattenableIteratee);
+      function wrapper() {
+        var length = arguments.length,
+            args = Array(length),
+            index = length;
 
-      return baseOrderBy(collection, iteratees, []);
-    });
+        while (index--) {
+          args[index] = arguments[index];
+        }
+        if (isCurried) {
+          var placeholder = getHolder(wrapper),
+              holdersCount = countHolders(args, placeholder);
+        }
+        if (partials) {
+          args = composeArgs(args, partials, holders, isCurried);
+        }
+        if (partialsRight) {
+          args = composeArgsRight(args, partialsRight, holdersRight, isCurried);
+        }
+        length -= holdersCount;
+        if (isCurried && length < arity) {
+          var newHolders = replaceHolders(args, placeholder);
+          return createRecurry(
+            func, bitmask, createHybrid, wrapper.placeholder, thisArg,
+            args, newHolders, argPos, ary, arity - length
+          );
+        }
+        var thisBinding = isBind ? thisArg : this,
+            fn = isBindKey ? thisBinding[func] : func;
 
-    /*------------------------------------------------------------------------*/
+        length = args.length;
+        if (argPos) {
+          args = reorder(args, argPos);
+        } else if (isFlip && length > 1) {
+          args.reverse();
+        }
+        if (isAry && ary < length) {
+          args.length = ary;
+        }
+        if (this && this !== root && this instanceof wrapper) {
+          fn = Ctor || createCtor(fn);
+        }
+        return fn.apply(thisBinding, args);
+      }
+      return wrapper;
+    }
 
     /**
-     * Gets the timestamp of the number of milliseconds that have elapsed since
-     * the Unix epoch (1 January 1970 00:00:00 UTC).
-     *
-     * @static
-     * @memberOf _
-     * @since 2.4.0
-     * @category Date
-     * @returns {number} Returns the timestamp.
-     * @example
+     * Creates a function like `_.invertBy`.
      *
-     * _.defer(function(stamp) {
-     *   console.log(_.now() - stamp);
-     * }, _.now());
-     * // => Logs the number of milliseconds it took for the deferred invocation.
+     * @private
+     * @param {Function} setter The function to set accumulator values.
+     * @param {Function} toIteratee The function to resolve iteratees.
+     * @returns {Function} Returns the new inverter function.
      */
-    function now() {
-      return Date.now();
+    function createInverter(setter, toIteratee) {
+      return function(object, iteratee) {
+        return baseInverter(object, setter, toIteratee(iteratee), {});
+      };
     }
 
-    /*------------------------------------------------------------------------*/
-
     /**
-     * The opposite of `_.before`; this method creates a function that invokes
-     * `func` once it's called `n` or more times.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Function
-     * @param {number} n The number of calls before `func` is invoked.
-     * @param {Function} func The function to restrict.
-     * @returns {Function} Returns the new restricted function.
-     * @example
-     *
-     * var saves = ['profile', 'settings'];
-     *
-     * var done = _.after(saves.length, function() {
-     *   console.log('done saving!');
-     * });
+     * Creates a function that performs a mathematical operation on two values.
      *
-     * _.forEach(saves, function(type) {
-     *   asyncSave({ 'type': type, 'complete': done });
-     * });
-     * // => Logs 'done saving!' after the two async saves have completed.
+     * @private
+     * @param {Function} operator The function to perform the operation.
+     * @param {number} [defaultValue] The value used for `undefined` arguments.
+     * @returns {Function} Returns the new mathematical operation function.
      */
-    function after(n, func) {
-      if (typeof func != 'function') {
-        throw new TypeError(FUNC_ERROR_TEXT);
-      }
-      n = toInteger(n);
-      return function() {
-        if (--n < 1) {
-          return func.apply(this, arguments);
+    function createMathOperation(operator, defaultValue) {
+      return function(value, other) {
+        var result;
+        if (value === undefined && other === undefined) {
+          return defaultValue;
+        }
+        if (value !== undefined) {
+          result = value;
+        }
+        if (other !== undefined) {
+          if (result === undefined) {
+            return other;
+          }
+          if (typeof value == 'string' || typeof other == 'string') {
+            value = baseToString(value);
+            other = baseToString(other);
+          } else {
+            value = baseToNumber(value);
+            other = baseToNumber(other);
+          }
+          result = operator(value, other);
         }
+        return result;
       };
     }
 
     /**
-     * Creates a function that invokes `func`, with up to `n` arguments,
-     * ignoring any additional arguments.
-     *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Function
-     * @param {Function} func The function to cap arguments for.
-     * @param {number} [n=func.length] The arity cap.
-     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
-     * @returns {Function} Returns the new capped function.
-     * @example
+     * Creates a function like `_.over`.
      *
-     * _.map(['6', '8', '10'], _.ary(parseInt, 1));
-     * // => [6, 8, 10]
+     * @private
+     * @param {Function} arrayFunc The function to iterate over iteratees.
+     * @returns {Function} Returns the new over function.
      */
-    function ary(func, n, guard) {
-      n = guard ? undefined : n;
-      n = (func && n == null) ? func.length : n;
-      return createWrapper(func, ARY_FLAG, undefined, undefined, undefined, undefined, n);
+    function createOver(arrayFunc) {
+      return flatRest(function(iteratees) {
+        iteratees = arrayMap(iteratees, baseUnary(getIteratee()));
+        return baseRest(function(args) {
+          var thisArg = this;
+          return arrayFunc(iteratees, function(iteratee) {
+            return apply(iteratee, thisArg, args);
+          });
+        });
+      });
     }
 
     /**
-     * Creates a function that invokes `func`, with the `this` binding and arguments
-     * of the created function, while it's called less than `n` times. Subsequent
-     * calls to the created function return the result of the last `func` invocation.
-     *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Function
-     * @param {number} n The number of calls at which `func` is no longer invoked.
-     * @param {Function} func The function to restrict.
-     * @returns {Function} Returns the new restricted function.
-     * @example
+     * Creates the padding for `string` based on `length`. The `chars` string
+     * is truncated if the number of characters exceeds `length`.
      *
-     * jQuery(element).on('click', _.before(5, addContactToList));
-     * // => allows adding up to 4 contacts to the list
+     * @private
+     * @param {number} length The padding length.
+     * @param {string} [chars=' '] The string used as padding.
+     * @returns {string} Returns the padding for `string`.
      */
-    function before(n, func) {
-      var result;
-      if (typeof func != 'function') {
-        throw new TypeError(FUNC_ERROR_TEXT);
+    function createPadding(length, chars) {
+      chars = chars === undefined ? ' ' : baseToString(chars);
+
+      var charsLength = chars.length;
+      if (charsLength < 2) {
+        return charsLength ? baseRepeat(chars, length) : chars;
       }
-      n = toInteger(n);
-      return function() {
-        if (--n > 0) {
-          result = func.apply(this, arguments);
-        }
-        if (n <= 1) {
-          func = undefined;
-        }
-        return result;
-      };
+      var result = baseRepeat(chars, nativeCeil(length / stringSize(chars)));
+      return hasUnicode(chars)
+        ? castSlice(stringToArray(result), 0, length).join('')
+        : result.slice(0, length);
     }
 
     /**
-     * Creates a function that invokes `func` with the `this` binding of `thisArg`
-     * and `partials` prepended to the arguments it receives.
-     *
-     * The `_.bind.placeholder` value, which defaults to `_` in monolithic builds,
-     * may be used as a placeholder for partially applied arguments.
-     *
-     * **Note:** Unlike native `Function#bind`, this method doesn't set the "length"
-     * property of bound functions.
+     * Creates a function that wraps `func` to invoke it with the `this` binding
+     * of `thisArg` and `partials` prepended to the arguments it receives.
      *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Function
-     * @param {Function} func The function to bind.
+     * @private
+     * @param {Function} func The function to wrap.
+     * @param {number} bitmask The bitmask flags. See `createWrap` for more details.
      * @param {*} thisArg The `this` binding of `func`.
-     * @param {...*} [partials] The arguments to be partially applied.
-     * @returns {Function} Returns the new bound function.
-     * @example
-     *
-     * var greet = function(greeting, punctuation) {
-     *   return greeting + ' ' + this.user + punctuation;
-     * };
-     *
-     * var object = { 'user': 'fred' };
-     *
-     * var bound = _.bind(greet, object, 'hi');
-     * bound('!');
-     * // => 'hi fred!'
-     *
-     * // Bound with placeholders.
-     * var bound = _.bind(greet, object, _, '!');
-     * bound('hi');
-     * // => 'hi fred!'
+     * @param {Array} partials The arguments to prepend to those provided to
+     *  the new function.
+     * @returns {Function} Returns the new wrapped function.
      */
-    var bind = rest(function(func, thisArg, partials) {
-      var bitmask = BIND_FLAG;
-      if (partials.length) {
-        var holders = replaceHolders(partials, getHolder(bind));
-        bitmask |= PARTIAL_FLAG;
+    function createPartial(func, bitmask, thisArg, partials) {
+      var isBind = bitmask & WRAP_BIND_FLAG,
+          Ctor = createCtor(func);
+
+      function wrapper() {
+        var argsIndex = -1,
+            argsLength = arguments.length,
+            leftIndex = -1,
+            leftLength = partials.length,
+            args = Array(leftLength + argsLength),
+            fn = (this && this !== root && this instanceof wrapper) ? Ctor : func;
+
+        while (++leftIndex < leftLength) {
+          args[leftIndex] = partials[leftIndex];
+        }
+        while (argsLength--) {
+          args[leftIndex++] = arguments[++argsIndex];
+        }
+        return apply(fn, isBind ? thisArg : this, args);
       }
-      return createWrapper(func, bitmask, thisArg, partials, holders);
-    });
+      return wrapper;
+    }
 
     /**
-     * Creates a function that invokes the method at `object[key]` with `partials`
-     * prepended to the arguments it receives.
-     *
-     * This method differs from `_.bind` by allowing bound functions to reference
-     * methods that may be redefined or don't yet exist. See
-     * [Peter Michaux's article](http://peter.michaux.ca/articles/lazy-function-definition-pattern)
-     * for more details.
-     *
-     * The `_.bindKey.placeholder` value, which defaults to `_` in monolithic
-     * builds, may be used as a placeholder for partially applied arguments.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.10.0
-     * @category Function
-     * @param {Object} object The object to invoke the method on.
-     * @param {string} key The key of the method.
-     * @param {...*} [partials] The arguments to be partially applied.
-     * @returns {Function} Returns the new bound function.
-     * @example
-     *
-     * var object = {
-     *   'user': 'fred',
-     *   'greet': function(greeting, punctuation) {
-     *     return greeting + ' ' + this.user + punctuation;
-     *   }
-     * };
-     *
-     * var bound = _.bindKey(object, 'greet', 'hi');
-     * bound('!');
-     * // => 'hi fred!'
-     *
-     * object.greet = function(greeting, punctuation) {
-     *   return greeting + 'ya ' + this.user + punctuation;
-     * };
-     *
-     * bound('!');
-     * // => 'hiya fred!'
+     * Creates a `_.range` or `_.rangeRight` function.
      *
-     * // Bound with placeholders.
-     * var bound = _.bindKey(object, 'greet', _, '!');
-     * bound('hi');
-     * // => 'hiya fred!'
+     * @private
+     * @param {boolean} [fromRight] Specify iterating from right to left.
+     * @returns {Function} Returns the new range function.
      */
-    var bindKey = rest(function(object, key, partials) {
-      var bitmask = BIND_FLAG | BIND_KEY_FLAG;
-      if (partials.length) {
-        var holders = replaceHolders(partials, getHolder(bindKey));
-        bitmask |= PARTIAL_FLAG;
-      }
-      return createWrapper(key, bitmask, object, partials, holders);
-    });
+    function createRange(fromRight) {
+      return function(start, end, step) {
+        if (step && typeof step != 'number' && isIterateeCall(start, end, step)) {
+          end = step = undefined;
+        }
+        // Ensure the sign of `-0` is preserved.
+        start = toFinite(start);
+        if (end === undefined) {
+          end = start;
+          start = 0;
+        } else {
+          end = toFinite(end);
+        }
+        step = step === undefined ? (start < end ? 1 : -1) : toFinite(step);
+        return baseRange(start, end, step, fromRight);
+      };
+    }
 
     /**
-     * Creates a function that accepts arguments of `func` and either invokes
-     * `func` returning its result, if at least `arity` number of arguments have
-     * been provided, or returns a function that accepts the remaining `func`
-     * arguments, and so on. The arity of `func` may be specified if `func.length`
-     * is not sufficient.
-     *
-     * The `_.curry.placeholder` value, which defaults to `_` in monolithic builds,
-     * may be used as a placeholder for provided arguments.
-     *
-     * **Note:** This method doesn't set the "length" property of curried functions.
-     *
-     * @static
-     * @memberOf _
-     * @since 2.0.0
-     * @category Function
-     * @param {Function} func The function to curry.
-     * @param {number} [arity=func.length] The arity of `func`.
-     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
-     * @returns {Function} Returns the new curried function.
-     * @example
-     *
-     * var abc = function(a, b, c) {
-     *   return [a, b, c];
-     * };
-     *
-     * var curried = _.curry(abc);
-     *
-     * curried(1)(2)(3);
-     * // => [1, 2, 3]
-     *
-     * curried(1, 2)(3);
-     * // => [1, 2, 3]
-     *
-     * curried(1, 2, 3);
-     * // => [1, 2, 3]
+     * Creates a function that performs a relational operation on two values.
      *
-     * // Curried with placeholders.
-     * curried(1)(_, 3)(2);
-     * // => [1, 2, 3]
+     * @private
+     * @param {Function} operator The function to perform the operation.
+     * @returns {Function} Returns the new relational operation function.
      */
-    function curry(func, arity, guard) {
-      arity = guard ? undefined : arity;
-      var result = createWrapper(func, CURRY_FLAG, undefined, undefined, undefined, undefined, undefined, arity);
-      result.placeholder = curry.placeholder;
-      return result;
+    function createRelationalOperation(operator) {
+      return function(value, other) {
+        if (!(typeof value == 'string' && typeof other == 'string')) {
+          value = toNumber(value);
+          other = toNumber(other);
+        }
+        return operator(value, other);
+      };
     }
 
     /**
-     * This method is like `_.curry` except that arguments are applied to `func`
-     * in the manner of `_.partialRight` instead of `_.partial`.
-     *
-     * The `_.curryRight.placeholder` value, which defaults to `_` in monolithic
-     * builds, may be used as a placeholder for provided arguments.
-     *
-     * **Note:** This method doesn't set the "length" property of curried functions.
-     *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Function
-     * @param {Function} func The function to curry.
-     * @param {number} [arity=func.length] The arity of `func`.
-     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
-     * @returns {Function} Returns the new curried function.
-     * @example
-     *
-     * var abc = function(a, b, c) {
-     *   return [a, b, c];
-     * };
-     *
-     * var curried = _.curryRight(abc);
-     *
-     * curried(3)(2)(1);
-     * // => [1, 2, 3]
-     *
-     * curried(2, 3)(1);
-     * // => [1, 2, 3]
-     *
-     * curried(1, 2, 3);
-     * // => [1, 2, 3]
+     * Creates a function that wraps `func` to continue currying.
      *
-     * // Curried with placeholders.
-     * curried(3)(1, _)(2);
-     * // => [1, 2, 3]
+     * @private
+     * @param {Function} func The function to wrap.
+     * @param {number} bitmask The bitmask flags. See `createWrap` for more details.
+     * @param {Function} wrapFunc The function to create the `func` wrapper.
+     * @param {*} placeholder The placeholder value.
+     * @param {*} [thisArg] The `this` binding of `func`.
+     * @param {Array} [partials] The arguments to prepend to those provided to
+     *  the new function.
+     * @param {Array} [holders] The `partials` placeholder indexes.
+     * @param {Array} [argPos] The argument positions of the new function.
+     * @param {number} [ary] The arity cap of `func`.
+     * @param {number} [arity] The arity of `func`.
+     * @returns {Function} Returns the new wrapped function.
      */
-    function curryRight(func, arity, guard) {
-      arity = guard ? undefined : arity;
-      var result = createWrapper(func, CURRY_RIGHT_FLAG, undefined, undefined, undefined, undefined, undefined, arity);
-      result.placeholder = curryRight.placeholder;
-      return result;
+    function createRecurry(func, bitmask, wrapFunc, placeholder, thisArg, partials, holders, argPos, ary, arity) {
+      var isCurry = bitmask & WRAP_CURRY_FLAG,
+          newHolders = isCurry ? holders : undefined,
+          newHoldersRight = isCurry ? undefined : holders,
+          newPartials = isCurry ? partials : undefined,
+          newPartialsRight = isCurry ? undefined : partials;
+
+      bitmask |= (isCurry ? WRAP_PARTIAL_FLAG : WRAP_PARTIAL_RIGHT_FLAG);
+      bitmask &= ~(isCurry ? WRAP_PARTIAL_RIGHT_FLAG : WRAP_PARTIAL_FLAG);
+
+      if (!(bitmask & WRAP_CURRY_BOUND_FLAG)) {
+        bitmask &= ~(WRAP_BIND_FLAG | WRAP_BIND_KEY_FLAG);
+      }
+      var newData = [
+        func, bitmask, thisArg, newPartials, newHolders, newPartialsRight,
+        newHoldersRight, argPos, ary, arity
+      ];
+
+      var result = wrapFunc.apply(undefined, newData);
+      if (isLaziable(func)) {
+        setData(result, newData);
+      }
+      result.placeholder = placeholder;
+      return setWrapToString(result, func, bitmask);
     }
 
     /**
-     * Creates a debounced function that delays invoking `func` until after `wait`
-     * milliseconds have elapsed since the last time the debounced function was
-     * invoked. The debounced function comes with a `cancel` method to cancel
-     * delayed `func` invocations and a `flush` method to immediately invoke them.
-     * Provide an options object to indicate whether `func` should be invoked on
-     * the leading and/or trailing edge of the `wait` timeout. The `func` is invoked
-     * with the last arguments provided to the debounced function. Subsequent calls
-     * to the debounced function return the result of the last `func` invocation.
-     *
-     * **Note:** If `leading` and `trailing` options are `true`, `func` is invoked
-     * on the trailing edge of the timeout only if the debounced function is
-     * invoked more than once during the `wait` timeout.
-     *
-     * See [David Corbacho's article](https://css-tricks.com/debouncing-throttling-explained-examples/)
-     * for details over the differences between `_.debounce` and `_.throttle`.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Function
-     * @param {Function} func The function to debounce.
-     * @param {number} [wait=0] The number of milliseconds to delay.
-     * @param {Object} [options={}] The options object.
-     * @param {boolean} [options.leading=false]
-     *  Specify invoking on the leading edge of the timeout.
-     * @param {number} [options.maxWait]
-     *  The maximum time `func` is allowed to be delayed before it's invoked.
-     * @param {boolean} [options.trailing=true]
-     *  Specify invoking on the trailing edge of the timeout.
-     * @returns {Function} Returns the new debounced function.
-     * @example
-     *
-     * // Avoid costly calculations while the window size is in flux.
-     * jQuery(window).on('resize', _.debounce(calculateLayout, 150));
+     * Creates a function like `_.round`.
      *
-     * // Invoke `sendMail` when clicked, debouncing subsequent calls.
-     * jQuery(element).on('click', _.debounce(sendMail, 300, {
-     *   'leading': true,
-     *   'trailing': false
-     * }));
+     * @private
+     * @param {string} methodName The name of the `Math` method to use when rounding.
+     * @returns {Function} Returns the new round function.
+     */
+    function createRound(methodName) {
+      var func = Math[methodName];
+      return function(number, precision) {
+        number = toNumber(number);
+        precision = precision == null ? 0 : nativeMin(toInteger(precision), 292);
+        if (precision) {
+          // Shift with exponential notation to avoid floating-point issues.
+          // See [MDN](https://mdn.io/round#Examples) for more details.
+          var pair = (toString(number) + 'e').split('e'),
+              value = func(pair[0] + 'e' + (+pair[1] + precision));
+
+          pair = (toString(value) + 'e').split('e');
+          return +(pair[0] + 'e' + (+pair[1] - precision));
+        }
+        return func(number);
+      };
+    }
+
+    /**
+     * Creates a set object of `values`.
      *
-     * // Ensure `batchLog` is invoked once after 1 second of debounced calls.
-     * var debounced = _.debounce(batchLog, 250, { 'maxWait': 1000 });
-     * var source = new EventSource('/stream');
-     * jQuery(source).on('message', debounced);
+     * @private
+     * @param {Array} values The values to add to the set.
+     * @returns {Object} Returns the new set.
+     */
+    var createSet = !(Set && (1 / setToArray(new Set([,-0]))[1]) == INFINITY) ? noop : function(values) {
+      return new Set(values);
+    };
+
+    /**
+     * Creates a `_.toPairs` or `_.toPairsIn` function.
      *
-     * // Cancel the trailing debounced invocation.
-     * jQuery(window).on('popstate', debounced.cancel);
+     * @private
+     * @param {Function} keysFunc The function to get the keys of a given object.
+     * @returns {Function} Returns the new pairs function.
      */
-    function debounce(func, wait, options) {
-      var lastArgs,
-          lastThis,
-          maxWait,
-          result,
-          timerId,
-          lastCallTime,
-          lastInvokeTime = 0,
-          leading = false,
-          maxing = false,
-          trailing = true;
+    function createToPairs(keysFunc) {
+      return function(object) {
+        var tag = getTag(object);
+        if (tag == mapTag) {
+          return mapToArray(object);
+        }
+        if (tag == setTag) {
+          return setToPairs(object);
+        }
+        return baseToPairs(object, keysFunc(object));
+      };
+    }
 
-      if (typeof func != 'function') {
+    /**
+     * Creates a function that either curries or invokes `func` with optional
+     * `this` binding and partially applied arguments.
+     *
+     * @private
+     * @param {Function|string} func The function or method name to wrap.
+     * @param {number} bitmask The bitmask flags.
+     *    1 - `_.bind`
+     *    2 - `_.bindKey`
+     *    4 - `_.curry` or `_.curryRight` of a bound function
+     *    8 - `_.curry`
+     *   16 - `_.curryRight`
+     *   32 - `_.partial`
+     *   64 - `_.partialRight`
+     *  128 - `_.rearg`
+     *  256 - `_.ary`
+     *  512 - `_.flip`
+     * @param {*} [thisArg] The `this` binding of `func`.
+     * @param {Array} [partials] The arguments to be partially applied.
+     * @param {Array} [holders] The `partials` placeholder indexes.
+     * @param {Array} [argPos] The argument positions of the new function.
+     * @param {number} [ary] The arity cap of `func`.
+     * @param {number} [arity] The arity of `func`.
+     * @returns {Function} Returns the new wrapped function.
+     */
+    function createWrap(func, bitmask, thisArg, partials, holders, argPos, ary, arity) {
+      var isBindKey = bitmask & WRAP_BIND_KEY_FLAG;
+      if (!isBindKey && typeof func != 'function') {
         throw new TypeError(FUNC_ERROR_TEXT);
       }
-      wait = toNumber(wait) || 0;
-      if (isObject(options)) {
-        leading = !!options.leading;
-        maxing = 'maxWait' in options;
-        maxWait = maxing ? nativeMax(toNumber(options.maxWait) || 0, wait) : maxWait;
-        trailing = 'trailing' in options ? !!options.trailing : trailing;
+      var length = partials ? partials.length : 0;
+      if (!length) {
+        bitmask &= ~(WRAP_PARTIAL_FLAG | WRAP_PARTIAL_RIGHT_FLAG);
+        partials = holders = undefined;
       }
+      ary = ary === undefined ? ary : nativeMax(toInteger(ary), 0);
+      arity = arity === undefined ? arity : toInteger(arity);
+      length -= holders ? holders.length : 0;
 
-      function invokeFunc(time) {
-        var args = lastArgs,
-            thisArg = lastThis;
-
-        lastArgs = lastThis = undefined;
-        lastInvokeTime = time;
-        result = func.apply(thisArg, args);
-        return result;
-      }
+      if (bitmask & WRAP_PARTIAL_RIGHT_FLAG) {
+        var partialsRight = partials,
+            holdersRight = holders;
 
-      function leadingEdge(time) {
-        // Reset any `maxWait` timer.
-        lastInvokeTime = time;
-        // Start the timer for the trailing edge.
-        timerId = setTimeout(timerExpired, wait);
-        // Invoke the leading edge.
-        return leading ? invokeFunc(time) : result;
+        partials = holders = undefined;
       }
+      var data = isBindKey ? undefined : getData(func);
 
-      function remainingWait(time) {
-        var timeSinceLastCall = time - lastCallTime,
-            timeSinceLastInvoke = time - lastInvokeTime,
-            result = wait - timeSinceLastCall;
+      var newData = [
+        func, bitmask, thisArg, partials, holders, partialsRight, holdersRight,
+        argPos, ary, arity
+      ];
 
-        return maxing ? nativeMin(result, maxWait - timeSinceLastInvoke) : result;
+      if (data) {
+        mergeData(newData, data);
       }
+      func = newData[0];
+      bitmask = newData[1];
+      thisArg = newData[2];
+      partials = newData[3];
+      holders = newData[4];
+      arity = newData[9] = newData[9] === undefined
+        ? (isBindKey ? 0 : func.length)
+        : nativeMax(newData[9] - length, 0);
 
-      function shouldInvoke(time) {
-        var timeSinceLastCall = time - lastCallTime,
-            timeSinceLastInvoke = time - lastInvokeTime;
+      if (!arity && bitmask & (WRAP_CURRY_FLAG | WRAP_CURRY_RIGHT_FLAG)) {
+        bitmask &= ~(WRAP_CURRY_FLAG | WRAP_CURRY_RIGHT_FLAG);
+      }
+      if (!bitmask || bitmask == WRAP_BIND_FLAG) {
+        var result = createBind(func, bitmask, thisArg);
+      } else if (bitmask == WRAP_CURRY_FLAG || bitmask == WRAP_CURRY_RIGHT_FLAG) {
+        result = createCurry(func, bitmask, arity);
+      } else if ((bitmask == WRAP_PARTIAL_FLAG || bitmask == (WRAP_BIND_FLAG | WRAP_PARTIAL_FLAG)) && !holders.length) {
+        result = createPartial(func, bitmask, thisArg, partials);
+      } else {
+        result = createHybrid.apply(undefined, newData);
+      }
+      var setter = data ? baseSetData : setData;
+      return setWrapToString(setter(result, newData), func, bitmask);
+    }
 
-        // Either this is the first call, activity has stopped and we're at the
-        // trailing edge, the system time has gone backwards and we're treating
-        // it as the trailing edge, or we've hit the `maxWait` limit.
-        return (lastCallTime === undefined || (timeSinceLastCall >= wait) ||
-          (timeSinceLastCall < 0) || (maxing && timeSinceLastInvoke >= maxWait));
+    /**
+     * Used by `_.defaults` to customize its `_.assignIn` use to assign properties
+     * of source objects to the destination object for all destination properties
+     * that resolve to `undefined`.
+     *
+     * @private
+     * @param {*} objValue The destination value.
+     * @param {*} srcValue The source value.
+     * @param {string} key The key of the property to assign.
+     * @param {Object} object The parent object of `objValue`.
+     * @returns {*} Returns the value to assign.
+     */
+    function customDefaultsAssignIn(objValue, srcValue, key, object) {
+      if (objValue === undefined ||
+          (eq(objValue, objectProto[key]) && !hasOwnProperty.call(object, key))) {
+        return srcValue;
       }
+      return objValue;
+    }
 
-      function timerExpired() {
-        var time = now();
-        if (shouldInvoke(time)) {
-          return trailingEdge(time);
-        }
-        // Restart the timer.
-        timerId = setTimeout(timerExpired, remainingWait(time));
+    /**
+     * Used by `_.defaultsDeep` to customize its `_.merge` use to merge source
+     * objects into destination objects that are passed thru.
+     *
+     * @private
+     * @param {*} objValue The destination value.
+     * @param {*} srcValue The source value.
+     * @param {string} key The key of the property to merge.
+     * @param {Object} object The parent object of `objValue`.
+     * @param {Object} source The parent object of `srcValue`.
+     * @param {Object} [stack] Tracks traversed source values and their merged
+     *  counterparts.
+     * @returns {*} Returns the value to assign.
+     */
+    function customDefaultsMerge(objValue, srcValue, key, object, source, stack) {
+      if (isObject(objValue) && isObject(srcValue)) {
+        // Recursively merge objects and arrays (susceptible to call stack limits).
+        stack.set(srcValue, objValue);
+        baseMerge(objValue, srcValue, undefined, customDefaultsMerge, stack);
+        stack['delete'](srcValue);
       }
+      return objValue;
+    }
 
-      function trailingEdge(time) {
-        timerId = undefined;
+    /**
+     * Used by `_.omit` to customize its `_.cloneDeep` use to only clone plain
+     * objects.
+     *
+     * @private
+     * @param {*} value The value to inspect.
+     * @param {string} key The key of the property to inspect.
+     * @returns {*} Returns the uncloned value or `undefined` to defer cloning to `_.cloneDeep`.
+     */
+    function customOmitClone(value) {
+      return isPlainObject(value) ? undefined : value;
+    }
 
-        // Only invoke if we have `lastArgs` which means `func` has been
-        // debounced at least once.
-        if (trailing && lastArgs) {
-          return invokeFunc(time);
-        }
-        lastArgs = lastThis = undefined;
-        return result;
-      }
+    /**
+     * A specialized version of `baseIsEqualDeep` for arrays with support for
+     * partial deep comparisons.
+     *
+     * @private
+     * @param {Array} array The array to compare.
+     * @param {Array} other The other array to compare.
+     * @param {number} bitmask The bitmask flags. See `baseIsEqual` for more details.
+     * @param {Function} customizer The function to customize comparisons.
+     * @param {Function} equalFunc The function to determine equivalents of values.
+     * @param {Object} stack Tracks traversed `array` and `other` objects.
+     * @returns {boolean} Returns `true` if the arrays are equivalent, else `false`.
+     */
+    function equalArrays(array, other, bitmask, customizer, equalFunc, stack) {
+      var isPartial = bitmask & COMPARE_PARTIAL_FLAG,
+          arrLength = array.length,
+          othLength = other.length;
 
-      function cancel() {
-        lastInvokeTime = 0;
-        lastArgs = lastCallTime = lastThis = timerId = undefined;
+      if (arrLength != othLength && !(isPartial && othLength > arrLength)) {
+        return false;
       }
-
-      function flush() {
-        return timerId === undefined ? result : trailingEdge(now());
+      // Assume cyclic values are equal.
+      var stacked = stack.get(array);
+      if (stacked && stack.get(other)) {
+        return stacked == other;
       }
+      var index = -1,
+          result = true,
+          seen = (bitmask & COMPARE_UNORDERED_FLAG) ? new SetCache : undefined;
 
-      function debounced() {
-        var time = now(),
-            isInvoking = shouldInvoke(time);
+      stack.set(array, other);
+      stack.set(other, array);
 
-        lastArgs = arguments;
-        lastThis = this;
-        lastCallTime = time;
+      // Ignore non-index properties.
+      while (++index < arrLength) {
+        var arrValue = array[index],
+            othValue = other[index];
 
-        if (isInvoking) {
-          if (timerId === undefined) {
-            return leadingEdge(lastCallTime);
-          }
-          if (maxing) {
-            // Handle invocations in a tight loop.
-            timerId = setTimeout(timerExpired, wait);
-            return invokeFunc(lastCallTime);
+        if (customizer) {
+          var compared = isPartial
+            ? customizer(othValue, arrValue, index, other, array, stack)
+            : customizer(arrValue, othValue, index, array, other, stack);
+        }
+        if (compared !== undefined) {
+          if (compared) {
+            continue;
           }
+          result = false;
+          break;
         }
-        if (timerId === undefined) {
-          timerId = setTimeout(timerExpired, wait);
+        // Recursively compare arrays (susceptible to call stack limits).
+        if (seen) {
+          if (!arraySome(other, function(othValue, othIndex) {
+                if (!cacheHas(seen, othIndex) &&
+                    (arrValue === othValue || equalFunc(arrValue, othValue, bitmask, customizer, stack))) {
+                  return seen.push(othIndex);
+                }
+              })) {
+            result = false;
+            break;
+          }
+        } else if (!(
+              arrValue === othValue ||
+                equalFunc(arrValue, othValue, bitmask, customizer, stack)
+            )) {
+          result = false;
+          break;
         }
-        return result;
       }
-      debounced.cancel = cancel;
-      debounced.flush = flush;
-      return debounced;
+      stack['delete'](array);
+      stack['delete'](other);
+      return result;
     }
 
     /**
-     * Defers invoking the `func` until the current call stack has cleared. Any
-     * additional arguments are provided to `func` when it's invoked.
+     * A specialized version of `baseIsEqualDeep` for comparing objects of
+     * the same `toStringTag`.
      *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Function
-     * @param {Function} func The function to defer.
-     * @param {...*} [args] The arguments to invoke `func` with.
-     * @returns {number} Returns the timer id.
-     * @example
+     * **Note:** This function only supports comparing values with tags of
+     * `Boolean`, `Date`, `Error`, `Number`, `RegExp`, or `String`.
      *
-     * _.defer(function(text) {
-     *   console.log(text);
-     * }, 'deferred');
-     * // => Logs 'deferred' after one or more milliseconds.
+     * @private
+     * @param {Object} object The object to compare.
+     * @param {Object} other The other object to compare.
+     * @param {string} tag The `toStringTag` of the objects to compare.
+     * @param {number} bitmask The bitmask flags. See `baseIsEqual` for more details.
+     * @param {Function} customizer The function to customize comparisons.
+     * @param {Function} equalFunc The function to determine equivalents of values.
+     * @param {Object} stack Tracks traversed `object` and `other` objects.
+     * @returns {boolean} Returns `true` if the objects are equivalent, else `false`.
      */
-    var defer = rest(function(func, args) {
-      return baseDelay(func, 1, args);
-    });
+    function equalByTag(object, other, tag, bitmask, customizer, equalFunc, stack) {
+      switch (tag) {
+        case dataViewTag:
+          if ((object.byteLength != other.byteLength) ||
+              (object.byteOffset != other.byteOffset)) {
+            return false;
+          }
+          object = object.buffer;
+          other = other.buffer;
+
+        case arrayBufferTag:
+          if ((object.byteLength != other.byteLength) ||
+              !equalFunc(new Uint8Array(object), new Uint8Array(other))) {
+            return false;
+          }
+          return true;
+
+        case boolTag:
+        case dateTag:
+        case numberTag:
+          // Coerce booleans to `1` or `0` and dates to milliseconds.
+          // Invalid dates are coerced to `NaN`.
+          return eq(+object, +other);
+
+        case errorTag:
+          return object.name == other.name && object.message == other.message;
+
+        case regexpTag:
+        case stringTag:
+          // Coerce regexes to strings and treat strings, primitives and objects,
+          // as equal. See http://www.ecma-international.org/ecma-262/7.0/#sec-regexp.prototype.tostring
+          // for more details.
+          return object == (other + '');
+
+        case mapTag:
+          var convert = mapToArray;
+
+        case setTag:
+          var isPartial = bitmask & COMPARE_PARTIAL_FLAG;
+          convert || (convert = setToArray);
+
+          if (object.size != other.size && !isPartial) {
+            return false;
+          }
+          // Assume cyclic values are equal.
+          var stacked = stack.get(object);
+          if (stacked) {
+            return stacked == other;
+          }
+          bitmask |= COMPARE_UNORDERED_FLAG;
+
+          // Recursively compare objects (susceptible to call stack limits).
+          stack.set(object, other);
+          var result = equalArrays(convert(object), convert(other), bitmask, customizer, equalFunc, stack);
+          stack['delete'](object);
+          return result;
+
+        case symbolTag:
+          if (symbolValueOf) {
+            return symbolValueOf.call(object) == symbolValueOf.call(other);
+          }
+      }
+      return false;
+    }
 
     /**
-     * Invokes `func` after `wait` milliseconds. Any additional arguments are
-     * provided to `func` when it's invoked.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Function
-     * @param {Function} func The function to delay.
-     * @param {number} wait The number of milliseconds to delay invocation.
-     * @param {...*} [args] The arguments to invoke `func` with.
-     * @returns {number} Returns the timer id.
-     * @example
+     * A specialized version of `baseIsEqualDeep` for objects with support for
+     * partial deep comparisons.
      *
-     * _.delay(function(text) {
-     *   console.log(text);
-     * }, 1000, 'later');
-     * // => Logs 'later' after one second.
+     * @private
+     * @param {Object} object The object to compare.
+     * @param {Object} other The other object to compare.
+     * @param {number} bitmask The bitmask flags. See `baseIsEqual` for more details.
+     * @param {Function} customizer The function to customize comparisons.
+     * @param {Function} equalFunc The function to determine equivalents of values.
+     * @param {Object} stack Tracks traversed `object` and `other` objects.
+     * @returns {boolean} Returns `true` if the objects are equivalent, else `false`.
      */
-    var delay = rest(function(func, wait, args) {
-      return baseDelay(func, toNumber(wait) || 0, args);
-    });
+    function equalObjects(object, other, bitmask, customizer, equalFunc, stack) {
+      var isPartial = bitmask & COMPARE_PARTIAL_FLAG,
+          objProps = getAllKeys(object),
+          objLength = objProps.length,
+          othProps = getAllKeys(other),
+          othLength = othProps.length;
+
+      if (objLength != othLength && !isPartial) {
+        return false;
+      }
+      var index = objLength;
+      while (index--) {
+        var key = objProps[index];
+        if (!(isPartial ? key in other : hasOwnProperty.call(other, key))) {
+          return false;
+        }
+      }
+      // Assume cyclic values are equal.
+      var stacked = stack.get(object);
+      if (stacked && stack.get(other)) {
+        return stacked == other;
+      }
+      var result = true;
+      stack.set(object, other);
+      stack.set(other, object);
+
+      var skipCtor = isPartial;
+      while (++index < objLength) {
+        key = objProps[index];
+        var objValue = object[key],
+            othValue = other[key];
+
+        if (customizer) {
+          var compared = isPartial
+            ? customizer(othValue, objValue, key, other, object, stack)
+            : customizer(objValue, othValue, key, object, other, stack);
+        }
+        // Recursively compare objects (susceptible to call stack limits).
+        if (!(compared === undefined
+              ? (objValue === othValue || equalFunc(objValue, othValue, bitmask, customizer, stack))
+              : compared
+            )) {
+          result = false;
+          break;
+        }
+        skipCtor || (skipCtor = key == 'constructor');
+      }
+      if (result && !skipCtor) {
+        var objCtor = object.constructor,
+            othCtor = other.constructor;
+
+        // Non `Object` object instances with different constructors are not equal.
+        if (objCtor != othCtor &&
+            ('constructor' in object && 'constructor' in other) &&
+            !(typeof objCtor == 'function' && objCtor instanceof objCtor &&
+              typeof othCtor == 'function' && othCtor instanceof othCtor)) {
+          result = false;
+        }
+      }
+      stack['delete'](object);
+      stack['delete'](other);
+      return result;
+    }
 
     /**
-     * Creates a function that invokes `func` with arguments reversed.
+     * A specialized version of `baseRest` which flattens the rest array.
      *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Function
-     * @param {Function} func The function to flip arguments for.
-     * @returns {Function} Returns the new flipped function.
-     * @example
-     *
-     * var flipped = _.flip(function() {
-     *   return _.toArray(arguments);
-     * });
+     * @private
+     * @param {Function} func The function to apply a rest parameter to.
+     * @returns {Function} Returns the new function.
+     */
+    function flatRest(func) {
+      return setToString(overRest(func, undefined, flatten), func + '');
+    }
+
+    /**
+     * Creates an array of own enumerable property names and symbols of `object`.
      *
-     * flipped('a', 'b', 'c', 'd');
-     * // => ['d', 'c', 'b', 'a']
+     * @private
+     * @param {Object} object The object to query.
+     * @returns {Array} Returns the array of property names and symbols.
      */
-    function flip(func) {
-      return createWrapper(func, FLIP_FLAG);
+    function getAllKeys(object) {
+      return baseGetAllKeys(object, keys, getSymbols);
     }
 
     /**
-     * Creates a function that memoizes the result of `func`. If `resolver` is
-     * provided, it determines the cache key for storing the result based on the
-     * arguments provided to the memoized function. By default, the first argument
-     * provided to the memoized function is used as the map cache key. The `func`
-     * is invoked with the `this` binding of the memoized function.
+     * Creates an array of own and inherited enumerable property names and
+     * symbols of `object`.
      *
-     * **Note:** The cache is exposed as the `cache` property on the memoized
-     * function. Its creation may be customized by replacing the `_.memoize.Cache`
-     * constructor with one whose instances implement the
-     * [`Map`](http://ecma-international.org/ecma-262/6.0/#sec-properties-of-the-map-prototype-object)
-     * method interface of `delete`, `get`, `has`, and `set`.
+     * @private
+     * @param {Object} object The object to query.
+     * @returns {Array} Returns the array of property names and symbols.
+     */
+    function getAllKeysIn(object) {
+      return baseGetAllKeys(object, keysIn, getSymbolsIn);
+    }
+
+    /**
+     * Gets metadata for `func`.
      *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Function
-     * @param {Function} func The function to have its output memoized.
-     * @param {Function} [resolver] The function to resolve the cache key.
-     * @returns {Function} Returns the new memoized function.
-     * @example
-     *
-     * var object = { 'a': 1, 'b': 2 };
-     * var other = { 'c': 3, 'd': 4 };
-     *
-     * var values = _.memoize(_.values);
-     * values(object);
-     * // => [1, 2]
-     *
-     * values(other);
-     * // => [3, 4]
-     *
-     * object.a = 2;
-     * values(object);
-     * // => [1, 2]
-     *
-     * // Modify the result cache.
-     * values.cache.set(object, ['a', 'b']);
-     * values(object);
-     * // => ['a', 'b']
+     * @private
+     * @param {Function} func The function to query.
+     * @returns {*} Returns the metadata for `func`.
+     */
+    var getData = !metaMap ? noop : function(func) {
+      return metaMap.get(func);
+    };
+
+    /**
+     * Gets the name of `func`.
      *
-     * // Replace `_.memoize.Cache`.
-     * _.memoize.Cache = WeakMap;
+     * @private
+     * @param {Function} func The function to query.
+     * @returns {string} Returns the function name.
      */
-    function memoize(func, resolver) {
-      if (typeof func != 'function' || (resolver && typeof resolver != 'function')) {
-        throw new TypeError(FUNC_ERROR_TEXT);
-      }
-      var memoized = function() {
-        var args = arguments,
-            key = resolver ? resolver.apply(this, args) : args[0],
-            cache = memoized.cache;
+    function getFuncName(func) {
+      var result = (func.name + ''),
+          array = realNames[result],
+          length = hasOwnProperty.call(realNames, result) ? array.length : 0;
 
-        if (cache.has(key)) {
-          return cache.get(key);
+      while (length--) {
+        var data = array[length],
+            otherFunc = data.func;
+        if (otherFunc == null || otherFunc == func) {
+          return data.name;
         }
-        var result = func.apply(this, args);
-        memoized.cache = cache.set(key, result);
-        return result;
-      };
-      memoized.cache = new (memoize.Cache || MapCache);
-      return memoized;
+      }
+      return result;
     }
 
-    // Assign cache to `_.memoize`.
-    memoize.Cache = MapCache;
+    /**
+     * Gets the argument placeholder value for `func`.
+     *
+     * @private
+     * @param {Function} func The function to inspect.
+     * @returns {*} Returns the placeholder value.
+     */
+    function getHolder(func) {
+      var object = hasOwnProperty.call(lodash, 'placeholder') ? lodash : func;
+      return object.placeholder;
+    }
 
     /**
-     * Creates a function that negates the result of the predicate `func`. The
-     * `func` predicate is invoked with the `this` binding and arguments of the
-     * created function.
+     * Gets the appropriate "iteratee" function. If `_.iteratee` is customized,
+     * this function returns the custom method, otherwise it returns `baseIteratee`.
+     * If arguments are provided, the chosen function is invoked with them and
+     * its result is returned.
      *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Function
-     * @param {Function} predicate The predicate to negate.
-     * @returns {Function} Returns the new negated function.
-     * @example
+     * @private
+     * @param {*} [value] The value to convert to an iteratee.
+     * @param {number} [arity] The arity of the created iteratee.
+     * @returns {Function} Returns the chosen function or its result.
+     */
+    function getIteratee() {
+      var result = lodash.iteratee || iteratee;
+      result = result === iteratee ? baseIteratee : result;
+      return arguments.length ? result(arguments[0], arguments[1]) : result;
+    }
+
+    /**
+     * Gets the data for `map`.
      *
-     * function isEven(n) {
-     *   return n % 2 == 0;
-     * }
+     * @private
+     * @param {Object} map The map to query.
+     * @param {string} key The reference key.
+     * @returns {*} Returns the map data.
+     */
+    function getMapData(map, key) {
+      var data = map.__data__;
+      return isKeyable(key)
+        ? data[typeof key == 'string' ? 'string' : 'hash']
+        : data.map;
+    }
+
+    /**
+     * Gets the property names, values, and compare flags of `object`.
      *
-     * _.filter([1, 2, 3, 4, 5, 6], _.negate(isEven));
-     * // => [1, 3, 5]
+     * @private
+     * @param {Object} object The object to query.
+     * @returns {Array} Returns the match data of `object`.
      */
-    function negate(predicate) {
-      if (typeof predicate != 'function') {
-        throw new TypeError(FUNC_ERROR_TEXT);
+    function getMatchData(object) {
+      var result = keys(object),
+          length = result.length;
+
+      while (length--) {
+        var key = result[length],
+            value = object[key];
+
+        result[length] = [key, value, isStrictComparable(value)];
       }
-      return function() {
-        return !predicate.apply(this, arguments);
-      };
+      return result;
     }
 
     /**
-     * Creates a function that is restricted to invoking `func` once. Repeat calls
-     * to the function return the value of the first invocation. The `func` is
-     * invoked with the `this` binding and arguments of the created function.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Function
-     * @param {Function} func The function to restrict.
-     * @returns {Function} Returns the new restricted function.
-     * @example
+     * Gets the native function at `key` of `object`.
      *
-     * var initialize = _.once(createApplication);
-     * initialize();
-     * initialize();
-     * // `initialize` invokes `createApplication` once
+     * @private
+     * @param {Object} object The object to query.
+     * @param {string} key The key of the method to get.
+     * @returns {*} Returns the function if it's native, else `undefined`.
      */
-    function once(func) {
-      return before(2, func);
+    function getNative(object, key) {
+      var value = getValue(object, key);
+      return baseIsNative(value) ? value : undefined;
     }
 
     /**
-     * Creates a function that invokes `func` with arguments transformed by
-     * corresponding `transforms`.
-     *
-     * @static
-     * @since 4.0.0
-     * @memberOf _
-     * @category Function
-     * @param {Function} func The function to wrap.
-     * @param {...(Array|Array[]|Function|Function[]|Object|Object[]|string|string[])}
-     *  [transforms[_.identity]] The functions to transform.
-     * @returns {Function} Returns the new function.
-     * @example
-     *
-     * function doubled(n) {
-     *   return n * 2;
-     * }
-     *
-     * function square(n) {
-     *   return n * n;
-     * }
-     *
-     * var func = _.overArgs(function(x, y) {
-     *   return [x, y];
-     * }, [square, doubled]);
-     *
-     * func(9, 3);
-     * // => [81, 6]
+     * A specialized version of `baseGetTag` which ignores `Symbol.toStringTag` values.
      *
-     * func(10, 5);
-     * // => [100, 10]
+     * @private
+     * @param {*} value The value to query.
+     * @returns {string} Returns the raw `toStringTag`.
      */
-    var overArgs = rest(function(func, transforms) {
-      transforms = (transforms.length == 1 && isArray(transforms[0]))
-        ? arrayMap(transforms[0], baseUnary(getIteratee()))
-        : arrayMap(baseFlatten(transforms, 1, isFlattenableIteratee), baseUnary(getIteratee()));
+    function getRawTag(value) {
+      var isOwn = hasOwnProperty.call(value, symToStringTag),
+          tag = value[symToStringTag];
 
-      var funcsLength = transforms.length;
-      return rest(function(args) {
-        var index = -1,
-            length = nativeMin(args.length, funcsLength);
+      try {
+        value[symToStringTag] = undefined;
+        var unmasked = true;
+      } catch (e) {}
 
-        while (++index < length) {
-          args[index] = transforms[index].call(this, args[index]);
+      var result = nativeObjectToString.call(value);
+      if (unmasked) {
+        if (isOwn) {
+          value[symToStringTag] = tag;
+        } else {
+          delete value[symToStringTag];
         }
-        return apply(func, this, args);
-      });
-    });
+      }
+      return result;
+    }
 
     /**
-     * Creates a function that invokes `func` with `partials` prepended to the
-     * arguments it receives. This method is like `_.bind` except it does **not**
-     * alter the `this` binding.
-     *
-     * The `_.partial.placeholder` value, which defaults to `_` in monolithic
-     * builds, may be used as a placeholder for partially applied arguments.
-     *
-     * **Note:** This method doesn't set the "length" property of partially
-     * applied functions.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.2.0
-     * @category Function
-     * @param {Function} func The function to partially apply arguments to.
-     * @param {...*} [partials] The arguments to be partially applied.
-     * @returns {Function} Returns the new partially applied function.
-     * @example
-     *
-     * var greet = function(greeting, name) {
-     *   return greeting + ' ' + name;
-     * };
-     *
-     * var sayHelloTo = _.partial(greet, 'hello');
-     * sayHelloTo('fred');
-     * // => 'hello fred'
+     * Creates an array of the own enumerable symbols of `object`.
      *
-     * // Partially applied with placeholders.
-     * var greetFred = _.partial(greet, _, 'fred');
-     * greetFred('hi');
-     * // => 'hi fred'
+     * @private
+     * @param {Object} object The object to query.
+     * @returns {Array} Returns the array of symbols.
      */
-    var partial = rest(function(func, partials) {
-      var holders = replaceHolders(partials, getHolder(partial));
-      return createWrapper(func, PARTIAL_FLAG, undefined, partials, holders);
-    });
+    var getSymbols = !nativeGetSymbols ? stubArray : function(object) {
+      if (object == null) {
+        return [];
+      }
+      object = Object(object);
+      return arrayFilter(nativeGetSymbols(object), function(symbol) {
+        return propertyIsEnumerable.call(object, symbol);
+      });
+    };
 
     /**
-     * This method is like `_.partial` except that partially applied arguments
-     * are appended to the arguments it receives.
-     *
-     * The `_.partialRight.placeholder` value, which defaults to `_` in monolithic
-     * builds, may be used as a placeholder for partially applied arguments.
+     * Creates an array of the own and inherited enumerable symbols of `object`.
      *
-     * **Note:** This method doesn't set the "length" property of partially
-     * applied functions.
-     *
-     * @static
-     * @memberOf _
-     * @since 1.0.0
-     * @category Function
-     * @param {Function} func The function to partially apply arguments to.
-     * @param {...*} [partials] The arguments to be partially applied.
-     * @returns {Function} Returns the new partially applied function.
-     * @example
-     *
-     * var greet = function(greeting, name) {
-     *   return greeting + ' ' + name;
-     * };
-     *
-     * var greetFred = _.partialRight(greet, 'fred');
-     * greetFred('hi');
-     * // => 'hi fred'
-     *
-     * // Partially applied with placeholders.
-     * var sayHelloTo = _.partialRight(greet, 'hello', _);
-     * sayHelloTo('fred');
-     * // => 'hello fred'
+     * @private
+     * @param {Object} object The object to query.
+     * @returns {Array} Returns the array of symbols.
      */
-    var partialRight = rest(function(func, partials) {
-      var holders = replaceHolders(partials, getHolder(partialRight));
-      return createWrapper(func, PARTIAL_RIGHT_FLAG, undefined, partials, holders);
-    });
+    var getSymbolsIn = !nativeGetSymbols ? stubArray : function(object) {
+      var result = [];
+      while (object) {
+        arrayPush(result, getSymbols(object));
+        object = getPrototype(object);
+      }
+      return result;
+    };
 
     /**
-     * Creates a function that invokes `func` with arguments arranged according
-     * to the specified `indexes` where the argument value at the first index is
-     * provided as the first argument, the argument value at the second index is
-     * provided as the second argument, and so on.
-     *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Function
-     * @param {Function} func The function to rearrange arguments for.
-     * @param {...(number|number[])} indexes The arranged argument indexes.
-     * @returns {Function} Returns the new function.
-     * @example
-     *
-     * var rearged = _.rearg(function(a, b, c) {
-     *   return [a, b, c];
-     * }, [2, 0, 1]);
+     * Gets the `toStringTag` of `value`.
      *
-     * rearged('b', 'c', 'a')
-     * // => ['a', 'b', 'c']
+     * @private
+     * @param {*} value The value to query.
+     * @returns {string} Returns the `toStringTag`.
      */
-    var rearg = rest(function(func, indexes) {
-      return createWrapper(func, REARG_FLAG, undefined, undefined, undefined, baseFlatten(indexes, 1));
-    });
+    var getTag = baseGetTag;
 
-    /**
-     * Creates a function that invokes `func` with the `this` binding of the
-     * created function and arguments from `start` and beyond provided as
-     * an array.
-     *
-     * **Note:** This method is based on the
-     * [rest parameter](https://mdn.io/rest_parameters).
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Function
-     * @param {Function} func The function to apply a rest parameter to.
-     * @param {number} [start=func.length-1] The start position of the rest parameter.
-     * @returns {Function} Returns the new function.
-     * @example
-     *
-     * var say = _.rest(function(what, names) {
-     *   return what + ' ' + _.initial(names).join(', ') +
-     *     (_.size(names) > 1 ? ', & ' : '') + _.last(names);
-     * });
-     *
-     * say('hello', 'fred', 'barney', 'pebbles');
-     * // => 'hello fred, barney, & pebbles'
-     */
-    function rest(func, start) {
-      if (typeof func != 'function') {
-        throw new TypeError(FUNC_ERROR_TEXT);
-      }
-      start = nativeMax(start === undefined ? (func.length - 1) : toInteger(start), 0);
-      return function() {
-        var args = arguments,
-            index = -1,
-            length = nativeMax(args.length - start, 0),
-            array = Array(length);
+    // Fallback for data views, maps, sets, and weak maps in IE 11 and promises in Node.js < 6.
+    if ((DataView && getTag(new DataView(new ArrayBuffer(1))) != dataViewTag) ||
+        (Map && getTag(new Map) != mapTag) ||
+        (Promise && getTag(Promise.resolve()) != promiseTag) ||
+        (Set && getTag(new Set) != setTag) ||
+        (WeakMap && getTag(new WeakMap) != weakMapTag)) {
+      getTag = function(value) {
+        var result = baseGetTag(value),
+            Ctor = result == objectTag ? value.constructor : undefined,
+            ctorString = Ctor ? toSource(Ctor) : '';
 
-        while (++index < length) {
-          array[index] = args[start + index];
-        }
-        switch (start) {
-          case 0: return func.call(this, array);
-          case 1: return func.call(this, args[0], array);
-          case 2: return func.call(this, args[0], args[1], array);
-        }
-        var otherArgs = Array(start + 1);
-        index = -1;
-        while (++index < start) {
-          otherArgs[index] = args[index];
+        if (ctorString) {
+          switch (ctorString) {
+            case dataViewCtorString: return dataViewTag;
+            case mapCtorString: return mapTag;
+            case promiseCtorString: return promiseTag;
+            case setCtorString: return setTag;
+            case weakMapCtorString: return weakMapTag;
+          }
         }
-        otherArgs[start] = array;
-        return apply(func, this, otherArgs);
+        return result;
       };
     }
 
     /**
-     * Creates a function that invokes `func` with the `this` binding of the
-     * create function and an array of arguments much like
-     * [`Function#apply`](http://www.ecma-international.org/ecma-262/6.0/#sec-function.prototype.apply).
-     *
-     * **Note:** This method is based on the
-     * [spread operator](https://mdn.io/spread_operator).
-     *
-     * @static
-     * @memberOf _
-     * @since 3.2.0
-     * @category Function
-     * @param {Function} func The function to spread arguments over.
-     * @param {number} [start=0] The start position of the spread.
-     * @returns {Function} Returns the new function.
-     * @example
-     *
-     * var say = _.spread(function(who, what) {
-     *   return who + ' says ' + what;
-     * });
-     *
-     * say(['fred', 'hello']);
-     * // => 'fred says hello'
-     *
-     * var numbers = Promise.all([
-     *   Promise.resolve(40),
-     *   Promise.resolve(36)
-     * ]);
+     * Gets the view, applying any `transforms` to the `start` and `end` positions.
      *
-     * numbers.then(_.spread(function(x, y) {
-     *   return x + y;
-     * }));
-     * // => a Promise of 76
+     * @private
+     * @param {number} start The start of the view.
+     * @param {number} end The end of the view.
+     * @param {Array} transforms The transformations to apply to the view.
+     * @returns {Object} Returns an object containing the `start` and `end`
+     *  positions of the view.
      */
-    function spread(func, start) {
-      if (typeof func != 'function') {
-        throw new TypeError(FUNC_ERROR_TEXT);
-      }
-      start = start === undefined ? 0 : nativeMax(toInteger(start), 0);
-      return rest(function(args) {
-        var array = args[start],
-            otherArgs = castSlice(args, 0, start);
+    function getView(start, end, transforms) {
+      var index = -1,
+          length = transforms.length;
 
-        if (array) {
-          arrayPush(otherArgs, array);
+      while (++index < length) {
+        var data = transforms[index],
+            size = data.size;
+
+        switch (data.type) {
+          case 'drop':      start += size; break;
+          case 'dropRight': end -= size; break;
+          case 'take':      end = nativeMin(end, start + size); break;
+          case 'takeRight': start = nativeMax(start, end - size); break;
         }
-        return apply(func, this, otherArgs);
-      });
+      }
+      return { 'start': start, 'end': end };
     }
 
     /**
-     * Creates a throttled function that only invokes `func` at most once per
-     * every `wait` milliseconds. The throttled function comes with a `cancel`
-     * method to cancel delayed `func` invocations and a `flush` method to
-     * immediately invoke them. Provide an options object to indicate whether
-     * `func` should be invoked on the leading and/or trailing edge of the `wait`
-     * timeout. The `func` is invoked with the last arguments provided to the
-     * throttled function. Subsequent calls to the throttled function return the
-     * result of the last `func` invocation.
-     *
-     * **Note:** If `leading` and `trailing` options are `true`, `func` is
-     * invoked on the trailing edge of the timeout only if the throttled function
-     * is invoked more than once during the `wait` timeout.
-     *
-     * See [David Corbacho's article](https://css-tricks.com/debouncing-throttling-explained-examples/)
-     * for details over the differences between `_.throttle` and `_.debounce`.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Function
-     * @param {Function} func The function to throttle.
-     * @param {number} [wait=0] The number of milliseconds to throttle invocations to.
-     * @param {Object} [options={}] The options object.
-     * @param {boolean} [options.leading=true]
-     *  Specify invoking on the leading edge of the timeout.
-     * @param {boolean} [options.trailing=true]
-     *  Specify invoking on the trailing edge of the timeout.
-     * @returns {Function} Returns the new throttled function.
-     * @example
+     * Extracts wrapper details from the `source` body comment.
      *
-     * // Avoid excessively updating the position while scrolling.
-     * jQuery(window).on('scroll', _.throttle(updatePosition, 100));
-     *
-     * // Invoke `renewToken` when the click event is fired, but not more than once every 5 minutes.
-     * var throttled = _.throttle(renewToken, 300000, { 'trailing': false });
-     * jQuery(element).on('click', throttled);
+     * @private
+     * @param {string} source The source to inspect.
+     * @returns {Array} Returns the wrapper details.
+     */
+    function getWrapDetails(source) {
+      var match = source.match(reWrapDetails);
+      return match ? match[1].split(reSplitDetails) : [];
+    }
+
+    /**
+     * Checks if `path` exists on `object`.
      *
-     * // Cancel the trailing throttled invocation.
-     * jQuery(window).on('popstate', throttled.cancel);
+     * @private
+     * @param {Object} object The object to query.
+     * @param {Array|string} path The path to check.
+     * @param {Function} hasFunc The function to check properties.
+     * @returns {boolean} Returns `true` if `path` exists, else `false`.
      */
-    function throttle(func, wait, options) {
-      var leading = true,
-          trailing = true;
+    function hasPath(object, path, hasFunc) {
+      path = castPath(path, object);
 
-      if (typeof func != 'function') {
-        throw new TypeError(FUNC_ERROR_TEXT);
+      var index = -1,
+          length = path.length,
+          result = false;
+
+      while (++index < length) {
+        var key = toKey(path[index]);
+        if (!(result = object != null && hasFunc(object, key))) {
+          break;
+        }
+        object = object[key];
       }
-      if (isObject(options)) {
-        leading = 'leading' in options ? !!options.leading : leading;
-        trailing = 'trailing' in options ? !!options.trailing : trailing;
+      if (result || ++index != length) {
+        return result;
       }
-      return debounce(func, wait, {
-        'leading': leading,
-        'maxWait': wait,
-        'trailing': trailing
-      });
+      length = object == null ? 0 : object.length;
+      return !!length && isLength(length) && isIndex(key, length) &&
+        (isArray(object) || isArguments(object));
     }
 
     /**
-     * Creates a function that accepts up to one argument, ignoring any
-     * additional arguments.
+     * Initializes an array clone.
      *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Function
-     * @param {Function} func The function to cap arguments for.
-     * @returns {Function} Returns the new capped function.
-     * @example
-     *
-     * _.map(['6', '8', '10'], _.unary(parseInt));
-     * // => [6, 8, 10]
+     * @private
+     * @param {Array} array The array to clone.
+     * @returns {Array} Returns the initialized clone.
      */
-    function unary(func) {
-      return ary(func, 1);
+    function initCloneArray(array) {
+      var length = array.length,
+          result = new array.constructor(length);
+
+      // Add properties assigned by `RegExp#exec`.
+      if (length && typeof array[0] == 'string' && hasOwnProperty.call(array, 'index')) {
+        result.index = array.index;
+        result.input = array.input;
+      }
+      return result;
     }
 
     /**
-     * Creates a function that provides `value` to the wrapper function as its
-     * first argument. Any additional arguments provided to the function are
-     * appended to those provided to the wrapper function. The wrapper is invoked
-     * with the `this` binding of the created function.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Function
-     * @param {*} value The value to wrap.
-     * @param {Function} [wrapper=identity] The wrapper function.
-     * @returns {Function} Returns the new function.
-     * @example
-     *
-     * var p = _.wrap(_.escape, function(func, text) {
-     *   return '<p>' + func(text) + '</p>';
-     * });
+     * Initializes an object clone.
      *
-     * p('fred, barney, & pebbles');
-     * // => '<p>fred, barney, &amp; pebbles</p>'
+     * @private
+     * @param {Object} object The object to clone.
+     * @returns {Object} Returns the initialized clone.
      */
-    function wrap(value, wrapper) {
-      wrapper = wrapper == null ? identity : wrapper;
-      return partial(wrapper, value);
+    function initCloneObject(object) {
+      return (typeof object.constructor == 'function' && !isPrototype(object))
+        ? baseCreate(getPrototype(object))
+        : {};
     }
 
-    /*------------------------------------------------------------------------*/
-
     /**
-     * Casts `value` as an array if it's not one.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.4.0
-     * @category Lang
-     * @param {*} value The value to inspect.
-     * @returns {Array} Returns the cast array.
-     * @example
-     *
-     * _.castArray(1);
-     * // => [1]
-     *
-     * _.castArray({ 'a': 1 });
-     * // => [{ 'a': 1 }]
-     *
-     * _.castArray('abc');
-     * // => ['abc']
-     *
-     * _.castArray(null);
-     * // => [null]
-     *
-     * _.castArray(undefined);
-     * // => [undefined]
+     * Initializes an object clone based on its `toStringTag`.
      *
-     * _.castArray();
-     * // => []
+     * **Note:** This function only supports cloning values with tags of
+     * `Boolean`, `Date`, `Error`, `Map`, `Number`, `RegExp`, `Set`, or `String`.
      *
-     * var array = [1, 2, 3];
-     * console.log(_.castArray(array) === array);
-     * // => true
+     * @private
+     * @param {Object} object The object to clone.
+     * @param {string} tag The `toStringTag` of the object to clone.
+     * @param {boolean} [isDeep] Specify a deep clone.
+     * @returns {Object} Returns the initialized clone.
      */
-    function castArray() {
-      if (!arguments.length) {
-        return [];
+    function initCloneByTag(object, tag, isDeep) {
+      var Ctor = object.constructor;
+      switch (tag) {
+        case arrayBufferTag:
+          return cloneArrayBuffer(object);
+
+        case boolTag:
+        case dateTag:
+          return new Ctor(+object);
+
+        case dataViewTag:
+          return cloneDataView(object, isDeep);
+
+        case float32Tag: case float64Tag:
+        case int8Tag: case int16Tag: case int32Tag:
+        case uint8Tag: case uint8ClampedTag: case uint16Tag: case uint32Tag:
+          return cloneTypedArray(object, isDeep);
+
+        case mapTag:
+          return new Ctor;
+
+        case numberTag:
+        case stringTag:
+          return new Ctor(object);
+
+        case regexpTag:
+          return cloneRegExp(object);
+
+        case setTag:
+          return new Ctor;
+
+        case symbolTag:
+          return cloneSymbol(object);
       }
-      var value = arguments[0];
-      return isArray(value) ? value : [value];
     }
 
     /**
-     * Creates a shallow clone of `value`.
-     *
-     * **Note:** This method is loosely based on the
-     * [structured clone algorithm](https://mdn.io/Structured_clone_algorithm)
-     * and supports cloning arrays, array buffers, booleans, date objects, maps,
-     * numbers, `Object` objects, regexes, sets, strings, symbols, and typed
-     * arrays. The own enumerable properties of `arguments` objects are cloned
-     * as plain objects. An empty object is returned for uncloneable values such
-     * as error objects, functions, DOM nodes, and WeakMaps.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Lang
-     * @param {*} value The value to clone.
-     * @returns {*} Returns the cloned value.
-     * @see _.cloneDeep
-     * @example
-     *
-     * var objects = [{ 'a': 1 }, { 'b': 2 }];
+     * Inserts wrapper `details` in a comment at the top of the `source` body.
      *
-     * var shallow = _.clone(objects);
-     * console.log(shallow[0] === objects[0]);
-     * // => true
+     * @private
+     * @param {string} source The source to modify.
+     * @returns {Array} details The details to insert.
+     * @returns {string} Returns the modified source.
      */
-    function clone(value) {
-      return baseClone(value, false, true);
+    function insertWrapDetails(source, details) {
+      var length = details.length;
+      if (!length) {
+        return source;
+      }
+      var lastIndex = length - 1;
+      details[lastIndex] = (length > 1 ? '& ' : '') + details[lastIndex];
+      details = details.join(length > 2 ? ', ' : ' ');
+      return source.replace(reWrapComment, '{\n/* [wrapped with ' + details + '] */\n');
     }
 
     /**
-     * This method is like `_.clone` except that it accepts `customizer` which
-     * is invoked to produce the cloned value. If `customizer` returns `undefined`,
-     * cloning is handled by the method instead. The `customizer` is invoked with
-     * up to four arguments; (value [, index|key, object, stack]).
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Lang
-     * @param {*} value The value to clone.
-     * @param {Function} [customizer] The function to customize cloning.
-     * @returns {*} Returns the cloned value.
-     * @see _.cloneDeepWith
-     * @example
-     *
-     * function customizer(value) {
-     *   if (_.isElement(value)) {
-     *     return value.cloneNode(false);
-     *   }
-     * }
-     *
-     * var el = _.cloneWith(document.body, customizer);
+     * Checks if `value` is a flattenable `arguments` object or array.
      *
-     * console.log(el === document.body);
-     * // => false
-     * console.log(el.nodeName);
-     * // => 'BODY'
-     * console.log(el.childNodes.length);
-     * // => 0
+     * @private
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is flattenable, else `false`.
      */
-    function cloneWith(value, customizer) {
-      return baseClone(value, false, true, customizer);
+    function isFlattenable(value) {
+      return isArray(value) || isArguments(value) ||
+        !!(spreadableSymbol && value && value[spreadableSymbol]);
     }
 
     /**
-     * This method is like `_.clone` except that it recursively clones `value`.
-     *
-     * @static
-     * @memberOf _
-     * @since 1.0.0
-     * @category Lang
-     * @param {*} value The value to recursively clone.
-     * @returns {*} Returns the deep cloned value.
-     * @see _.clone
-     * @example
-     *
-     * var objects = [{ 'a': 1 }, { 'b': 2 }];
+     * Checks if `value` is a valid array-like index.
      *
-     * var deep = _.cloneDeep(objects);
-     * console.log(deep[0] === objects[0]);
-     * // => false
+     * @private
+     * @param {*} value The value to check.
+     * @param {number} [length=MAX_SAFE_INTEGER] The upper bounds of a valid index.
+     * @returns {boolean} Returns `true` if `value` is a valid index, else `false`.
      */
-    function cloneDeep(value) {
-      return baseClone(value, true, true);
+    function isIndex(value, length) {
+      var type = typeof value;
+      length = length == null ? MAX_SAFE_INTEGER : length;
+
+      return !!length &&
+        (type == 'number' ||
+          (type != 'symbol' && reIsUint.test(value))) &&
+            (value > -1 && value % 1 == 0 && value < length);
     }
 
     /**
-     * This method is like `_.cloneWith` except that it recursively clones `value`.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Lang
-     * @param {*} value The value to recursively clone.
-     * @param {Function} [customizer] The function to customize cloning.
-     * @returns {*} Returns the deep cloned value.
-     * @see _.cloneWith
-     * @example
-     *
-     * function customizer(value) {
-     *   if (_.isElement(value)) {
-     *     return value.cloneNode(true);
-     *   }
-     * }
-     *
-     * var el = _.cloneDeepWith(document.body, customizer);
+     * Checks if the given arguments are from an iteratee call.
      *
-     * console.log(el === document.body);
-     * // => false
-     * console.log(el.nodeName);
-     * // => 'BODY'
-     * console.log(el.childNodes.length);
-     * // => 20
+     * @private
+     * @param {*} value The potential iteratee value argument.
+     * @param {*} index The potential iteratee index or key argument.
+     * @param {*} object The potential iteratee object argument.
+     * @returns {boolean} Returns `true` if the arguments are from an iteratee call,
+     *  else `false`.
      */
-    function cloneDeepWith(value, customizer) {
-      return baseClone(value, true, true, customizer);
+    function isIterateeCall(value, index, object) {
+      if (!isObject(object)) {
+        return false;
+      }
+      var type = typeof index;
+      if (type == 'number'
+            ? (isArrayLike(object) && isIndex(index, object.length))
+            : (type == 'string' && index in object)
+          ) {
+        return eq(object[index], value);
+      }
+      return false;
     }
 
     /**
-     * Performs a
-     * [`SameValueZero`](http://ecma-international.org/ecma-262/6.0/#sec-samevaluezero)
-     * comparison between two values to determine if they are equivalent.
+     * Checks if `value` is a property name and not a property path.
      *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Lang
-     * @param {*} value The value to compare.
-     * @param {*} other The other value to compare.
-     * @returns {boolean} Returns `true` if the values are equivalent, else `false`.
-     * @example
-     *
-     * var object = { 'user': 'fred' };
-     * var other = { 'user': 'fred' };
-     *
-     * _.eq(object, object);
-     * // => true
-     *
-     * _.eq(object, other);
-     * // => false
-     *
-     * _.eq('a', 'a');
-     * // => true
-     *
-     * _.eq('a', Object('a'));
-     * // => false
-     *
-     * _.eq(NaN, NaN);
-     * // => true
+     * @private
+     * @param {*} value The value to check.
+     * @param {Object} [object] The object to query keys on.
+     * @returns {boolean} Returns `true` if `value` is a property name, else `false`.
      */
-    function eq(value, other) {
-      return value === other || (value !== value && other !== other);
+    function isKey(value, object) {
+      if (isArray(value)) {
+        return false;
+      }
+      var type = typeof value;
+      if (type == 'number' || type == 'symbol' || type == 'boolean' ||
+          value == null || isSymbol(value)) {
+        return true;
+      }
+      return reIsPlainProp.test(value) || !reIsDeepProp.test(value) ||
+        (object != null && value in Object(object));
     }
 
     /**
-     * Checks if `value` is greater than `other`.
-     *
-     * @static
-     * @memberOf _
-     * @since 3.9.0
-     * @category Lang
-     * @param {*} value The value to compare.
-     * @param {*} other The other value to compare.
-     * @returns {boolean} Returns `true` if `value` is greater than `other`,
-     *  else `false`.
-     * @see _.lt
-     * @example
-     *
-     * _.gt(3, 1);
-     * // => true
-     *
-     * _.gt(3, 3);
-     * // => false
+     * Checks if `value` is suitable for use as unique object key.
      *
-     * _.gt(1, 3);
-     * // => false
+     * @private
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is suitable, else `false`.
      */
-    var gt = createRelationalOperation(baseGt);
+    function isKeyable(value) {
+      var type = typeof value;
+      return (type == 'string' || type == 'number' || type == 'symbol' || type == 'boolean')
+        ? (value !== '__proto__')
+        : (value === null);
+    }
 
     /**
-     * Checks if `value` is greater than or equal to `other`.
-     *
-     * @static
-     * @memberOf _
-     * @since 3.9.0
-     * @category Lang
-     * @param {*} value The value to compare.
-     * @param {*} other The other value to compare.
-     * @returns {boolean} Returns `true` if `value` is greater than or equal to
-     *  `other`, else `false`.
-     * @see _.lte
-     * @example
-     *
-     * _.gte(3, 1);
-     * // => true
-     *
-     * _.gte(3, 3);
-     * // => true
+     * Checks if `func` has a lazy counterpart.
      *
-     * _.gte(1, 3);
-     * // => false
+     * @private
+     * @param {Function} func The function to check.
+     * @returns {boolean} Returns `true` if `func` has a lazy counterpart,
+     *  else `false`.
      */
-    var gte = createRelationalOperation(function(value, other) {
-      return value >= other;
-    });
+    function isLaziable(func) {
+      var funcName = getFuncName(func),
+          other = lodash[funcName];
+
+      if (typeof other != 'function' || !(funcName in LazyWrapper.prototype)) {
+        return false;
+      }
+      if (func === other) {
+        return true;
+      }
+      var data = getData(other);
+      return !!data && func === data[0];
+    }
 
     /**
-     * Checks if `value` is likely an `arguments` object.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is correctly classified,
-     *  else `false`.
-     * @example
-     *
-     * _.isArguments(function() { return arguments; }());
-     * // => true
+     * Checks if `func` has its source masked.
      *
-     * _.isArguments([1, 2, 3]);
-     * // => false
+     * @private
+     * @param {Function} func The function to check.
+     * @returns {boolean} Returns `true` if `func` is masked, else `false`.
      */
-    function isArguments(value) {
-      // Safari 8.1 incorrectly makes `arguments.callee` enumerable in strict mode.
-      return isArrayLikeObject(value) && hasOwnProperty.call(value, 'callee') &&
-        (!propertyIsEnumerable.call(value, 'callee') || objectToString.call(value) == argsTag);
+    function isMasked(func) {
+      return !!maskSrcKey && (maskSrcKey in func);
     }
 
     /**
-     * Checks if `value` is classified as an `Array` object.
+     * Checks if `func` is capable of being masked.
      *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @type {Function}
-     * @category Lang
+     * @private
      * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is correctly classified,
-     *  else `false`.
-     * @example
-     *
-     * _.isArray([1, 2, 3]);
-     * // => true
-     *
-     * _.isArray(document.body.children);
-     * // => false
-     *
-     * _.isArray('abc');
-     * // => false
-     *
-     * _.isArray(_.noop);
-     * // => false
+     * @returns {boolean} Returns `true` if `func` is maskable, else `false`.
      */
-    var isArray = Array.isArray;
+    var isMaskable = coreJsData ? isFunction : stubFalse;
 
     /**
-     * Checks if `value` is classified as an `ArrayBuffer` object.
+     * Checks if `value` is likely a prototype object.
      *
-     * @static
-     * @memberOf _
-     * @since 4.3.0
-     * @category Lang
+     * @private
      * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is correctly classified,
-     *  else `false`.
-     * @example
-     *
-     * _.isArrayBuffer(new ArrayBuffer(2));
-     * // => true
-     *
-     * _.isArrayBuffer(new Array(2));
-     * // => false
+     * @returns {boolean} Returns `true` if `value` is a prototype, else `false`.
      */
-    function isArrayBuffer(value) {
-      return isObjectLike(value) && objectToString.call(value) == arrayBufferTag;
+    function isPrototype(value) {
+      var Ctor = value && value.constructor,
+          proto = (typeof Ctor == 'function' && Ctor.prototype) || objectProto;
+
+      return value === proto;
     }
 
     /**
-     * Checks if `value` is array-like. A value is considered array-like if it's
-     * not a function and has a `value.length` that's an integer greater than or
-     * equal to `0` and less than or equal to `Number.MAX_SAFE_INTEGER`.
+     * Checks if `value` is suitable for strict equality comparisons, i.e. `===`.
      *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Lang
+     * @private
      * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is array-like, else `false`.
-     * @example
-     *
-     * _.isArrayLike([1, 2, 3]);
-     * // => true
-     *
-     * _.isArrayLike(document.body.children);
-     * // => true
-     *
-     * _.isArrayLike('abc');
-     * // => true
-     *
-     * _.isArrayLike(_.noop);
-     * // => false
+     * @returns {boolean} Returns `true` if `value` if suitable for strict
+     *  equality comparisons, else `false`.
      */
-    function isArrayLike(value) {
-      return value != null && isLength(getLength(value)) && !isFunction(value);
+    function isStrictComparable(value) {
+      return value === value && !isObject(value);
     }
 
     /**
-     * This method is like `_.isArrayLike` except that it also checks if `value`
-     * is an object.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is an array-like object,
-     *  else `false`.
-     * @example
-     *
-     * _.isArrayLikeObject([1, 2, 3]);
-     * // => true
-     *
-     * _.isArrayLikeObject(document.body.children);
-     * // => true
+     * A specialized version of `matchesProperty` for source values suitable
+     * for strict equality comparisons, i.e. `===`.
      *
-     * _.isArrayLikeObject('abc');
-     * // => false
+     * @private
+     * @param {string} key The key of the property to get.
+     * @param {*} srcValue The value to match.
+     * @returns {Function} Returns the new spec function.
+     */
+    function matchesStrictComparable(key, srcValue) {
+      return function(object) {
+        if (object == null) {
+          return false;
+        }
+        return object[key] === srcValue &&
+          (srcValue !== undefined || (key in Object(object)));
+      };
+    }
+
+    /**
+     * A specialized version of `_.memoize` which clears the memoized function's
+     * cache when it exceeds `MAX_MEMOIZE_SIZE`.
      *
-     * _.isArrayLikeObject(_.noop);
-     * // => false
+     * @private
+     * @param {Function} func The function to have its output memoized.
+     * @returns {Function} Returns the new memoized function.
      */
-    function isArrayLikeObject(value) {
-      return isObjectLike(value) && isArrayLike(value);
+    function memoizeCapped(func) {
+      var result = memoize(func, function(key) {
+        if (cache.size === MAX_MEMOIZE_SIZE) {
+          cache.clear();
+        }
+        return key;
+      });
+
+      var cache = result.cache;
+      return result;
     }
 
     /**
-     * Checks if `value` is classified as a boolean primitive or object.
+     * Merges the function metadata of `source` into `data`.
      *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is correctly classified,
-     *  else `false`.
-     * @example
-     *
-     * _.isBoolean(false);
-     * // => true
+     * Merging metadata reduces the number of wrappers used to invoke a function.
+     * This is possible because methods like `_.bind`, `_.curry`, and `_.partial`
+     * may be applied regardless of execution order. Methods like `_.ary` and
+     * `_.rearg` modify function arguments, making the order in which they are
+     * executed important, preventing the merging of metadata. However, we make
+     * an exception for a safe combined case where curried functions have `_.ary`
+     * and or `_.rearg` applied.
      *
-     * _.isBoolean(null);
-     * // => false
+     * @private
+     * @param {Array} data The destination metadata.
+     * @param {Array} source The source metadata.
+     * @returns {Array} Returns `data`.
      */
-    function isBoolean(value) {
-      return value === true || value === false ||
-        (isObjectLike(value) && objectToString.call(value) == boolTag);
+    function mergeData(data, source) {
+      var bitmask = data[1],
+          srcBitmask = source[1],
+          newBitmask = bitmask | srcBitmask,
+          isCommon = newBitmask < (WRAP_BIND_FLAG | WRAP_BIND_KEY_FLAG | WRAP_ARY_FLAG);
+
+      var isCombo =
+        ((srcBitmask == WRAP_ARY_FLAG) && (bitmask == WRAP_CURRY_FLAG)) ||
+        ((srcBitmask == WRAP_ARY_FLAG) && (bitmask == WRAP_REARG_FLAG) && (data[7].length <= source[8])) ||
+        ((srcBitmask == (WRAP_ARY_FLAG | WRAP_REARG_FLAG)) && (source[7].length <= source[8]) && (bitmask == WRAP_CURRY_FLAG));
+
+      // Exit early if metadata can't be merged.
+      if (!(isCommon || isCombo)) {
+        return data;
+      }
+      // Use source `thisArg` if available.
+      if (srcBitmask & WRAP_BIND_FLAG) {
+        data[2] = source[2];
+        // Set when currying a bound function.
+        newBitmask |= bitmask & WRAP_BIND_FLAG ? 0 : WRAP_CURRY_BOUND_FLAG;
+      }
+      // Compose partial arguments.
+      var value = source[3];
+      if (value) {
+        var partials = data[3];
+        data[3] = partials ? composeArgs(partials, value, source[4]) : value;
+        data[4] = partials ? replaceHolders(data[3], PLACEHOLDER) : source[4];
+      }
+      // Compose partial right arguments.
+      value = source[5];
+      if (value) {
+        partials = data[5];
+        data[5] = partials ? composeArgsRight(partials, value, source[6]) : value;
+        data[6] = partials ? replaceHolders(data[5], PLACEHOLDER) : source[6];
+      }
+      // Use source `argPos` if available.
+      value = source[7];
+      if (value) {
+        data[7] = value;
+      }
+      // Use source `ary` if it's smaller.
+      if (srcBitmask & WRAP_ARY_FLAG) {
+        data[8] = data[8] == null ? source[8] : nativeMin(data[8], source[8]);
+      }
+      // Use source `arity` if one is not provided.
+      if (data[9] == null) {
+        data[9] = source[9];
+      }
+      // Use source `func` and merge bitmasks.
+      data[0] = source[0];
+      data[1] = newBitmask;
+
+      return data;
     }
 
     /**
-     * Checks if `value` is a buffer.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.3.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is a buffer, else `false`.
-     * @example
-     *
-     * _.isBuffer(new Buffer(2));
-     * // => true
+     * This function is like
+     * [`Object.keys`](http://ecma-international.org/ecma-262/7.0/#sec-object.keys)
+     * except that it includes inherited enumerable properties.
      *
-     * _.isBuffer(new Uint8Array(2));
-     * // => false
+     * @private
+     * @param {Object} object The object to query.
+     * @returns {Array} Returns the array of property names.
      */
-    var isBuffer = !Buffer ? stubFalse : function(value) {
-      return value instanceof Buffer;
-    };
+    function nativeKeysIn(object) {
+      var result = [];
+      if (object != null) {
+        for (var key in Object(object)) {
+          result.push(key);
+        }
+      }
+      return result;
+    }
 
     /**
-     * Checks if `value` is classified as a `Date` object.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is correctly classified,
-     *  else `false`.
-     * @example
-     *
-     * _.isDate(new Date);
-     * // => true
+     * Converts `value` to a string using `Object.prototype.toString`.
      *
-     * _.isDate('Mon April 23 2012');
-     * // => false
+     * @private
+     * @param {*} value The value to convert.
+     * @returns {string} Returns the converted string.
      */
-    function isDate(value) {
-      return isObjectLike(value) && objectToString.call(value) == dateTag;
+    function objectToString(value) {
+      return nativeObjectToString.call(value);
     }
 
     /**
-     * Checks if `value` is likely a DOM element.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is a DOM element,
-     *  else `false`.
-     * @example
-     *
-     * _.isElement(document.body);
-     * // => true
+     * A specialized version of `baseRest` which transforms the rest array.
      *
-     * _.isElement('<body>');
-     * // => false
+     * @private
+     * @param {Function} func The function to apply a rest parameter to.
+     * @param {number} [start=func.length-1] The start position of the rest parameter.
+     * @param {Function} transform The rest array transform.
+     * @returns {Function} Returns the new function.
      */
-    function isElement(value) {
-      return !!value && value.nodeType === 1 && isObjectLike(value) && !isPlainObject(value);
+    function overRest(func, start, transform) {
+      start = nativeMax(start === undefined ? (func.length - 1) : start, 0);
+      return function() {
+        var args = arguments,
+            index = -1,
+            length = nativeMax(args.length - start, 0),
+            array = Array(length);
+
+        while (++index < length) {
+          array[index] = args[start + index];
+        }
+        index = -1;
+        var otherArgs = Array(start + 1);
+        while (++index < start) {
+          otherArgs[index] = args[index];
+        }
+        otherArgs[start] = transform(array);
+        return apply(func, this, otherArgs);
+      };
     }
 
     /**
-     * Checks if `value` is an empty object, collection, map, or set.
-     *
-     * Objects are considered empty if they have no own enumerable string keyed
-     * properties.
-     *
-     * Array-like values such as `arguments` objects, arrays, buffers, strings, or
-     * jQuery-like collections are considered empty if they have a `length` of `0`.
-     * Similarly, maps and sets are considered empty if they have a `size` of `0`.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is empty, else `false`.
-     * @example
-     *
-     * _.isEmpty(null);
-     * // => true
-     *
-     * _.isEmpty(true);
-     * // => true
-     *
-     * _.isEmpty(1);
-     * // => true
+     * Gets the parent value at `path` of `object`.
      *
-     * _.isEmpty([1, 2, 3]);
-     * // => false
+     * @private
+     * @param {Object} object The object to query.
+     * @param {Array} path The path to get the parent value of.
+     * @returns {*} Returns the parent value.
+     */
+    function parent(object, path) {
+      return path.length < 2 ? object : baseGet(object, baseSlice(path, 0, -1));
+    }
+
+    /**
+     * Reorder `array` according to the specified indexes where the element at
+     * the first index is assigned as the first element, the element at
+     * the second index is assigned as the second element, and so on.
      *
-     * _.isEmpty({ 'a': 1 });
-     * // => false
+     * @private
+     * @param {Array} array The array to reorder.
+     * @param {Array} indexes The arranged array indexes.
+     * @returns {Array} Returns `array`.
      */
-    function isEmpty(value) {
-      if (isArrayLike(value) &&
-          (isArray(value) || isString(value) || isFunction(value.splice) ||
-            isArguments(value) || isBuffer(value))) {
-        return !value.length;
-      }
-      if (isObjectLike(value)) {
-        var tag = getTag(value);
-        if (tag == mapTag || tag == setTag) {
-          return !value.size;
-        }
-      }
-      for (var key in value) {
-        if (hasOwnProperty.call(value, key)) {
-          return false;
-        }
+    function reorder(array, indexes) {
+      var arrLength = array.length,
+          length = nativeMin(indexes.length, arrLength),
+          oldArray = copyArray(array);
+
+      while (length--) {
+        var index = indexes[length];
+        array[length] = isIndex(index, arrLength) ? oldArray[index] : undefined;
       }
-      return !(nonEnumShadows && keys(value).length);
+      return array;
     }
 
     /**
-     * Performs a deep comparison between two values to determine if they are
-     * equivalent.
-     *
-     * **Note:** This method supports comparing arrays, array buffers, booleans,
-     * date objects, error objects, maps, numbers, `Object` objects, regexes,
-     * sets, strings, symbols, and typed arrays. `Object` objects are compared
-     * by their own, not inherited, enumerable properties. Functions and DOM
-     * nodes are **not** supported.
-     *
-     * @static
-     * @memberOf _
-     * @since 0.1.0
-     * @category Lang
-     * @param {*} value The value to compare.
-     * @param {*} other The other value to compare.
-     * @returns {boolean} Returns `true` if the values are equivalent,
-     *  else `false`.
-     * @example
-     *
-     * var object = { 'user': 'fred' };
-     * var other = { 'user': 'fred' };
+     * Gets the value at `key`, unless `key` is "__proto__".
      *
-     * _.isEqual(object, other);
-     * // => true
-     *
-     * object === other;
-     * // => false
+     * @private
+     * @param {Object} object The object to query.
+     * @param {string} key The key of the property to get.
+     * @returns {*} Returns the property value.
      */
-    function isEqual(value, other) {
-      return baseIsEqual(value, other);
+    function safeGet(object, key) {
+      if (key == '__proto__') {
+        return;
+      }
+
+      return object[key];
     }
 
     /**
-     * This method is like `_.isEqual` except that it accepts `customizer` which
-     * is invoked to compare values. If `customizer` returns `undefined`, comparisons
-     * are handled by the method instead. The `customizer` is invoked with up to
-     * six arguments: (objValue, othValue [, index|key, object, other, stack]).
+     * Sets metadata for `func`.
      *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Lang
-     * @param {*} value The value to compare.
-     * @param {*} other The other value to compare.
-     * @param {Function} [customizer] The function to customize comparisons.
-     * @returns {boolean} Returns `true` if the values are equivalent,
-     *  else `false`.
-     * @example
+     * **Note:** If this function becomes hot, i.e. is invoked a lot in a short
+     * period of time, it will trip its breaker and transition to an identity
+     * function to avoid garbage collection pauses in V8. See
+     * [V8 issue 2070](https://bugs.chromium.org/p/v8/issues/detail?id=2070)
+     * for more details.
      *
-     * function isGreeting(value) {
-     *   return /^h(?:i|ello)$/.test(value);
-     * }
+     * @private
+     * @param {Function} func The function to associate metadata with.
+     * @param {*} data The metadata.
+     * @returns {Function} Returns `func`.
+     */
+    var setData = shortOut(baseSetData);
+
+    /**
+     * A simple wrapper around the global [`setTimeout`](https://mdn.io/setTimeout).
      *
-     * function customizer(objValue, othValue) {
-     *   if (isGreeting(objValue) && isGreeting(othValue)) {
-     *     return true;
-     *   }
-     * }
+     * @private
+     * @param {Function} func The function to delay.
+     * @param {number} wait The number of milliseconds to delay invocation.
+     * @returns {number|Object} Returns the timer id or timeout object.
+     */
+    var setTimeout = ctxSetTimeout || function(func, wait) {
+      return root.setTimeout(func, wait);
+    };
+
+    /**
+     * Sets the `toString` method of `func` to return `string`.
      *
-     * var array = ['hello', 'goodbye'];
-     * var other = ['hi', 'goodbye'];
+     * @private
+     * @param {Function} func The function to modify.
+     * @param {Function} string The `toString` result.
+     * @returns {Function} Returns `func`.
+     */
+    var setToString = shortOut(baseSetToString);
+
+    /**
+     * Sets the `toString` method of `wrapper` to mimic the source of `reference`
+     * with wrapper details in a comment at the top of the source body.
      *
-     * _.isEqualWith(array, other, customizer);
-     * // => true
+     * @private
+     * @param {Function} wrapper The function to modify.
+     * @param {Function} reference The reference function.
+     * @param {number} bitmask The bitmask flags. See `createWrap` for more details.
+     * @returns {Function} Returns `wrapper`.
      */
-    function isEqualWith(value, other, customizer) {
-      customizer = typeof customizer == 'function' ? customizer : undefined;
-      var result = customizer ? customizer(value, other) : undefined;
-      return result === undefined ? baseIsEqual(value, other, customizer) : !!result;
+    function setWrapToString(wrapper, reference, bitmask) {
+      var source = (reference + '');
+      return setToString(wrapper, insertWrapDetails(source, updateWrapDetails(getWrapDetails(source), bitmask)));
     }
 
     /**
-     * Checks if `value` is an `Error`, `EvalError`, `RangeError`, `ReferenceError`,
-     * `SyntaxError`, `TypeError`, or `URIError` object.
+     * Creates a function that'll short out and invoke `identity` instead
+     * of `func` when it's called `HOT_COUNT` or more times in `HOT_SPAN`
+     * milliseconds.
      *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is an error object,
-     *  else `false`.
-     * @example
+     * @private
+     * @param {Function} func The function to restrict.
+     * @returns {Function} Returns the new shortable function.
+     */
+    function shortOut(func) {
+      var count = 0,
+          lastCalled = 0;
+
+      return function() {
+        var stamp = nativeNow(),
+            remaining = HOT_SPAN - (stamp - lastCalled);
+
+        lastCalled = stamp;
+        if (remaining > 0) {
+          if (++count >= HOT_COUNT) {
+            return arguments[0];
+          }
+        } else {
+          count = 0;
+        }
+        return func.apply(undefined, arguments);
+      };
+    }
+
+    /**
+     * A specialized version of `_.shuffle` which mutates and sets the size of `array`.
      *
-     * _.isError(new Error);
-     * // => true
+     * @private
+     * @param {Array} array The array to shuffle.
+     * @param {number} [size=array.length] The size of `array`.
+     * @returns {Array} Returns `array`.
+     */
+    function shuffleSelf(array, size) {
+      var index = -1,
+          length = array.length,
+          lastIndex = length - 1;
+
+      size = size === undefined ? length : size;
+      while (++index < size) {
+        var rand = baseRandom(index, lastIndex),
+            value = array[rand];
+
+        array[rand] = array[index];
+        array[index] = value;
+      }
+      array.length = size;
+      return array;
+    }
+
+    /**
+     * Converts `string` to a property path array.
      *
-     * _.isError(Error);
-     * // => false
+     * @private
+     * @param {string} string The string to convert.
+     * @returns {Array} Returns the property path array.
      */
-    function isError(value) {
-      if (!isObjectLike(value)) {
-        return false;
+    var stringToPath = memoizeCapped(function(string) {
+      var result = [];
+      if (string.charCodeAt(0) === 46 /* . */) {
+        result.push('');
+      }
+      string.replace(rePropName, function(match, number, quote, subString) {
+        result.push(quote ? subString.replace(reEscapeChar, '$1') : (number || match));
+      });
+      return result;
+    });
+
+    /**
+     * Converts `value` to a string key if it's not a string or symbol.
+     *
+     * @private
+     * @param {*} value The value to inspect.
+     * @returns {string|symbol} Returns the key.
+     */
+    function toKey(value) {
+      if (typeof value == 'string' || isSymbol(value)) {
+        return value;
       }
-      return (objectToString.call(value) == errorTag) ||
-        (typeof value.message == 'string' && typeof value.name == 'string');
+      var result = (value + '');
+      return (result == '0' && (1 / value) == -INFINITY) ? '-0' : result;
     }
 
     /**
-     * Checks if `value` is a finite primitive number.
+     * Converts `func` to its source code.
      *
-     * **Note:** This method is based on
-     * [`Number.isFinite`](https://mdn.io/Number/isFinite).
+     * @private
+     * @param {Function} func The function to convert.
+     * @returns {string} Returns the source code.
+     */
+    function toSource(func) {
+      if (func != null) {
+        try {
+          return funcToString.call(func);
+        } catch (e) {}
+        try {
+          return (func + '');
+        } catch (e) {}
+      }
+      return '';
+    }
+
+    /**
+     * Updates wrapper `details` based on `bitmask` flags.
+     *
+     * @private
+     * @returns {Array} details The details to modify.
+     * @param {number} bitmask The bitmask flags. See `createWrap` for more details.
+     * @returns {Array} Returns `details`.
+     */
+    function updateWrapDetails(details, bitmask) {
+      arrayEach(wrapFlags, function(pair) {
+        var value = '_.' + pair[0];
+        if ((bitmask & pair[1]) && !arrayIncludes(details, value)) {
+          details.push(value);
+        }
+      });
+      return details.sort();
+    }
+
+    /**
+     * Creates a clone of `wrapper`.
+     *
+     * @private
+     * @param {Object} wrapper The wrapper to clone.
+     * @returns {Object} Returns the cloned wrapper.
+     */
+    function wrapperClone(wrapper) {
+      if (wrapper instanceof LazyWrapper) {
+        return wrapper.clone();
+      }
+      var result = new LodashWrapper(wrapper.__wrapped__, wrapper.__chain__);
+      result.__actions__ = copyArray(wrapper.__actions__);
+      result.__index__  = wrapper.__index__;
+      result.__values__ = wrapper.__values__;
+      return result;
+    }
+
+    /*------------------------------------------------------------------------*/
+
+    /**
+     * Creates an array of elements split into groups the length of `size`.
+     * If `array` can't be split evenly, the final chunk will be the remaining
+     * elements.
      *
      * @static
      * @memberOf _
-     * @since 0.1.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is a finite number,
-     *  else `false`.
+     * @since 3.0.0
+     * @category Array
+     * @param {Array} array The array to process.
+     * @param {number} [size=1] The length of each chunk
+     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
+     * @returns {Array} Returns the new array of chunks.
      * @example
      *
-     * _.isFinite(3);
-     * // => true
-     *
-     * _.isFinite(Number.MIN_VALUE);
-     * // => true
-     *
-     * _.isFinite(Infinity);
-     * // => false
+     * _.chunk(['a', 'b', 'c', 'd'], 2);
+     * // => [['a', 'b'], ['c', 'd']]
      *
-     * _.isFinite('3');
-     * // => false
+     * _.chunk(['a', 'b', 'c', 'd'], 3);
+     * // => [['a', 'b', 'c'], ['d']]
      */
-    function isFinite(value) {
-      return typeof value == 'number' && nativeIsFinite(value);
+    function chunk(array, size, guard) {
+      if ((guard ? isIterateeCall(array, size, guard) : size === undefined)) {
+        size = 1;
+      } else {
+        size = nativeMax(toInteger(size), 0);
+      }
+      var length = array == null ? 0 : array.length;
+      if (!length || size < 1) {
+        return [];
+      }
+      var index = 0,
+          resIndex = 0,
+          result = Array(nativeCeil(length / size));
+
+      while (index < length) {
+        result[resIndex++] = baseSlice(array, index, (index += size));
+      }
+      return result;
     }
 
     /**
-     * Checks if `value` is classified as a `Function` object.
+     * Creates an array with all falsey values removed. The values `false`, `null`,
+     * `0`, `""`, `undefined`, and `NaN` are falsey.
      *
      * @static
      * @memberOf _
      * @since 0.1.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is correctly classified,
-     *  else `false`.
+     * @category Array
+     * @param {Array} array The array to compact.
+     * @returns {Array} Returns the new array of filtered values.
      * @example
      *
-     * _.isFunction(_);
-     * // => true
-     *
-     * _.isFunction(/abc/);
-     * // => false
+     * _.compact([0, 1, false, 2, '', 3]);
+     * // => [1, 2, 3]
      */
-    function isFunction(value) {
-      // The use of `Object#toString` avoids issues with the `typeof` operator
-      // in Safari 8 which returns 'object' for typed array and weak map constructors,
-      // and PhantomJS 1.9 which returns 'function' for `NodeList` instances.
-      var tag = isObject(value) ? objectToString.call(value) : '';
-      return tag == funcTag || tag == genTag;
+    function compact(array) {
+      var index = -1,
+          length = array == null ? 0 : array.length,
+          resIndex = 0,
+          result = [];
+
+      while (++index < length) {
+        var value = array[index];
+        if (value) {
+          result[resIndex++] = value;
+        }
+      }
+      return result;
     }
 
     /**
-     * Checks if `value` is an integer.
-     *
-     * **Note:** This method is based on
-     * [`Number.isInteger`](https://mdn.io/Number/isInteger).
+     * Creates a new array concatenating `array` with any additional arrays
+     * and/or values.
      *
      * @static
      * @memberOf _
      * @since 4.0.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is an integer, else `false`.
+     * @category Array
+     * @param {Array} array The array to concatenate.
+     * @param {...*} [values] The values to concatenate.
+     * @returns {Array} Returns the new concatenated array.
      * @example
      *
-     * _.isInteger(3);
-     * // => true
+     * var array = [1];
+     * var other = _.concat(array, 2, [3], [[4]]);
      *
-     * _.isInteger(Number.MIN_VALUE);
-     * // => false
+     * console.log(other);
+     * // => [1, 2, 3, [4]]
      *
-     * _.isInteger(Infinity);
-     * // => false
-     *
-     * _.isInteger('3');
-     * // => false
+     * console.log(array);
+     * // => [1]
      */
-    function isInteger(value) {
-      return typeof value == 'number' && value == toInteger(value);
+    function concat() {
+      var length = arguments.length;
+      if (!length) {
+        return [];
+      }
+      var args = Array(length - 1),
+          array = arguments[0],
+          index = length;
+
+      while (index--) {
+        args[index - 1] = arguments[index];
+      }
+      return arrayPush(isArray(array) ? copyArray(array) : [array], baseFlatten(args, 1));
     }
 
     /**
-     * Checks if `value` is a valid array-like length.
+     * Creates an array of `array` values not included in the other given arrays
+     * using [`SameValueZero`](http://ecma-international.org/ecma-262/7.0/#sec-samevaluezero)
+     * for equality comparisons. The order and references of result values are
+     * determined by the first array.
      *
-     * **Note:** This function is loosely based on
-     * [`ToLength`](http://ecma-international.org/ecma-262/6.0/#sec-tolength).
+     * **Note:** Unlike `_.pullAll`, this method returns a new array.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is a valid length,
-     *  else `false`.
+     * @since 0.1.0
+     * @category Array
+     * @param {Array} array The array to inspect.
+     * @param {...Array} [values] The values to exclude.
+     * @returns {Array} Returns the new array of filtered values.
+     * @see _.without, _.xor
      * @example
      *
-     * _.isLength(3);
-     * // => true
-     *
-     * _.isLength(Number.MIN_VALUE);
-     * // => false
-     *
-     * _.isLength(Infinity);
-     * // => false
-     *
-     * _.isLength('3');
-     * // => false
+     * _.difference([2, 1], [2, 3]);
+     * // => [1]
      */
-    function isLength(value) {
-      return typeof value == 'number' &&
-        value > -1 && value % 1 == 0 && value <= MAX_SAFE_INTEGER;
-    }
+    var difference = baseRest(function(array, values) {
+      return isArrayLikeObject(array)
+        ? baseDifference(array, baseFlatten(values, 1, isArrayLikeObject, true))
+        : [];
+    });
 
     /**
-     * Checks if `value` is the
-     * [language type](http://www.ecma-international.org/ecma-262/6.0/#sec-ecmascript-language-types)
-     * of `Object`. (e.g. arrays, functions, objects, regexes, `new Number(0)`, and `new String('')`)
+     * This method is like `_.difference` except that it accepts `iteratee` which
+     * is invoked for each element of `array` and `values` to generate the criterion
+     * by which they're compared. The order and references of result values are
+     * determined by the first array. The iteratee is invoked with one argument:
+     * (value).
+     *
+     * **Note:** Unlike `_.pullAllBy`, this method returns a new array.
      *
      * @static
      * @memberOf _
-     * @since 0.1.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is an object, else `false`.
+     * @since 4.0.0
+     * @category Array
+     * @param {Array} array The array to inspect.
+     * @param {...Array} [values] The values to exclude.
+     * @param {Function} [iteratee=_.identity] The iteratee invoked per element.
+     * @returns {Array} Returns the new array of filtered values.
      * @example
      *
-     * _.isObject({});
-     * // => true
-     *
-     * _.isObject([1, 2, 3]);
-     * // => true
-     *
-     * _.isObject(_.noop);
-     * // => true
+     * _.differenceBy([2.1, 1.2], [2.3, 3.4], Math.floor);
+     * // => [1.2]
      *
-     * _.isObject(null);
-     * // => false
+     * // The `_.property` iteratee shorthand.
+     * _.differenceBy([{ 'x': 2 }, { 'x': 1 }], [{ 'x': 1 }], 'x');
+     * // => [{ 'x': 2 }]
      */
-    function isObject(value) {
-      var type = typeof value;
-      return !!value && (type == 'object' || type == 'function');
-    }
+    var differenceBy = baseRest(function(array, values) {
+      var iteratee = last(values);
+      if (isArrayLikeObject(iteratee)) {
+        iteratee = undefined;
+      }
+      return isArrayLikeObject(array)
+        ? baseDifference(array, baseFlatten(values, 1, isArrayLikeObject, true), getIteratee(iteratee, 2))
+        : [];
+    });
 
     /**
-     * Checks if `value` is object-like. A value is object-like if it's not `null`
-     * and has a `typeof` result of "object".
+     * This method is like `_.difference` except that it accepts `comparator`
+     * which is invoked to compare elements of `array` to `values`. The order and
+     * references of result values are determined by the first array. The comparator
+     * is invoked with two arguments: (arrVal, othVal).
+     *
+     * **Note:** Unlike `_.pullAllWith`, this method returns a new array.
      *
      * @static
      * @memberOf _
      * @since 4.0.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is object-like, else `false`.
+     * @category Array
+     * @param {Array} array The array to inspect.
+     * @param {...Array} [values] The values to exclude.
+     * @param {Function} [comparator] The comparator invoked per element.
+     * @returns {Array} Returns the new array of filtered values.
      * @example
      *
-     * _.isObjectLike({});
-     * // => true
-     *
-     * _.isObjectLike([1, 2, 3]);
-     * // => true
-     *
-     * _.isObjectLike(_.noop);
-     * // => false
+     * var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }];
      *
-     * _.isObjectLike(null);
-     * // => false
+     * _.differenceWith(objects, [{ 'x': 1, 'y': 2 }], _.isEqual);
+     * // => [{ 'x': 2, 'y': 1 }]
      */
-    function isObjectLike(value) {
-      return !!value && typeof value == 'object';
-    }
+    var differenceWith = baseRest(function(array, values) {
+      var comparator = last(values);
+      if (isArrayLikeObject(comparator)) {
+        comparator = undefined;
+      }
+      return isArrayLikeObject(array)
+        ? baseDifference(array, baseFlatten(values, 1, isArrayLikeObject, true), undefined, comparator)
+        : [];
+    });
 
     /**
-     * Checks if `value` is classified as a `Map` object.
+     * Creates a slice of `array` with `n` elements dropped from the beginning.
      *
      * @static
      * @memberOf _
-     * @since 4.3.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is correctly classified,
-     *  else `false`.
+     * @since 0.5.0
+     * @category Array
+     * @param {Array} array The array to query.
+     * @param {number} [n=1] The number of elements to drop.
+     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
+     * @returns {Array} Returns the slice of `array`.
      * @example
      *
-     * _.isMap(new Map);
-     * // => true
+     * _.drop([1, 2, 3]);
+     * // => [2, 3]
      *
-     * _.isMap(new WeakMap);
-     * // => false
+     * _.drop([1, 2, 3], 2);
+     * // => [3]
+     *
+     * _.drop([1, 2, 3], 5);
+     * // => []
+     *
+     * _.drop([1, 2, 3], 0);
+     * // => [1, 2, 3]
      */
-    function isMap(value) {
-      return isObjectLike(value) && getTag(value) == mapTag;
+    function drop(array, n, guard) {
+      var length = array == null ? 0 : array.length;
+      if (!length) {
+        return [];
+      }
+      n = (guard || n === undefined) ? 1 : toInteger(n);
+      return baseSlice(array, n < 0 ? 0 : n, length);
     }
 
     /**
-     * Performs a partial deep comparison between `object` and `source` to
-     * determine if `object` contains equivalent property values. This method is
-     * equivalent to a `_.matches` function when `source` is partially applied.
-     *
-     * **Note:** This method supports comparing the same values as `_.isEqual`.
+     * Creates a slice of `array` with `n` elements dropped from the end.
      *
      * @static
      * @memberOf _
      * @since 3.0.0
-     * @category Lang
-     * @param {Object} object The object to inspect.
-     * @param {Object} source The object of property values to match.
-     * @returns {boolean} Returns `true` if `object` is a match, else `false`.
+     * @category Array
+     * @param {Array} array The array to query.
+     * @param {number} [n=1] The number of elements to drop.
+     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
+     * @returns {Array} Returns the slice of `array`.
      * @example
      *
-     * var object = { 'user': 'fred', 'age': 40 };
+     * _.dropRight([1, 2, 3]);
+     * // => [1, 2]
      *
-     * _.isMatch(object, { 'age': 40 });
-     * // => true
+     * _.dropRight([1, 2, 3], 2);
+     * // => [1]
      *
-     * _.isMatch(object, { 'age': 36 });
-     * // => false
+     * _.dropRight([1, 2, 3], 5);
+     * // => []
+     *
+     * _.dropRight([1, 2, 3], 0);
+     * // => [1, 2, 3]
      */
-    function isMatch(object, source) {
-      return object === source || baseIsMatch(object, source, getMatchData(source));
+    function dropRight(array, n, guard) {
+      var length = array == null ? 0 : array.length;
+      if (!length) {
+        return [];
+      }
+      n = (guard || n === undefined) ? 1 : toInteger(n);
+      n = length - n;
+      return baseSlice(array, 0, n < 0 ? 0 : n);
     }
 
     /**
-     * This method is like `_.isMatch` except that it accepts `customizer` which
-     * is invoked to compare values. If `customizer` returns `undefined`, comparisons
-     * are handled by the method instead. The `customizer` is invoked with five
-     * arguments: (objValue, srcValue, index|key, object, source).
+     * Creates a slice of `array` excluding elements dropped from the end.
+     * Elements are dropped until `predicate` returns falsey. The predicate is
+     * invoked with three arguments: (value, index, array).
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category Lang
-     * @param {Object} object The object to inspect.
-     * @param {Object} source The object of property values to match.
-     * @param {Function} [customizer] The function to customize comparisons.
-     * @returns {boolean} Returns `true` if `object` is a match, else `false`.
+     * @since 3.0.0
+     * @category Array
+     * @param {Array} array The array to query.
+     * @param {Function} [predicate=_.identity] The function invoked per iteration.
+     * @returns {Array} Returns the slice of `array`.
      * @example
      *
-     * function isGreeting(value) {
-     *   return /^h(?:i|ello)$/.test(value);
-     * }
+     * var users = [
+     *   { 'user': 'barney',  'active': true },
+     *   { 'user': 'fred',    'active': false },
+     *   { 'user': 'pebbles', 'active': false }
+     * ];
      *
-     * function customizer(objValue, srcValue) {
-     *   if (isGreeting(objValue) && isGreeting(srcValue)) {
-     *     return true;
-     *   }
-     * }
+     * _.dropRightWhile(users, function(o) { return !o.active; });
+     * // => objects for ['barney']
      *
-     * var object = { 'greeting': 'hello' };
-     * var source = { 'greeting': 'hi' };
+     * // The `_.matches` iteratee shorthand.
+     * _.dropRightWhile(users, { 'user': 'pebbles', 'active': false });
+     * // => objects for ['barney', 'fred']
      *
-     * _.isMatchWith(object, source, customizer);
-     * // => true
+     * // The `_.matchesProperty` iteratee shorthand.
+     * _.dropRightWhile(users, ['active', false]);
+     * // => objects for ['barney']
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.dropRightWhile(users, 'active');
+     * // => objects for ['barney', 'fred', 'pebbles']
      */
-    function isMatchWith(object, source, customizer) {
-      customizer = typeof customizer == 'function' ? customizer : undefined;
-      return baseIsMatch(object, source, getMatchData(source), customizer);
+    function dropRightWhile(array, predicate) {
+      return (array && array.length)
+        ? baseWhile(array, getIteratee(predicate, 3), true, true)
+        : [];
     }
 
     /**
-     * Checks if `value` is `NaN`.
-     *
-     * **Note:** This method is based on
-     * [`Number.isNaN`](https://mdn.io/Number/isNaN) and is not the same as
-     * global [`isNaN`](https://mdn.io/isNaN) which returns `true` for
-     * `undefined` and other non-number values.
+     * Creates a slice of `array` excluding elements dropped from the beginning.
+     * Elements are dropped until `predicate` returns falsey. The predicate is
+     * invoked with three arguments: (value, index, array).
      *
      * @static
      * @memberOf _
-     * @since 0.1.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is `NaN`, else `false`.
+     * @since 3.0.0
+     * @category Array
+     * @param {Array} array The array to query.
+     * @param {Function} [predicate=_.identity] The function invoked per iteration.
+     * @returns {Array} Returns the slice of `array`.
      * @example
      *
-     * _.isNaN(NaN);
-     * // => true
+     * var users = [
+     *   { 'user': 'barney',  'active': false },
+     *   { 'user': 'fred',    'active': false },
+     *   { 'user': 'pebbles', 'active': true }
+     * ];
      *
-     * _.isNaN(new Number(NaN));
-     * // => true
+     * _.dropWhile(users, function(o) { return !o.active; });
+     * // => objects for ['pebbles']
      *
-     * isNaN(undefined);
-     * // => true
+     * // The `_.matches` iteratee shorthand.
+     * _.dropWhile(users, { 'user': 'barney', 'active': false });
+     * // => objects for ['fred', 'pebbles']
      *
-     * _.isNaN(undefined);
-     * // => false
+     * // The `_.matchesProperty` iteratee shorthand.
+     * _.dropWhile(users, ['active', false]);
+     * // => objects for ['pebbles']
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.dropWhile(users, 'active');
+     * // => objects for ['barney', 'fred', 'pebbles']
      */
-    function isNaN(value) {
-      // An `NaN` primitive is the only value that is not equal to itself.
-      // Perform the `toStringTag` check first to avoid errors with some
-      // ActiveX objects in IE.
-      return isNumber(value) && value != +value;
+    function dropWhile(array, predicate) {
+      return (array && array.length)
+        ? baseWhile(array, getIteratee(predicate, 3), true)
+        : [];
     }
 
     /**
-     * Checks if `value` is a pristine native function.
+     * Fills elements of `array` with `value` from `start` up to, but not
+     * including, `end`.
      *
-     * **Note:** This method can't reliably detect native functions in the
-     * presence of the `core-js` package because `core-js` circumvents this kind
-     * of detection. Despite multiple requests, the `core-js` maintainer has made
-     * it clear: any attempt to fix the detection will be obstructed. As a result,
-     * we're left with little choice but to throw an error. Unfortunately, this
-     * also affects packages, like [babel-polyfill](https://www.npmjs.com/package/babel-polyfill),
-     * which rely on `core-js`.
+     * **Note:** This method mutates `array`.
      *
      * @static
      * @memberOf _
-     * @since 3.0.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is a native function,
-     *  else `false`.
+     * @since 3.2.0
+     * @category Array
+     * @param {Array} array The array to fill.
+     * @param {*} value The value to fill `array` with.
+     * @param {number} [start=0] The start position.
+     * @param {number} [end=array.length] The end position.
+     * @returns {Array} Returns `array`.
      * @example
      *
-     * _.isNative(Array.prototype.push);
-     * // => true
+     * var array = [1, 2, 3];
      *
-     * _.isNative(_);
-     * // => false
+     * _.fill(array, 'a');
+     * console.log(array);
+     * // => ['a', 'a', 'a']
+     *
+     * _.fill(Array(3), 2);
+     * // => [2, 2, 2]
+     *
+     * _.fill([4, 6, 8, 10], '*', 1, 3);
+     * // => [4, '*', '*', 10]
      */
-    function isNative(value) {
-      if (isMaskable(value)) {
-        throw new Error('This method is not supported with `core-js`. Try https://github.com/es-shims.');
+    function fill(array, value, start, end) {
+      var length = array == null ? 0 : array.length;
+      if (!length) {
+        return [];
       }
-      return baseIsNative(value);
+      if (start && typeof start != 'number' && isIterateeCall(array, value, start)) {
+        start = 0;
+        end = length;
+      }
+      return baseFill(array, value, start, end);
     }
 
     /**
-     * Checks if `value` is `null`.
+     * This method is like `_.find` except that it returns the index of the first
+     * element `predicate` returns truthy for instead of the element itself.
      *
      * @static
      * @memberOf _
-     * @since 0.1.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is `null`, else `false`.
+     * @since 1.1.0
+     * @category Array
+     * @param {Array} array The array to inspect.
+     * @param {Function} [predicate=_.identity] The function invoked per iteration.
+     * @param {number} [fromIndex=0] The index to search from.
+     * @returns {number} Returns the index of the found element, else `-1`.
      * @example
      *
-     * _.isNull(null);
-     * // => true
+     * var users = [
+     *   { 'user': 'barney',  'active': false },
+     *   { 'user': 'fred',    'active': false },
+     *   { 'user': 'pebbles', 'active': true }
+     * ];
      *
-     * _.isNull(void 0);
-     * // => false
+     * _.findIndex(users, function(o) { return o.user == 'barney'; });
+     * // => 0
+     *
+     * // The `_.matches` iteratee shorthand.
+     * _.findIndex(users, { 'user': 'fred', 'active': false });
+     * // => 1
+     *
+     * // The `_.matchesProperty` iteratee shorthand.
+     * _.findIndex(users, ['active', false]);
+     * // => 0
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.findIndex(users, 'active');
+     * // => 2
      */
-    function isNull(value) {
-      return value === null;
+    function findIndex(array, predicate, fromIndex) {
+      var length = array == null ? 0 : array.length;
+      if (!length) {
+        return -1;
+      }
+      var index = fromIndex == null ? 0 : toInteger(fromIndex);
+      if (index < 0) {
+        index = nativeMax(length + index, 0);
+      }
+      return baseFindIndex(array, getIteratee(predicate, 3), index);
     }
 
     /**
-     * Checks if `value` is `null` or `undefined`.
+     * This method is like `_.findIndex` except that it iterates over elements
+     * of `collection` from right to left.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is nullish, else `false`.
+     * @since 2.0.0
+     * @category Array
+     * @param {Array} array The array to inspect.
+     * @param {Function} [predicate=_.identity] The function invoked per iteration.
+     * @param {number} [fromIndex=array.length-1] The index to search from.
+     * @returns {number} Returns the index of the found element, else `-1`.
      * @example
      *
-     * _.isNil(null);
-     * // => true
+     * var users = [
+     *   { 'user': 'barney',  'active': true },
+     *   { 'user': 'fred',    'active': false },
+     *   { 'user': 'pebbles', 'active': false }
+     * ];
      *
-     * _.isNil(void 0);
-     * // => true
+     * _.findLastIndex(users, function(o) { return o.user == 'pebbles'; });
+     * // => 2
      *
-     * _.isNil(NaN);
-     * // => false
+     * // The `_.matches` iteratee shorthand.
+     * _.findLastIndex(users, { 'user': 'barney', 'active': true });
+     * // => 0
+     *
+     * // The `_.matchesProperty` iteratee shorthand.
+     * _.findLastIndex(users, ['active', false]);
+     * // => 2
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.findLastIndex(users, 'active');
+     * // => 0
      */
-    function isNil(value) {
-      return value == null;
+    function findLastIndex(array, predicate, fromIndex) {
+      var length = array == null ? 0 : array.length;
+      if (!length) {
+        return -1;
+      }
+      var index = length - 1;
+      if (fromIndex !== undefined) {
+        index = toInteger(fromIndex);
+        index = fromIndex < 0
+          ? nativeMax(length + index, 0)
+          : nativeMin(index, length - 1);
+      }
+      return baseFindIndex(array, getIteratee(predicate, 3), index, true);
     }
 
     /**
-     * Checks if `value` is classified as a `Number` primitive or object.
-     *
-     * **Note:** To exclude `Infinity`, `-Infinity`, and `NaN`, which are
-     * classified as numbers, use the `_.isFinite` method.
+     * Flattens `array` a single level deep.
      *
      * @static
      * @memberOf _
      * @since 0.1.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is correctly classified,
-     *  else `false`.
+     * @category Array
+     * @param {Array} array The array to flatten.
+     * @returns {Array} Returns the new flattened array.
      * @example
      *
-     * _.isNumber(3);
-     * // => true
-     *
-     * _.isNumber(Number.MIN_VALUE);
-     * // => true
-     *
-     * _.isNumber(Infinity);
-     * // => true
-     *
-     * _.isNumber('3');
-     * // => false
+     * _.flatten([1, [2, [3, [4]], 5]]);
+     * // => [1, 2, [3, [4]], 5]
      */
-    function isNumber(value) {
-      return typeof value == 'number' ||
-        (isObjectLike(value) && objectToString.call(value) == numberTag);
+    function flatten(array) {
+      var length = array == null ? 0 : array.length;
+      return length ? baseFlatten(array, 1) : [];
     }
 
     /**
-     * Checks if `value` is a plain object, that is, an object created by the
-     * `Object` constructor or one with a `[[Prototype]]` of `null`.
+     * Recursively flattens `array`.
      *
      * @static
      * @memberOf _
-     * @since 0.8.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is a plain object,
-     *  else `false`.
+     * @since 3.0.0
+     * @category Array
+     * @param {Array} array The array to flatten.
+     * @returns {Array} Returns the new flattened array.
      * @example
      *
-     * function Foo() {
-     *   this.a = 1;
-     * }
-     *
-     * _.isPlainObject(new Foo);
-     * // => false
-     *
-     * _.isPlainObject([1, 2, 3]);
-     * // => false
-     *
-     * _.isPlainObject({ 'x': 0, 'y': 0 });
-     * // => true
-     *
-     * _.isPlainObject(Object.create(null));
-     * // => true
+     * _.flattenDeep([1, [2, [3, [4]], 5]]);
+     * // => [1, 2, 3, 4, 5]
      */
-    function isPlainObject(value) {
-      if (!isObjectLike(value) ||
-          objectToString.call(value) != objectTag || isHostObject(value)) {
-        return false;
-      }
-      var proto = getPrototype(value);
-      if (proto === null) {
-        return true;
-      }
-      var Ctor = hasOwnProperty.call(proto, 'constructor') && proto.constructor;
-      return (typeof Ctor == 'function' &&
-        Ctor instanceof Ctor && funcToString.call(Ctor) == objectCtorString);
+    function flattenDeep(array) {
+      var length = array == null ? 0 : array.length;
+      return length ? baseFlatten(array, INFINITY) : [];
     }
 
     /**
-     * Checks if `value` is classified as a `RegExp` object.
+     * Recursively flatten `array` up to `depth` times.
      *
      * @static
      * @memberOf _
-     * @since 0.1.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is correctly classified,
-     *  else `false`.
+     * @since 4.4.0
+     * @category Array
+     * @param {Array} array The array to flatten.
+     * @param {number} [depth=1] The maximum recursion depth.
+     * @returns {Array} Returns the new flattened array.
      * @example
      *
-     * _.isRegExp(/abc/);
-     * // => true
+     * var array = [1, [2, [3, [4]], 5]];
      *
-     * _.isRegExp('/abc/');
-     * // => false
+     * _.flattenDepth(array, 1);
+     * // => [1, 2, [3, [4]], 5]
+     *
+     * _.flattenDepth(array, 2);
+     * // => [1, 2, 3, [4], 5]
      */
-    function isRegExp(value) {
-      return isObject(value) && objectToString.call(value) == regexpTag;
+    function flattenDepth(array, depth) {
+      var length = array == null ? 0 : array.length;
+      if (!length) {
+        return [];
+      }
+      depth = depth === undefined ? 1 : toInteger(depth);
+      return baseFlatten(array, depth);
     }
 
     /**
-     * Checks if `value` is a safe integer. An integer is safe if it's an IEEE-754
-     * double precision number which isn't the result of a rounded unsafe integer.
-     *
-     * **Note:** This method is based on
-     * [`Number.isSafeInteger`](https://mdn.io/Number/isSafeInteger).
+     * The inverse of `_.toPairs`; this method returns an object composed
+     * from key-value `pairs`.
      *
      * @static
      * @memberOf _
      * @since 4.0.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is a safe integer,
-     *  else `false`.
+     * @category Array
+     * @param {Array} pairs The key-value pairs.
+     * @returns {Object} Returns the new object.
      * @example
      *
-     * _.isSafeInteger(3);
-     * // => true
-     *
-     * _.isSafeInteger(Number.MIN_VALUE);
-     * // => false
-     *
-     * _.isSafeInteger(Infinity);
-     * // => false
-     *
-     * _.isSafeInteger('3');
-     * // => false
+     * _.fromPairs([['a', 1], ['b', 2]]);
+     * // => { 'a': 1, 'b': 2 }
      */
-    function isSafeInteger(value) {
-      return isInteger(value) && value >= -MAX_SAFE_INTEGER && value <= MAX_SAFE_INTEGER;
+    function fromPairs(pairs) {
+      var index = -1,
+          length = pairs == null ? 0 : pairs.length,
+          result = {};
+
+      while (++index < length) {
+        var pair = pairs[index];
+        result[pair[0]] = pair[1];
+      }
+      return result;
     }
 
     /**
-     * Checks if `value` is classified as a `Set` object.
+     * Gets the first element of `array`.
      *
      * @static
      * @memberOf _
-     * @since 4.3.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is correctly classified,
-     *  else `false`.
+     * @since 0.1.0
+     * @alias first
+     * @category Array
+     * @param {Array} array The array to query.
+     * @returns {*} Returns the first element of `array`.
      * @example
      *
-     * _.isSet(new Set);
-     * // => true
+     * _.head([1, 2, 3]);
+     * // => 1
      *
-     * _.isSet(new WeakSet);
-     * // => false
+     * _.head([]);
+     * // => undefined
      */
-    function isSet(value) {
-      return isObjectLike(value) && getTag(value) == setTag;
+    function head(array) {
+      return (array && array.length) ? array[0] : undefined;
     }
 
     /**
-     * Checks if `value` is classified as a `String` primitive or object.
+     * Gets the index at which the first occurrence of `value` is found in `array`
+     * using [`SameValueZero`](http://ecma-international.org/ecma-262/7.0/#sec-samevaluezero)
+     * for equality comparisons. If `fromIndex` is negative, it's used as the
+     * offset from the end of `array`.
      *
      * @static
-     * @since 0.1.0
      * @memberOf _
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is correctly classified,
-     *  else `false`.
+     * @since 0.1.0
+     * @category Array
+     * @param {Array} array The array to inspect.
+     * @param {*} value The value to search for.
+     * @param {number} [fromIndex=0] The index to search from.
+     * @returns {number} Returns the index of the matched value, else `-1`.
      * @example
      *
-     * _.isString('abc');
-     * // => true
+     * _.indexOf([1, 2, 1, 2], 2);
+     * // => 1
      *
-     * _.isString(1);
-     * // => false
+     * // Search from the `fromIndex`.
+     * _.indexOf([1, 2, 1, 2], 2, 2);
+     * // => 3
      */
-    function isString(value) {
-      return typeof value == 'string' ||
-        (!isArray(value) && isObjectLike(value) && objectToString.call(value) == stringTag);
+    function indexOf(array, value, fromIndex) {
+      var length = array == null ? 0 : array.length;
+      if (!length) {
+        return -1;
+      }
+      var index = fromIndex == null ? 0 : toInteger(fromIndex);
+      if (index < 0) {
+        index = nativeMax(length + index, 0);
+      }
+      return baseIndexOf(array, value, index);
     }
 
     /**
-     * Checks if `value` is classified as a `Symbol` primitive or object.
+     * Gets all but the last element of `array`.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is correctly classified,
-     *  else `false`.
+     * @since 0.1.0
+     * @category Array
+     * @param {Array} array The array to query.
+     * @returns {Array} Returns the slice of `array`.
      * @example
      *
-     * _.isSymbol(Symbol.iterator);
-     * // => true
-     *
-     * _.isSymbol('abc');
-     * // => false
+     * _.initial([1, 2, 3]);
+     * // => [1, 2]
      */
-    function isSymbol(value) {
-      return typeof value == 'symbol' ||
-        (isObjectLike(value) && objectToString.call(value) == symbolTag);
+    function initial(array) {
+      var length = array == null ? 0 : array.length;
+      return length ? baseSlice(array, 0, -1) : [];
     }
 
     /**
-     * Checks if `value` is classified as a typed array.
+     * Creates an array of unique values that are included in all given arrays
+     * using [`SameValueZero`](http://ecma-international.org/ecma-262/7.0/#sec-samevaluezero)
+     * for equality comparisons. The order and references of result values are
+     * determined by the first array.
      *
      * @static
      * @memberOf _
-     * @since 3.0.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is correctly classified,
-     *  else `false`.
+     * @since 0.1.0
+     * @category Array
+     * @param {...Array} [arrays] The arrays to inspect.
+     * @returns {Array} Returns the new array of intersecting values.
      * @example
      *
-     * _.isTypedArray(new Uint8Array);
-     * // => true
-     *
-     * _.isTypedArray([]);
-     * // => false
+     * _.intersection([2, 1], [2, 3]);
+     * // => [2]
      */
-    function isTypedArray(value) {
-      return isObjectLike(value) &&
-        isLength(value.length) && !!typedArrayTags[objectToString.call(value)];
-    }
+    var intersection = baseRest(function(arrays) {
+      var mapped = arrayMap(arrays, castArrayLikeObject);
+      return (mapped.length && mapped[0] === arrays[0])
+        ? baseIntersection(mapped)
+        : [];
+    });
 
     /**
-     * Checks if `value` is `undefined`.
+     * This method is like `_.intersection` except that it accepts `iteratee`
+     * which is invoked for each element of each `arrays` to generate the criterion
+     * by which they're compared. The order and references of result values are
+     * determined by the first array. The iteratee is invoked with one argument:
+     * (value).
      *
      * @static
-     * @since 0.1.0
      * @memberOf _
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is `undefined`, else `false`.
+     * @since 4.0.0
+     * @category Array
+     * @param {...Array} [arrays] The arrays to inspect.
+     * @param {Function} [iteratee=_.identity] The iteratee invoked per element.
+     * @returns {Array} Returns the new array of intersecting values.
      * @example
      *
-     * _.isUndefined(void 0);
-     * // => true
+     * _.intersectionBy([2.1, 1.2], [2.3, 3.4], Math.floor);
+     * // => [2.1]
      *
-     * _.isUndefined(null);
-     * // => false
+     * // The `_.property` iteratee shorthand.
+     * _.intersectionBy([{ 'x': 1 }], [{ 'x': 2 }, { 'x': 1 }], 'x');
+     * // => [{ 'x': 1 }]
      */
-    function isUndefined(value) {
-      return value === undefined;
-    }
+    var intersectionBy = baseRest(function(arrays) {
+      var iteratee = last(arrays),
+          mapped = arrayMap(arrays, castArrayLikeObject);
+
+      if (iteratee === last(mapped)) {
+        iteratee = undefined;
+      } else {
+        mapped.pop();
+      }
+      return (mapped.length && mapped[0] === arrays[0])
+        ? baseIntersection(mapped, getIteratee(iteratee, 2))
+        : [];
+    });
 
     /**
-     * Checks if `value` is classified as a `WeakMap` object.
+     * This method is like `_.intersection` except that it accepts `comparator`
+     * which is invoked to compare elements of `arrays`. The order and references
+     * of result values are determined by the first array. The comparator is
+     * invoked with two arguments: (arrVal, othVal).
      *
      * @static
      * @memberOf _
-     * @since 4.3.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is correctly classified,
-     *  else `false`.
+     * @since 4.0.0
+     * @category Array
+     * @param {...Array} [arrays] The arrays to inspect.
+     * @param {Function} [comparator] The comparator invoked per element.
+     * @returns {Array} Returns the new array of intersecting values.
      * @example
      *
-     * _.isWeakMap(new WeakMap);
-     * // => true
+     * var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }];
+     * var others = [{ 'x': 1, 'y': 1 }, { 'x': 1, 'y': 2 }];
      *
-     * _.isWeakMap(new Map);
-     * // => false
+     * _.intersectionWith(objects, others, _.isEqual);
+     * // => [{ 'x': 1, 'y': 2 }]
      */
-    function isWeakMap(value) {
-      return isObjectLike(value) && getTag(value) == weakMapTag;
-    }
+    var intersectionWith = baseRest(function(arrays) {
+      var comparator = last(arrays),
+          mapped = arrayMap(arrays, castArrayLikeObject);
+
+      comparator = typeof comparator == 'function' ? comparator : undefined;
+      if (comparator) {
+        mapped.pop();
+      }
+      return (mapped.length && mapped[0] === arrays[0])
+        ? baseIntersection(mapped, undefined, comparator)
+        : [];
+    });
 
     /**
-     * Checks if `value` is classified as a `WeakSet` object.
+     * Converts all elements in `array` into a string separated by `separator`.
      *
      * @static
      * @memberOf _
-     * @since 4.3.0
-     * @category Lang
-     * @param {*} value The value to check.
-     * @returns {boolean} Returns `true` if `value` is correctly classified,
-     *  else `false`.
+     * @since 4.0.0
+     * @category Array
+     * @param {Array} array The array to convert.
+     * @param {string} [separator=','] The element separator.
+     * @returns {string} Returns the joined string.
      * @example
      *
-     * _.isWeakSet(new WeakSet);
-     * // => true
-     *
-     * _.isWeakSet(new Set);
-     * // => false
+     * _.join(['a', 'b', 'c'], '~');
+     * // => 'a~b~c'
      */
-    function isWeakSet(value) {
-      return isObjectLike(value) && objectToString.call(value) == weakSetTag;
+    function join(array, separator) {
+      return array == null ? '' : nativeJoin.call(array, separator);
     }
 
     /**
-     * Checks if `value` is less than `other`.
+     * Gets the last element of `array`.
      *
      * @static
      * @memberOf _
-     * @since 3.9.0
-     * @category Lang
-     * @param {*} value The value to compare.
-     * @param {*} other The other value to compare.
-     * @returns {boolean} Returns `true` if `value` is less than `other`,
-     *  else `false`.
-     * @see _.gt
+     * @since 0.1.0
+     * @category Array
+     * @param {Array} array The array to query.
+     * @returns {*} Returns the last element of `array`.
      * @example
      *
-     * _.lt(1, 3);
-     * // => true
-     *
-     * _.lt(3, 3);
-     * // => false
-     *
-     * _.lt(3, 1);
-     * // => false
+     * _.last([1, 2, 3]);
+     * // => 3
      */
-    var lt = createRelationalOperation(baseLt);
+    function last(array) {
+      var length = array == null ? 0 : array.length;
+      return length ? array[length - 1] : undefined;
+    }
 
     /**
-     * Checks if `value` is less than or equal to `other`.
+     * This method is like `_.indexOf` except that it iterates over elements of
+     * `array` from right to left.
      *
      * @static
      * @memberOf _
-     * @since 3.9.0
-     * @category Lang
-     * @param {*} value The value to compare.
-     * @param {*} other The other value to compare.
-     * @returns {boolean} Returns `true` if `value` is less than or equal to
-     *  `other`, else `false`.
-     * @see _.gte
+     * @since 0.1.0
+     * @category Array
+     * @param {Array} array The array to inspect.
+     * @param {*} value The value to search for.
+     * @param {number} [fromIndex=array.length-1] The index to search from.
+     * @returns {number} Returns the index of the matched value, else `-1`.
      * @example
      *
-     * _.lte(1, 3);
-     * // => true
-     *
-     * _.lte(3, 3);
-     * // => true
+     * _.lastIndexOf([1, 2, 1, 2], 2);
+     * // => 3
      *
-     * _.lte(3, 1);
-     * // => false
+     * // Search from the `fromIndex`.
+     * _.lastIndexOf([1, 2, 1, 2], 2, 2);
+     * // => 1
      */
-    var lte = createRelationalOperation(function(value, other) {
-      return value <= other;
-    });
+    function lastIndexOf(array, value, fromIndex) {
+      var length = array == null ? 0 : array.length;
+      if (!length) {
+        return -1;
+      }
+      var index = length;
+      if (fromIndex !== undefined) {
+        index = toInteger(fromIndex);
+        index = index < 0 ? nativeMax(length + index, 0) : nativeMin(index, length - 1);
+      }
+      return value === value
+        ? strictLastIndexOf(array, value, index)
+        : baseFindIndex(array, baseIsNaN, index, true);
+    }
 
     /**
-     * Converts `value` to an array.
+     * Gets the element at index `n` of `array`. If `n` is negative, the nth
+     * element from the end is returned.
      *
      * @static
-     * @since 0.1.0
      * @memberOf _
-     * @category Lang
-     * @param {*} value The value to convert.
-     * @returns {Array} Returns the converted array.
+     * @since 4.11.0
+     * @category Array
+     * @param {Array} array The array to query.
+     * @param {number} [n=0] The index of the element to return.
+     * @returns {*} Returns the nth element of `array`.
      * @example
      *
-     * _.toArray({ 'a': 1, 'b': 2 });
-     * // => [1, 2]
-     *
-     * _.toArray('abc');
-     * // => ['a', 'b', 'c']
+     * var array = ['a', 'b', 'c', 'd'];
      *
-     * _.toArray(1);
-     * // => []
+     * _.nth(array, 1);
+     * // => 'b'
      *
-     * _.toArray(null);
-     * // => []
+     * _.nth(array, -2);
+     * // => 'c';
      */
-    function toArray(value) {
-      if (!value) {
-        return [];
-      }
-      if (isArrayLike(value)) {
-        return isString(value) ? stringToArray(value) : copyArray(value);
-      }
-      if (iteratorSymbol && value[iteratorSymbol]) {
-        return iteratorToArray(value[iteratorSymbol]());
-      }
-      var tag = getTag(value),
-          func = tag == mapTag ? mapToArray : (tag == setTag ? setToArray : values);
-
-      return func(value);
+    function nth(array, n) {
+      return (array && array.length) ? baseNth(array, toInteger(n)) : undefined;
     }
 
     /**
-     * Converts `value` to a finite number.
+     * Removes all given values from `array` using
+     * [`SameValueZero`](http://ecma-international.org/ecma-262/7.0/#sec-samevaluezero)
+     * for equality comparisons.
+     *
+     * **Note:** Unlike `_.without`, this method mutates `array`. Use `_.remove`
+     * to remove elements from an array by predicate.
      *
      * @static
      * @memberOf _
-     * @since 4.12.0
-     * @category Lang
-     * @param {*} value The value to convert.
-     * @returns {number} Returns the converted number.
+     * @since 2.0.0
+     * @category Array
+     * @param {Array} array The array to modify.
+     * @param {...*} [values] The values to remove.
+     * @returns {Array} Returns `array`.
      * @example
      *
-     * _.toFinite(3.2);
-     * // => 3.2
-     *
-     * _.toFinite(Number.MIN_VALUE);
-     * // => 5e-324
-     *
-     * _.toFinite(Infinity);
-     * // => 1.7976931348623157e+308
+     * var array = ['a', 'b', 'c', 'a', 'b', 'c'];
      *
-     * _.toFinite('3.2');
-     * // => 3.2
+     * _.pull(array, 'a', 'c');
+     * console.log(array);
+     * // => ['b', 'b']
      */
-    function toFinite(value) {
-      if (!value) {
-        return value === 0 ? value : 0;
-      }
-      value = toNumber(value);
-      if (value === INFINITY || value === -INFINITY) {
-        var sign = (value < 0 ? -1 : 1);
-        return sign * MAX_INTEGER;
-      }
-      return value === value ? value : 0;
-    }
+    var pull = baseRest(pullAll);
 
     /**
-     * Converts `value` to an integer.
+     * This method is like `_.pull` except that it accepts an array of values to remove.
      *
-     * **Note:** This method is loosely based on
-     * [`ToInteger`](http://www.ecma-international.org/ecma-262/6.0/#sec-tointeger).
+     * **Note:** Unlike `_.difference`, this method mutates `array`.
      *
      * @static
      * @memberOf _
      * @since 4.0.0
-     * @category Lang
-     * @param {*} value The value to convert.
-     * @returns {number} Returns the converted integer.
+     * @category Array
+     * @param {Array} array The array to modify.
+     * @param {Array} values The values to remove.
+     * @returns {Array} Returns `array`.
      * @example
      *
-     * _.toInteger(3.2);
-     * // => 3
-     *
-     * _.toInteger(Number.MIN_VALUE);
-     * // => 0
-     *
-     * _.toInteger(Infinity);
-     * // => 1.7976931348623157e+308
+     * var array = ['a', 'b', 'c', 'a', 'b', 'c'];
      *
-     * _.toInteger('3.2');
-     * // => 3
+     * _.pullAll(array, ['a', 'c']);
+     * console.log(array);
+     * // => ['b', 'b']
      */
-    function toInteger(value) {
-      var result = toFinite(value),
-          remainder = result % 1;
-
-      return result === result ? (remainder ? result - remainder : result) : 0;
+    function pullAll(array, values) {
+      return (array && array.length && values && values.length)
+        ? basePullAll(array, values)
+        : array;
     }
 
     /**
-     * Converts `value` to an integer suitable for use as the length of an
-     * array-like object.
+     * This method is like `_.pullAll` except that it accepts `iteratee` which is
+     * invoked for each element of `array` and `values` to generate the criterion
+     * by which they're compared. The iteratee is invoked with one argument: (value).
      *
-     * **Note:** This method is based on
-     * [`ToLength`](http://ecma-international.org/ecma-262/6.0/#sec-tolength).
+     * **Note:** Unlike `_.differenceBy`, this method mutates `array`.
      *
      * @static
      * @memberOf _
      * @since 4.0.0
-     * @category Lang
-     * @param {*} value The value to convert.
-     * @returns {number} Returns the converted integer.
+     * @category Array
+     * @param {Array} array The array to modify.
+     * @param {Array} values The values to remove.
+     * @param {Function} [iteratee=_.identity] The iteratee invoked per element.
+     * @returns {Array} Returns `array`.
      * @example
      *
-     * _.toLength(3.2);
-     * // => 3
-     *
-     * _.toLength(Number.MIN_VALUE);
-     * // => 0
-     *
-     * _.toLength(Infinity);
-     * // => 4294967295
+     * var array = [{ 'x': 1 }, { 'x': 2 }, { 'x': 3 }, { 'x': 1 }];
      *
-     * _.toLength('3.2');
-     * // => 3
+     * _.pullAllBy(array, [{ 'x': 1 }, { 'x': 3 }], 'x');
+     * console.log(array);
+     * // => [{ 'x': 2 }]
      */
-    function toLength(value) {
-      return value ? baseClamp(toInteger(value), 0, MAX_ARRAY_LENGTH) : 0;
+    function pullAllBy(array, values, iteratee) {
+      return (array && array.length && values && values.length)
+        ? basePullAll(array, values, getIteratee(iteratee, 2))
+        : array;
     }
 
     /**
-     * Converts `value` to a number.
+     * This method is like `_.pullAll` except that it accepts `comparator` which
+     * is invoked to compare elements of `array` to `values`. The comparator is
+     * invoked with two arguments: (arrVal, othVal).
+     *
+     * **Note:** Unlike `_.differenceWith`, this method mutates `array`.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category Lang
-     * @param {*} value The value to process.
-     * @returns {number} Returns the number.
+     * @since 4.6.0
+     * @category Array
+     * @param {Array} array The array to modify.
+     * @param {Array} values The values to remove.
+     * @param {Function} [comparator] The comparator invoked per element.
+     * @returns {Array} Returns `array`.
      * @example
      *
-     * _.toNumber(3.2);
-     * // => 3.2
-     *
-     * _.toNumber(Number.MIN_VALUE);
-     * // => 5e-324
-     *
-     * _.toNumber(Infinity);
-     * // => Infinity
+     * var array = [{ 'x': 1, 'y': 2 }, { 'x': 3, 'y': 4 }, { 'x': 5, 'y': 6 }];
      *
-     * _.toNumber('3.2');
-     * // => 3.2
+     * _.pullAllWith(array, [{ 'x': 3, 'y': 4 }], _.isEqual);
+     * console.log(array);
+     * // => [{ 'x': 1, 'y': 2 }, { 'x': 5, 'y': 6 }]
      */
-    function toNumber(value) {
-      if (typeof value == 'number') {
-        return value;
-      }
-      if (isSymbol(value)) {
-        return NAN;
-      }
-      if (isObject(value)) {
-        var other = isFunction(value.valueOf) ? value.valueOf() : value;
-        value = isObject(other) ? (other + '') : other;
-      }
-      if (typeof value != 'string') {
-        return value === 0 ? value : +value;
-      }
-      value = value.replace(reTrim, '');
-      var isBinary = reIsBinary.test(value);
-      return (isBinary || reIsOctal.test(value))
-        ? freeParseInt(value.slice(2), isBinary ? 2 : 8)
-        : (reIsBadHex.test(value) ? NAN : +value);
+    function pullAllWith(array, values, comparator) {
+      return (array && array.length && values && values.length)
+        ? basePullAll(array, values, undefined, comparator)
+        : array;
     }
 
     /**
-     * Converts `value` to a plain object flattening inherited enumerable string
-     * keyed properties of `value` to own properties of the plain object.
+     * Removes elements from `array` corresponding to `indexes` and returns an
+     * array of removed elements.
+     *
+     * **Note:** Unlike `_.at`, this method mutates `array`.
      *
      * @static
      * @memberOf _
      * @since 3.0.0
-     * @category Lang
-     * @param {*} value The value to convert.
-     * @returns {Object} Returns the converted plain object.
+     * @category Array
+     * @param {Array} array The array to modify.
+     * @param {...(number|number[])} [indexes] The indexes of elements to remove.
+     * @returns {Array} Returns the new array of removed elements.
      * @example
      *
-     * function Foo() {
-     *   this.b = 2;
-     * }
-     *
-     * Foo.prototype.c = 3;
+     * var array = ['a', 'b', 'c', 'd'];
+     * var pulled = _.pullAt(array, [1, 3]);
      *
-     * _.assign({ 'a': 1 }, new Foo);
-     * // => { 'a': 1, 'b': 2 }
+     * console.log(array);
+     * // => ['a', 'c']
      *
-     * _.assign({ 'a': 1 }, _.toPlainObject(new Foo));
-     * // => { 'a': 1, 'b': 2, 'c': 3 }
+     * console.log(pulled);
+     * // => ['b', 'd']
      */
-    function toPlainObject(value) {
-      return copyObject(value, keysIn(value));
-    }
+    var pullAt = flatRest(function(array, indexes) {
+      var length = array == null ? 0 : array.length,
+          result = baseAt(array, indexes);
+
+      basePullAt(array, arrayMap(indexes, function(index) {
+        return isIndex(index, length) ? +index : index;
+      }).sort(compareAscending));
+
+      return result;
+    });
 
     /**
-     * Converts `value` to a safe integer. A safe integer can be compared and
-     * represented correctly.
+     * Removes all elements from `array` that `predicate` returns truthy for
+     * and returns an array of the removed elements. The predicate is invoked
+     * with three arguments: (value, index, array).
+     *
+     * **Note:** Unlike `_.filter`, this method mutates `array`. Use `_.pull`
+     * to pull elements from an array by value.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category Lang
-     * @param {*} value The value to convert.
-     * @returns {number} Returns the converted integer.
+     * @since 2.0.0
+     * @category Array
+     * @param {Array} array The array to modify.
+     * @param {Function} [predicate=_.identity] The function invoked per iteration.
+     * @returns {Array} Returns the new array of removed elements.
      * @example
      *
-     * _.toSafeInteger(3.2);
-     * // => 3
-     *
-     * _.toSafeInteger(Number.MIN_VALUE);
-     * // => 0
+     * var array = [1, 2, 3, 4];
+     * var evens = _.remove(array, function(n) {
+     *   return n % 2 == 0;
+     * });
      *
-     * _.toSafeInteger(Infinity);
-     * // => 9007199254740991
+     * console.log(array);
+     * // => [1, 3]
      *
-     * _.toSafeInteger('3.2');
-     * // => 3
+     * console.log(evens);
+     * // => [2, 4]
      */
-    function toSafeInteger(value) {
-      return baseClamp(toInteger(value), -MAX_SAFE_INTEGER, MAX_SAFE_INTEGER);
+    function remove(array, predicate) {
+      var result = [];
+      if (!(array && array.length)) {
+        return result;
+      }
+      var index = -1,
+          indexes = [],
+          length = array.length;
+
+      predicate = getIteratee(predicate, 3);
+      while (++index < length) {
+        var value = array[index];
+        if (predicate(value, index, array)) {
+          result.push(value);
+          indexes.push(index);
+        }
+      }
+      basePullAt(array, indexes);
+      return result;
     }
 
     /**
-     * Converts `value` to a string. An empty string is returned for `null`
-     * and `undefined` values. The sign of `-0` is preserved.
+     * Reverses `array` so that the first element becomes the last, the second
+     * element becomes the second to last, and so on.
+     *
+     * **Note:** This method mutates `array` and is based on
+     * [`Array#reverse`](https://mdn.io/Array/reverse).
      *
      * @static
      * @memberOf _
      * @since 4.0.0
-     * @category Lang
-     * @param {*} value The value to process.
-     * @returns {string} Returns the string.
+     * @category Array
+     * @param {Array} array The array to modify.
+     * @returns {Array} Returns `array`.
      * @example
      *
-     * _.toString(null);
-     * // => ''
+     * var array = [1, 2, 3];
      *
-     * _.toString(-0);
-     * // => '-0'
+     * _.reverse(array);
+     * // => [3, 2, 1]
      *
-     * _.toString([1, 2, 3]);
-     * // => '1,2,3'
+     * console.log(array);
+     * // => [3, 2, 1]
      */
-    function toString(value) {
-      return value == null ? '' : baseToString(value);
+    function reverse(array) {
+      return array == null ? array : nativeReverse.call(array);
     }
 
-    /*------------------------------------------------------------------------*/
-
     /**
-     * Assigns own enumerable string keyed properties of source objects to the
-     * destination object. Source objects are applied from left to right.
-     * Subsequent sources overwrite property assignments of previous sources.
+     * Creates a slice of `array` from `start` up to, but not including, `end`.
      *
-     * **Note:** This method mutates `object` and is loosely based on
-     * [`Object.assign`](https://mdn.io/Object/assign).
+     * **Note:** This method is used instead of
+     * [`Array#slice`](https://mdn.io/Array/slice) to ensure dense arrays are
+     * returned.
      *
      * @static
      * @memberOf _
-     * @since 0.10.0
-     * @category Object
-     * @param {Object} object The destination object.
-     * @param {...Object} [sources] The source objects.
-     * @returns {Object} Returns `object`.
-     * @see _.assignIn
-     * @example
-     *
-     * function Foo() {
-     *   this.c = 3;
-     * }
-     *
-     * function Bar() {
-     *   this.e = 5;
-     * }
-     *
-     * Foo.prototype.d = 4;
-     * Bar.prototype.f = 6;
-     *
-     * _.assign({ 'a': 1 }, new Foo, new Bar);
-     * // => { 'a': 1, 'c': 3, 'e': 5 }
+     * @since 3.0.0
+     * @category Array
+     * @param {Array} array The array to slice.
+     * @param {number} [start=0] The start position.
+     * @param {number} [end=array.length] The end position.
+     * @returns {Array} Returns the slice of `array`.
      */
-    var assign = createAssigner(function(object, source) {
-      if (nonEnumShadows || isPrototype(source) || isArrayLike(source)) {
-        copyObject(source, keys(source), object);
-        return;
+    function slice(array, start, end) {
+      var length = array == null ? 0 : array.length;
+      if (!length) {
+        return [];
       }
-      for (var key in source) {
-        if (hasOwnProperty.call(source, key)) {
-          assignValue(object, key, source[key]);
-        }
+      if (end && typeof end != 'number' && isIterateeCall(array, start, end)) {
+        start = 0;
+        end = length;
       }
-    });
+      else {
+        start = start == null ? 0 : toInteger(start);
+        end = end === undefined ? length : toInteger(end);
+      }
+      return baseSlice(array, start, end);
+    }
 
     /**
-     * This method is like `_.assign` except that it iterates over own and
-     * inherited source properties.
-     *
-     * **Note:** This method mutates `object`.
+     * Uses a binary search to determine the lowest index at which `value`
+     * should be inserted into `array` in order to maintain its sort order.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @alias extend
-     * @category Object
-     * @param {Object} object The destination object.
-     * @param {...Object} [sources] The source objects.
-     * @returns {Object} Returns `object`.
-     * @see _.assign
+     * @since 0.1.0
+     * @category Array
+     * @param {Array} array The sorted array to inspect.
+     * @param {*} value The value to evaluate.
+     * @returns {number} Returns the index at which `value` should be inserted
+     *  into `array`.
      * @example
      *
-     * function Foo() {
-     *   this.b = 2;
-     * }
-     *
-     * function Bar() {
-     *   this.d = 4;
-     * }
-     *
-     * Foo.prototype.c = 3;
-     * Bar.prototype.e = 5;
-     *
-     * _.assignIn({ 'a': 1 }, new Foo, new Bar);
-     * // => { 'a': 1, 'b': 2, 'c': 3, 'd': 4, 'e': 5 }
+     * _.sortedIndex([30, 50], 40);
+     * // => 1
      */
-    var assignIn = createAssigner(function(object, source) {
-      if (nonEnumShadows || isPrototype(source) || isArrayLike(source)) {
-        copyObject(source, keysIn(source), object);
-        return;
-      }
-      for (var key in source) {
-        assignValue(object, key, source[key]);
-      }
-    });
+    function sortedIndex(array, value) {
+      return baseSortedIndex(array, value);
+    }
 
     /**
-     * This method is like `_.assignIn` except that it accepts `customizer`
-     * which is invoked to produce the assigned values. If `customizer` returns
-     * `undefined`, assignment is handled by the method instead. The `customizer`
-     * is invoked with five arguments: (objValue, srcValue, key, object, source).
-     *
-     * **Note:** This method mutates `object`.
+     * This method is like `_.sortedIndex` except that it accepts `iteratee`
+     * which is invoked for `value` and each element of `array` to compute their
+     * sort ranking. The iteratee is invoked with one argument: (value).
      *
      * @static
      * @memberOf _
      * @since 4.0.0
-     * @alias extendWith
-     * @category Object
-     * @param {Object} object The destination object.
-     * @param {...Object} sources The source objects.
-     * @param {Function} [customizer] The function to customize assigned values.
-     * @returns {Object} Returns `object`.
-     * @see _.assignWith
+     * @category Array
+     * @param {Array} array The sorted array to inspect.
+     * @param {*} value The value to evaluate.
+     * @param {Function} [iteratee=_.identity] The iteratee invoked per element.
+     * @returns {number} Returns the index at which `value` should be inserted
+     *  into `array`.
      * @example
      *
-     * function customizer(objValue, srcValue) {
-     *   return _.isUndefined(objValue) ? srcValue : objValue;
-     * }
+     * var objects = [{ 'x': 4 }, { 'x': 5 }];
      *
-     * var defaults = _.partialRight(_.assignInWith, customizer);
+     * _.sortedIndexBy(objects, { 'x': 4 }, function(o) { return o.x; });
+     * // => 0
      *
-     * defaults({ 'a': 1 }, { 'b': 2 }, { 'a': 3 });
-     * // => { 'a': 1, 'b': 2 }
+     * // The `_.property` iteratee shorthand.
+     * _.sortedIndexBy(objects, { 'x': 4 }, 'x');
+     * // => 0
      */
-    var assignInWith = createAssigner(function(object, source, srcIndex, customizer) {
-      copyObject(source, keysIn(source), object, customizer);
-    });
+    function sortedIndexBy(array, value, iteratee) {
+      return baseSortedIndexBy(array, value, getIteratee(iteratee, 2));
+    }
 
     /**
-     * This method is like `_.assign` except that it accepts `customizer`
-     * which is invoked to produce the assigned values. If `customizer` returns
-     * `undefined`, assignment is handled by the method instead. The `customizer`
-     * is invoked with five arguments: (objValue, srcValue, key, object, source).
-     *
-     * **Note:** This method mutates `object`.
+     * This method is like `_.indexOf` except that it performs a binary
+     * search on a sorted `array`.
      *
      * @static
      * @memberOf _
      * @since 4.0.0
-     * @category Object
-     * @param {Object} object The destination object.
-     * @param {...Object} sources The source objects.
-     * @param {Function} [customizer] The function to customize assigned values.
-     * @returns {Object} Returns `object`.
-     * @see _.assignInWith
-     * @example
-     *
-     * function customizer(objValue, srcValue) {
-     *   return _.isUndefined(objValue) ? srcValue : objValue;
-     * }
-     *
-     * var defaults = _.partialRight(_.assignWith, customizer);
+     * @category Array
+     * @param {Array} array The array to inspect.
+     * @param {*} value The value to search for.
+     * @returns {number} Returns the index of the matched value, else `-1`.
+     * @example
      *
-     * defaults({ 'a': 1 }, { 'b': 2 }, { 'a': 3 });
-     * // => { 'a': 1, 'b': 2 }
+     * _.sortedIndexOf([4, 5, 5, 5, 6], 5);
+     * // => 1
      */
-    var assignWith = createAssigner(function(object, source, srcIndex, customizer) {
-      copyObject(source, keys(source), object, customizer);
-    });
+    function sortedIndexOf(array, value) {
+      var length = array == null ? 0 : array.length;
+      if (length) {
+        var index = baseSortedIndex(array, value);
+        if (index < length && eq(array[index], value)) {
+          return index;
+        }
+      }
+      return -1;
+    }
 
     /**
-     * Creates an array of values corresponding to `paths` of `object`.
+     * This method is like `_.sortedIndex` except that it returns the highest
+     * index at which `value` should be inserted into `array` in order to
+     * maintain its sort order.
      *
      * @static
      * @memberOf _
-     * @since 1.0.0
-     * @category Object
-     * @param {Object} object The object to iterate over.
-     * @param {...(string|string[])} [paths] The property paths of elements to pick.
-     * @returns {Array} Returns the picked values.
+     * @since 3.0.0
+     * @category Array
+     * @param {Array} array The sorted array to inspect.
+     * @param {*} value The value to evaluate.
+     * @returns {number} Returns the index at which `value` should be inserted
+     *  into `array`.
      * @example
      *
-     * var object = { 'a': [{ 'b': { 'c': 3 } }, 4] };
-     *
-     * _.at(object, ['a[0].b.c', 'a[1]']);
-     * // => [3, 4]
+     * _.sortedLastIndex([4, 5, 5, 5, 6], 5);
+     * // => 4
      */
-    var at = rest(function(object, paths) {
-      return baseAt(object, baseFlatten(paths, 1));
-    });
+    function sortedLastIndex(array, value) {
+      return baseSortedIndex(array, value, true);
+    }
 
     /**
-     * Creates an object that inherits from the `prototype` object. If a
-     * `properties` object is given, its own enumerable string keyed properties
-     * are assigned to the created object.
+     * This method is like `_.sortedLastIndex` except that it accepts `iteratee`
+     * which is invoked for `value` and each element of `array` to compute their
+     * sort ranking. The iteratee is invoked with one argument: (value).
      *
      * @static
      * @memberOf _
-     * @since 2.3.0
-     * @category Object
-     * @param {Object} prototype The object to inherit from.
-     * @param {Object} [properties] The properties to assign to the object.
-     * @returns {Object} Returns the new object.
+     * @since 4.0.0
+     * @category Array
+     * @param {Array} array The sorted array to inspect.
+     * @param {*} value The value to evaluate.
+     * @param {Function} [iteratee=_.identity] The iteratee invoked per element.
+     * @returns {number} Returns the index at which `value` should be inserted
+     *  into `array`.
      * @example
      *
-     * function Shape() {
-     *   this.x = 0;
-     *   this.y = 0;
-     * }
-     *
-     * function Circle() {
-     *   Shape.call(this);
-     * }
-     *
-     * Circle.prototype = _.create(Shape.prototype, {
-     *   'constructor': Circle
-     * });
+     * var objects = [{ 'x': 4 }, { 'x': 5 }];
      *
-     * var circle = new Circle;
-     * circle instanceof Circle;
-     * // => true
+     * _.sortedLastIndexBy(objects, { 'x': 4 }, function(o) { return o.x; });
+     * // => 1
      *
-     * circle instanceof Shape;
-     * // => true
+     * // The `_.property` iteratee shorthand.
+     * _.sortedLastIndexBy(objects, { 'x': 4 }, 'x');
+     * // => 1
      */
-    function create(prototype, properties) {
-      var result = baseCreate(prototype);
-      return properties ? baseAssign(result, properties) : result;
+    function sortedLastIndexBy(array, value, iteratee) {
+      return baseSortedIndexBy(array, value, getIteratee(iteratee, 2), true);
     }
 
     /**
-     * Assigns own and inherited enumerable string keyed properties of source
-     * objects to the destination object for all destination properties that
-     * resolve to `undefined`. Source objects are applied from left to right.
-     * Once a property is set, additional values of the same property are ignored.
-     *
-     * **Note:** This method mutates `object`.
+     * This method is like `_.lastIndexOf` except that it performs a binary
+     * search on a sorted `array`.
      *
      * @static
-     * @since 0.1.0
      * @memberOf _
-     * @category Object
-     * @param {Object} object The destination object.
-     * @param {...Object} [sources] The source objects.
-     * @returns {Object} Returns `object`.
-     * @see _.defaultsDeep
+     * @since 4.0.0
+     * @category Array
+     * @param {Array} array The array to inspect.
+     * @param {*} value The value to search for.
+     * @returns {number} Returns the index of the matched value, else `-1`.
      * @example
      *
-     * _.defaults({ 'user': 'barney' }, { 'age': 36 }, { 'user': 'fred' });
-     * // => { 'user': 'barney', 'age': 36 }
+     * _.sortedLastIndexOf([4, 5, 5, 5, 6], 5);
+     * // => 3
      */
-    var defaults = rest(function(args) {
-      args.push(undefined, assignInDefaults);
-      return apply(assignInWith, undefined, args);
-    });
+    function sortedLastIndexOf(array, value) {
+      var length = array == null ? 0 : array.length;
+      if (length) {
+        var index = baseSortedIndex(array, value, true) - 1;
+        if (eq(array[index], value)) {
+          return index;
+        }
+      }
+      return -1;
+    }
 
     /**
-     * This method is like `_.defaults` except that it recursively assigns
-     * default properties.
-     *
-     * **Note:** This method mutates `object`.
+     * This method is like `_.uniq` except that it's designed and optimized
+     * for sorted arrays.
      *
      * @static
      * @memberOf _
-     * @since 3.10.0
-     * @category Object
-     * @param {Object} object The destination object.
-     * @param {...Object} [sources] The source objects.
-     * @returns {Object} Returns `object`.
-     * @see _.defaults
+     * @since 4.0.0
+     * @category Array
+     * @param {Array} array The array to inspect.
+     * @returns {Array} Returns the new duplicate free array.
      * @example
      *
-     * _.defaultsDeep({ 'user': { 'name': 'barney' } }, { 'user': { 'name': 'fred', 'age': 36 } });
-     * // => { 'user': { 'name': 'barney', 'age': 36 } }
-     *
+     * _.sortedUniq([1, 1, 2]);
+     * // => [1, 2]
      */
-    var defaultsDeep = rest(function(args) {
-      args.push(undefined, mergeDefaults);
-      return apply(mergeWith, undefined, args);
-    });
+    function sortedUniq(array) {
+      return (array && array.length)
+        ? baseSortedUniq(array)
+        : [];
+    }
 
     /**
-     * This method is like `_.find` except that it returns the key of the first
-     * element `predicate` returns truthy for instead of the element itself.
+     * This method is like `_.uniqBy` except that it's designed and optimized
+     * for sorted arrays.
      *
      * @static
      * @memberOf _
-     * @since 1.1.0
-     * @category Object
-     * @param {Object} object The object to search.
-     * @param {Array|Function|Object|string} [predicate=_.identity]
-     *  The function invoked per iteration.
-     * @returns {string|undefined} Returns the key of the matched element,
-     *  else `undefined`.
+     * @since 4.0.0
+     * @category Array
+     * @param {Array} array The array to inspect.
+     * @param {Function} [iteratee] The iteratee invoked per element.
+     * @returns {Array} Returns the new duplicate free array.
      * @example
      *
-     * var users = {
-     *   'barney':  { 'age': 36, 'active': true },
-     *   'fred':    { 'age': 40, 'active': false },
-     *   'pebbles': { 'age': 1,  'active': true }
-     * };
-     *
-     * _.findKey(users, function(o) { return o.age < 40; });
-     * // => 'barney' (iteration order is not guaranteed)
-     *
-     * // The `_.matches` iteratee shorthand.
-     * _.findKey(users, { 'age': 1, 'active': true });
-     * // => 'pebbles'
+     * _.sortedUniqBy([1.1, 1.2, 2.3, 2.4], Math.floor);
+     * // => [1.1, 2.3]
+     */
+    function sortedUniqBy(array, iteratee) {
+      return (array && array.length)
+        ? baseSortedUniq(array, getIteratee(iteratee, 2))
+        : [];
+    }
+
+    /**
+     * Gets all but the first element of `array`.
      *
-     * // The `_.matchesProperty` iteratee shorthand.
-     * _.findKey(users, ['active', false]);
-     * // => 'fred'
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Array
+     * @param {Array} array The array to query.
+     * @returns {Array} Returns the slice of `array`.
+     * @example
      *
-     * // The `_.property` iteratee shorthand.
-     * _.findKey(users, 'active');
-     * // => 'barney'
+     * _.tail([1, 2, 3]);
+     * // => [2, 3]
      */
-    function findKey(object, predicate) {
-      return baseFindKey(object, getIteratee(predicate, 3), baseForOwn);
+    function tail(array) {
+      var length = array == null ? 0 : array.length;
+      return length ? baseSlice(array, 1, length) : [];
     }
 
     /**
-     * This method is like `_.findKey` except that it iterates over elements of
-     * a collection in the opposite order.
+     * Creates a slice of `array` with `n` elements taken from the beginning.
      *
      * @static
      * @memberOf _
-     * @since 2.0.0
-     * @category Object
-     * @param {Object} object The object to search.
-     * @param {Array|Function|Object|string} [predicate=_.identity]
-     *  The function invoked per iteration.
-     * @returns {string|undefined} Returns the key of the matched element,
-     *  else `undefined`.
+     * @since 0.1.0
+     * @category Array
+     * @param {Array} array The array to query.
+     * @param {number} [n=1] The number of elements to take.
+     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
+     * @returns {Array} Returns the slice of `array`.
      * @example
      *
-     * var users = {
-     *   'barney':  { 'age': 36, 'active': true },
-     *   'fred':    { 'age': 40, 'active': false },
-     *   'pebbles': { 'age': 1,  'active': true }
-     * };
-     *
-     * _.findLastKey(users, function(o) { return o.age < 40; });
-     * // => returns 'pebbles' assuming `_.findKey` returns 'barney'
+     * _.take([1, 2, 3]);
+     * // => [1]
      *
-     * // The `_.matches` iteratee shorthand.
-     * _.findLastKey(users, { 'age': 36, 'active': true });
-     * // => 'barney'
+     * _.take([1, 2, 3], 2);
+     * // => [1, 2]
      *
-     * // The `_.matchesProperty` iteratee shorthand.
-     * _.findLastKey(users, ['active', false]);
-     * // => 'fred'
+     * _.take([1, 2, 3], 5);
+     * // => [1, 2, 3]
      *
-     * // The `_.property` iteratee shorthand.
-     * _.findLastKey(users, 'active');
-     * // => 'pebbles'
+     * _.take([1, 2, 3], 0);
+     * // => []
      */
-    function findLastKey(object, predicate) {
-      return baseFindKey(object, getIteratee(predicate, 3), baseForOwnRight);
+    function take(array, n, guard) {
+      if (!(array && array.length)) {
+        return [];
+      }
+      n = (guard || n === undefined) ? 1 : toInteger(n);
+      return baseSlice(array, 0, n < 0 ? 0 : n);
     }
 
     /**
-     * Iterates over own and inherited enumerable string keyed properties of an
-     * object and invokes `iteratee` for each property. The iteratee is invoked
-     * with three arguments: (value, key, object). Iteratee functions may exit
-     * iteration early by explicitly returning `false`.
+     * Creates a slice of `array` with `n` elements taken from the end.
      *
      * @static
      * @memberOf _
-     * @since 0.3.0
-     * @category Object
-     * @param {Object} object The object to iterate over.
-     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
-     * @returns {Object} Returns `object`.
-     * @see _.forInRight
+     * @since 3.0.0
+     * @category Array
+     * @param {Array} array The array to query.
+     * @param {number} [n=1] The number of elements to take.
+     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
+     * @returns {Array} Returns the slice of `array`.
      * @example
      *
-     * function Foo() {
-     *   this.a = 1;
-     *   this.b = 2;
-     * }
+     * _.takeRight([1, 2, 3]);
+     * // => [3]
      *
-     * Foo.prototype.c = 3;
+     * _.takeRight([1, 2, 3], 2);
+     * // => [2, 3]
      *
-     * _.forIn(new Foo, function(value, key) {
-     *   console.log(key);
-     * });
-     * // => Logs 'a', 'b', then 'c' (iteration order is not guaranteed).
+     * _.takeRight([1, 2, 3], 5);
+     * // => [1, 2, 3]
+     *
+     * _.takeRight([1, 2, 3], 0);
+     * // => []
      */
-    function forIn(object, iteratee) {
-      return object == null
-        ? object
-        : baseFor(object, getIteratee(iteratee, 3), keysIn);
+    function takeRight(array, n, guard) {
+      var length = array == null ? 0 : array.length;
+      if (!length) {
+        return [];
+      }
+      n = (guard || n === undefined) ? 1 : toInteger(n);
+      n = length - n;
+      return baseSlice(array, n < 0 ? 0 : n, length);
     }
 
     /**
-     * This method is like `_.forIn` except that it iterates over properties of
-     * `object` in the opposite order.
+     * Creates a slice of `array` with elements taken from the end. Elements are
+     * taken until `predicate` returns falsey. The predicate is invoked with
+     * three arguments: (value, index, array).
      *
      * @static
      * @memberOf _
-     * @since 2.0.0
-     * @category Object
-     * @param {Object} object The object to iterate over.
-     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
-     * @returns {Object} Returns `object`.
-     * @see _.forIn
+     * @since 3.0.0
+     * @category Array
+     * @param {Array} array The array to query.
+     * @param {Function} [predicate=_.identity] The function invoked per iteration.
+     * @returns {Array} Returns the slice of `array`.
      * @example
      *
-     * function Foo() {
-     *   this.a = 1;
-     *   this.b = 2;
-     * }
+     * var users = [
+     *   { 'user': 'barney',  'active': true },
+     *   { 'user': 'fred',    'active': false },
+     *   { 'user': 'pebbles', 'active': false }
+     * ];
      *
-     * Foo.prototype.c = 3;
+     * _.takeRightWhile(users, function(o) { return !o.active; });
+     * // => objects for ['fred', 'pebbles']
      *
-     * _.forInRight(new Foo, function(value, key) {
-     *   console.log(key);
-     * });
-     * // => Logs 'c', 'b', then 'a' assuming `_.forIn` logs 'a', 'b', then 'c'.
+     * // The `_.matches` iteratee shorthand.
+     * _.takeRightWhile(users, { 'user': 'pebbles', 'active': false });
+     * // => objects for ['pebbles']
+     *
+     * // The `_.matchesProperty` iteratee shorthand.
+     * _.takeRightWhile(users, ['active', false]);
+     * // => objects for ['fred', 'pebbles']
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.takeRightWhile(users, 'active');
+     * // => []
      */
-    function forInRight(object, iteratee) {
-      return object == null
-        ? object
-        : baseForRight(object, getIteratee(iteratee, 3), keysIn);
+    function takeRightWhile(array, predicate) {
+      return (array && array.length)
+        ? baseWhile(array, getIteratee(predicate, 3), false, true)
+        : [];
     }
 
     /**
-     * Iterates over own enumerable string keyed properties of an object and
-     * invokes `iteratee` for each property. The iteratee is invoked with three
-     * arguments: (value, key, object). Iteratee functions may exit iteration
-     * early by explicitly returning `false`.
+     * Creates a slice of `array` with elements taken from the beginning. Elements
+     * are taken until `predicate` returns falsey. The predicate is invoked with
+     * three arguments: (value, index, array).
      *
      * @static
      * @memberOf _
-     * @since 0.3.0
-     * @category Object
-     * @param {Object} object The object to iterate over.
-     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
-     * @returns {Object} Returns `object`.
-     * @see _.forOwnRight
+     * @since 3.0.0
+     * @category Array
+     * @param {Array} array The array to query.
+     * @param {Function} [predicate=_.identity] The function invoked per iteration.
+     * @returns {Array} Returns the slice of `array`.
      * @example
      *
-     * function Foo() {
-     *   this.a = 1;
-     *   this.b = 2;
-     * }
+     * var users = [
+     *   { 'user': 'barney',  'active': false },
+     *   { 'user': 'fred',    'active': false },
+     *   { 'user': 'pebbles', 'active': true }
+     * ];
      *
-     * Foo.prototype.c = 3;
+     * _.takeWhile(users, function(o) { return !o.active; });
+     * // => objects for ['barney', 'fred']
      *
-     * _.forOwn(new Foo, function(value, key) {
-     *   console.log(key);
-     * });
-     * // => Logs 'a' then 'b' (iteration order is not guaranteed).
+     * // The `_.matches` iteratee shorthand.
+     * _.takeWhile(users, { 'user': 'barney', 'active': false });
+     * // => objects for ['barney']
+     *
+     * // The `_.matchesProperty` iteratee shorthand.
+     * _.takeWhile(users, ['active', false]);
+     * // => objects for ['barney', 'fred']
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.takeWhile(users, 'active');
+     * // => []
      */
-    function forOwn(object, iteratee) {
-      return object && baseForOwn(object, getIteratee(iteratee, 3));
+    function takeWhile(array, predicate) {
+      return (array && array.length)
+        ? baseWhile(array, getIteratee(predicate, 3))
+        : [];
     }
 
     /**
-     * This method is like `_.forOwn` except that it iterates over properties of
-     * `object` in the opposite order.
+     * Creates an array of unique values, in order, from all given arrays using
+     * [`SameValueZero`](http://ecma-international.org/ecma-262/7.0/#sec-samevaluezero)
+     * for equality comparisons.
      *
      * @static
      * @memberOf _
-     * @since 2.0.0
-     * @category Object
-     * @param {Object} object The object to iterate over.
-     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
-     * @returns {Object} Returns `object`.
-     * @see _.forOwn
+     * @since 0.1.0
+     * @category Array
+     * @param {...Array} [arrays] The arrays to inspect.
+     * @returns {Array} Returns the new array of combined values.
      * @example
      *
-     * function Foo() {
-     *   this.a = 1;
-     *   this.b = 2;
-     * }
-     *
-     * Foo.prototype.c = 3;
-     *
-     * _.forOwnRight(new Foo, function(value, key) {
-     *   console.log(key);
-     * });
-     * // => Logs 'b' then 'a' assuming `_.forOwn` logs 'a' then 'b'.
+     * _.union([2], [1, 2]);
+     * // => [2, 1]
      */
-    function forOwnRight(object, iteratee) {
-      return object && baseForOwnRight(object, getIteratee(iteratee, 3));
-    }
+    var union = baseRest(function(arrays) {
+      return baseUniq(baseFlatten(arrays, 1, isArrayLikeObject, true));
+    });
 
     /**
-     * Creates an array of function property names from own enumerable properties
-     * of `object`.
+     * This method is like `_.union` except that it accepts `iteratee` which is
+     * invoked for each element of each `arrays` to generate the criterion by
+     * which uniqueness is computed. Result values are chosen from the first
+     * array in which the value occurs. The iteratee is invoked with one argument:
+     * (value).
      *
      * @static
-     * @since 0.1.0
      * @memberOf _
-     * @category Object
-     * @param {Object} object The object to inspect.
-     * @returns {Array} Returns the function names.
-     * @see _.functionsIn
+     * @since 4.0.0
+     * @category Array
+     * @param {...Array} [arrays] The arrays to inspect.
+     * @param {Function} [iteratee=_.identity] The iteratee invoked per element.
+     * @returns {Array} Returns the new array of combined values.
      * @example
      *
-     * function Foo() {
-     *   this.a = _.constant('a');
-     *   this.b = _.constant('b');
-     * }
-     *
-     * Foo.prototype.c = _.constant('c');
+     * _.unionBy([2.1], [1.2, 2.3], Math.floor);
+     * // => [2.1, 1.2]
      *
-     * _.functions(new Foo);
-     * // => ['a', 'b']
+     * // The `_.property` iteratee shorthand.
+     * _.unionBy([{ 'x': 1 }], [{ 'x': 2 }, { 'x': 1 }], 'x');
+     * // => [{ 'x': 1 }, { 'x': 2 }]
      */
-    function functions(object) {
-      return object == null ? [] : baseFunctions(object, keys(object));
-    }
+    var unionBy = baseRest(function(arrays) {
+      var iteratee = last(arrays);
+      if (isArrayLikeObject(iteratee)) {
+        iteratee = undefined;
+      }
+      return baseUniq(baseFlatten(arrays, 1, isArrayLikeObject, true), getIteratee(iteratee, 2));
+    });
 
     /**
-     * Creates an array of function property names from own and inherited
-     * enumerable properties of `object`.
+     * This method is like `_.union` except that it accepts `comparator` which
+     * is invoked to compare elements of `arrays`. Result values are chosen from
+     * the first array in which the value occurs. The comparator is invoked
+     * with two arguments: (arrVal, othVal).
      *
      * @static
      * @memberOf _
      * @since 4.0.0
-     * @category Object
-     * @param {Object} object The object to inspect.
-     * @returns {Array} Returns the function names.
-     * @see _.functions
+     * @category Array
+     * @param {...Array} [arrays] The arrays to inspect.
+     * @param {Function} [comparator] The comparator invoked per element.
+     * @returns {Array} Returns the new array of combined values.
      * @example
      *
-     * function Foo() {
-     *   this.a = _.constant('a');
-     *   this.b = _.constant('b');
-     * }
-     *
-     * Foo.prototype.c = _.constant('c');
+     * var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }];
+     * var others = [{ 'x': 1, 'y': 1 }, { 'x': 1, 'y': 2 }];
      *
-     * _.functionsIn(new Foo);
-     * // => ['a', 'b', 'c']
+     * _.unionWith(objects, others, _.isEqual);
+     * // => [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }, { 'x': 1, 'y': 1 }]
      */
-    function functionsIn(object) {
-      return object == null ? [] : baseFunctions(object, keysIn(object));
-    }
+    var unionWith = baseRest(function(arrays) {
+      var comparator = last(arrays);
+      comparator = typeof comparator == 'function' ? comparator : undefined;
+      return baseUniq(baseFlatten(arrays, 1, isArrayLikeObject, true), undefined, comparator);
+    });
 
     /**
-     * Gets the value at `path` of `object`. If the resolved value is
-     * `undefined`, the `defaultValue` is used in its place.
+     * Creates a duplicate-free version of an array, using
+     * [`SameValueZero`](http://ecma-international.org/ecma-262/7.0/#sec-samevaluezero)
+     * for equality comparisons, in which only the first occurrence of each element
+     * is kept. The order of result values is determined by the order they occur
+     * in the array.
      *
      * @static
      * @memberOf _
-     * @since 3.7.0
-     * @category Object
-     * @param {Object} object The object to query.
-     * @param {Array|string} path The path of the property to get.
-     * @param {*} [defaultValue] The value returned for `undefined` resolved values.
-     * @returns {*} Returns the resolved value.
+     * @since 0.1.0
+     * @category Array
+     * @param {Array} array The array to inspect.
+     * @returns {Array} Returns the new duplicate free array.
      * @example
      *
-     * var object = { 'a': [{ 'b': { 'c': 3 } }] };
-     *
-     * _.get(object, 'a[0].b.c');
-     * // => 3
-     *
-     * _.get(object, ['a', '0', 'b', 'c']);
-     * // => 3
-     *
-     * _.get(object, 'a.b.c', 'default');
-     * // => 'default'
+     * _.uniq([2, 1, 2]);
+     * // => [2, 1]
      */
-    function get(object, path, defaultValue) {
-      var result = object == null ? undefined : baseGet(object, path);
-      return result === undefined ? defaultValue : result;
+    function uniq(array) {
+      return (array && array.length) ? baseUniq(array) : [];
     }
 
     /**
-     * Checks if `path` is a direct property of `object`.
+     * This method is like `_.uniq` except that it accepts `iteratee` which is
+     * invoked for each element in `array` to generate the criterion by which
+     * uniqueness is computed. The order of result values is determined by the
+     * order they occur in the array. The iteratee is invoked with one argument:
+     * (value).
      *
      * @static
-     * @since 0.1.0
      * @memberOf _
-     * @category Object
-     * @param {Object} object The object to query.
-     * @param {Array|string} path The path to check.
-     * @returns {boolean} Returns `true` if `path` exists, else `false`.
+     * @since 4.0.0
+     * @category Array
+     * @param {Array} array The array to inspect.
+     * @param {Function} [iteratee=_.identity] The iteratee invoked per element.
+     * @returns {Array} Returns the new duplicate free array.
      * @example
      *
-     * var object = { 'a': { 'b': 2 } };
-     * var other = _.create({ 'a': _.create({ 'b': 2 }) });
-     *
-     * _.has(object, 'a');
-     * // => true
-     *
-     * _.has(object, 'a.b');
-     * // => true
-     *
-     * _.has(object, ['a', 'b']);
-     * // => true
+     * _.uniqBy([2.1, 1.2, 2.3], Math.floor);
+     * // => [2.1, 1.2]
      *
-     * _.has(other, 'a');
-     * // => false
+     * // The `_.property` iteratee shorthand.
+     * _.uniqBy([{ 'x': 1 }, { 'x': 2 }, { 'x': 1 }], 'x');
+     * // => [{ 'x': 1 }, { 'x': 2 }]
      */
-    function has(object, path) {
-      return object != null && hasPath(object, path, baseHas);
+    function uniqBy(array, iteratee) {
+      return (array && array.length) ? baseUniq(array, getIteratee(iteratee, 2)) : [];
     }
 
     /**
-     * Checks if `path` is a direct or inherited property of `object`.
+     * This method is like `_.uniq` except that it accepts `comparator` which
+     * is invoked to compare elements of `array`. The order of result values is
+     * determined by the order they occur in the array.The comparator is invoked
+     * with two arguments: (arrVal, othVal).
      *
      * @static
      * @memberOf _
      * @since 4.0.0
-     * @category Object
-     * @param {Object} object The object to query.
-     * @param {Array|string} path The path to check.
-     * @returns {boolean} Returns `true` if `path` exists, else `false`.
+     * @category Array
+     * @param {Array} array The array to inspect.
+     * @param {Function} [comparator] The comparator invoked per element.
+     * @returns {Array} Returns the new duplicate free array.
      * @example
      *
-     * var object = _.create({ 'a': _.create({ 'b': 2 }) });
-     *
-     * _.hasIn(object, 'a');
-     * // => true
-     *
-     * _.hasIn(object, 'a.b');
-     * // => true
-     *
-     * _.hasIn(object, ['a', 'b']);
-     * // => true
+     * var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }, { 'x': 1, 'y': 2 }];
      *
-     * _.hasIn(object, 'b');
-     * // => false
+     * _.uniqWith(objects, _.isEqual);
+     * // => [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }]
      */
-    function hasIn(object, path) {
-      return object != null && hasPath(object, path, baseHasIn);
+    function uniqWith(array, comparator) {
+      comparator = typeof comparator == 'function' ? comparator : undefined;
+      return (array && array.length) ? baseUniq(array, undefined, comparator) : [];
     }
 
     /**
-     * Creates an object composed of the inverted keys and values of `object`.
-     * If `object` contains duplicate values, subsequent values overwrite
-     * property assignments of previous values.
+     * This method is like `_.zip` except that it accepts an array of grouped
+     * elements and creates an array regrouping the elements to their pre-zip
+     * configuration.
      *
      * @static
      * @memberOf _
-     * @since 0.7.0
-     * @category Object
-     * @param {Object} object The object to invert.
-     * @returns {Object} Returns the new inverted object.
+     * @since 1.2.0
+     * @category Array
+     * @param {Array} array The array of grouped elements to process.
+     * @returns {Array} Returns the new array of regrouped elements.
      * @example
      *
-     * var object = { 'a': 1, 'b': 2, 'c': 1 };
+     * var zipped = _.zip(['a', 'b'], [1, 2], [true, false]);
+     * // => [['a', 1, true], ['b', 2, false]]
      *
-     * _.invert(object);
-     * // => { '1': 'c', '2': 'b' }
+     * _.unzip(zipped);
+     * // => [['a', 'b'], [1, 2], [true, false]]
      */
-    var invert = createInverter(function(result, value, key) {
-      result[value] = key;
-    }, constant(identity));
+    function unzip(array) {
+      if (!(array && array.length)) {
+        return [];
+      }
+      var length = 0;
+      array = arrayFilter(array, function(group) {
+        if (isArrayLikeObject(group)) {
+          length = nativeMax(group.length, length);
+          return true;
+        }
+      });
+      return baseTimes(length, function(index) {
+        return arrayMap(array, baseProperty(index));
+      });
+    }
 
     /**
-     * This method is like `_.invert` except that the inverted object is generated
-     * from the results of running each element of `object` thru `iteratee`. The
-     * corresponding inverted value of each inverted key is an array of keys
-     * responsible for generating the inverted value. The iteratee is invoked
-     * with one argument: (value).
+     * This method is like `_.unzip` except that it accepts `iteratee` to specify
+     * how regrouped values should be combined. The iteratee is invoked with the
+     * elements of each group: (...group).
      *
      * @static
      * @memberOf _
-     * @since 4.1.0
-     * @category Object
-     * @param {Object} object The object to invert.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The iteratee invoked per element.
-     * @returns {Object} Returns the new inverted object.
+     * @since 3.8.0
+     * @category Array
+     * @param {Array} array The array of grouped elements to process.
+     * @param {Function} [iteratee=_.identity] The function to combine
+     *  regrouped values.
+     * @returns {Array} Returns the new array of regrouped elements.
      * @example
      *
-     * var object = { 'a': 1, 'b': 2, 'c': 1 };
-     *
-     * _.invertBy(object);
-     * // => { '1': ['a', 'c'], '2': ['b'] }
+     * var zipped = _.zip([1, 2], [10, 20], [100, 200]);
+     * // => [[1, 10, 100], [2, 20, 200]]
      *
-     * _.invertBy(object, function(value) {
-     *   return 'group' + value;
-     * });
-     * // => { 'group1': ['a', 'c'], 'group2': ['b'] }
+     * _.unzipWith(zipped, _.add);
+     * // => [3, 30, 300]
      */
-    var invertBy = createInverter(function(result, value, key) {
-      if (hasOwnProperty.call(result, value)) {
-        result[value].push(key);
-      } else {
-        result[value] = [key];
+    function unzipWith(array, iteratee) {
+      if (!(array && array.length)) {
+        return [];
       }
-    }, getIteratee);
+      var result = unzip(array);
+      if (iteratee == null) {
+        return result;
+      }
+      return arrayMap(result, function(group) {
+        return apply(iteratee, undefined, group);
+      });
+    }
 
     /**
-     * Invokes the method at `path` of `object`.
+     * Creates an array excluding all given values using
+     * [`SameValueZero`](http://ecma-international.org/ecma-262/7.0/#sec-samevaluezero)
+     * for equality comparisons.
+     *
+     * **Note:** Unlike `_.pull`, this method returns a new array.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category Object
-     * @param {Object} object The object to query.
-     * @param {Array|string} path The path of the method to invoke.
-     * @param {...*} [args] The arguments to invoke the method with.
-     * @returns {*} Returns the result of the invoked method.
+     * @since 0.1.0
+     * @category Array
+     * @param {Array} array The array to inspect.
+     * @param {...*} [values] The values to exclude.
+     * @returns {Array} Returns the new array of filtered values.
+     * @see _.difference, _.xor
      * @example
      *
-     * var object = { 'a': [{ 'b': { 'c': [1, 2, 3, 4] } }] };
-     *
-     * _.invoke(object, 'a[0].b.c.slice', 1, 3);
-     * // => [2, 3]
+     * _.without([2, 1, 2, 3], 1, 2);
+     * // => [3]
      */
-    var invoke = rest(baseInvoke);
+    var without = baseRest(function(array, values) {
+      return isArrayLikeObject(array)
+        ? baseDifference(array, values)
+        : [];
+    });
 
     /**
-     * Creates an array of the own enumerable property names of `object`.
-     *
-     * **Note:** Non-object values are coerced to objects. See the
-     * [ES spec](http://ecma-international.org/ecma-262/6.0/#sec-object.keys)
-     * for more details.
+     * Creates an array of unique values that is the
+     * [symmetric difference](https://en.wikipedia.org/wiki/Symmetric_difference)
+     * of the given arrays. The order of result values is determined by the order
+     * they occur in the arrays.
      *
      * @static
-     * @since 0.1.0
      * @memberOf _
-     * @category Object
-     * @param {Object} object The object to query.
-     * @returns {Array} Returns the array of property names.
+     * @since 2.4.0
+     * @category Array
+     * @param {...Array} [arrays] The arrays to inspect.
+     * @returns {Array} Returns the new array of filtered values.
+     * @see _.difference, _.without
      * @example
      *
-     * function Foo() {
-     *   this.a = 1;
-     *   this.b = 2;
-     * }
+     * _.xor([2, 1], [2, 3]);
+     * // => [1, 3]
+     */
+    var xor = baseRest(function(arrays) {
+      return baseXor(arrayFilter(arrays, isArrayLikeObject));
+    });
+
+    /**
+     * This method is like `_.xor` except that it accepts `iteratee` which is
+     * invoked for each element of each `arrays` to generate the criterion by
+     * which by which they're compared. The order of result values is determined
+     * by the order they occur in the arrays. The iteratee is invoked with one
+     * argument: (value).
      *
-     * Foo.prototype.c = 3;
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Array
+     * @param {...Array} [arrays] The arrays to inspect.
+     * @param {Function} [iteratee=_.identity] The iteratee invoked per element.
+     * @returns {Array} Returns the new array of filtered values.
+     * @example
      *
-     * _.keys(new Foo);
-     * // => ['a', 'b'] (iteration order is not guaranteed)
+     * _.xorBy([2.1, 1.2], [2.3, 3.4], Math.floor);
+     * // => [1.2, 3.4]
      *
-     * _.keys('hi');
-     * // => ['0', '1']
+     * // The `_.property` iteratee shorthand.
+     * _.xorBy([{ 'x': 1 }], [{ 'x': 2 }, { 'x': 1 }], 'x');
+     * // => [{ 'x': 2 }]
      */
-    function keys(object) {
-      var isProto = isPrototype(object);
-      if (!(isProto || isArrayLike(object))) {
-        return baseKeys(object);
-      }
-      var indexes = indexKeys(object),
-          skipIndexes = !!indexes,
-          result = indexes || [],
-          length = result.length;
-
-      for (var key in object) {
-        if (baseHas(object, key) &&
-            !(skipIndexes && (key == 'length' || isIndex(key, length))) &&
-            !(isProto && key == 'constructor')) {
-          result.push(key);
-        }
+    var xorBy = baseRest(function(arrays) {
+      var iteratee = last(arrays);
+      if (isArrayLikeObject(iteratee)) {
+        iteratee = undefined;
       }
-      return result;
-    }
+      return baseXor(arrayFilter(arrays, isArrayLikeObject), getIteratee(iteratee, 2));
+    });
 
     /**
-     * Creates an array of the own and inherited enumerable property names of `object`.
-     *
-     * **Note:** Non-object values are coerced to objects.
+     * This method is like `_.xor` except that it accepts `comparator` which is
+     * invoked to compare elements of `arrays`. The order of result values is
+     * determined by the order they occur in the arrays. The comparator is invoked
+     * with two arguments: (arrVal, othVal).
      *
      * @static
      * @memberOf _
-     * @since 3.0.0
-     * @category Object
-     * @param {Object} object The object to query.
-     * @returns {Array} Returns the array of property names.
+     * @since 4.0.0
+     * @category Array
+     * @param {...Array} [arrays] The arrays to inspect.
+     * @param {Function} [comparator] The comparator invoked per element.
+     * @returns {Array} Returns the new array of filtered values.
      * @example
      *
-     * function Foo() {
-     *   this.a = 1;
-     *   this.b = 2;
-     * }
-     *
-     * Foo.prototype.c = 3;
+     * var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }];
+     * var others = [{ 'x': 1, 'y': 1 }, { 'x': 1, 'y': 2 }];
      *
-     * _.keysIn(new Foo);
-     * // => ['a', 'b', 'c'] (iteration order is not guaranteed)
+     * _.xorWith(objects, others, _.isEqual);
+     * // => [{ 'x': 2, 'y': 1 }, { 'x': 1, 'y': 1 }]
      */
-    function keysIn(object) {
-      var index = -1,
-          isProto = isPrototype(object),
-          props = baseKeysIn(object),
-          propsLength = props.length,
-          indexes = indexKeys(object),
-          skipIndexes = !!indexes,
-          result = indexes || [],
-          length = result.length;
-
-      while (++index < propsLength) {
-        var key = props[index];
-        if (!(skipIndexes && (key == 'length' || isIndex(key, length))) &&
-            !(key == 'constructor' && (isProto || !hasOwnProperty.call(object, key)))) {
-          result.push(key);
-        }
-      }
-      return result;
-    }
+    var xorWith = baseRest(function(arrays) {
+      var comparator = last(arrays);
+      comparator = typeof comparator == 'function' ? comparator : undefined;
+      return baseXor(arrayFilter(arrays, isArrayLikeObject), undefined, comparator);
+    });
 
     /**
-     * The opposite of `_.mapValues`; this method creates an object with the
-     * same values as `object` and keys generated by running each own enumerable
-     * string keyed property of `object` thru `iteratee`. The iteratee is invoked
-     * with three arguments: (value, key, object).
+     * Creates an array of grouped elements, the first of which contains the
+     * first elements of the given arrays, the second of which contains the
+     * second elements of the given arrays, and so on.
      *
      * @static
      * @memberOf _
-     * @since 3.8.0
-     * @category Object
-     * @param {Object} object The object to iterate over.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The function invoked per iteration.
-     * @returns {Object} Returns the new mapped object.
-     * @see _.mapValues
+     * @since 0.1.0
+     * @category Array
+     * @param {...Array} [arrays] The arrays to process.
+     * @returns {Array} Returns the new array of grouped elements.
      * @example
      *
-     * _.mapKeys({ 'a': 1, 'b': 2 }, function(value, key) {
-     *   return key + value;
-     * });
-     * // => { 'a1': 1, 'b2': 2 }
+     * _.zip(['a', 'b'], [1, 2], [true, false]);
+     * // => [['a', 1, true], ['b', 2, false]]
      */
-    function mapKeys(object, iteratee) {
-      var result = {};
-      iteratee = getIteratee(iteratee, 3);
-
-      baseForOwn(object, function(value, key, object) {
-        result[iteratee(value, key, object)] = value;
-      });
-      return result;
-    }
+    var zip = baseRest(unzip);
 
     /**
-     * Creates an object with the same keys as `object` and values generated
-     * by running each own enumerable string keyed property of `object` thru
-     * `iteratee`. The iteratee is invoked with three arguments:
-     * (value, key, object).
+     * This method is like `_.fromPairs` except that it accepts two arrays,
+     * one of property identifiers and one of corresponding values.
      *
      * @static
      * @memberOf _
-     * @since 2.4.0
-     * @category Object
-     * @param {Object} object The object to iterate over.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The function invoked per iteration.
-     * @returns {Object} Returns the new mapped object.
-     * @see _.mapKeys
+     * @since 0.4.0
+     * @category Array
+     * @param {Array} [props=[]] The property identifiers.
+     * @param {Array} [values=[]] The property values.
+     * @returns {Object} Returns the new object.
      * @example
      *
-     * var users = {
-     *   'fred':    { 'user': 'fred',    'age': 40 },
-     *   'pebbles': { 'user': 'pebbles', 'age': 1 }
-     * };
-     *
-     * _.mapValues(users, function(o) { return o.age; });
-     * // => { 'fred': 40, 'pebbles': 1 } (iteration order is not guaranteed)
-     *
-     * // The `_.property` iteratee shorthand.
-     * _.mapValues(users, 'age');
-     * // => { 'fred': 40, 'pebbles': 1 } (iteration order is not guaranteed)
+     * _.zipObject(['a', 'b'], [1, 2]);
+     * // => { 'a': 1, 'b': 2 }
      */
-    function mapValues(object, iteratee) {
-      var result = {};
-      iteratee = getIteratee(iteratee, 3);
-
-      baseForOwn(object, function(value, key, object) {
-        result[key] = iteratee(value, key, object);
-      });
-      return result;
+    function zipObject(props, values) {
+      return baseZipObject(props || [], values || [], assignValue);
     }
 
     /**
-     * This method is like `_.assign` except that it recursively merges own and
-     * inherited enumerable string keyed properties of source objects into the
-     * destination object. Source properties that resolve to `undefined` are
-     * skipped if a destination value exists. Array and plain object properties
-     * are merged recursively. Other objects and value types are overridden by
-     * assignment. Source objects are applied from left to right. Subsequent
-     * sources overwrite property assignments of previous sources.
-     *
-     * **Note:** This method mutates `object`.
+     * This method is like `_.zipObject` except that it supports property paths.
      *
      * @static
      * @memberOf _
-     * @since 0.5.0
-     * @category Object
-     * @param {Object} object The destination object.
-     * @param {...Object} [sources] The source objects.
-     * @returns {Object} Returns `object`.
+     * @since 4.1.0
+     * @category Array
+     * @param {Array} [props=[]] The property identifiers.
+     * @param {Array} [values=[]] The property values.
+     * @returns {Object} Returns the new object.
      * @example
      *
-     * var users = {
-     *   'data': [{ 'user': 'barney' }, { 'user': 'fred' }]
-     * };
-     *
-     * var ages = {
-     *   'data': [{ 'age': 36 }, { 'age': 40 }]
-     * };
-     *
-     * _.merge(users, ages);
-     * // => { 'data': [{ 'user': 'barney', 'age': 36 }, { 'user': 'fred', 'age': 40 }] }
+     * _.zipObjectDeep(['a.b[0].c', 'a.b[1].d'], [1, 2]);
+     * // => { 'a': { 'b': [{ 'c': 1 }, { 'd': 2 }] } }
      */
-    var merge = createAssigner(function(object, source, srcIndex) {
-      baseMerge(object, source, srcIndex);
-    });
+    function zipObjectDeep(props, values) {
+      return baseZipObject(props || [], values || [], baseSet);
+    }
 
     /**
-     * This method is like `_.merge` except that it accepts `customizer` which
-     * is invoked to produce the merged values of the destination and source
-     * properties. If `customizer` returns `undefined`, merging is handled by the
-     * method instead. The `customizer` is invoked with seven arguments:
-     * (objValue, srcValue, key, object, source, stack).
-     *
-     * **Note:** This method mutates `object`.
+     * This method is like `_.zip` except that it accepts `iteratee` to specify
+     * how grouped values should be combined. The iteratee is invoked with the
+     * elements of each group: (...group).
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category Object
-     * @param {Object} object The destination object.
-     * @param {...Object} sources The source objects.
-     * @param {Function} customizer The function to customize assigned values.
-     * @returns {Object} Returns `object`.
+     * @since 3.8.0
+     * @category Array
+     * @param {...Array} [arrays] The arrays to process.
+     * @param {Function} [iteratee=_.identity] The function to combine
+     *  grouped values.
+     * @returns {Array} Returns the new array of grouped elements.
      * @example
      *
-     * function customizer(objValue, srcValue) {
-     *   if (_.isArray(objValue)) {
-     *     return objValue.concat(srcValue);
-     *   }
-     * }
-     *
-     * var object = {
-     *   'fruits': ['apple'],
-     *   'vegetables': ['beet']
-     * };
-     *
-     * var other = {
-     *   'fruits': ['banana'],
-     *   'vegetables': ['carrot']
-     * };
-     *
-     * _.mergeWith(object, other, customizer);
-     * // => { 'fruits': ['apple', 'banana'], 'vegetables': ['beet', 'carrot'] }
+     * _.zipWith([1, 2], [10, 20], [100, 200], function(a, b, c) {
+     *   return a + b + c;
+     * });
+     * // => [111, 222]
      */
-    var mergeWith = createAssigner(function(object, source, srcIndex, customizer) {
-      baseMerge(object, source, srcIndex, customizer);
+    var zipWith = baseRest(function(arrays) {
+      var length = arrays.length,
+          iteratee = length > 1 ? arrays[length - 1] : undefined;
+
+      iteratee = typeof iteratee == 'function' ? (arrays.pop(), iteratee) : undefined;
+      return unzipWith(arrays, iteratee);
     });
 
+    /*------------------------------------------------------------------------*/
+
     /**
-     * The opposite of `_.pick`; this method creates an object composed of the
-     * own and inherited enumerable string keyed properties of `object` that are
-     * not omitted.
+     * Creates a `lodash` wrapper instance that wraps `value` with explicit method
+     * chain sequences enabled. The result of such sequences must be unwrapped
+     * with `_#value`.
      *
      * @static
-     * @since 0.1.0
      * @memberOf _
-     * @category Object
-     * @param {Object} object The source object.
-     * @param {...(string|string[])} [props] The property identifiers to omit.
-     * @returns {Object} Returns the new object.
+     * @since 1.3.0
+     * @category Seq
+     * @param {*} value The value to wrap.
+     * @returns {Object} Returns the new `lodash` wrapper instance.
      * @example
      *
-     * var object = { 'a': 1, 'b': '2', 'c': 3 };
+     * var users = [
+     *   { 'user': 'barney',  'age': 36 },
+     *   { 'user': 'fred',    'age': 40 },
+     *   { 'user': 'pebbles', 'age': 1 }
+     * ];
      *
-     * _.omit(object, ['a', 'c']);
-     * // => { 'b': '2' }
+     * var youngest = _
+     *   .chain(users)
+     *   .sortBy('age')
+     *   .map(function(o) {
+     *     return o.user + ' is ' + o.age;
+     *   })
+     *   .head()
+     *   .value();
+     * // => 'pebbles is 1'
      */
-    var omit = rest(function(object, props) {
-      if (object == null) {
-        return {};
-      }
-      props = arrayMap(baseFlatten(props, 1), toKey);
-      return basePick(object, baseDifference(getAllKeysIn(object), props));
-    });
+    function chain(value) {
+      var result = lodash(value);
+      result.__chain__ = true;
+      return result;
+    }
 
     /**
-     * The opposite of `_.pickBy`; this method creates an object composed of
-     * the own and inherited enumerable string keyed properties of `object` that
-     * `predicate` doesn't return truthy for. The predicate is invoked with two
-     * arguments: (value, key).
+     * This method invokes `interceptor` and returns `value`. The interceptor
+     * is invoked with one argument; (value). The purpose of this method is to
+     * "tap into" a method chain sequence in order to modify intermediate results.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category Object
-     * @param {Object} object The source object.
-     * @param {Array|Function|Object|string} [predicate=_.identity]
-     *  The function invoked per property.
-     * @returns {Object} Returns the new object.
+     * @since 0.1.0
+     * @category Seq
+     * @param {*} value The value to provide to `interceptor`.
+     * @param {Function} interceptor The function to invoke.
+     * @returns {*} Returns `value`.
      * @example
      *
-     * var object = { 'a': 1, 'b': '2', 'c': 3 };
-     *
-     * _.omitBy(object, _.isNumber);
-     * // => { 'b': '2' }
+     * _([1, 2, 3])
+     *  .tap(function(array) {
+     *    // Mutate input array.
+     *    array.pop();
+     *  })
+     *  .reverse()
+     *  .value();
+     * // => [2, 1]
      */
-    function omitBy(object, predicate) {
-      predicate = getIteratee(predicate);
-      return basePickBy(object, function(value, key) {
-        return !predicate(value, key);
-      });
+    function tap(value, interceptor) {
+      interceptor(value);
+      return value;
     }
 
     /**
-     * Creates an object composed of the picked `object` properties.
+     * This method is like `_.tap` except that it returns the result of `interceptor`.
+     * The purpose of this method is to "pass thru" values replacing intermediate
+     * results in a method chain sequence.
      *
      * @static
-     * @since 0.1.0
      * @memberOf _
-     * @category Object
-     * @param {Object} object The source object.
-     * @param {...(string|string[])} [props] The property identifiers to pick.
-     * @returns {Object} Returns the new object.
+     * @since 3.0.0
+     * @category Seq
+     * @param {*} value The value to provide to `interceptor`.
+     * @param {Function} interceptor The function to invoke.
+     * @returns {*} Returns the result of `interceptor`.
      * @example
      *
-     * var object = { 'a': 1, 'b': '2', 'c': 3 };
-     *
-     * _.pick(object, ['a', 'c']);
-     * // => { 'a': 1, 'c': 3 }
+     * _('  abc  ')
+     *  .chain()
+     *  .trim()
+     *  .thru(function(value) {
+     *    return [value];
+     *  })
+     *  .value();
+     * // => ['abc']
      */
-    var pick = rest(function(object, props) {
-      return object == null ? {} : basePick(object, arrayMap(baseFlatten(props, 1), toKey));
-    });
+    function thru(value, interceptor) {
+      return interceptor(value);
+    }
 
     /**
-     * Creates an object composed of the `object` properties `predicate` returns
-     * truthy for. The predicate is invoked with two arguments: (value, key).
+     * This method is the wrapper version of `_.at`.
      *
-     * @static
+     * @name at
      * @memberOf _
-     * @since 4.0.0
-     * @category Object
-     * @param {Object} object The source object.
-     * @param {Array|Function|Object|string} [predicate=_.identity]
-     *  The function invoked per property.
-     * @returns {Object} Returns the new object.
+     * @since 1.0.0
+     * @category Seq
+     * @param {...(string|string[])} [paths] The property paths to pick.
+     * @returns {Object} Returns the new `lodash` wrapper instance.
      * @example
      *
-     * var object = { 'a': 1, 'b': '2', 'c': 3 };
+     * var object = { 'a': [{ 'b': { 'c': 3 } }, 4] };
      *
-     * _.pickBy(object, _.isNumber);
-     * // => { 'a': 1, 'c': 3 }
+     * _(object).at(['a[0].b.c', 'a[1]']).value();
+     * // => [3, 4]
      */
-    function pickBy(object, predicate) {
-      return object == null ? {} : basePickBy(object, getIteratee(predicate));
-    }
+    var wrapperAt = flatRest(function(paths) {
+      var length = paths.length,
+          start = length ? paths[0] : 0,
+          value = this.__wrapped__,
+          interceptor = function(object) { return baseAt(object, paths); };
+
+      if (length > 1 || this.__actions__.length ||
+          !(value instanceof LazyWrapper) || !isIndex(start)) {
+        return this.thru(interceptor);
+      }
+      value = value.slice(start, +start + (length ? 1 : 0));
+      value.__actions__.push({
+        'func': thru,
+        'args': [interceptor],
+        'thisArg': undefined
+      });
+      return new LodashWrapper(value, this.__chain__).thru(function(array) {
+        if (length && !array.length) {
+          array.push(undefined);
+        }
+        return array;
+      });
+    });
 
     /**
-     * This method is like `_.get` except that if the resolved value is a
-     * function it's invoked with the `this` binding of its parent object and
-     * its result is returned.
+     * Creates a `lodash` wrapper instance with explicit method chain sequences enabled.
      *
-     * @static
-     * @since 0.1.0
+     * @name chain
      * @memberOf _
-     * @category Object
-     * @param {Object} object The object to query.
-     * @param {Array|string} path The path of the property to resolve.
-     * @param {*} [defaultValue] The value returned for `undefined` resolved values.
-     * @returns {*} Returns the resolved value.
+     * @since 0.1.0
+     * @category Seq
+     * @returns {Object} Returns the new `lodash` wrapper instance.
      * @example
      *
-     * var object = { 'a': [{ 'b': { 'c1': 3, 'c2': _.constant(4) } }] };
-     *
-     * _.result(object, 'a[0].b.c1');
-     * // => 3
-     *
-     * _.result(object, 'a[0].b.c2');
-     * // => 4
+     * var users = [
+     *   { 'user': 'barney', 'age': 36 },
+     *   { 'user': 'fred',   'age': 40 }
+     * ];
      *
-     * _.result(object, 'a[0].b.c3', 'default');
-     * // => 'default'
+     * // A sequence without explicit chaining.
+     * _(users).head();
+     * // => { 'user': 'barney', 'age': 36 }
      *
-     * _.result(object, 'a[0].b.c3', _.constant('default'));
-     * // => 'default'
+     * // A sequence with explicit chaining.
+     * _(users)
+     *   .chain()
+     *   .head()
+     *   .pick('user')
+     *   .value();
+     * // => { 'user': 'barney' }
      */
-    function result(object, path, defaultValue) {
-      path = isKey(path, object) ? [path] : castPath(path);
-
-      var index = -1,
-          length = path.length;
-
-      // Ensure the loop is entered when path is empty.
-      if (!length) {
-        object = undefined;
-        length = 1;
-      }
-      while (++index < length) {
-        var value = object == null ? undefined : object[toKey(path[index])];
-        if (value === undefined) {
-          index = length;
-          value = defaultValue;
-        }
-        object = isFunction(value) ? value.call(object) : value;
-      }
-      return object;
+    function wrapperChain() {
+      return chain(this);
     }
 
     /**
-     * Sets the value at `path` of `object`. If a portion of `path` doesn't exist,
-     * it's created. Arrays are created for missing index properties while objects
-     * are created for all other missing properties. Use `_.setWith` to customize
-     * `path` creation.
-     *
-     * **Note:** This method mutates `object`.
+     * Executes the chain sequence and returns the wrapped result.
      *
-     * @static
+     * @name commit
      * @memberOf _
-     * @since 3.7.0
-     * @category Object
-     * @param {Object} object The object to modify.
-     * @param {Array|string} path The path of the property to set.
-     * @param {*} value The value to set.
-     * @returns {Object} Returns `object`.
+     * @since 3.2.0
+     * @category Seq
+     * @returns {Object} Returns the new `lodash` wrapper instance.
      * @example
      *
-     * var object = { 'a': [{ 'b': { 'c': 3 } }] };
+     * var array = [1, 2];
+     * var wrapped = _(array).push(3);
      *
-     * _.set(object, 'a[0].b.c', 4);
-     * console.log(object.a[0].b.c);
-     * // => 4
+     * console.log(array);
+     * // => [1, 2]
      *
-     * _.set(object, ['x', '0', 'y', 'z'], 5);
-     * console.log(object.x[0].y.z);
-     * // => 5
+     * wrapped = wrapped.commit();
+     * console.log(array);
+     * // => [1, 2, 3]
+     *
+     * wrapped.last();
+     * // => 3
+     *
+     * console.log(array);
+     * // => [1, 2, 3]
      */
-    function set(object, path, value) {
-      return object == null ? object : baseSet(object, path, value);
+    function wrapperCommit() {
+      return new LodashWrapper(this.value(), this.__chain__);
     }
 
     /**
-     * This method is like `_.set` except that it accepts `customizer` which is
-     * invoked to produce the objects of `path`.  If `customizer` returns `undefined`
-     * path creation is handled by the method instead. The `customizer` is invoked
-     * with three arguments: (nsValue, key, nsObject).
-     *
-     * **Note:** This method mutates `object`.
+     * Gets the next value on a wrapped object following the
+     * [iterator protocol](https://mdn.io/iteration_protocols#iterator).
      *
-     * @static
+     * @name next
      * @memberOf _
      * @since 4.0.0
-     * @category Object
-     * @param {Object} object The object to modify.
-     * @param {Array|string} path The path of the property to set.
-     * @param {*} value The value to set.
-     * @param {Function} [customizer] The function to customize assigned values.
-     * @returns {Object} Returns `object`.
+     * @category Seq
+     * @returns {Object} Returns the next iterator value.
      * @example
      *
-     * var object = {};
+     * var wrapped = _([1, 2]);
      *
-     * _.setWith(object, '[0][1]', 'a', Object);
-     * // => { '0': { '1': 'a' } }
+     * wrapped.next();
+     * // => { 'done': false, 'value': 1 }
+     *
+     * wrapped.next();
+     * // => { 'done': false, 'value': 2 }
+     *
+     * wrapped.next();
+     * // => { 'done': true, 'value': undefined }
      */
-    function setWith(object, path, value, customizer) {
-      customizer = typeof customizer == 'function' ? customizer : undefined;
-      return object == null ? object : baseSet(object, path, value, customizer);
+    function wrapperNext() {
+      if (this.__values__ === undefined) {
+        this.__values__ = toArray(this.value());
+      }
+      var done = this.__index__ >= this.__values__.length,
+          value = done ? undefined : this.__values__[this.__index__++];
+
+      return { 'done': done, 'value': value };
     }
 
     /**
-     * Creates an array of own enumerable string keyed-value pairs for `object`
-     * which can be consumed by `_.fromPairs`. If `object` is a map or set, its
-     * entries are returned.
+     * Enables the wrapper to be iterable.
      *
-     * @static
+     * @name Symbol.iterator
      * @memberOf _
      * @since 4.0.0
-     * @alias entries
-     * @category Object
-     * @param {Object} object The object to query.
-     * @returns {Array} Returns the key-value pairs.
+     * @category Seq
+     * @returns {Object} Returns the wrapper object.
      * @example
      *
-     * function Foo() {
-     *   this.a = 1;
-     *   this.b = 2;
-     * }
+     * var wrapped = _([1, 2]);
      *
-     * Foo.prototype.c = 3;
+     * wrapped[Symbol.iterator]() === wrapped;
+     * // => true
      *
-     * _.toPairs(new Foo);
-     * // => [['a', 1], ['b', 2]] (iteration order is not guaranteed)
+     * Array.from(wrapped);
+     * // => [1, 2]
      */
-    var toPairs = createToPairs(keys);
+    function wrapperToIterator() {
+      return this;
+    }
 
     /**
-     * Creates an array of own and inherited enumerable string keyed-value pairs
-     * for `object` which can be consumed by `_.fromPairs`. If `object` is a map
-     * or set, its entries are returned.
+     * Creates a clone of the chain sequence planting `value` as the wrapped value.
      *
-     * @static
+     * @name plant
      * @memberOf _
-     * @since 4.0.0
-     * @alias entriesIn
-     * @category Object
-     * @param {Object} object The object to query.
-     * @returns {Array} Returns the key-value pairs.
+     * @since 3.2.0
+     * @category Seq
+     * @param {*} value The value to plant.
+     * @returns {Object} Returns the new `lodash` wrapper instance.
      * @example
      *
-     * function Foo() {
-     *   this.a = 1;
-     *   this.b = 2;
+     * function square(n) {
+     *   return n * n;
      * }
      *
-     * Foo.prototype.c = 3;
+     * var wrapped = _([1, 2]).map(square);
+     * var other = wrapped.plant([3, 4]);
      *
-     * _.toPairsIn(new Foo);
-     * // => [['a', 1], ['b', 2], ['c', 3]] (iteration order is not guaranteed)
-     */
-    var toPairsIn = createToPairs(keysIn);
-
-    /**
-     * An alternative to `_.reduce`; this method transforms `object` to a new
-     * `accumulator` object which is the result of running each of its own
-     * enumerable string keyed properties thru `iteratee`, with each invocation
-     * potentially mutating the `accumulator` object. If `accumulator` is not
-     * provided, a new object with the same `[[Prototype]]` will be used. The
-     * iteratee is invoked with four arguments: (accumulator, value, key, object).
-     * Iteratee functions may exit iteration early by explicitly returning `false`.
-     *
-     * @static
-     * @memberOf _
-     * @since 1.3.0
-     * @category Object
-     * @param {Object} object The object to iterate over.
-     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
-     * @param {*} [accumulator] The custom accumulator value.
-     * @returns {*} Returns the accumulated value.
-     * @example
-     *
-     * _.transform([2, 3, 4], function(result, n) {
-     *   result.push(n *= n);
-     *   return n % 2 == 0;
-     * }, []);
-     * // => [4, 9]
+     * other.value();
+     * // => [9, 16]
      *
-     * _.transform({ 'a': 1, 'b': 2, 'c': 1 }, function(result, value, key) {
-     *   (result[value] || (result[value] = [])).push(key);
-     * }, {});
-     * // => { '1': ['a', 'c'], '2': ['b'] }
+     * wrapped.value();
+     * // => [1, 4]
      */
-    function transform(object, iteratee, accumulator) {
-      var isArr = isArray(object) || isTypedArray(object);
-      iteratee = getIteratee(iteratee, 4);
+    function wrapperPlant(value) {
+      var result,
+          parent = this;
 
-      if (accumulator == null) {
-        if (isArr || isObject(object)) {
-          var Ctor = object.constructor;
-          if (isArr) {
-            accumulator = isArray(object) ? new Ctor : [];
-          } else {
-            accumulator = isFunction(Ctor) ? baseCreate(getPrototype(object)) : {};
-          }
+      while (parent instanceof baseLodash) {
+        var clone = wrapperClone(parent);
+        clone.__index__ = 0;
+        clone.__values__ = undefined;
+        if (result) {
+          previous.__wrapped__ = clone;
         } else {
-          accumulator = {};
+          result = clone;
         }
+        var previous = clone;
+        parent = parent.__wrapped__;
       }
-      (isArr ? arrayEach : baseForOwn)(object, function(value, index, object) {
-        return iteratee(accumulator, value, index, object);
-      });
-      return accumulator;
+      previous.__wrapped__ = value;
+      return result;
     }
 
     /**
-     * Removes the property at `path` of `object`.
+     * This method is the wrapper version of `_.reverse`.
      *
-     * **Note:** This method mutates `object`.
+     * **Note:** This method mutates the wrapped array.
      *
-     * @static
+     * @name reverse
      * @memberOf _
-     * @since 4.0.0
-     * @category Object
-     * @param {Object} object The object to modify.
-     * @param {Array|string} path The path of the property to unset.
-     * @returns {boolean} Returns `true` if the property is deleted, else `false`.
+     * @since 0.1.0
+     * @category Seq
+     * @returns {Object} Returns the new `lodash` wrapper instance.
      * @example
      *
-     * var object = { 'a': [{ 'b': { 'c': 7 } }] };
-     * _.unset(object, 'a[0].b.c');
-     * // => true
-     *
-     * console.log(object);
-     * // => { 'a': [{ 'b': {} }] };
+     * var array = [1, 2, 3];
      *
-     * _.unset(object, ['a', '0', 'b', 'c']);
-     * // => true
+     * _(array).reverse().value()
+     * // => [3, 2, 1]
      *
-     * console.log(object);
-     * // => { 'a': [{ 'b': {} }] };
+     * console.log(array);
+     * // => [3, 2, 1]
      */
-    function unset(object, path) {
-      return object == null ? true : baseUnset(object, path);
+    function wrapperReverse() {
+      var value = this.__wrapped__;
+      if (value instanceof LazyWrapper) {
+        var wrapped = value;
+        if (this.__actions__.length) {
+          wrapped = new LazyWrapper(this);
+        }
+        wrapped = wrapped.reverse();
+        wrapped.__actions__.push({
+          'func': thru,
+          'args': [reverse],
+          'thisArg': undefined
+        });
+        return new LodashWrapper(wrapped, this.__chain__);
+      }
+      return this.thru(reverse);
     }
 
     /**
-     * This method is like `_.set` except that accepts `updater` to produce the
-     * value to set. Use `_.updateWith` to customize `path` creation. The `updater`
-     * is invoked with one argument: (value).
-     *
-     * **Note:** This method mutates `object`.
+     * Executes the chain sequence to resolve the unwrapped value.
      *
-     * @static
+     * @name value
      * @memberOf _
-     * @since 4.6.0
-     * @category Object
-     * @param {Object} object The object to modify.
-     * @param {Array|string} path The path of the property to set.
-     * @param {Function} updater The function to produce the updated value.
-     * @returns {Object} Returns `object`.
+     * @since 0.1.0
+     * @alias toJSON, valueOf
+     * @category Seq
+     * @returns {*} Returns the resolved unwrapped value.
      * @example
      *
-     * var object = { 'a': [{ 'b': { 'c': 3 } }] };
-     *
-     * _.update(object, 'a[0].b.c', function(n) { return n * n; });
-     * console.log(object.a[0].b.c);
-     * // => 9
-     *
-     * _.update(object, 'x[0].y.z', function(n) { return n ? n + 1 : 0; });
-     * console.log(object.x[0].y.z);
-     * // => 0
+     * _([1, 2, 3]).value();
+     * // => [1, 2, 3]
      */
-    function update(object, path, updater) {
-      return object == null ? object : baseUpdate(object, path, castFunction(updater));
+    function wrapperValue() {
+      return baseWrapperValue(this.__wrapped__, this.__actions__);
     }
 
+    /*------------------------------------------------------------------------*/
+
     /**
-     * This method is like `_.update` except that it accepts `customizer` which is
-     * invoked to produce the objects of `path`.  If `customizer` returns `undefined`
-     * path creation is handled by the method instead. The `customizer` is invoked
-     * with three arguments: (nsValue, key, nsObject).
-     *
-     * **Note:** This method mutates `object`.
+     * Creates an object composed of keys generated from the results of running
+     * each element of `collection` thru `iteratee`. The corresponding value of
+     * each key is the number of times the key was returned by `iteratee`. The
+     * iteratee is invoked with one argument: (value).
      *
      * @static
      * @memberOf _
-     * @since 4.6.0
-     * @category Object
-     * @param {Object} object The object to modify.
-     * @param {Array|string} path The path of the property to set.
-     * @param {Function} updater The function to produce the updated value.
-     * @param {Function} [customizer] The function to customize assigned values.
-     * @returns {Object} Returns `object`.
+     * @since 0.5.0
+     * @category Collection
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} [iteratee=_.identity] The iteratee to transform keys.
+     * @returns {Object} Returns the composed aggregate object.
      * @example
      *
-     * var object = {};
+     * _.countBy([6.1, 4.2, 6.3], Math.floor);
+     * // => { '4': 1, '6': 2 }
      *
-     * _.updateWith(object, '[0][1]', _.constant('a'), Object);
-     * // => { '0': { '1': 'a' } }
+     * // The `_.property` iteratee shorthand.
+     * _.countBy(['one', 'two', 'three'], 'length');
+     * // => { '3': 2, '5': 1 }
      */
-    function updateWith(object, path, updater, customizer) {
-      customizer = typeof customizer == 'function' ? customizer : undefined;
-      return object == null ? object : baseUpdate(object, path, castFunction(updater), customizer);
-    }
+    var countBy = createAggregator(function(result, value, key) {
+      if (hasOwnProperty.call(result, key)) {
+        ++result[key];
+      } else {
+        baseAssignValue(result, key, 1);
+      }
+    });
 
     /**
-     * Creates an array of the own enumerable string keyed property values of `object`.
+     * Checks if `predicate` returns truthy for **all** elements of `collection`.
+     * Iteration is stopped once `predicate` returns falsey. The predicate is
+     * invoked with three arguments: (value, index|key, collection).
      *
-     * **Note:** Non-object values are coerced to objects.
+     * **Note:** This method returns `true` for
+     * [empty collections](https://en.wikipedia.org/wiki/Empty_set) because
+     * [everything is true](https://en.wikipedia.org/wiki/Vacuous_truth) of
+     * elements of empty collections.
      *
      * @static
-     * @since 0.1.0
      * @memberOf _
-     * @category Object
-     * @param {Object} object The object to query.
-     * @returns {Array} Returns the array of property values.
+     * @since 0.1.0
+     * @category Collection
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} [predicate=_.identity] The function invoked per iteration.
+     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
+     * @returns {boolean} Returns `true` if all elements pass the predicate check,
+     *  else `false`.
      * @example
      *
-     * function Foo() {
-     *   this.a = 1;
-     *   this.b = 2;
-     * }
+     * _.every([true, 1, null, 'yes'], Boolean);
+     * // => false
      *
-     * Foo.prototype.c = 3;
+     * var users = [
+     *   { 'user': 'barney', 'age': 36, 'active': false },
+     *   { 'user': 'fred',   'age': 40, 'active': false }
+     * ];
      *
-     * _.values(new Foo);
-     * // => [1, 2] (iteration order is not guaranteed)
+     * // The `_.matches` iteratee shorthand.
+     * _.every(users, { 'user': 'barney', 'active': false });
+     * // => false
      *
-     * _.values('hi');
-     * // => ['h', 'i']
+     * // The `_.matchesProperty` iteratee shorthand.
+     * _.every(users, ['active', false]);
+     * // => true
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.every(users, 'active');
+     * // => false
      */
-    function values(object) {
-      return object ? baseValues(object, keys(object)) : [];
+    function every(collection, predicate, guard) {
+      var func = isArray(collection) ? arrayEvery : baseEvery;
+      if (guard && isIterateeCall(collection, predicate, guard)) {
+        predicate = undefined;
+      }
+      return func(collection, getIteratee(predicate, 3));
     }
 
     /**
-     * Creates an array of the own and inherited enumerable string keyed property
-     * values of `object`.
+     * Iterates over elements of `collection`, returning an array of all elements
+     * `predicate` returns truthy for. The predicate is invoked with three
+     * arguments: (value, index|key, collection).
      *
-     * **Note:** Non-object values are coerced to objects.
+     * **Note:** Unlike `_.remove`, this method returns a new array.
      *
      * @static
      * @memberOf _
-     * @since 3.0.0
-     * @category Object
-     * @param {Object} object The object to query.
-     * @returns {Array} Returns the array of property values.
+     * @since 0.1.0
+     * @category Collection
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} [predicate=_.identity] The function invoked per iteration.
+     * @returns {Array} Returns the new filtered array.
+     * @see _.reject
      * @example
      *
-     * function Foo() {
-     *   this.a = 1;
-     *   this.b = 2;
-     * }
+     * var users = [
+     *   { 'user': 'barney', 'age': 36, 'active': true },
+     *   { 'user': 'fred',   'age': 40, 'active': false }
+     * ];
      *
-     * Foo.prototype.c = 3;
+     * _.filter(users, function(o) { return !o.active; });
+     * // => objects for ['fred']
      *
-     * _.valuesIn(new Foo);
-     * // => [1, 2, 3] (iteration order is not guaranteed)
-     */
-    function valuesIn(object) {
-      return object == null ? [] : baseValues(object, keysIn(object));
-    }
-
-    /*------------------------------------------------------------------------*/
-
-    /**
-     * Clamps `number` within the inclusive `lower` and `upper` bounds.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category Number
-     * @param {number} number The number to clamp.
-     * @param {number} [lower] The lower bound.
-     * @param {number} upper The upper bound.
-     * @returns {number} Returns the clamped number.
-     * @example
+     * // The `_.matches` iteratee shorthand.
+     * _.filter(users, { 'age': 36, 'active': true });
+     * // => objects for ['barney']
      *
-     * _.clamp(-10, -5, 5);
-     * // => -5
+     * // The `_.matchesProperty` iteratee shorthand.
+     * _.filter(users, ['active', false]);
+     * // => objects for ['fred']
      *
-     * _.clamp(10, -5, 5);
-     * // => 5
+     * // The `_.property` iteratee shorthand.
+     * _.filter(users, 'active');
+     * // => objects for ['barney']
      */
-    function clamp(number, lower, upper) {
-      if (upper === undefined) {
-        upper = lower;
-        lower = undefined;
-      }
-      if (upper !== undefined) {
-        upper = toNumber(upper);
-        upper = upper === upper ? upper : 0;
-      }
-      if (lower !== undefined) {
-        lower = toNumber(lower);
-        lower = lower === lower ? lower : 0;
-      }
-      return baseClamp(toNumber(number), lower, upper);
+    function filter(collection, predicate) {
+      var func = isArray(collection) ? arrayFilter : baseFilter;
+      return func(collection, getIteratee(predicate, 3));
     }
 
     /**
-     * Checks if `n` is between `start` and up to, but not including, `end`. If
-     * `end` is not specified, it's set to `start` with `start` then set to `0`.
-     * If `start` is greater than `end` the params are swapped to support
-     * negative ranges.
+     * Iterates over elements of `collection`, returning the first element
+     * `predicate` returns truthy for. The predicate is invoked with three
+     * arguments: (value, index|key, collection).
      *
      * @static
      * @memberOf _
-     * @since 3.3.0
-     * @category Number
-     * @param {number} number The number to check.
-     * @param {number} [start=0] The start of the range.
-     * @param {number} end The end of the range.
-     * @returns {boolean} Returns `true` if `number` is in the range, else `false`.
-     * @see _.range, _.rangeRight
+     * @since 0.1.0
+     * @category Collection
+     * @param {Array|Object} collection The collection to inspect.
+     * @param {Function} [predicate=_.identity] The function invoked per iteration.
+     * @param {number} [fromIndex=0] The index to search from.
+     * @returns {*} Returns the matched element, else `undefined`.
      * @example
      *
-     * _.inRange(3, 2, 4);
-     * // => true
-     *
-     * _.inRange(4, 8);
-     * // => true
-     *
-     * _.inRange(4, 2);
-     * // => false
+     * var users = [
+     *   { 'user': 'barney',  'age': 36, 'active': true },
+     *   { 'user': 'fred',    'age': 40, 'active': false },
+     *   { 'user': 'pebbles', 'age': 1,  'active': true }
+     * ];
      *
-     * _.inRange(2, 2);
-     * // => false
+     * _.find(users, function(o) { return o.age < 40; });
+     * // => object for 'barney'
      *
-     * _.inRange(1.2, 2);
-     * // => true
+     * // The `_.matches` iteratee shorthand.
+     * _.find(users, { 'age': 1, 'active': true });
+     * // => object for 'pebbles'
      *
-     * _.inRange(5.2, 4);
-     * // => false
+     * // The `_.matchesProperty` iteratee shorthand.
+     * _.find(users, ['active', false]);
+     * // => object for 'fred'
      *
-     * _.inRange(-3, -2, -6);
-     * // => true
+     * // The `_.property` iteratee shorthand.
+     * _.find(users, 'active');
+     * // => object for 'barney'
      */
-    function inRange(number, start, end) {
-      start = toNumber(start) || 0;
-      if (end === undefined) {
-        end = start;
-        start = 0;
-      } else {
-        end = toNumber(end) || 0;
-      }
-      number = toNumber(number);
-      return baseInRange(number, start, end);
-    }
+    var find = createFind(findIndex);
 
     /**
-     * Produces a random number between the inclusive `lower` and `upper` bounds.
-     * If only one argument is provided a number between `0` and the given number
-     * is returned. If `floating` is `true`, or either `lower` or `upper` are
-     * floats, a floating-point number is returned instead of an integer.
-     *
-     * **Note:** JavaScript follows the IEEE-754 standard for resolving
-     * floating-point values which can produce unexpected results.
+     * This method is like `_.find` except that it iterates over elements of
+     * `collection` from right to left.
      *
      * @static
      * @memberOf _
-     * @since 0.7.0
-     * @category Number
-     * @param {number} [lower=0] The lower bound.
-     * @param {number} [upper=1] The upper bound.
-     * @param {boolean} [floating] Specify returning a floating-point number.
-     * @returns {number} Returns the random number.
+     * @since 2.0.0
+     * @category Collection
+     * @param {Array|Object} collection The collection to inspect.
+     * @param {Function} [predicate=_.identity] The function invoked per iteration.
+     * @param {number} [fromIndex=collection.length-1] The index to search from.
+     * @returns {*} Returns the matched element, else `undefined`.
      * @example
      *
-     * _.random(0, 5);
-     * // => an integer between 0 and 5
-     *
-     * _.random(5);
-     * // => also an integer between 0 and 5
-     *
-     * _.random(5, true);
-     * // => a floating-point number between 0 and 5
-     *
-     * _.random(1.2, 5.2);
-     * // => a floating-point number between 1.2 and 5.2
+     * _.findLast([1, 2, 3, 4], function(n) {
+     *   return n % 2 == 1;
+     * });
+     * // => 3
      */
-    function random(lower, upper, floating) {
-      if (floating && typeof floating != 'boolean' && isIterateeCall(lower, upper, floating)) {
-        upper = floating = undefined;
-      }
-      if (floating === undefined) {
-        if (typeof upper == 'boolean') {
-          floating = upper;
-          upper = undefined;
-        }
-        else if (typeof lower == 'boolean') {
-          floating = lower;
-          lower = undefined;
-        }
-      }
-      if (lower === undefined && upper === undefined) {
-        lower = 0;
-        upper = 1;
-      }
-      else {
-        lower = toNumber(lower) || 0;
-        if (upper === undefined) {
-          upper = lower;
-          lower = 0;
-        } else {
-          upper = toNumber(upper) || 0;
-        }
-      }
-      if (lower > upper) {
-        var temp = lower;
-        lower = upper;
-        upper = temp;
-      }
-      if (floating || lower % 1 || upper % 1) {
-        var rand = nativeRandom();
-        return nativeMin(lower + (rand * (upper - lower + freeParseFloat('1e-' + ((rand + '').length - 1)))), upper);
-      }
-      return baseRandom(lower, upper);
-    }
-
-    /*------------------------------------------------------------------------*/
+    var findLast = createFind(findLastIndex);
 
     /**
-     * Converts `string` to [camel case](https://en.wikipedia.org/wiki/CamelCase).
+     * Creates a flattened array of values by running each element in `collection`
+     * thru `iteratee` and flattening the mapped results. The iteratee is invoked
+     * with three arguments: (value, index|key, collection).
      *
      * @static
      * @memberOf _
-     * @since 3.0.0
-     * @category String
-     * @param {string} [string=''] The string to convert.
-     * @returns {string} Returns the camel cased string.
+     * @since 4.0.0
+     * @category Collection
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
+     * @returns {Array} Returns the new flattened array.
      * @example
      *
-     * _.camelCase('Foo Bar');
-     * // => 'fooBar'
-     *
-     * _.camelCase('--foo-bar--');
-     * // => 'fooBar'
+     * function duplicate(n) {
+     *   return [n, n];
+     * }
      *
-     * _.camelCase('__FOO_BAR__');
-     * // => 'fooBar'
+     * _.flatMap([1, 2], duplicate);
+     * // => [1, 1, 2, 2]
      */
-    var camelCase = createCompounder(function(result, word, index) {
-      word = word.toLowerCase();
-      return result + (index ? capitalize(word) : word);
-    });
+    function flatMap(collection, iteratee) {
+      return baseFlatten(map(collection, iteratee), 1);
+    }
 
     /**
-     * Converts the first character of `string` to upper case and the remaining
-     * to lower case.
+     * This method is like `_.flatMap` except that it recursively flattens the
+     * mapped results.
      *
      * @static
      * @memberOf _
-     * @since 3.0.0
-     * @category String
-     * @param {string} [string=''] The string to capitalize.
-     * @returns {string} Returns the capitalized string.
+     * @since 4.7.0
+     * @category Collection
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
+     * @returns {Array} Returns the new flattened array.
      * @example
      *
-     * _.capitalize('FRED');
-     * // => 'Fred'
+     * function duplicate(n) {
+     *   return [[[n, n]]];
+     * }
+     *
+     * _.flatMapDeep([1, 2], duplicate);
+     * // => [1, 1, 2, 2]
      */
-    function capitalize(string) {
-      return upperFirst(toString(string).toLowerCase());
+    function flatMapDeep(collection, iteratee) {
+      return baseFlatten(map(collection, iteratee), INFINITY);
     }
 
     /**
-     * Deburrs `string` by converting
-     * [latin-1 supplementary letters](https://en.wikipedia.org/wiki/Latin-1_Supplement_(Unicode_block)#Character_table)
-     * to basic latin letters and removing
-     * [combining diacritical marks](https://en.wikipedia.org/wiki/Combining_Diacritical_Marks).
+     * This method is like `_.flatMap` except that it recursively flattens the
+     * mapped results up to `depth` times.
      *
      * @static
      * @memberOf _
-     * @since 3.0.0
-     * @category String
-     * @param {string} [string=''] The string to deburr.
-     * @returns {string} Returns the deburred string.
+     * @since 4.7.0
+     * @category Collection
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
+     * @param {number} [depth=1] The maximum recursion depth.
+     * @returns {Array} Returns the new flattened array.
      * @example
      *
-     * _.deburr('déjà vu');
-     * // => 'deja vu'
-     */
-    function deburr(string) {
-      string = toString(string);
-      return string && string.replace(reLatin1, deburrLetter).replace(reComboMark, '');
-    }
-
-    /**
-     * Checks if `string` ends with the given target string.
-     *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category String
-     * @param {string} [string=''] The string to search.
-     * @param {string} [target] The string to search for.
-     * @param {number} [position=string.length] The position to search up to.
-     * @returns {boolean} Returns `true` if `string` ends with `target`,
-     *  else `false`.
-     * @example
-     *
-     * _.endsWith('abc', 'c');
-     * // => true
-     *
-     * _.endsWith('abc', 'b');
-     * // => false
+     * function duplicate(n) {
+     *   return [[[n, n]]];
+     * }
      *
-     * _.endsWith('abc', 'b', 2);
-     * // => true
+     * _.flatMapDepth([1, 2], duplicate, 2);
+     * // => [[1, 1], [2, 2]]
      */
-    function endsWith(string, target, position) {
-      string = toString(string);
-      target = baseToString(target);
-
-      var length = string.length;
-      position = position === undefined
-        ? length
-        : baseClamp(toInteger(position), 0, length);
-
-      position -= target.length;
-      return position >= 0 && string.indexOf(target, position) == position;
+    function flatMapDepth(collection, iteratee, depth) {
+      depth = depth === undefined ? 1 : toInteger(depth);
+      return baseFlatten(map(collection, iteratee), depth);
     }
 
     /**
-     * Converts the characters "&", "<", ">", '"', "'", and "\`" in `string` to
-     * their corresponding HTML entities.
-     *
-     * **Note:** No other characters are escaped. To escape additional
-     * characters use a third-party library like [_he_](https://mths.be/he).
-     *
-     * Though the ">" character is escaped for symmetry, characters like
-     * ">" and "/" don't need escaping in HTML and have no special meaning
-     * unless they're part of a tag or unquoted attribute value. See
-     * [Mathias Bynens's article](https://mathiasbynens.be/notes/ambiguous-ampersands)
-     * (under "semi-related fun fact") for more details.
-     *
-     * Backticks are escaped because in IE < 9, they can break out of
-     * attribute values or HTML comments. See [#59](https://html5sec.org/#59),
-     * [#102](https://html5sec.org/#102), [#108](https://html5sec.org/#108), and
-     * [#133](https://html5sec.org/#133) of the
-     * [HTML5 Security Cheatsheet](https://html5sec.org/) for more details.
+     * Iterates over elements of `collection` and invokes `iteratee` for each element.
+     * The iteratee is invoked with three arguments: (value, index|key, collection).
+     * Iteratee functions may exit iteration early by explicitly returning `false`.
      *
-     * When working with HTML you should always
-     * [quote attribute values](http://wonko.com/post/html-escaping) to reduce
-     * XSS vectors.
+     * **Note:** As with other "Collections" methods, objects with a "length"
+     * property are iterated like arrays. To avoid this behavior use `_.forIn`
+     * or `_.forOwn` for object iteration.
      *
      * @static
-     * @since 0.1.0
      * @memberOf _
-     * @category String
-     * @param {string} [string=''] The string to escape.
-     * @returns {string} Returns the escaped string.
+     * @since 0.1.0
+     * @alias each
+     * @category Collection
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
+     * @returns {Array|Object} Returns `collection`.
+     * @see _.forEachRight
      * @example
      *
-     * _.escape('fred, barney, & pebbles');
-     * // => 'fred, barney, &amp; pebbles'
+     * _.forEach([1, 2], function(value) {
+     *   console.log(value);
+     * });
+     * // => Logs `1` then `2`.
+     *
+     * _.forEach({ 'a': 1, 'b': 2 }, function(value, key) {
+     *   console.log(key);
+     * });
+     * // => Logs 'a' then 'b' (iteration order is not guaranteed).
      */
-    function escape(string) {
-      string = toString(string);
-      return (string && reHasUnescapedHtml.test(string))
-        ? string.replace(reUnescapedHtml, escapeHtmlChar)
-        : string;
+    function forEach(collection, iteratee) {
+      var func = isArray(collection) ? arrayEach : baseEach;
+      return func(collection, getIteratee(iteratee, 3));
     }
 
     /**
-     * Escapes the `RegExp` special characters "^", "$", "\", ".", "*", "+",
-     * "?", "(", ")", "[", "]", "{", "}", and "|" in `string`.
+     * This method is like `_.forEach` except that it iterates over elements of
+     * `collection` from right to left.
      *
      * @static
      * @memberOf _
-     * @since 3.0.0
-     * @category String
-     * @param {string} [string=''] The string to escape.
-     * @returns {string} Returns the escaped string.
+     * @since 2.0.0
+     * @alias eachRight
+     * @category Collection
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
+     * @returns {Array|Object} Returns `collection`.
+     * @see _.forEach
      * @example
      *
-     * _.escapeRegExp('[lodash](https://lodash.com/)');
-     * // => '\[lodash\]\(https://lodash\.com/\)'
+     * _.forEachRight([1, 2], function(value) {
+     *   console.log(value);
+     * });
+     * // => Logs `2` then `1`.
      */
-    function escapeRegExp(string) {
-      string = toString(string);
-      return (string && reHasRegExpChar.test(string))
-        ? string.replace(reRegExpChar, '\\$&')
-        : string;
+    function forEachRight(collection, iteratee) {
+      var func = isArray(collection) ? arrayEachRight : baseEachRight;
+      return func(collection, getIteratee(iteratee, 3));
     }
 
     /**
-     * Converts `string` to
-     * [kebab case](https://en.wikipedia.org/wiki/Letter_case#Special_case_styles).
+     * Creates an object composed of keys generated from the results of running
+     * each element of `collection` thru `iteratee`. The order of grouped values
+     * is determined by the order they occur in `collection`. The corresponding
+     * value of each key is an array of elements responsible for generating the
+     * key. The iteratee is invoked with one argument: (value).
      *
      * @static
      * @memberOf _
-     * @since 3.0.0
-     * @category String
-     * @param {string} [string=''] The string to convert.
-     * @returns {string} Returns the kebab cased string.
+     * @since 0.1.0
+     * @category Collection
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} [iteratee=_.identity] The iteratee to transform keys.
+     * @returns {Object} Returns the composed aggregate object.
      * @example
      *
-     * _.kebabCase('Foo Bar');
-     * // => 'foo-bar'
-     *
-     * _.kebabCase('fooBar');
-     * // => 'foo-bar'
+     * _.groupBy([6.1, 4.2, 6.3], Math.floor);
+     * // => { '4': [4.2], '6': [6.1, 6.3] }
      *
-     * _.kebabCase('__FOO_BAR__');
-     * // => 'foo-bar'
+     * // The `_.property` iteratee shorthand.
+     * _.groupBy(['one', 'two', 'three'], 'length');
+     * // => { '3': ['one', 'two'], '5': ['three'] }
      */
-    var kebabCase = createCompounder(function(result, word, index) {
-      return result + (index ? '-' : '') + word.toLowerCase();
+    var groupBy = createAggregator(function(result, value, key) {
+      if (hasOwnProperty.call(result, key)) {
+        result[key].push(value);
+      } else {
+        baseAssignValue(result, key, [value]);
+      }
     });
 
     /**
-     * Converts `string`, as space separated words, to lower case.
+     * Checks if `value` is in `collection`. If `collection` is a string, it's
+     * checked for a substring of `value`, otherwise
+     * [`SameValueZero`](http://ecma-international.org/ecma-262/7.0/#sec-samevaluezero)
+     * is used for equality comparisons. If `fromIndex` is negative, it's used as
+     * the offset from the end of `collection`.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category String
-     * @param {string} [string=''] The string to convert.
-     * @returns {string} Returns the lower cased string.
+     * @since 0.1.0
+     * @category Collection
+     * @param {Array|Object|string} collection The collection to inspect.
+     * @param {*} value The value to search for.
+     * @param {number} [fromIndex=0] The index to search from.
+     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.reduce`.
+     * @returns {boolean} Returns `true` if `value` is found, else `false`.
      * @example
      *
-     * _.lowerCase('--Foo-Bar--');
-     * // => 'foo bar'
+     * _.includes([1, 2, 3], 1);
+     * // => true
      *
-     * _.lowerCase('fooBar');
-     * // => 'foo bar'
+     * _.includes([1, 2, 3], 1, 2);
+     * // => false
      *
-     * _.lowerCase('__FOO_BAR__');
-     * // => 'foo bar'
+     * _.includes({ 'a': 1, 'b': 2 }, 1);
+     * // => true
+     *
+     * _.includes('abcd', 'bc');
+     * // => true
      */
-    var lowerCase = createCompounder(function(result, word, index) {
-      return result + (index ? ' ' : '') + word.toLowerCase();
-    });
+    function includes(collection, value, fromIndex, guard) {
+      collection = isArrayLike(collection) ? collection : values(collection);
+      fromIndex = (fromIndex && !guard) ? toInteger(fromIndex) : 0;
+
+      var length = collection.length;
+      if (fromIndex < 0) {
+        fromIndex = nativeMax(length + fromIndex, 0);
+      }
+      return isString(collection)
+        ? (fromIndex <= length && collection.indexOf(value, fromIndex) > -1)
+        : (!!length && baseIndexOf(collection, value, fromIndex) > -1);
+    }
 
     /**
-     * Converts the first character of `string` to lower case.
+     * Invokes the method at `path` of each element in `collection`, returning
+     * an array of the results of each invoked method. Any additional arguments
+     * are provided to each invoked method. If `path` is a function, it's invoked
+     * for, and `this` bound to, each element in `collection`.
      *
      * @static
      * @memberOf _
      * @since 4.0.0
-     * @category String
-     * @param {string} [string=''] The string to convert.
-     * @returns {string} Returns the converted string.
+     * @category Collection
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Array|Function|string} path The path of the method to invoke or
+     *  the function invoked per iteration.
+     * @param {...*} [args] The arguments to invoke each method with.
+     * @returns {Array} Returns the array of results.
      * @example
      *
-     * _.lowerFirst('Fred');
-     * // => 'fred'
+     * _.invokeMap([[5, 1, 7], [3, 2, 1]], 'sort');
+     * // => [[1, 5, 7], [1, 2, 3]]
      *
-     * _.lowerFirst('FRED');
-     * // => 'fRED'
+     * _.invokeMap([123, 456], String.prototype.split, '');
+     * // => [['1', '2', '3'], ['4', '5', '6']]
      */
-    var lowerFirst = createCaseFirst('toLowerCase');
+    var invokeMap = baseRest(function(collection, path, args) {
+      var index = -1,
+          isFunc = typeof path == 'function',
+          result = isArrayLike(collection) ? Array(collection.length) : [];
+
+      baseEach(collection, function(value) {
+        result[++index] = isFunc ? apply(path, value, args) : baseInvoke(value, path, args);
+      });
+      return result;
+    });
 
     /**
-     * Pads `string` on the left and right sides if it's shorter than `length`.
-     * Padding characters are truncated if they can't be evenly divided by `length`.
+     * Creates an object composed of keys generated from the results of running
+     * each element of `collection` thru `iteratee`. The corresponding value of
+     * each key is the last element responsible for generating the key. The
+     * iteratee is invoked with one argument: (value).
      *
      * @static
      * @memberOf _
-     * @since 3.0.0
-     * @category String
-     * @param {string} [string=''] The string to pad.
-     * @param {number} [length=0] The padding length.
-     * @param {string} [chars=' '] The string used as padding.
-     * @returns {string} Returns the padded string.
+     * @since 4.0.0
+     * @category Collection
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} [iteratee=_.identity] The iteratee to transform keys.
+     * @returns {Object} Returns the composed aggregate object.
      * @example
      *
-     * _.pad('abc', 8);
-     * // => '  abc   '
+     * var array = [
+     *   { 'dir': 'left', 'code': 97 },
+     *   { 'dir': 'right', 'code': 100 }
+     * ];
      *
-     * _.pad('abc', 8, '_-');
-     * // => '_-abc_-_'
+     * _.keyBy(array, function(o) {
+     *   return String.fromCharCode(o.code);
+     * });
+     * // => { 'a': { 'dir': 'left', 'code': 97 }, 'd': { 'dir': 'right', 'code': 100 } }
      *
-     * _.pad('abc', 3);
-     * // => 'abc'
+     * _.keyBy(array, 'dir');
+     * // => { 'left': { 'dir': 'left', 'code': 97 }, 'right': { 'dir': 'right', 'code': 100 } }
      */
-    function pad(string, length, chars) {
-      string = toString(string);
-      length = toInteger(length);
-
-      var strLength = length ? stringSize(string) : 0;
-      if (!length || strLength >= length) {
-        return string;
-      }
-      var mid = (length - strLength) / 2;
-      return (
-        createPadding(nativeFloor(mid), chars) +
-        string +
-        createPadding(nativeCeil(mid), chars)
-      );
-    }
+    var keyBy = createAggregator(function(result, value, key) {
+      baseAssignValue(result, key, value);
+    });
 
     /**
-     * Pads `string` on the right side if it's shorter than `length`. Padding
-     * characters are truncated if they exceed `length`.
-     *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category String
-     * @param {string} [string=''] The string to pad.
-     * @param {number} [length=0] The padding length.
-     * @param {string} [chars=' '] The string used as padding.
-     * @returns {string} Returns the padded string.
-     * @example
-     *
-     * _.padEnd('abc', 6);
-     * // => 'abc   '
+     * Creates an array of values by running each element in `collection` thru
+     * `iteratee`. The iteratee is invoked with three arguments:
+     * (value, index|key, collection).
      *
-     * _.padEnd('abc', 6, '_-');
-     * // => 'abc_-_'
+     * Many lodash methods are guarded to work as iteratees for methods like
+     * `_.every`, `_.filter`, `_.map`, `_.mapValues`, `_.reject`, and `_.some`.
      *
-     * _.padEnd('abc', 3);
-     * // => 'abc'
-     */
-    function padEnd(string, length, chars) {
-      string = toString(string);
-      length = toInteger(length);
-
-      var strLength = length ? stringSize(string) : 0;
-      return (length && strLength < length)
-        ? (string + createPadding(length - strLength, chars))
-        : string;
-    }
-
-    /**
-     * Pads `string` on the left side if it's shorter than `length`. Padding
-     * characters are truncated if they exceed `length`.
+     * The guarded methods are:
+     * `ary`, `chunk`, `curry`, `curryRight`, `drop`, `dropRight`, `every`,
+     * `fill`, `invert`, `parseInt`, `random`, `range`, `rangeRight`, `repeat`,
+     * `sampleSize`, `slice`, `some`, `sortBy`, `split`, `take`, `takeRight`,
+     * `template`, `trim`, `trimEnd`, `trimStart`, and `words`
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category String
-     * @param {string} [string=''] The string to pad.
-     * @param {number} [length=0] The padding length.
-     * @param {string} [chars=' '] The string used as padding.
-     * @returns {string} Returns the padded string.
+     * @since 0.1.0
+     * @category Collection
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
+     * @returns {Array} Returns the new mapped array.
      * @example
      *
-     * _.padStart('abc', 6);
-     * // => '   abc'
+     * function square(n) {
+     *   return n * n;
+     * }
      *
-     * _.padStart('abc', 6, '_-');
-     * // => '_-_abc'
+     * _.map([4, 8], square);
+     * // => [16, 64]
      *
-     * _.padStart('abc', 3);
-     * // => 'abc'
+     * _.map({ 'a': 4, 'b': 8 }, square);
+     * // => [16, 64] (iteration order is not guaranteed)
+     *
+     * var users = [
+     *   { 'user': 'barney' },
+     *   { 'user': 'fred' }
+     * ];
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.map(users, 'user');
+     * // => ['barney', 'fred']
      */
-    function padStart(string, length, chars) {
-      string = toString(string);
-      length = toInteger(length);
-
-      var strLength = length ? stringSize(string) : 0;
-      return (length && strLength < length)
-        ? (createPadding(length - strLength, chars) + string)
-        : string;
+    function map(collection, iteratee) {
+      var func = isArray(collection) ? arrayMap : baseMap;
+      return func(collection, getIteratee(iteratee, 3));
     }
 
     /**
-     * Converts `string` to an integer of the specified radix. If `radix` is
-     * `undefined` or `0`, a `radix` of `10` is used unless `value` is a
-     * hexadecimal, in which case a `radix` of `16` is used.
-     *
-     * **Note:** This method aligns with the
-     * [ES5 implementation](https://es5.github.io/#x15.1.2.2) of `parseInt`.
+     * This method is like `_.sortBy` except that it allows specifying the sort
+     * orders of the iteratees to sort by. If `orders` is unspecified, all values
+     * are sorted in ascending order. Otherwise, specify an order of "desc" for
+     * descending or "asc" for ascending sort order of corresponding values.
      *
      * @static
      * @memberOf _
-     * @since 1.1.0
-     * @category String
-     * @param {string} string The string to convert.
-     * @param {number} [radix=10] The radix to interpret `value` by.
-     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
-     * @returns {number} Returns the converted integer.
+     * @since 4.0.0
+     * @category Collection
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Array[]|Function[]|Object[]|string[]} [iteratees=[_.identity]]
+     *  The iteratees to sort by.
+     * @param {string[]} [orders] The sort orders of `iteratees`.
+     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.reduce`.
+     * @returns {Array} Returns the new sorted array.
      * @example
      *
-     * _.parseInt('08');
-     * // => 8
+     * var users = [
+     *   { 'user': 'fred',   'age': 48 },
+     *   { 'user': 'barney', 'age': 34 },
+     *   { 'user': 'fred',   'age': 40 },
+     *   { 'user': 'barney', 'age': 36 }
+     * ];
      *
-     * _.map(['6', '08', '10'], _.parseInt);
-     * // => [6, 8, 10]
+     * // Sort by `user` in ascending order and by `age` in descending order.
+     * _.orderBy(users, ['user', 'age'], ['asc', 'desc']);
+     * // => objects for [['barney', 36], ['barney', 34], ['fred', 48], ['fred', 40]]
      */
-    function parseInt(string, radix, guard) {
-      // Chrome fails to trim leading <BOM> whitespace characters.
-      // See https://bugs.chromium.org/p/v8/issues/detail?id=3109 for more details.
-      if (guard || radix == null) {
-        radix = 0;
-      } else if (radix) {
-        radix = +radix;
+    function orderBy(collection, iteratees, orders, guard) {
+      if (collection == null) {
+        return [];
+      }
+      if (!isArray(iteratees)) {
+        iteratees = iteratees == null ? [] : [iteratees];
+      }
+      orders = guard ? undefined : orders;
+      if (!isArray(orders)) {
+        orders = orders == null ? [] : [orders];
       }
-      string = toString(string).replace(reTrim, '');
-      return nativeParseInt(string, radix || (reHasHexPrefix.test(string) ? 16 : 10));
+      return baseOrderBy(collection, iteratees, orders);
     }
 
     /**
-     * Repeats the given string `n` times.
+     * Creates an array of elements split into two groups, the first of which
+     * contains elements `predicate` returns truthy for, the second of which
+     * contains elements `predicate` returns falsey for. The predicate is
+     * invoked with one argument: (value).
      *
      * @static
      * @memberOf _
      * @since 3.0.0
-     * @category String
-     * @param {string} [string=''] The string to repeat.
-     * @param {number} [n=1] The number of times to repeat the string.
-     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
-     * @returns {string} Returns the repeated string.
+     * @category Collection
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} [predicate=_.identity] The function invoked per iteration.
+     * @returns {Array} Returns the array of grouped elements.
      * @example
      *
-     * _.repeat('*', 3);
-     * // => '***'
+     * var users = [
+     *   { 'user': 'barney',  'age': 36, 'active': false },
+     *   { 'user': 'fred',    'age': 40, 'active': true },
+     *   { 'user': 'pebbles', 'age': 1,  'active': false }
+     * ];
      *
-     * _.repeat('abc', 2);
-     * // => 'abcabc'
+     * _.partition(users, function(o) { return o.active; });
+     * // => objects for [['fred'], ['barney', 'pebbles']]
      *
-     * _.repeat('abc', 0);
-     * // => ''
+     * // The `_.matches` iteratee shorthand.
+     * _.partition(users, { 'age': 1, 'active': false });
+     * // => objects for [['pebbles'], ['barney', 'fred']]
+     *
+     * // The `_.matchesProperty` iteratee shorthand.
+     * _.partition(users, ['active', false]);
+     * // => objects for [['barney', 'pebbles'], ['fred']]
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.partition(users, 'active');
+     * // => objects for [['fred'], ['barney', 'pebbles']]
      */
-    function repeat(string, n, guard) {
-      if ((guard ? isIterateeCall(string, n, guard) : n === undefined)) {
-        n = 1;
-      } else {
-        n = toInteger(n);
-      }
-      return baseRepeat(toString(string), n);
-    }
+    var partition = createAggregator(function(result, value, key) {
+      result[key ? 0 : 1].push(value);
+    }, function() { return [[], []]; });
 
     /**
-     * Replaces matches for `pattern` in `string` with `replacement`.
+     * Reduces `collection` to a value which is the accumulated result of running
+     * each element in `collection` thru `iteratee`, where each successive
+     * invocation is supplied the return value of the previous. If `accumulator`
+     * is not given, the first element of `collection` is used as the initial
+     * value. The iteratee is invoked with four arguments:
+     * (accumulator, value, index|key, collection).
      *
-     * **Note:** This method is based on
-     * [`String#replace`](https://mdn.io/String/replace).
+     * Many lodash methods are guarded to work as iteratees for methods like
+     * `_.reduce`, `_.reduceRight`, and `_.transform`.
+     *
+     * The guarded methods are:
+     * `assign`, `defaults`, `defaultsDeep`, `includes`, `merge`, `orderBy`,
+     * and `sortBy`
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category String
-     * @param {string} [string=''] The string to modify.
-     * @param {RegExp|string} pattern The pattern to replace.
-     * @param {Function|string} replacement The match replacement.
-     * @returns {string} Returns the modified string.
+     * @since 0.1.0
+     * @category Collection
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
+     * @param {*} [accumulator] The initial value.
+     * @returns {*} Returns the accumulated value.
+     * @see _.reduceRight
      * @example
      *
-     * _.replace('Hi Fred', 'Fred', 'Barney');
-     * // => 'Hi Barney'
+     * _.reduce([1, 2], function(sum, n) {
+     *   return sum + n;
+     * }, 0);
+     * // => 3
+     *
+     * _.reduce({ 'a': 1, 'b': 2, 'c': 1 }, function(result, value, key) {
+     *   (result[value] || (result[value] = [])).push(key);
+     *   return result;
+     * }, {});
+     * // => { '1': ['a', 'c'], '2': ['b'] } (iteration order is not guaranteed)
      */
-    function replace() {
-      var args = arguments,
-          string = toString(args[0]);
+    function reduce(collection, iteratee, accumulator) {
+      var func = isArray(collection) ? arrayReduce : baseReduce,
+          initAccum = arguments.length < 3;
 
-      return args.length < 3 ? string : nativeReplace.call(string, args[1], args[2]);
+      return func(collection, getIteratee(iteratee, 4), accumulator, initAccum, baseEach);
     }
 
     /**
-     * Converts `string` to
-     * [snake case](https://en.wikipedia.org/wiki/Snake_case).
+     * This method is like `_.reduce` except that it iterates over elements of
+     * `collection` from right to left.
      *
      * @static
      * @memberOf _
-     * @since 3.0.0
-     * @category String
-     * @param {string} [string=''] The string to convert.
-     * @returns {string} Returns the snake cased string.
+     * @since 0.1.0
+     * @category Collection
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
+     * @param {*} [accumulator] The initial value.
+     * @returns {*} Returns the accumulated value.
+     * @see _.reduce
      * @example
      *
-     * _.snakeCase('Foo Bar');
-     * // => 'foo_bar'
+     * var array = [[0, 1], [2, 3], [4, 5]];
      *
-     * _.snakeCase('fooBar');
-     * // => 'foo_bar'
+     * _.reduceRight(array, function(flattened, other) {
+     *   return flattened.concat(other);
+     * }, []);
+     * // => [4, 5, 2, 3, 0, 1]
+     */
+    function reduceRight(collection, iteratee, accumulator) {
+      var func = isArray(collection) ? arrayReduceRight : baseReduce,
+          initAccum = arguments.length < 3;
+
+      return func(collection, getIteratee(iteratee, 4), accumulator, initAccum, baseEachRight);
+    }
+
+    /**
+     * The opposite of `_.filter`; this method returns the elements of `collection`
+     * that `predicate` does **not** return truthy for.
      *
-     * _.snakeCase('--FOO-BAR--');
-     * // => 'foo_bar'
+     * @static
+     * @memberOf _
+     * @since 0.1.0
+     * @category Collection
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} [predicate=_.identity] The function invoked per iteration.
+     * @returns {Array} Returns the new filtered array.
+     * @see _.filter
+     * @example
+     *
+     * var users = [
+     *   { 'user': 'barney', 'age': 36, 'active': false },
+     *   { 'user': 'fred',   'age': 40, 'active': true }
+     * ];
+     *
+     * _.reject(users, function(o) { return !o.active; });
+     * // => objects for ['fred']
+     *
+     * // The `_.matches` iteratee shorthand.
+     * _.reject(users, { 'age': 40, 'active': true });
+     * // => objects for ['barney']
+     *
+     * // The `_.matchesProperty` iteratee shorthand.
+     * _.reject(users, ['active', false]);
+     * // => objects for ['fred']
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.reject(users, 'active');
+     * // => objects for ['barney']
      */
-    var snakeCase = createCompounder(function(result, word, index) {
-      return result + (index ? '_' : '') + word.toLowerCase();
-    });
+    function reject(collection, predicate) {
+      var func = isArray(collection) ? arrayFilter : baseFilter;
+      return func(collection, negate(getIteratee(predicate, 3)));
+    }
 
     /**
-     * Splits `string` by `separator`.
+     * Gets a random element from `collection`.
      *
-     * **Note:** This method is based on
-     * [`String#split`](https://mdn.io/String/split).
+     * @static
+     * @memberOf _
+     * @since 2.0.0
+     * @category Collection
+     * @param {Array|Object} collection The collection to sample.
+     * @returns {*} Returns the random element.
+     * @example
+     *
+     * _.sample([1, 2, 3, 4]);
+     * // => 2
+     */
+    function sample(collection) {
+      var func = isArray(collection) ? arraySample : baseSample;
+      return func(collection);
+    }
+
+    /**
+     * Gets `n` random elements at unique keys from `collection` up to the
+     * size of `collection`.
      *
      * @static
      * @memberOf _
      * @since 4.0.0
-     * @category String
-     * @param {string} [string=''] The string to split.
-     * @param {RegExp|string} separator The separator pattern to split by.
-     * @param {number} [limit] The length to truncate results to.
-     * @returns {Array} Returns the string segments.
+     * @category Collection
+     * @param {Array|Object} collection The collection to sample.
+     * @param {number} [n=1] The number of elements to sample.
+     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
+     * @returns {Array} Returns the random elements.
      * @example
      *
-     * _.split('a-b-c', '-', 2);
-     * // => ['a', 'b']
+     * _.sampleSize([1, 2, 3], 2);
+     * // => [3, 1]
+     *
+     * _.sampleSize([1, 2, 3], 4);
+     * // => [2, 3, 1]
      */
-    function split(string, separator, limit) {
-      if (limit && typeof limit != 'number' && isIterateeCall(string, separator, limit)) {
-        separator = limit = undefined;
-      }
-      limit = limit === undefined ? MAX_ARRAY_LENGTH : limit >>> 0;
-      if (!limit) {
-        return [];
-      }
-      string = toString(string);
-      if (string && (
-            typeof separator == 'string' ||
-            (separator != null && !isRegExp(separator))
-          )) {
-        separator = baseToString(separator);
-        if (separator == '' && reHasComplexSymbol.test(string)) {
-          return castSlice(stringToArray(string), 0, limit);
-        }
+    function sampleSize(collection, n, guard) {
+      if ((guard ? isIterateeCall(collection, n, guard) : n === undefined)) {
+        n = 1;
+      } else {
+        n = toInteger(n);
       }
-      return nativeSplit.call(string, separator, limit);
+      var func = isArray(collection) ? arraySampleSize : baseSampleSize;
+      return func(collection, n);
     }
 
     /**
-     * Converts `string` to
-     * [start case](https://en.wikipedia.org/wiki/Letter_case#Stylistic_or_specialised_usage).
+     * Creates an array of shuffled values, using a version of the
+     * [Fisher-Yates shuffle](https://en.wikipedia.org/wiki/Fisher-Yates_shuffle).
      *
      * @static
      * @memberOf _
-     * @since 3.1.0
-     * @category String
-     * @param {string} [string=''] The string to convert.
-     * @returns {string} Returns the start cased string.
+     * @since 0.1.0
+     * @category Collection
+     * @param {Array|Object} collection The collection to shuffle.
+     * @returns {Array} Returns the new shuffled array.
      * @example
      *
-     * _.startCase('--foo-bar--');
-     * // => 'Foo Bar'
+     * _.shuffle([1, 2, 3, 4]);
+     * // => [4, 1, 3, 2]
+     */
+    function shuffle(collection) {
+      var func = isArray(collection) ? arrayShuffle : baseShuffle;
+      return func(collection);
+    }
+
+    /**
+     * Gets the size of `collection` by returning its length for array-like
+     * values or the number of own enumerable string keyed properties for objects.
      *
-     * _.startCase('fooBar');
-     * // => 'Foo Bar'
+     * @static
+     * @memberOf _
+     * @since 0.1.0
+     * @category Collection
+     * @param {Array|Object|string} collection The collection to inspect.
+     * @returns {number} Returns the collection size.
+     * @example
      *
-     * _.startCase('__FOO_BAR__');
-     * // => 'FOO BAR'
+     * _.size([1, 2, 3]);
+     * // => 3
+     *
+     * _.size({ 'a': 1, 'b': 2 });
+     * // => 2
+     *
+     * _.size('pebbles');
+     * // => 7
      */
-    var startCase = createCompounder(function(result, word, index) {
-      return result + (index ? ' ' : '') + upperFirst(word);
-    });
+    function size(collection) {
+      if (collection == null) {
+        return 0;
+      }
+      if (isArrayLike(collection)) {
+        return isString(collection) ? stringSize(collection) : collection.length;
+      }
+      var tag = getTag(collection);
+      if (tag == mapTag || tag == setTag) {
+        return collection.size;
+      }
+      return baseKeys(collection).length;
+    }
 
     /**
-     * Checks if `string` starts with the given target string.
+     * Checks if `predicate` returns truthy for **any** element of `collection`.
+     * Iteration is stopped once `predicate` returns truthy. The predicate is
+     * invoked with three arguments: (value, index|key, collection).
      *
      * @static
      * @memberOf _
-     * @since 3.0.0
-     * @category String
-     * @param {string} [string=''] The string to search.
-     * @param {string} [target] The string to search for.
-     * @param {number} [position=0] The position to search from.
-     * @returns {boolean} Returns `true` if `string` starts with `target`,
+     * @since 0.1.0
+     * @category Collection
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {Function} [predicate=_.identity] The function invoked per iteration.
+     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
+     * @returns {boolean} Returns `true` if any element passes the predicate check,
      *  else `false`.
      * @example
      *
-     * _.startsWith('abc', 'a');
+     * _.some([null, 0, 'yes', false], Boolean);
      * // => true
      *
-     * _.startsWith('abc', 'b');
+     * var users = [
+     *   { 'user': 'barney', 'active': true },
+     *   { 'user': 'fred',   'active': false }
+     * ];
+     *
+     * // The `_.matches` iteratee shorthand.
+     * _.some(users, { 'user': 'barney', 'active': false });
      * // => false
      *
-     * _.startsWith('abc', 'b', 1);
+     * // The `_.matchesProperty` iteratee shorthand.
+     * _.some(users, ['active', false]);
+     * // => true
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.some(users, 'active');
      * // => true
      */
-    function startsWith(string, target, position) {
-      string = toString(string);
-      position = baseClamp(toInteger(position), 0, string.length);
-      return string.lastIndexOf(baseToString(target), position) == position;
+    function some(collection, predicate, guard) {
+      var func = isArray(collection) ? arraySome : baseSome;
+      if (guard && isIterateeCall(collection, predicate, guard)) {
+        predicate = undefined;
+      }
+      return func(collection, getIteratee(predicate, 3));
     }
 
     /**
-     * Creates a compiled template function that can interpolate data properties
-     * in "interpolate" delimiters, HTML-escape interpolated data properties in
-     * "escape" delimiters, and execute JavaScript in "evaluate" delimiters. Data
-     * properties may be accessed as free variables in the template. If a setting
-     * object is given, it takes precedence over `_.templateSettings` values.
-     *
-     * **Note:** In the development build `_.template` utilizes
-     * [sourceURLs](http://www.html5rocks.com/en/tutorials/developertools/sourcemaps/#toc-sourceurl)
-     * for easier debugging.
-     *
-     * For more information on precompiling templates see
-     * [lodash's custom builds documentation](https://lodash.com/custom-builds).
-     *
-     * For more information on Chrome extension sandboxes see
-     * [Chrome's extensions documentation](https://developer.chrome.com/extensions/sandboxingEval).
+     * Creates an array of elements, sorted in ascending order by the results of
+     * running each element in a collection thru each iteratee. This method
+     * performs a stable sort, that is, it preserves the original sort order of
+     * equal elements. The iteratees are invoked with one argument: (value).
      *
      * @static
-     * @since 0.1.0
      * @memberOf _
-     * @category String
-     * @param {string} [string=''] The template string.
-     * @param {Object} [options={}] The options object.
-     * @param {RegExp} [options.escape=_.templateSettings.escape]
-     *  The HTML "escape" delimiter.
-     * @param {RegExp} [options.evaluate=_.templateSettings.evaluate]
-     *  The "evaluate" delimiter.
-     * @param {Object} [options.imports=_.templateSettings.imports]
-     *  An object to import into the template as free variables.
-     * @param {RegExp} [options.interpolate=_.templateSettings.interpolate]
-     *  The "interpolate" delimiter.
-     * @param {string} [options.sourceURL='lodash.templateSources[n]']
-     *  The sourceURL of the compiled template.
-     * @param {string} [options.variable='obj']
-     *  The data object variable name.
-     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
-     * @returns {Function} Returns the compiled template function.
+     * @since 0.1.0
+     * @category Collection
+     * @param {Array|Object} collection The collection to iterate over.
+     * @param {...(Function|Function[])} [iteratees=[_.identity]]
+     *  The iteratees to sort by.
+     * @returns {Array} Returns the new sorted array.
      * @example
      *
-     * // Use the "interpolate" delimiter to create a compiled template.
-     * var compiled = _.template('hello <%= user %>!');
-     * compiled({ 'user': 'fred' });
-     * // => 'hello fred!'
-     *
-     * // Use the HTML "escape" delimiter to escape data property values.
-     * var compiled = _.template('<b><%- value %></b>');
-     * compiled({ 'value': '<script>' });
-     * // => '<b>&lt;script&gt;</b>'
-     *
-     * // Use the "evaluate" delimiter to execute JavaScript and generate HTML.
-     * var compiled = _.template('<% _.forEach(users, function(user) { %><li><%- user %></li><% }); %>');
-     * compiled({ 'users': ['fred', 'barney'] });
-     * // => '<li>fred</li><li>barney</li>'
-     *
-     * // Use the internal `print` function in "evaluate" delimiters.
-     * var compiled = _.template('<% print("hello " + user); %>!');
-     * compiled({ 'user': 'barney' });
-     * // => 'hello barney!'
-     *
-     * // Use the ES delimiter as an alternative to the default "interpolate" delimiter.
-     * var compiled = _.template('hello ${ user }!');
-     * compiled({ 'user': 'pebbles' });
-     * // => 'hello pebbles!'
-     *
-     * // Use backslashes to treat delimiters as plain text.
-     * var compiled = _.template('<%= "\\<%- value %\\>" %>');
-     * compiled({ 'value': 'ignored' });
-     * // => '<%- value %>'
-     *
-     * // Use the `imports` option to import `jQuery` as `jq`.
-     * var text = '<% jq.each(users, function(user) { %><li><%- user %></li><% }); %>';
-     * var compiled = _.template(text, { 'imports': { 'jq': jQuery } });
-     * compiled({ 'users': ['fred', 'barney'] });
-     * // => '<li>fred</li><li>barney</li>'
-     *
-     * // Use the `sourceURL` option to specify a custom sourceURL for the template.
-     * var compiled = _.template('hello <%= user %>!', { 'sourceURL': '/basic/greeting.jst' });
-     * compiled(data);
-     * // => Find the source of "greeting.jst" under the Sources tab or Resources panel of the web inspector.
-     *
-     * // Use the `variable` option to ensure a with-statement isn't used in the compiled template.
-     * var compiled = _.template('hi <%= data.user %>!', { 'variable': 'data' });
-     * compiled.source;
-     * // => function(data) {
-     * //   var __t, __p = '';
-     * //   __p += 'hi ' + ((__t = ( data.user )) == null ? '' : __t) + '!';
-     * //   return __p;
-     * // }
+     * var users = [
+     *   { 'user': 'fred',   'age': 48 },
+     *   { 'user': 'barney', 'age': 36 },
+     *   { 'user': 'fred',   'age': 40 },
+     *   { 'user': 'barney', 'age': 34 }
+     * ];
      *
-     * // Use custom template delimiters.
-     * _.templateSettings.interpolate = /{{([\s\S]+?)}}/g;
-     * var compiled = _.template('hello {{ user }}!');
-     * compiled({ 'user': 'mustache' });
-     * // => 'hello mustache!'
+     * _.sortBy(users, [function(o) { return o.user; }]);
+     * // => objects for [['barney', 36], ['barney', 34], ['fred', 48], ['fred', 40]]
      *
-     * // Use the `source` property to inline compiled templates for meaningful
-     * // line numbers in error messages and stack traces.
-     * fs.writeFileSync(path.join(process.cwd(), 'jst.js'), '\
-     *   var JST = {\
-     *     "main": ' + _.template(mainText).source + '\
-     *   };\
-     * ');
+     * _.sortBy(users, ['user', 'age']);
+     * // => objects for [['barney', 34], ['barney', 36], ['fred', 40], ['fred', 48]]
      */
-    function template(string, options, guard) {
-      // Based on John Resig's `tmpl` implementation
-      // (http://ejohn.org/blog/javascript-micro-templating/)
-      // and Laura Doktorova's doT.js (https://github.com/olado/doT).
-      var settings = lodash.templateSettings;
-
-      if (guard && isIterateeCall(string, options, guard)) {
-        options = undefined;
+    var sortBy = baseRest(function(collection, iteratees) {
+      if (collection == null) {
+        return [];
       }
-      string = toString(string);
-      options = assignInWith({}, options, settings, assignInDefaults);
-
-      var imports = assignInWith({}, options.imports, settings.imports, assignInDefaults),
-          importsKeys = keys(imports),
-          importsValues = baseValues(imports, importsKeys);
-
-      var isEscaping,
-          isEvaluating,
-          index = 0,
-          interpolate = options.interpolate || reNoMatch,
-          source = "__p += '";
-
-      // Compile the regexp to match each delimiter.
-      var reDelimiters = RegExp(
-        (options.escape || reNoMatch).source + '|' +
-        interpolate.source + '|' +
-        (interpolate === reInterpolate ? reEsTemplate : reNoMatch).source + '|' +
-        (options.evaluate || reNoMatch).source + '|$'
-      , 'g');
-
-      // Use a sourceURL for easier debugging.
-      var sourceURL = '//# sourceURL=' +
-        ('sourceURL' in options
-          ? options.sourceURL
-          : ('lodash.templateSources[' + (++templateCounter) + ']')
-        ) + '\n';
-
-      string.replace(reDelimiters, function(match, escapeValue, interpolateValue, esTemplateValue, evaluateValue, offset) {
-        interpolateValue || (interpolateValue = esTemplateValue);
-
-        // Escape characters that can't be included in string literals.
-        source += string.slice(index, offset).replace(reUnescapedString, escapeStringChar);
-
-        // Replace delimiters with snippets.
-        if (escapeValue) {
-          isEscaping = true;
-          source += "' +\n__e(" + escapeValue + ") +\n'";
-        }
-        if (evaluateValue) {
-          isEvaluating = true;
-          source += "';\n" + evaluateValue + ";\n__p += '";
-        }
-        if (interpolateValue) {
-          source += "' +\n((__t = (" + interpolateValue + ")) == null ? '' : __t) +\n'";
-        }
-        index = offset + match.length;
-
-        // The JS engine embedded in Adobe products needs `match` returned in
-        // order to produce the correct `offset` value.
-        return match;
-      });
-
-      source += "';\n";
-
-      // If `variable` is not specified wrap a with-statement around the generated
-      // code to add the data object to the top of the scope chain.
-      var variable = options.variable;
-      if (!variable) {
-        source = 'with (obj) {\n' + source + '\n}\n';
+      var length = iteratees.length;
+      if (length > 1 && isIterateeCall(collection, iteratees[0], iteratees[1])) {
+        iteratees = [];
+      } else if (length > 2 && isIterateeCall(iteratees[0], iteratees[1], iteratees[2])) {
+        iteratees = [iteratees[0]];
       }
-      // Cleanup code by stripping empty strings.
-      source = (isEvaluating ? source.replace(reEmptyStringLeading, '') : source)
-        .replace(reEmptyStringMiddle, '$1')
-        .replace(reEmptyStringTrailing, '$1;');
-
-      // Frame code as the function body.
-      source = 'function(' + (variable || 'obj') + ') {\n' +
-        (variable
-          ? ''
-          : 'obj || (obj = {});\n'
-        ) +
-        "var __t, __p = ''" +
-        (isEscaping
-           ? ', __e = _.escape'
-           : ''
-        ) +
-        (isEvaluating
-          ? ', __j = Array.prototype.join;\n' +
-            "function print() { __p += __j.call(arguments, '') }\n"
-          : ';\n'
-        ) +
-        source +
-        'return __p\n}';
-
-      var result = attempt(function() {
-        return Function(importsKeys, sourceURL + 'return ' + source)
-          .apply(undefined, importsValues);
-      });
+      return baseOrderBy(collection, baseFlatten(iteratees, 1), []);
+    });
 
-      // Provide the compiled function's source by its `toString` method or
-      // the `source` property as a convenience for inlining compiled templates.
-      result.source = source;
-      if (isError(result)) {
-        throw result;
-      }
-      return result;
-    }
+    /*------------------------------------------------------------------------*/
 
     /**
-     * Converts `string`, as a whole, to lower case just like
-     * [String#toLowerCase](https://mdn.io/toLowerCase).
+     * Gets the timestamp of the number of milliseconds that have elapsed since
+     * the Unix epoch (1 January 1970 00:00:00 UTC).
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category String
-     * @param {string} [string=''] The string to convert.
-     * @returns {string} Returns the lower cased string.
+     * @since 2.4.0
+     * @category Date
+     * @returns {number} Returns the timestamp.
      * @example
      *
-     * _.toLower('--Foo-Bar--');
-     * // => '--foo-bar--'
-     *
-     * _.toLower('fooBar');
-     * // => 'foobar'
-     *
-     * _.toLower('__FOO_BAR__');
-     * // => '__foo_bar__'
+     * _.defer(function(stamp) {
+     *   console.log(_.now() - stamp);
+     * }, _.now());
+     * // => Logs the number of milliseconds it took for the deferred invocation.
      */
-    function toLower(value) {
-      return toString(value).toLowerCase();
-    }
+    var now = ctxNow || function() {
+      return root.Date.now();
+    };
+
+    /*------------------------------------------------------------------------*/
 
     /**
-     * Converts `string`, as a whole, to upper case just like
-     * [String#toUpperCase](https://mdn.io/toUpperCase).
+     * The opposite of `_.before`; this method creates a function that invokes
+     * `func` once it's called `n` or more times.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category String
-     * @param {string} [string=''] The string to convert.
-     * @returns {string} Returns the upper cased string.
+     * @since 0.1.0
+     * @category Function
+     * @param {number} n The number of calls before `func` is invoked.
+     * @param {Function} func The function to restrict.
+     * @returns {Function} Returns the new restricted function.
      * @example
      *
-     * _.toUpper('--foo-bar--');
-     * // => '--FOO-BAR--'
+     * var saves = ['profile', 'settings'];
      *
-     * _.toUpper('fooBar');
-     * // => 'FOOBAR'
+     * var done = _.after(saves.length, function() {
+     *   console.log('done saving!');
+     * });
      *
-     * _.toUpper('__foo_bar__');
-     * // => '__FOO_BAR__'
+     * _.forEach(saves, function(type) {
+     *   asyncSave({ 'type': type, 'complete': done });
+     * });
+     * // => Logs 'done saving!' after the two async saves have completed.
      */
-    function toUpper(value) {
-      return toString(value).toUpperCase();
+    function after(n, func) {
+      if (typeof func != 'function') {
+        throw new TypeError(FUNC_ERROR_TEXT);
+      }
+      n = toInteger(n);
+      return function() {
+        if (--n < 1) {
+          return func.apply(this, arguments);
+        }
+      };
     }
 
     /**
-     * Removes leading and trailing whitespace or specified characters from `string`.
+     * Creates a function that invokes `func`, with up to `n` arguments,
+     * ignoring any additional arguments.
      *
      * @static
      * @memberOf _
      * @since 3.0.0
-     * @category String
-     * @param {string} [string=''] The string to trim.
-     * @param {string} [chars=whitespace] The characters to trim.
-     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
-     * @returns {string} Returns the trimmed string.
+     * @category Function
+     * @param {Function} func The function to cap arguments for.
+     * @param {number} [n=func.length] The arity cap.
+     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
+     * @returns {Function} Returns the new capped function.
      * @example
      *
-     * _.trim('  abc  ');
-     * // => 'abc'
-     *
-     * _.trim('-_-abc-_-', '_-');
-     * // => 'abc'
-     *
-     * _.map(['  foo  ', '  bar  '], _.trim);
-     * // => ['foo', 'bar']
+     * _.map(['6', '8', '10'], _.ary(parseInt, 1));
+     * // => [6, 8, 10]
      */
-    function trim(string, chars, guard) {
-      string = toString(string);
-      if (string && (guard || chars === undefined)) {
-        return string.replace(reTrim, '');
-      }
-      if (!string || !(chars = baseToString(chars))) {
-        return string;
-      }
-      var strSymbols = stringToArray(string),
-          chrSymbols = stringToArray(chars),
-          start = charsStartIndex(strSymbols, chrSymbols),
-          end = charsEndIndex(strSymbols, chrSymbols) + 1;
-
-      return castSlice(strSymbols, start, end).join('');
+    function ary(func, n, guard) {
+      n = guard ? undefined : n;
+      n = (func && n == null) ? func.length : n;
+      return createWrap(func, WRAP_ARY_FLAG, undefined, undefined, undefined, undefined, n);
     }
 
     /**
-     * Removes trailing whitespace or specified characters from `string`.
+     * Creates a function that invokes `func`, with the `this` binding and arguments
+     * of the created function, while it's called less than `n` times. Subsequent
+     * calls to the created function return the result of the last `func` invocation.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category String
-     * @param {string} [string=''] The string to trim.
-     * @param {string} [chars=whitespace] The characters to trim.
-     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
-     * @returns {string} Returns the trimmed string.
+     * @since 3.0.0
+     * @category Function
+     * @param {number} n The number of calls at which `func` is no longer invoked.
+     * @param {Function} func The function to restrict.
+     * @returns {Function} Returns the new restricted function.
      * @example
      *
-     * _.trimEnd('  abc  ');
-     * // => '  abc'
-     *
-     * _.trimEnd('-_-abc-_-', '_-');
-     * // => '-_-abc'
+     * jQuery(element).on('click', _.before(5, addContactToList));
+     * // => Allows adding up to 4 contacts to the list.
      */
-    function trimEnd(string, chars, guard) {
-      string = toString(string);
-      if (string && (guard || chars === undefined)) {
-        return string.replace(reTrimEnd, '');
-      }
-      if (!string || !(chars = baseToString(chars))) {
-        return string;
+    function before(n, func) {
+      var result;
+      if (typeof func != 'function') {
+        throw new TypeError(FUNC_ERROR_TEXT);
       }
-      var strSymbols = stringToArray(string),
-          end = charsEndIndex(strSymbols, stringToArray(chars)) + 1;
-
-      return castSlice(strSymbols, 0, end).join('');
+      n = toInteger(n);
+      return function() {
+        if (--n > 0) {
+          result = func.apply(this, arguments);
+        }
+        if (n <= 1) {
+          func = undefined;
+        }
+        return result;
+      };
     }
 
     /**
-     * Removes leading whitespace or specified characters from `string`.
+     * Creates a function that invokes `func` with the `this` binding of `thisArg`
+     * and `partials` prepended to the arguments it receives.
+     *
+     * The `_.bind.placeholder` value, which defaults to `_` in monolithic builds,
+     * may be used as a placeholder for partially applied arguments.
+     *
+     * **Note:** Unlike native `Function#bind`, this method doesn't set the "length"
+     * property of bound functions.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category String
-     * @param {string} [string=''] The string to trim.
-     * @param {string} [chars=whitespace] The characters to trim.
-     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
-     * @returns {string} Returns the trimmed string.
+     * @since 0.1.0
+     * @category Function
+     * @param {Function} func The function to bind.
+     * @param {*} thisArg The `this` binding of `func`.
+     * @param {...*} [partials] The arguments to be partially applied.
+     * @returns {Function} Returns the new bound function.
      * @example
      *
-     * _.trimStart('  abc  ');
-     * // => 'abc  '
+     * function greet(greeting, punctuation) {
+     *   return greeting + ' ' + this.user + punctuation;
+     * }
      *
-     * _.trimStart('-_-abc-_-', '_-');
-     * // => 'abc-_-'
+     * var object = { 'user': 'fred' };
+     *
+     * var bound = _.bind(greet, object, 'hi');
+     * bound('!');
+     * // => 'hi fred!'
+     *
+     * // Bound with placeholders.
+     * var bound = _.bind(greet, object, _, '!');
+     * bound('hi');
+     * // => 'hi fred!'
      */
-    function trimStart(string, chars, guard) {
-      string = toString(string);
-      if (string && (guard || chars === undefined)) {
-        return string.replace(reTrimStart, '');
-      }
-      if (!string || !(chars = baseToString(chars))) {
-        return string;
+    var bind = baseRest(function(func, thisArg, partials) {
+      var bitmask = WRAP_BIND_FLAG;
+      if (partials.length) {
+        var holders = replaceHolders(partials, getHolder(bind));
+        bitmask |= WRAP_PARTIAL_FLAG;
       }
-      var strSymbols = stringToArray(string),
-          start = charsStartIndex(strSymbols, stringToArray(chars));
-
-      return castSlice(strSymbols, start).join('');
-    }
+      return createWrap(func, bitmask, thisArg, partials, holders);
+    });
 
     /**
-     * Truncates `string` if it's longer than the given maximum string length.
-     * The last characters of the truncated string are replaced with the omission
-     * string which defaults to "...".
+     * Creates a function that invokes the method at `object[key]` with `partials`
+     * prepended to the arguments it receives.
+     *
+     * This method differs from `_.bind` by allowing bound functions to reference
+     * methods that may be redefined or don't yet exist. See
+     * [Peter Michaux's article](http://peter.michaux.ca/articles/lazy-function-definition-pattern)
+     * for more details.
+     *
+     * The `_.bindKey.placeholder` value, which defaults to `_` in monolithic
+     * builds, may be used as a placeholder for partially applied arguments.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category String
-     * @param {string} [string=''] The string to truncate.
-     * @param {Object} [options={}] The options object.
-     * @param {number} [options.length=30] The maximum string length.
-     * @param {string} [options.omission='...'] The string to indicate text is omitted.
-     * @param {RegExp|string} [options.separator] The separator pattern to truncate to.
-     * @returns {string} Returns the truncated string.
+     * @since 0.10.0
+     * @category Function
+     * @param {Object} object The object to invoke the method on.
+     * @param {string} key The key of the method.
+     * @param {...*} [partials] The arguments to be partially applied.
+     * @returns {Function} Returns the new bound function.
      * @example
      *
-     * _.truncate('hi-diddly-ho there, neighborino');
-     * // => 'hi-diddly-ho there, neighbo...'
+     * var object = {
+     *   'user': 'fred',
+     *   'greet': function(greeting, punctuation) {
+     *     return greeting + ' ' + this.user + punctuation;
+     *   }
+     * };
      *
-     * _.truncate('hi-diddly-ho there, neighborino', {
-     *   'length': 24,
-     *   'separator': ' '
-     * });
-     * // => 'hi-diddly-ho there,...'
+     * var bound = _.bindKey(object, 'greet', 'hi');
+     * bound('!');
+     * // => 'hi fred!'
      *
-     * _.truncate('hi-diddly-ho there, neighborino', {
-     *   'length': 24,
-     *   'separator': /,? +/
-     * });
-     * // => 'hi-diddly-ho there...'
+     * object.greet = function(greeting, punctuation) {
+     *   return greeting + 'ya ' + this.user + punctuation;
+     * };
      *
-     * _.truncate('hi-diddly-ho there, neighborino', {
-     *   'omission': ' [...]'
-     * });
-     * // => 'hi-diddly-ho there, neig [...]'
+     * bound('!');
+     * // => 'hiya fred!'
+     *
+     * // Bound with placeholders.
+     * var bound = _.bindKey(object, 'greet', _, '!');
+     * bound('hi');
+     * // => 'hiya fred!'
      */
-    function truncate(string, options) {
-      var length = DEFAULT_TRUNC_LENGTH,
-          omission = DEFAULT_TRUNC_OMISSION;
-
-      if (isObject(options)) {
-        var separator = 'separator' in options ? options.separator : separator;
-        length = 'length' in options ? toInteger(options.length) : length;
-        omission = 'omission' in options ? baseToString(options.omission) : omission;
-      }
-      string = toString(string);
-
-      var strLength = string.length;
-      if (reHasComplexSymbol.test(string)) {
-        var strSymbols = stringToArray(string);
-        strLength = strSymbols.length;
-      }
-      if (length >= strLength) {
-        return string;
-      }
-      var end = length - stringSize(omission);
-      if (end < 1) {
-        return omission;
-      }
-      var result = strSymbols
-        ? castSlice(strSymbols, 0, end).join('')
-        : string.slice(0, end);
-
-      if (separator === undefined) {
-        return result + omission;
-      }
-      if (strSymbols) {
-        end += (result.length - end);
-      }
-      if (isRegExp(separator)) {
-        if (string.slice(end).search(separator)) {
-          var match,
-              substring = result;
-
-          if (!separator.global) {
-            separator = RegExp(separator.source, toString(reFlags.exec(separator)) + 'g');
-          }
-          separator.lastIndex = 0;
-          while ((match = separator.exec(substring))) {
-            var newEnd = match.index;
-          }
-          result = result.slice(0, newEnd === undefined ? end : newEnd);
-        }
-      } else if (string.indexOf(baseToString(separator), end) != end) {
-        var index = result.lastIndexOf(separator);
-        if (index > -1) {
-          result = result.slice(0, index);
-        }
+    var bindKey = baseRest(function(object, key, partials) {
+      var bitmask = WRAP_BIND_FLAG | WRAP_BIND_KEY_FLAG;
+      if (partials.length) {
+        var holders = replaceHolders(partials, getHolder(bindKey));
+        bitmask |= WRAP_PARTIAL_FLAG;
       }
-      return result + omission;
-    }
+      return createWrap(key, bitmask, object, partials, holders);
+    });
 
     /**
-     * The inverse of `_.escape`; this method converts the HTML entities
-     * `&amp;`, `&lt;`, `&gt;`, `&quot;`, `&#39;`, and `&#96;` in `string` to
-     * their corresponding characters.
+     * Creates a function that accepts arguments of `func` and either invokes
+     * `func` returning its result, if at least `arity` number of arguments have
+     * been provided, or returns a function that accepts the remaining `func`
+     * arguments, and so on. The arity of `func` may be specified if `func.length`
+     * is not sufficient.
      *
-     * **Note:** No other HTML entities are unescaped. To unescape additional
-     * HTML entities use a third-party library like [_he_](https://mths.be/he).
-     *
-     * @static
-     * @memberOf _
-     * @since 0.6.0
-     * @category String
-     * @param {string} [string=''] The string to unescape.
-     * @returns {string} Returns the unescaped string.
-     * @example
+     * The `_.curry.placeholder` value, which defaults to `_` in monolithic builds,
+     * may be used as a placeholder for provided arguments.
      *
-     * _.unescape('fred, barney, &amp; pebbles');
-     * // => 'fred, barney, & pebbles'
-     */
-    function unescape(string) {
-      string = toString(string);
-      return (string && reHasEscapedHtml.test(string))
-        ? string.replace(reEscapedHtml, unescapeHtmlChar)
-        : string;
-    }
-
-    /**
-     * Converts `string`, as space separated words, to upper case.
+     * **Note:** This method doesn't set the "length" property of curried functions.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category String
-     * @param {string} [string=''] The string to convert.
-     * @returns {string} Returns the upper cased string.
+     * @since 2.0.0
+     * @category Function
+     * @param {Function} func The function to curry.
+     * @param {number} [arity=func.length] The arity of `func`.
+     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
+     * @returns {Function} Returns the new curried function.
      * @example
      *
-     * _.upperCase('--foo-bar');
-     * // => 'FOO BAR'
+     * var abc = function(a, b, c) {
+     *   return [a, b, c];
+     * };
      *
-     * _.upperCase('fooBar');
-     * // => 'FOO BAR'
+     * var curried = _.curry(abc);
      *
-     * _.upperCase('__foo_bar__');
-     * // => 'FOO BAR'
-     */
-    var upperCase = createCompounder(function(result, word, index) {
-      return result + (index ? ' ' : '') + word.toUpperCase();
-    });
-
-    /**
-     * Converts the first character of `string` to upper case.
+     * curried(1)(2)(3);
+     * // => [1, 2, 3]
      *
-     * @static
-     * @memberOf _
-     * @since 4.0.0
-     * @category String
-     * @param {string} [string=''] The string to convert.
-     * @returns {string} Returns the converted string.
-     * @example
+     * curried(1, 2)(3);
+     * // => [1, 2, 3]
      *
-     * _.upperFirst('fred');
-     * // => 'Fred'
+     * curried(1, 2, 3);
+     * // => [1, 2, 3]
      *
-     * _.upperFirst('FRED');
-     * // => 'FRED'
+     * // Curried with placeholders.
+     * curried(1)(_, 3)(2);
+     * // => [1, 2, 3]
      */
-    var upperFirst = createCaseFirst('toUpperCase');
+    function curry(func, arity, guard) {
+      arity = guard ? undefined : arity;
+      var result = createWrap(func, WRAP_CURRY_FLAG, undefined, undefined, undefined, undefined, undefined, arity);
+      result.placeholder = curry.placeholder;
+      return result;
+    }
 
     /**
-     * Splits `string` into an array of its words.
+     * This method is like `_.curry` except that arguments are applied to `func`
+     * in the manner of `_.partialRight` instead of `_.partial`.
+     *
+     * The `_.curryRight.placeholder` value, which defaults to `_` in monolithic
+     * builds, may be used as a placeholder for provided arguments.
+     *
+     * **Note:** This method doesn't set the "length" property of curried functions.
      *
      * @static
      * @memberOf _
      * @since 3.0.0
-     * @category String
-     * @param {string} [string=''] The string to inspect.
-     * @param {RegExp|string} [pattern] The pattern to match words.
+     * @category Function
+     * @param {Function} func The function to curry.
+     * @param {number} [arity=func.length] The arity of `func`.
      * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
-     * @returns {Array} Returns the words of `string`.
+     * @returns {Function} Returns the new curried function.
      * @example
      *
-     * _.words('fred, barney, & pebbles');
-     * // => ['fred', 'barney', 'pebbles']
+     * var abc = function(a, b, c) {
+     *   return [a, b, c];
+     * };
      *
-     * _.words('fred, barney, & pebbles', /[^, ]+/g);
-     * // => ['fred', 'barney', '&', 'pebbles']
-     */
-    function words(string, pattern, guard) {
-      string = toString(string);
-      pattern = guard ? undefined : pattern;
-
-      if (pattern === undefined) {
-        pattern = reHasComplexWord.test(string) ? reComplexWord : reBasicWord;
-      }
-      return string.match(pattern) || [];
-    }
-
-    /*------------------------------------------------------------------------*/
-
-    /**
-     * Attempts to invoke `func`, returning either the result or the caught error
-     * object. Any additional arguments are provided to `func` when it's invoked.
+     * var curried = _.curryRight(abc);
      *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Util
-     * @param {Function} func The function to attempt.
-     * @param {...*} [args] The arguments to invoke `func` with.
-     * @returns {*} Returns the `func` result or error object.
-     * @example
+     * curried(3)(2)(1);
+     * // => [1, 2, 3]
      *
-     * // Avoid throwing errors for invalid selectors.
-     * var elements = _.attempt(function(selector) {
-     *   return document.querySelectorAll(selector);
-     * }, '>_>');
+     * curried(2, 3)(1);
+     * // => [1, 2, 3]
      *
-     * if (_.isError(elements)) {
-     *   elements = [];
-     * }
+     * curried(1, 2, 3);
+     * // => [1, 2, 3]
+     *
+     * // Curried with placeholders.
+     * curried(3)(1, _)(2);
+     * // => [1, 2, 3]
      */
-    var attempt = rest(function(func, args) {
-      try {
-        return apply(func, undefined, args);
-      } catch (e) {
-        return isError(e) ? e : new Error(e);
-      }
-    });
+    function curryRight(func, arity, guard) {
+      arity = guard ? undefined : arity;
+      var result = createWrap(func, WRAP_CURRY_RIGHT_FLAG, undefined, undefined, undefined, undefined, undefined, arity);
+      result.placeholder = curryRight.placeholder;
+      return result;
+    }
 
     /**
-     * Binds methods of an object to the object itself, overwriting the existing
-     * method.
-     *
-     * **Note:** This method doesn't set the "length" property of bound functions.
+     * Creates a debounced function that delays invoking `func` until after `wait`
+     * milliseconds have elapsed since the last time the debounced function was
+     * invoked. The debounced function comes with a `cancel` method to cancel
+     * delayed `func` invocations and a `flush` method to immediately invoke them.
+     * Provide `options` to indicate whether `func` should be invoked on the
+     * leading and/or trailing edge of the `wait` timeout. The `func` is invoked
+     * with the last arguments provided to the debounced function. Subsequent
+     * calls to the debounced function return the result of the last `func`
+     * invocation.
      *
-     * @static
-     * @since 0.1.0
-     * @memberOf _
-     * @category Util
-     * @param {Object} object The object to bind and assign the bound methods to.
-     * @param {...(string|string[])} methodNames The object method names to bind.
-     * @returns {Object} Returns `object`.
-     * @example
+     * **Note:** If `leading` and `trailing` options are `true`, `func` is
+     * invoked on the trailing edge of the timeout only if the debounced function
+     * is invoked more than once during the `wait` timeout.
      *
-     * var view = {
-     *   'label': 'docs',
-     *   'onClick': function() {
-     *     console.log('clicked ' + this.label);
-     *   }
-     * };
+     * If `wait` is `0` and `leading` is `false`, `func` invocation is deferred
+     * until to the next tick, similar to `setTimeout` with a timeout of `0`.
      *
-     * _.bindAll(view, ['onClick']);
-     * jQuery(element).on('click', view.onClick);
-     * // => Logs 'clicked docs' when clicked.
-     */
-    var bindAll = rest(function(object, methodNames) {
-      arrayEach(baseFlatten(methodNames, 1), function(key) {
-        key = toKey(key);
-        object[key] = bind(object[key], object);
-      });
-      return object;
-    });
-
-    /**
-     * Creates a function that iterates over `pairs` and invokes the corresponding
-     * function of the first predicate to return truthy. The predicate-function
-     * pairs are invoked with the `this` binding and arguments of the created
-     * function.
+     * See [David Corbacho's article](https://css-tricks.com/debouncing-throttling-explained-examples/)
+     * for details over the differences between `_.debounce` and `_.throttle`.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category Util
-     * @param {Array} pairs The predicate-function pairs.
-     * @returns {Function} Returns the new composite function.
+     * @since 0.1.0
+     * @category Function
+     * @param {Function} func The function to debounce.
+     * @param {number} [wait=0] The number of milliseconds to delay.
+     * @param {Object} [options={}] The options object.
+     * @param {boolean} [options.leading=false]
+     *  Specify invoking on the leading edge of the timeout.
+     * @param {number} [options.maxWait]
+     *  The maximum time `func` is allowed to be delayed before it's invoked.
+     * @param {boolean} [options.trailing=true]
+     *  Specify invoking on the trailing edge of the timeout.
+     * @returns {Function} Returns the new debounced function.
      * @example
      *
-     * var func = _.cond([
-     *   [_.matches({ 'a': 1 }),           _.constant('matches A')],
-     *   [_.conforms({ 'b': _.isNumber }), _.constant('matches B')],
-     *   [_.constant(true),                _.constant('no match')]
-     * ]);
+     * // Avoid costly calculations while the window size is in flux.
+     * jQuery(window).on('resize', _.debounce(calculateLayout, 150));
      *
-     * func({ 'a': 1, 'b': 2 });
-     * // => 'matches A'
+     * // Invoke `sendMail` when clicked, debouncing subsequent calls.
+     * jQuery(element).on('click', _.debounce(sendMail, 300, {
+     *   'leading': true,
+     *   'trailing': false
+     * }));
      *
-     * func({ 'a': 0, 'b': 1 });
-     * // => 'matches B'
+     * // Ensure `batchLog` is invoked once after 1 second of debounced calls.
+     * var debounced = _.debounce(batchLog, 250, { 'maxWait': 1000 });
+     * var source = new EventSource('/stream');
+     * jQuery(source).on('message', debounced);
      *
-     * func({ 'a': '1', 'b': '2' });
-     * // => 'no match'
+     * // Cancel the trailing debounced invocation.
+     * jQuery(window).on('popstate', debounced.cancel);
      */
-    function cond(pairs) {
-      var length = pairs ? pairs.length : 0,
-          toIteratee = getIteratee();
-
-      pairs = !length ? [] : arrayMap(pairs, function(pair) {
-        if (typeof pair[1] != 'function') {
-          throw new TypeError(FUNC_ERROR_TEXT);
-        }
-        return [toIteratee(pair[0]), pair[1]];
-      });
+    function debounce(func, wait, options) {
+      var lastArgs,
+          lastThis,
+          maxWait,
+          result,
+          timerId,
+          lastCallTime,
+          lastInvokeTime = 0,
+          leading = false,
+          maxing = false,
+          trailing = true;
 
-      return rest(function(args) {
-        var index = -1;
-        while (++index < length) {
-          var pair = pairs[index];
-          if (apply(pair[0], this, args)) {
-            return apply(pair[1], this, args);
-          }
-        }
-      });
+      if (typeof func != 'function') {
+        throw new TypeError(FUNC_ERROR_TEXT);
+      }
+      wait = toNumber(wait) || 0;
+      if (isObject(options)) {
+        leading = !!options.leading;
+        maxing = 'maxWait' in options;
+        maxWait = maxing ? nativeMax(toNumber(options.maxWait) || 0, wait) : maxWait;
+        trailing = 'trailing' in options ? !!options.trailing : trailing;
+      }
+
+      function invokeFunc(time) {
+        var args = lastArgs,
+            thisArg = lastThis;
+
+        lastArgs = lastThis = undefined;
+        lastInvokeTime = time;
+        result = func.apply(thisArg, args);
+        return result;
+      }
+
+      function leadingEdge(time) {
+        // Reset any `maxWait` timer.
+        lastInvokeTime = time;
+        // Start the timer for the trailing edge.
+        timerId = setTimeout(timerExpired, wait);
+        // Invoke the leading edge.
+        return leading ? invokeFunc(time) : result;
+      }
+
+      function remainingWait(time) {
+        var timeSinceLastCall = time - lastCallTime,
+            timeSinceLastInvoke = time - lastInvokeTime,
+            timeWaiting = wait - timeSinceLastCall;
+
+        return maxing
+          ? nativeMin(timeWaiting, maxWait - timeSinceLastInvoke)
+          : timeWaiting;
+      }
+
+      function shouldInvoke(time) {
+        var timeSinceLastCall = time - lastCallTime,
+            timeSinceLastInvoke = time - lastInvokeTime;
+
+        // Either this is the first call, activity has stopped and we're at the
+        // trailing edge, the system time has gone backwards and we're treating
+        // it as the trailing edge, or we've hit the `maxWait` limit.
+        return (lastCallTime === undefined || (timeSinceLastCall >= wait) ||
+          (timeSinceLastCall < 0) || (maxing && timeSinceLastInvoke >= maxWait));
+      }
+
+      function timerExpired() {
+        var time = now();
+        if (shouldInvoke(time)) {
+          return trailingEdge(time);
+        }
+        // Restart the timer.
+        timerId = setTimeout(timerExpired, remainingWait(time));
+      }
+
+      function trailingEdge(time) {
+        timerId = undefined;
+
+        // Only invoke if we have `lastArgs` which means `func` has been
+        // debounced at least once.
+        if (trailing && lastArgs) {
+          return invokeFunc(time);
+        }
+        lastArgs = lastThis = undefined;
+        return result;
+      }
+
+      function cancel() {
+        if (timerId !== undefined) {
+          clearTimeout(timerId);
+        }
+        lastInvokeTime = 0;
+        lastArgs = lastCallTime = lastThis = timerId = undefined;
+      }
+
+      function flush() {
+        return timerId === undefined ? result : trailingEdge(now());
+      }
+
+      function debounced() {
+        var time = now(),
+            isInvoking = shouldInvoke(time);
+
+        lastArgs = arguments;
+        lastThis = this;
+        lastCallTime = time;
+
+        if (isInvoking) {
+          if (timerId === undefined) {
+            return leadingEdge(lastCallTime);
+          }
+          if (maxing) {
+            // Handle invocations in a tight loop.
+            timerId = setTimeout(timerExpired, wait);
+            return invokeFunc(lastCallTime);
+          }
+        }
+        if (timerId === undefined) {
+          timerId = setTimeout(timerExpired, wait);
+        }
+        return result;
+      }
+      debounced.cancel = cancel;
+      debounced.flush = flush;
+      return debounced;
     }
 
     /**
-     * Creates a function that invokes the predicate properties of `source` with
-     * the corresponding property values of a given object, returning `true` if
-     * all predicates return truthy, else `false`.
+     * Defers invoking the `func` until the current call stack has cleared. Any
+     * additional arguments are provided to `func` when it's invoked.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category Util
-     * @param {Object} source The object of property predicates to conform to.
-     * @returns {Function} Returns the new spec function.
+     * @since 0.1.0
+     * @category Function
+     * @param {Function} func The function to defer.
+     * @param {...*} [args] The arguments to invoke `func` with.
+     * @returns {number} Returns the timer id.
      * @example
      *
-     * var users = [
-     *   { 'user': 'barney', 'age': 36 },
-     *   { 'user': 'fred',   'age': 40 }
-     * ];
-     *
-     * _.filter(users, _.conforms({ 'age': function(n) { return n > 38; } }));
-     * // => [{ 'user': 'fred', 'age': 40 }]
+     * _.defer(function(text) {
+     *   console.log(text);
+     * }, 'deferred');
+     * // => Logs 'deferred' after one millisecond.
      */
-    function conforms(source) {
-      return baseConforms(baseClone(source, true));
-    }
+    var defer = baseRest(function(func, args) {
+      return baseDelay(func, 1, args);
+    });
 
     /**
-     * Creates a function that returns `value`.
+     * Invokes `func` after `wait` milliseconds. Any additional arguments are
+     * provided to `func` when it's invoked.
      *
      * @static
      * @memberOf _
-     * @since 2.4.0
-     * @category Util
-     * @param {*} value The value to return from the new function.
-     * @returns {Function} Returns the new constant function.
+     * @since 0.1.0
+     * @category Function
+     * @param {Function} func The function to delay.
+     * @param {number} wait The number of milliseconds to delay invocation.
+     * @param {...*} [args] The arguments to invoke `func` with.
+     * @returns {number} Returns the timer id.
      * @example
      *
-     * var objects = _.times(2, _.constant({ 'a': 1 }));
-     *
-     * console.log(objects);
-     * // => [{ 'a': 1 }, { 'a': 1 }]
-     *
-     * console.log(objects[0] === objects[1]);
-     * // => true
+     * _.delay(function(text) {
+     *   console.log(text);
+     * }, 1000, 'later');
+     * // => Logs 'later' after one second.
      */
-    function constant(value) {
-      return function() {
-        return value;
-      };
-    }
+    var delay = baseRest(function(func, wait, args) {
+      return baseDelay(func, toNumber(wait) || 0, args);
+    });
 
     /**
-     * Creates a function that returns the result of invoking the given functions
-     * with the `this` binding of the created function, where each successive
-     * invocation is supplied the return value of the previous.
+     * Creates a function that invokes `func` with arguments reversed.
      *
      * @static
      * @memberOf _
-     * @since 3.0.0
-     * @category Util
-     * @param {...(Function|Function[])} [funcs] Functions to invoke.
-     * @returns {Function} Returns the new composite function.
-     * @see _.flowRight
+     * @since 4.0.0
+     * @category Function
+     * @param {Function} func The function to flip arguments for.
+     * @returns {Function} Returns the new flipped function.
      * @example
      *
-     * function square(n) {
-     *   return n * n;
-     * }
+     * var flipped = _.flip(function() {
+     *   return _.toArray(arguments);
+     * });
      *
-     * var addSquare = _.flow([_.add, square]);
-     * addSquare(1, 2);
-     * // => 9
+     * flipped('a', 'b', 'c', 'd');
+     * // => ['d', 'c', 'b', 'a']
      */
-    var flow = createFlow();
+    function flip(func) {
+      return createWrap(func, WRAP_FLIP_FLAG);
+    }
 
     /**
-     * This method is like `_.flow` except that it creates a function that
-     * invokes the given functions from right to left.
+     * Creates a function that memoizes the result of `func`. If `resolver` is
+     * provided, it determines the cache key for storing the result based on the
+     * arguments provided to the memoized function. By default, the first argument
+     * provided to the memoized function is used as the map cache key. The `func`
+     * is invoked with the `this` binding of the memoized function.
+     *
+     * **Note:** The cache is exposed as the `cache` property on the memoized
+     * function. Its creation may be customized by replacing the `_.memoize.Cache`
+     * constructor with one whose instances implement the
+     * [`Map`](http://ecma-international.org/ecma-262/7.0/#sec-properties-of-the-map-prototype-object)
+     * method interface of `clear`, `delete`, `get`, `has`, and `set`.
      *
      * @static
-     * @since 3.0.0
      * @memberOf _
-     * @category Util
-     * @param {...(Function|Function[])} [funcs] Functions to invoke.
-     * @returns {Function} Returns the new composite function.
-     * @see _.flow
+     * @since 0.1.0
+     * @category Function
+     * @param {Function} func The function to have its output memoized.
+     * @param {Function} [resolver] The function to resolve the cache key.
+     * @returns {Function} Returns the new memoized function.
      * @example
      *
-     * function square(n) {
-     *   return n * n;
-     * }
+     * var object = { 'a': 1, 'b': 2 };
+     * var other = { 'c': 3, 'd': 4 };
      *
-     * var addSquare = _.flowRight([square, _.add]);
-     * addSquare(1, 2);
-     * // => 9
-     */
-    var flowRight = createFlow(true);
-
-    /**
-     * This method returns the first argument given to it.
+     * var values = _.memoize(_.values);
+     * values(object);
+     * // => [1, 2]
      *
-     * @static
-     * @since 0.1.0
-     * @memberOf _
-     * @category Util
-     * @param {*} value Any value.
-     * @returns {*} Returns `value`.
-     * @example
+     * values(other);
+     * // => [3, 4]
      *
-     * var object = { 'user': 'fred' };
+     * object.a = 2;
+     * values(object);
+     * // => [1, 2]
      *
-     * console.log(_.identity(object) === object);
-     * // => true
+     * // Modify the result cache.
+     * values.cache.set(object, ['a', 'b']);
+     * values(object);
+     * // => ['a', 'b']
+     *
+     * // Replace `_.memoize.Cache`.
+     * _.memoize.Cache = WeakMap;
      */
-    function identity(value) {
-      return value;
-    }
+    function memoize(func, resolver) {
+      if (typeof func != 'function' || (resolver != null && typeof resolver != 'function')) {
+        throw new TypeError(FUNC_ERROR_TEXT);
+      }
+      var memoized = function() {
+        var args = arguments,
+            key = resolver ? resolver.apply(this, args) : args[0],
+            cache = memoized.cache;
 
-    /**
-     * Creates a function that invokes `func` with the arguments of the created
-     * function. If `func` is a property name, the created function returns the
-     * property value for a given element. If `func` is an array or object, the
-     * created function returns `true` for elements that contain the equivalent
-     * source properties, otherwise it returns `false`.
-     *
-     * @static
-     * @since 4.0.0
-     * @memberOf _
-     * @category Util
-     * @param {*} [func=_.identity] The value to convert to a callback.
-     * @returns {Function} Returns the callback.
-     * @example
-     *
-     * var users = [
-     *   { 'user': 'barney', 'age': 36, 'active': true },
-     *   { 'user': 'fred',   'age': 40, 'active': false }
-     * ];
-     *
-     * // The `_.matches` iteratee shorthand.
-     * _.filter(users, _.iteratee({ 'user': 'barney', 'active': true }));
-     * // => [{ 'user': 'barney', 'age': 36, 'active': true }]
-     *
-     * // The `_.matchesProperty` iteratee shorthand.
-     * _.filter(users, _.iteratee(['user', 'fred']));
-     * // => [{ 'user': 'fred', 'age': 40 }]
-     *
-     * // The `_.property` iteratee shorthand.
-     * _.map(users, _.iteratee('user'));
-     * // => ['barney', 'fred']
-     *
-     * // Create custom iteratee shorthands.
-     * _.iteratee = _.wrap(_.iteratee, function(iteratee, func) {
-     *   return !_.isRegExp(func) ? iteratee(func) : function(string) {
-     *     return func.test(string);
-     *   };
-     * });
-     *
-     * _.filter(['abc', 'def'], /ef/);
-     * // => ['def']
-     */
-    function iteratee(func) {
-      return baseIteratee(typeof func == 'function' ? func : baseClone(func, true));
+        if (cache.has(key)) {
+          return cache.get(key);
+        }
+        var result = func.apply(this, args);
+        memoized.cache = cache.set(key, result) || cache;
+        return result;
+      };
+      memoized.cache = new (memoize.Cache || MapCache);
+      return memoized;
     }
 
+    // Expose `MapCache`.
+    memoize.Cache = MapCache;
+
     /**
-     * Creates a function that performs a partial deep comparison between a given
-     * object and `source`, returning `true` if the given object has equivalent
-     * property values, else `false`. The created function is equivalent to
-     * `_.isMatch` with a `source` partially applied.
-     *
-     * **Note:** This method supports comparing the same values as `_.isEqual`.
+     * Creates a function that negates the result of the predicate `func`. The
+     * `func` predicate is invoked with the `this` binding and arguments of the
+     * created function.
      *
      * @static
      * @memberOf _
      * @since 3.0.0
-     * @category Util
-     * @param {Object} source The object of property values to match.
-     * @returns {Function} Returns the new spec function.
+     * @category Function
+     * @param {Function} predicate The predicate to negate.
+     * @returns {Function} Returns the new negated function.
      * @example
      *
-     * var users = [
-     *   { 'user': 'barney', 'age': 36, 'active': true },
-     *   { 'user': 'fred',   'age': 40, 'active': false }
-     * ];
+     * function isEven(n) {
+     *   return n % 2 == 0;
+     * }
      *
-     * _.filter(users, _.matches({ 'age': 40, 'active': false }));
-     * // => [{ 'user': 'fred', 'age': 40, 'active': false }]
+     * _.filter([1, 2, 3, 4, 5, 6], _.negate(isEven));
+     * // => [1, 3, 5]
      */
-    function matches(source) {
-      return baseMatches(baseClone(source, true));
+    function negate(predicate) {
+      if (typeof predicate != 'function') {
+        throw new TypeError(FUNC_ERROR_TEXT);
+      }
+      return function() {
+        var args = arguments;
+        switch (args.length) {
+          case 0: return !predicate.call(this);
+          case 1: return !predicate.call(this, args[0]);
+          case 2: return !predicate.call(this, args[0], args[1]);
+          case 3: return !predicate.call(this, args[0], args[1], args[2]);
+        }
+        return !predicate.apply(this, args);
+      };
     }
 
     /**
-     * Creates a function that performs a partial deep comparison between the
-     * value at `path` of a given object to `srcValue`, returning `true` if the
-     * object value is equivalent, else `false`.
-     *
-     * **Note:** This method supports comparing the same values as `_.isEqual`.
+     * Creates a function that is restricted to invoking `func` once. Repeat calls
+     * to the function return the value of the first invocation. The `func` is
+     * invoked with the `this` binding and arguments of the created function.
      *
      * @static
      * @memberOf _
-     * @since 3.2.0
-     * @category Util
-     * @param {Array|string} path The path of the property to get.
-     * @param {*} srcValue The value to match.
-     * @returns {Function} Returns the new spec function.
+     * @since 0.1.0
+     * @category Function
+     * @param {Function} func The function to restrict.
+     * @returns {Function} Returns the new restricted function.
      * @example
      *
-     * var users = [
-     *   { 'user': 'barney' },
-     *   { 'user': 'fred' }
-     * ];
-     *
-     * _.find(users, _.matchesProperty('user', 'fred'));
-     * // => { 'user': 'fred' }
+     * var initialize = _.once(createApplication);
+     * initialize();
+     * initialize();
+     * // => `createApplication` is invoked once
      */
-    function matchesProperty(path, srcValue) {
-      return baseMatchesProperty(path, baseClone(srcValue, true));
+    function once(func) {
+      return before(2, func);
     }
 
     /**
-     * Creates a function that invokes the method at `path` of a given object.
-     * Any additional arguments are provided to the invoked method.
+     * Creates a function that invokes `func` with its arguments transformed.
      *
      * @static
+     * @since 4.0.0
      * @memberOf _
-     * @since 3.7.0
-     * @category Util
-     * @param {Array|string} path The path of the method to invoke.
-     * @param {...*} [args] The arguments to invoke the method with.
-     * @returns {Function} Returns the new invoker function.
+     * @category Function
+     * @param {Function} func The function to wrap.
+     * @param {...(Function|Function[])} [transforms=[_.identity]]
+     *  The argument transforms.
+     * @returns {Function} Returns the new function.
      * @example
      *
-     * var objects = [
-     *   { 'a': { 'b': _.constant(2) } },
-     *   { 'a': { 'b': _.constant(1) } }
-     * ];
+     * function doubled(n) {
+     *   return n * 2;
+     * }
      *
-     * _.map(objects, _.method('a.b'));
-     * // => [2, 1]
+     * function square(n) {
+     *   return n * n;
+     * }
      *
-     * _.map(objects, _.method(['a', 'b']));
-     * // => [2, 1]
+     * var func = _.overArgs(function(x, y) {
+     *   return [x, y];
+     * }, [square, doubled]);
+     *
+     * func(9, 3);
+     * // => [81, 6]
+     *
+     * func(10, 5);
+     * // => [100, 10]
      */
-    var method = rest(function(path, args) {
-      return function(object) {
-        return baseInvoke(object, path, args);
-      };
+    var overArgs = castRest(function(func, transforms) {
+      transforms = (transforms.length == 1 && isArray(transforms[0]))
+        ? arrayMap(transforms[0], baseUnary(getIteratee()))
+        : arrayMap(baseFlatten(transforms, 1), baseUnary(getIteratee()));
+
+      var funcsLength = transforms.length;
+      return baseRest(function(args) {
+        var index = -1,
+            length = nativeMin(args.length, funcsLength);
+
+        while (++index < length) {
+          args[index] = transforms[index].call(this, args[index]);
+        }
+        return apply(func, this, args);
+      });
     });
 
     /**
-     * The opposite of `_.method`; this method creates a function that invokes
-     * the method at a given path of `object`. Any additional arguments are
-     * provided to the invoked method.
+     * Creates a function that invokes `func` with `partials` prepended to the
+     * arguments it receives. This method is like `_.bind` except it does **not**
+     * alter the `this` binding.
+     *
+     * The `_.partial.placeholder` value, which defaults to `_` in monolithic
+     * builds, may be used as a placeholder for partially applied arguments.
+     *
+     * **Note:** This method doesn't set the "length" property of partially
+     * applied functions.
      *
      * @static
      * @memberOf _
-     * @since 3.7.0
-     * @category Util
-     * @param {Object} object The object to query.
-     * @param {...*} [args] The arguments to invoke the method with.
-     * @returns {Function} Returns the new invoker function.
+     * @since 0.2.0
+     * @category Function
+     * @param {Function} func The function to partially apply arguments to.
+     * @param {...*} [partials] The arguments to be partially applied.
+     * @returns {Function} Returns the new partially applied function.
      * @example
      *
-     * var array = _.times(3, _.constant),
-     *     object = { 'a': array, 'b': array, 'c': array };
+     * function greet(greeting, name) {
+     *   return greeting + ' ' + name;
+     * }
      *
-     * _.map(['a[2]', 'c[0]'], _.methodOf(object));
-     * // => [2, 0]
+     * var sayHelloTo = _.partial(greet, 'hello');
+     * sayHelloTo('fred');
+     * // => 'hello fred'
      *
-     * _.map([['a', '2'], ['c', '0']], _.methodOf(object));
-     * // => [2, 0]
+     * // Partially applied with placeholders.
+     * var greetFred = _.partial(greet, _, 'fred');
+     * greetFred('hi');
+     * // => 'hi fred'
      */
-    var methodOf = rest(function(object, args) {
-      return function(path) {
-        return baseInvoke(object, path, args);
-      };
+    var partial = baseRest(function(func, partials) {
+      var holders = replaceHolders(partials, getHolder(partial));
+      return createWrap(func, WRAP_PARTIAL_FLAG, undefined, partials, holders);
     });
 
     /**
-     * Adds all own enumerable string keyed function properties of a source
-     * object to the destination object. If `object` is a function, then methods
-     * are added to its prototype as well.
+     * This method is like `_.partial` except that partially applied arguments
+     * are appended to the arguments it receives.
      *
-     * **Note:** Use `_.runInContext` to create a pristine `lodash` function to
-     * avoid conflicts caused by modifying the original.
+     * The `_.partialRight.placeholder` value, which defaults to `_` in monolithic
+     * builds, may be used as a placeholder for partially applied arguments.
+     *
+     * **Note:** This method doesn't set the "length" property of partially
+     * applied functions.
      *
      * @static
-     * @since 0.1.0
      * @memberOf _
-     * @category Util
-     * @param {Function|Object} [object=lodash] The destination object.
-     * @param {Object} source The object of functions to add.
-     * @param {Object} [options={}] The options object.
-     * @param {boolean} [options.chain=true] Specify whether mixins are chainable.
-     * @returns {Function|Object} Returns `object`.
+     * @since 1.0.0
+     * @category Function
+     * @param {Function} func The function to partially apply arguments to.
+     * @param {...*} [partials] The arguments to be partially applied.
+     * @returns {Function} Returns the new partially applied function.
      * @example
      *
-     * function vowels(string) {
-     *   return _.filter(string, function(v) {
-     *     return /[aeiou]/i.test(v);
-     *   });
+     * function greet(greeting, name) {
+     *   return greeting + ' ' + name;
      * }
      *
-     * _.mixin({ 'vowels': vowels });
-     * _.vowels('fred');
-     * // => ['e']
-     *
-     * _('fred').vowels().value();
-     * // => ['e']
+     * var greetFred = _.partialRight(greet, 'fred');
+     * greetFred('hi');
+     * // => 'hi fred'
      *
-     * _.mixin({ 'vowels': vowels }, { 'chain': false });
-     * _('fred').vowels();
-     * // => ['e']
+     * // Partially applied with placeholders.
+     * var sayHelloTo = _.partialRight(greet, 'hello', _);
+     * sayHelloTo('fred');
+     * // => 'hello fred'
      */
-    function mixin(object, source, options) {
-      var props = keys(source),
-          methodNames = baseFunctions(source, props);
-
-      if (options == null &&
-          !(isObject(source) && (methodNames.length || !props.length))) {
-        options = source;
-        source = object;
-        object = this;
-        methodNames = baseFunctions(source, keys(source));
-      }
-      var chain = !(isObject(options) && 'chain' in options) || !!options.chain,
-          isFunc = isFunction(object);
-
-      arrayEach(methodNames, function(methodName) {
-        var func = source[methodName];
-        object[methodName] = func;
-        if (isFunc) {
-          object.prototype[methodName] = function() {
-            var chainAll = this.__chain__;
-            if (chain || chainAll) {
-              var result = object(this.__wrapped__),
-                  actions = result.__actions__ = copyArray(this.__actions__);
-
-              actions.push({ 'func': func, 'args': arguments, 'thisArg': object });
-              result.__chain__ = chainAll;
-              return result;
-            }
-            return func.apply(object, arrayPush([this.value()], arguments));
-          };
-        }
-      });
-
-      return object;
-    }
+    var partialRight = baseRest(function(func, partials) {
+      var holders = replaceHolders(partials, getHolder(partialRight));
+      return createWrap(func, WRAP_PARTIAL_RIGHT_FLAG, undefined, partials, holders);
+    });
 
     /**
-     * Reverts the `_` variable to its previous value and returns a reference to
-     * the `lodash` function.
+     * Creates a function that invokes `func` with arguments arranged according
+     * to the specified `indexes` where the argument value at the first index is
+     * provided as the first argument, the argument value at the second index is
+     * provided as the second argument, and so on.
      *
      * @static
-     * @since 0.1.0
      * @memberOf _
-     * @category Util
-     * @returns {Function} Returns the `lodash` function.
+     * @since 3.0.0
+     * @category Function
+     * @param {Function} func The function to rearrange arguments for.
+     * @param {...(number|number[])} indexes The arranged argument indexes.
+     * @returns {Function} Returns the new function.
      * @example
      *
-     * var lodash = _.noConflict();
+     * var rearged = _.rearg(function(a, b, c) {
+     *   return [a, b, c];
+     * }, [2, 0, 1]);
+     *
+     * rearged('b', 'c', 'a')
+     * // => ['a', 'b', 'c']
      */
-    function noConflict() {
-      if (root._ === this) {
-        root._ = oldDash;
-      }
-      return this;
-    }
+    var rearg = flatRest(function(func, indexes) {
+      return createWrap(func, WRAP_REARG_FLAG, undefined, undefined, undefined, indexes);
+    });
 
     /**
-     * A method that returns `undefined`.
+     * Creates a function that invokes `func` with the `this` binding of the
+     * created function and arguments from `start` and beyond provided as
+     * an array.
+     *
+     * **Note:** This method is based on the
+     * [rest parameter](https://mdn.io/rest_parameters).
      *
      * @static
      * @memberOf _
-     * @since 2.3.0
-     * @category Util
+     * @since 4.0.0
+     * @category Function
+     * @param {Function} func The function to apply a rest parameter to.
+     * @param {number} [start=func.length-1] The start position of the rest parameter.
+     * @returns {Function} Returns the new function.
      * @example
      *
-     * _.times(2, _.noop);
-     * // => [undefined, undefined]
+     * var say = _.rest(function(what, names) {
+     *   return what + ' ' + _.initial(names).join(', ') +
+     *     (_.size(names) > 1 ? ', & ' : '') + _.last(names);
+     * });
+     *
+     * say('hello', 'fred', 'barney', 'pebbles');
+     * // => 'hello fred, barney, & pebbles'
      */
-    function noop() {
-      // No operation performed.
+    function rest(func, start) {
+      if (typeof func != 'function') {
+        throw new TypeError(FUNC_ERROR_TEXT);
+      }
+      start = start === undefined ? start : toInteger(start);
+      return baseRest(func, start);
     }
 
     /**
-     * Creates a function that gets the argument at index `n`. If `n` is negative,
-     * the nth argument from the end is returned.
+     * Creates a function that invokes `func` with the `this` binding of the
+     * create function and an array of arguments much like
+     * [`Function#apply`](http://www.ecma-international.org/ecma-262/7.0/#sec-function.prototype.apply).
+     *
+     * **Note:** This method is based on the
+     * [spread operator](https://mdn.io/spread_operator).
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category Util
-     * @param {number} [n=0] The index of the argument to return.
-     * @returns {Function} Returns the new pass-thru function.
+     * @since 3.2.0
+     * @category Function
+     * @param {Function} func The function to spread arguments over.
+     * @param {number} [start=0] The start position of the spread.
+     * @returns {Function} Returns the new function.
      * @example
      *
-     * var func = _.nthArg(1);
-     * func('a', 'b', 'c', 'd');
-     * // => 'b'
+     * var say = _.spread(function(who, what) {
+     *   return who + ' says ' + what;
+     * });
      *
-     * var func = _.nthArg(-2);
-     * func('a', 'b', 'c', 'd');
-     * // => 'c'
+     * say(['fred', 'hello']);
+     * // => 'fred says hello'
+     *
+     * var numbers = Promise.all([
+     *   Promise.resolve(40),
+     *   Promise.resolve(36)
+     * ]);
+     *
+     * numbers.then(_.spread(function(x, y) {
+     *   return x + y;
+     * }));
+     * // => a Promise of 76
      */
-    function nthArg(n) {
-      n = toInteger(n);
-      return rest(function(args) {
-        return baseNth(args, n);
+    function spread(func, start) {
+      if (typeof func != 'function') {
+        throw new TypeError(FUNC_ERROR_TEXT);
+      }
+      start = start == null ? 0 : nativeMax(toInteger(start), 0);
+      return baseRest(function(args) {
+        var array = args[start],
+            otherArgs = castSlice(args, 0, start);
+
+        if (array) {
+          arrayPush(otherArgs, array);
+        }
+        return apply(func, this, otherArgs);
       });
     }
 
     /**
-     * Creates a function that invokes `iteratees` with the arguments it receives
-     * and returns their results.
+     * Creates a throttled function that only invokes `func` at most once per
+     * every `wait` milliseconds. The throttled function comes with a `cancel`
+     * method to cancel delayed `func` invocations and a `flush` method to
+     * immediately invoke them. Provide `options` to indicate whether `func`
+     * should be invoked on the leading and/or trailing edge of the `wait`
+     * timeout. The `func` is invoked with the last arguments provided to the
+     * throttled function. Subsequent calls to the throttled function return the
+     * result of the last `func` invocation.
+     *
+     * **Note:** If `leading` and `trailing` options are `true`, `func` is
+     * invoked on the trailing edge of the timeout only if the throttled function
+     * is invoked more than once during the `wait` timeout.
+     *
+     * If `wait` is `0` and `leading` is `false`, `func` invocation is deferred
+     * until to the next tick, similar to `setTimeout` with a timeout of `0`.
+     *
+     * See [David Corbacho's article](https://css-tricks.com/debouncing-throttling-explained-examples/)
+     * for details over the differences between `_.throttle` and `_.debounce`.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category Util
-     * @param {...(Array|Array[]|Function|Function[]|Object|Object[]|string|string[])}
-     *  [iteratees=[_.identity]] The iteratees to invoke.
-     * @returns {Function} Returns the new function.
+     * @since 0.1.0
+     * @category Function
+     * @param {Function} func The function to throttle.
+     * @param {number} [wait=0] The number of milliseconds to throttle invocations to.
+     * @param {Object} [options={}] The options object.
+     * @param {boolean} [options.leading=true]
+     *  Specify invoking on the leading edge of the timeout.
+     * @param {boolean} [options.trailing=true]
+     *  Specify invoking on the trailing edge of the timeout.
+     * @returns {Function} Returns the new throttled function.
      * @example
      *
-     * var func = _.over([Math.max, Math.min]);
+     * // Avoid excessively updating the position while scrolling.
+     * jQuery(window).on('scroll', _.throttle(updatePosition, 100));
      *
-     * func(1, 2, 3, 4);
-     * // => [4, 1]
+     * // Invoke `renewToken` when the click event is fired, but not more than once every 5 minutes.
+     * var throttled = _.throttle(renewToken, 300000, { 'trailing': false });
+     * jQuery(element).on('click', throttled);
+     *
+     * // Cancel the trailing throttled invocation.
+     * jQuery(window).on('popstate', throttled.cancel);
      */
-    var over = createOver(arrayMap);
+    function throttle(func, wait, options) {
+      var leading = true,
+          trailing = true;
+
+      if (typeof func != 'function') {
+        throw new TypeError(FUNC_ERROR_TEXT);
+      }
+      if (isObject(options)) {
+        leading = 'leading' in options ? !!options.leading : leading;
+        trailing = 'trailing' in options ? !!options.trailing : trailing;
+      }
+      return debounce(func, wait, {
+        'leading': leading,
+        'maxWait': wait,
+        'trailing': trailing
+      });
+    }
 
     /**
-     * Creates a function that checks if **all** of the `predicates` return
-     * truthy when invoked with the arguments it receives.
+     * Creates a function that accepts up to one argument, ignoring any
+     * additional arguments.
      *
      * @static
      * @memberOf _
      * @since 4.0.0
-     * @category Util
-     * @param {...(Array|Array[]|Function|Function[]|Object|Object[]|string|string[])}
-     *  [predicates=[_.identity]] The predicates to check.
-     * @returns {Function} Returns the new function.
+     * @category Function
+     * @param {Function} func The function to cap arguments for.
+     * @returns {Function} Returns the new capped function.
      * @example
      *
-     * var func = _.overEvery([Boolean, isFinite]);
-     *
-     * func('1');
-     * // => true
-     *
-     * func(null);
-     * // => false
-     *
-     * func(NaN);
-     * // => false
+     * _.map(['6', '8', '10'], _.unary(parseInt));
+     * // => [6, 8, 10]
      */
-    var overEvery = createOver(arrayEvery);
+    function unary(func) {
+      return ary(func, 1);
+    }
 
     /**
-     * Creates a function that checks if **any** of the `predicates` return
-     * truthy when invoked with the arguments it receives.
+     * Creates a function that provides `value` to `wrapper` as its first
+     * argument. Any additional arguments provided to the function are appended
+     * to those provided to the `wrapper`. The wrapper is invoked with the `this`
+     * binding of the created function.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category Util
-     * @param {...(Array|Array[]|Function|Function[]|Object|Object[]|string|string[])}
-     *  [predicates=[_.identity]] The predicates to check.
+     * @since 0.1.0
+     * @category Function
+     * @param {*} value The value to wrap.
+     * @param {Function} [wrapper=identity] The wrapper function.
      * @returns {Function} Returns the new function.
      * @example
      *
-     * var func = _.overSome([Boolean, isFinite]);
-     *
-     * func('1');
-     * // => true
-     *
-     * func(null);
-     * // => true
+     * var p = _.wrap(_.escape, function(func, text) {
+     *   return '<p>' + func(text) + '</p>';
+     * });
      *
-     * func(NaN);
-     * // => false
+     * p('fred, barney, & pebbles');
+     * // => '<p>fred, barney, &amp; pebbles</p>'
      */
-    var overSome = createOver(arraySome);
+    function wrap(value, wrapper) {
+      return partial(castFunction(wrapper), value);
+    }
+
+    /*------------------------------------------------------------------------*/
 
     /**
-     * Creates a function that returns the value at `path` of a given object.
+     * Casts `value` as an array if it's not one.
      *
      * @static
      * @memberOf _
-     * @since 2.4.0
-     * @category Util
-     * @param {Array|string} path The path of the property to get.
-     * @returns {Function} Returns the new accessor function.
+     * @since 4.4.0
+     * @category Lang
+     * @param {*} value The value to inspect.
+     * @returns {Array} Returns the cast array.
      * @example
      *
-     * var objects = [
-     *   { 'a': { 'b': 2 } },
-     *   { 'a': { 'b': 1 } }
-     * ];
+     * _.castArray(1);
+     * // => [1]
      *
-     * _.map(objects, _.property('a.b'));
-     * // => [2, 1]
+     * _.castArray({ 'a': 1 });
+     * // => [{ 'a': 1 }]
      *
-     * _.map(_.sortBy(objects, _.property(['a', 'b'])), 'a.b');
-     * // => [1, 2]
-     */
-    function property(path) {
-      return isKey(path) ? baseProperty(toKey(path)) : basePropertyDeep(path);
-    }
-
-    /**
-     * The opposite of `_.property`; this method creates a function that returns
-     * the value at a given path of `object`.
+     * _.castArray('abc');
+     * // => ['abc']
      *
-     * @static
-     * @memberOf _
-     * @since 3.0.0
-     * @category Util
-     * @param {Object} object The object to query.
-     * @returns {Function} Returns the new accessor function.
-     * @example
+     * _.castArray(null);
+     * // => [null]
      *
-     * var array = [0, 1, 2],
-     *     object = { 'a': array, 'b': array, 'c': array };
+     * _.castArray(undefined);
+     * // => [undefined]
      *
-     * _.map(['a[2]', 'c[0]'], _.propertyOf(object));
-     * // => [2, 0]
+     * _.castArray();
+     * // => []
      *
-     * _.map([['a', '2'], ['c', '0']], _.propertyOf(object));
-     * // => [2, 0]
+     * var array = [1, 2, 3];
+     * console.log(_.castArray(array) === array);
+     * // => true
      */
-    function propertyOf(object) {
-      return function(path) {
-        return object == null ? undefined : baseGet(object, path);
-      };
+    function castArray() {
+      if (!arguments.length) {
+        return [];
+      }
+      var value = arguments[0];
+      return isArray(value) ? value : [value];
     }
 
     /**
-     * Creates an array of numbers (positive and/or negative) progressing from
-     * `start` up to, but not including, `end`. A step of `-1` is used if a negative
-     * `start` is specified without an `end` or `step`. If `end` is not specified,
-     * it's set to `start` with `start` then set to `0`.
+     * Creates a shallow clone of `value`.
      *
-     * **Note:** JavaScript follows the IEEE-754 standard for resolving
-     * floating-point values which can produce unexpected results.
+     * **Note:** This method is loosely based on the
+     * [structured clone algorithm](https://mdn.io/Structured_clone_algorithm)
+     * and supports cloning arrays, array buffers, booleans, date objects, maps,
+     * numbers, `Object` objects, regexes, sets, strings, symbols, and typed
+     * arrays. The own enumerable properties of `arguments` objects are cloned
+     * as plain objects. An empty object is returned for uncloneable values such
+     * as error objects, functions, DOM nodes, and WeakMaps.
      *
      * @static
-     * @since 0.1.0
      * @memberOf _
-     * @category Util
-     * @param {number} [start=0] The start of the range.
-     * @param {number} end The end of the range.
-     * @param {number} [step=1] The value to increment or decrement by.
-     * @returns {Array} Returns the range of numbers.
-     * @see _.inRange, _.rangeRight
+     * @since 0.1.0
+     * @category Lang
+     * @param {*} value The value to clone.
+     * @returns {*} Returns the cloned value.
+     * @see _.cloneDeep
      * @example
      *
-     * _.range(4);
-     * // => [0, 1, 2, 3]
-     *
-     * _.range(-4);
-     * // => [0, -1, -2, -3]
-     *
-     * _.range(1, 5);
-     * // => [1, 2, 3, 4]
-     *
-     * _.range(0, 20, 5);
-     * // => [0, 5, 10, 15]
-     *
-     * _.range(0, -4, -1);
-     * // => [0, -1, -2, -3]
-     *
-     * _.range(1, 4, 0);
-     * // => [1, 1, 1]
+     * var objects = [{ 'a': 1 }, { 'b': 2 }];
      *
-     * _.range(0);
-     * // => []
+     * var shallow = _.clone(objects);
+     * console.log(shallow[0] === objects[0]);
+     * // => true
      */
-    var range = createRange();
+    function clone(value) {
+      return baseClone(value, CLONE_SYMBOLS_FLAG);
+    }
 
     /**
-     * This method is like `_.range` except that it populates values in
-     * descending order.
+     * This method is like `_.clone` except that it accepts `customizer` which
+     * is invoked to produce the cloned value. If `customizer` returns `undefined`,
+     * cloning is handled by the method instead. The `customizer` is invoked with
+     * up to four arguments; (value [, index|key, object, stack]).
      *
      * @static
      * @memberOf _
      * @since 4.0.0
-     * @category Util
-     * @param {number} [start=0] The start of the range.
-     * @param {number} end The end of the range.
-     * @param {number} [step=1] The value to increment or decrement by.
-     * @returns {Array} Returns the range of numbers.
-     * @see _.inRange, _.range
+     * @category Lang
+     * @param {*} value The value to clone.
+     * @param {Function} [customizer] The function to customize cloning.
+     * @returns {*} Returns the cloned value.
+     * @see _.cloneDeepWith
      * @example
      *
-     * _.rangeRight(4);
-     * // => [3, 2, 1, 0]
-     *
-     * _.rangeRight(-4);
-     * // => [-3, -2, -1, 0]
-     *
-     * _.rangeRight(1, 5);
-     * // => [4, 3, 2, 1]
-     *
-     * _.rangeRight(0, 20, 5);
-     * // => [15, 10, 5, 0]
-     *
-     * _.rangeRight(0, -4, -1);
-     * // => [-3, -2, -1, 0]
+     * function customizer(value) {
+     *   if (_.isElement(value)) {
+     *     return value.cloneNode(false);
+     *   }
+     * }
      *
-     * _.rangeRight(1, 4, 0);
-     * // => [1, 1, 1]
+     * var el = _.cloneWith(document.body, customizer);
      *
-     * _.rangeRight(0);
-     * // => []
+     * console.log(el === document.body);
+     * // => false
+     * console.log(el.nodeName);
+     * // => 'BODY'
+     * console.log(el.childNodes.length);
+     * // => 0
      */
-    var rangeRight = createRange(true);
+    function cloneWith(value, customizer) {
+      customizer = typeof customizer == 'function' ? customizer : undefined;
+      return baseClone(value, CLONE_SYMBOLS_FLAG, customizer);
+    }
 
     /**
-     * A method that returns a new empty array.
+     * This method is like `_.clone` except that it recursively clones `value`.
      *
      * @static
      * @memberOf _
-     * @since 4.13.0
-     * @category Util
-     * @returns {Array} Returns the new empty array.
+     * @since 1.0.0
+     * @category Lang
+     * @param {*} value The value to recursively clone.
+     * @returns {*} Returns the deep cloned value.
+     * @see _.clone
      * @example
      *
-     * var arrays = _.times(2, _.stubArray);
-     *
-     * console.log(arrays);
-     * // => [[], []]
+     * var objects = [{ 'a': 1 }, { 'b': 2 }];
      *
-     * console.log(arrays[0] === arrays[1]);
+     * var deep = _.cloneDeep(objects);
+     * console.log(deep[0] === objects[0]);
      * // => false
      */
-    function stubArray() {
-      return [];
+    function cloneDeep(value) {
+      return baseClone(value, CLONE_DEEP_FLAG | CLONE_SYMBOLS_FLAG);
     }
 
     /**
-     * A method that returns `false`.
+     * This method is like `_.cloneWith` except that it recursively clones `value`.
      *
      * @static
      * @memberOf _
-     * @since 4.13.0
-     * @category Util
-     * @returns {boolean} Returns `false`.
+     * @since 4.0.0
+     * @category Lang
+     * @param {*} value The value to recursively clone.
+     * @param {Function} [customizer] The function to customize cloning.
+     * @returns {*} Returns the deep cloned value.
+     * @see _.cloneWith
      * @example
      *
-     * _.times(2, _.stubFalse);
-     * // => [false, false]
+     * function customizer(value) {
+     *   if (_.isElement(value)) {
+     *     return value.cloneNode(true);
+     *   }
+     * }
+     *
+     * var el = _.cloneDeepWith(document.body, customizer);
+     *
+     * console.log(el === document.body);
+     * // => false
+     * console.log(el.nodeName);
+     * // => 'BODY'
+     * console.log(el.childNodes.length);
+     * // => 20
      */
-    function stubFalse() {
-      return false;
+    function cloneDeepWith(value, customizer) {
+      customizer = typeof customizer == 'function' ? customizer : undefined;
+      return baseClone(value, CLONE_DEEP_FLAG | CLONE_SYMBOLS_FLAG, customizer);
     }
 
     /**
-     * A method that returns a new empty object.
+     * Checks if `object` conforms to `source` by invoking the predicate
+     * properties of `source` with the corresponding property values of `object`.
+     *
+     * **Note:** This method is equivalent to `_.conforms` when `source` is
+     * partially applied.
      *
      * @static
      * @memberOf _
-     * @since 4.13.0
-     * @category Util
-     * @returns {Object} Returns the new empty object.
+     * @since 4.14.0
+     * @category Lang
+     * @param {Object} object The object to inspect.
+     * @param {Object} source The object of property predicates to conform to.
+     * @returns {boolean} Returns `true` if `object` conforms, else `false`.
      * @example
      *
-     * var objects = _.times(2, _.stubObject);
+     * var object = { 'a': 1, 'b': 2 };
      *
-     * console.log(objects);
-     * // => [{}, {}]
+     * _.conformsTo(object, { 'b': function(n) { return n > 1; } });
+     * // => true
      *
-     * console.log(objects[0] === objects[1]);
+     * _.conformsTo(object, { 'b': function(n) { return n > 2; } });
      * // => false
      */
-    function stubObject() {
-      return {};
+    function conformsTo(object, source) {
+      return source == null || baseConformsTo(object, source, keys(source));
     }
 
     /**
-     * A method that returns an empty string.
+     * Performs a
+     * [`SameValueZero`](http://ecma-international.org/ecma-262/7.0/#sec-samevaluezero)
+     * comparison between two values to determine if they are equivalent.
      *
      * @static
      * @memberOf _
-     * @since 4.13.0
-     * @category Util
-     * @returns {string} Returns the empty string.
+     * @since 4.0.0
+     * @category Lang
+     * @param {*} value The value to compare.
+     * @param {*} other The other value to compare.
+     * @returns {boolean} Returns `true` if the values are equivalent, else `false`.
      * @example
      *
-     * _.times(2, _.stubString);
-     * // => ['', '']
+     * var object = { 'a': 1 };
+     * var other = { 'a': 1 };
+     *
+     * _.eq(object, object);
+     * // => true
+     *
+     * _.eq(object, other);
+     * // => false
+     *
+     * _.eq('a', 'a');
+     * // => true
+     *
+     * _.eq('a', Object('a'));
+     * // => false
+     *
+     * _.eq(NaN, NaN);
+     * // => true
      */
-    function stubString() {
-      return '';
+    function eq(value, other) {
+      return value === other || (value !== value && other !== other);
     }
 
     /**
-     * A method that returns `true`.
+     * Checks if `value` is greater than `other`.
      *
      * @static
      * @memberOf _
-     * @since 4.13.0
-     * @category Util
-     * @returns {boolean} Returns `true`.
-     * @example
-     *
-     * _.times(2, _.stubTrue);
-     * // => [true, true]
+     * @since 3.9.0
+     * @category Lang
+     * @param {*} value The value to compare.
+     * @param {*} other The other value to compare.
+     * @returns {boolean} Returns `true` if `value` is greater than `other`,
+     *  else `false`.
+     * @see _.lt
+     * @example
+     *
+     * _.gt(3, 1);
+     * // => true
+     *
+     * _.gt(3, 3);
+     * // => false
+     *
+     * _.gt(1, 3);
+     * // => false
      */
-    function stubTrue() {
-      return true;
-    }
+    var gt = createRelationalOperation(baseGt);
 
     /**
-     * Invokes the iteratee `n` times, returning an array of the results of
-     * each invocation. The iteratee is invoked with one argument; (index).
+     * Checks if `value` is greater than or equal to `other`.
      *
      * @static
-     * @since 0.1.0
      * @memberOf _
-     * @category Util
-     * @param {number} n The number of times to invoke `iteratee`.
-     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
-     * @returns {Array} Returns the array of results.
+     * @since 3.9.0
+     * @category Lang
+     * @param {*} value The value to compare.
+     * @param {*} other The other value to compare.
+     * @returns {boolean} Returns `true` if `value` is greater than or equal to
+     *  `other`, else `false`.
+     * @see _.lte
      * @example
      *
-     * _.times(3, String);
-     * // => ['0', '1', '2']
+     * _.gte(3, 1);
+     * // => true
      *
-     *  _.times(4, _.constant(0));
-     * // => [0, 0, 0, 0]
+     * _.gte(3, 3);
+     * // => true
+     *
+     * _.gte(1, 3);
+     * // => false
      */
-    function times(n, iteratee) {
-      n = toInteger(n);
-      if (n < 1 || n > MAX_SAFE_INTEGER) {
-        return [];
-      }
-      var index = MAX_ARRAY_LENGTH,
-          length = nativeMin(n, MAX_ARRAY_LENGTH);
-
-      iteratee = getIteratee(iteratee);
-      n -= MAX_ARRAY_LENGTH;
-
-      var result = baseTimes(length, iteratee);
-      while (++index < n) {
-        iteratee(index);
-      }
-      return result;
-    }
+    var gte = createRelationalOperation(function(value, other) {
+      return value >= other;
+    });
 
     /**
-     * Converts `value` to a property path array.
+     * Checks if `value` is likely an `arguments` object.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category Util
-     * @param {*} value The value to convert.
-     * @returns {Array} Returns the new property path array.
+     * @since 0.1.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is an `arguments` object,
+     *  else `false`.
      * @example
      *
-     * _.toPath('a.b.c');
-     * // => ['a', 'b', 'c']
+     * _.isArguments(function() { return arguments; }());
+     * // => true
      *
-     * _.toPath('a[0].b.c');
-     * // => ['a', '0', 'b', 'c']
+     * _.isArguments([1, 2, 3]);
+     * // => false
      */
-    function toPath(value) {
-      if (isArray(value)) {
-        return arrayMap(value, toKey);
-      }
-      return isSymbol(value) ? [value] : copyArray(stringToPath(value));
-    }
+    var isArguments = baseIsArguments(function() { return arguments; }()) ? baseIsArguments : function(value) {
+      return isObjectLike(value) && hasOwnProperty.call(value, 'callee') &&
+        !propertyIsEnumerable.call(value, 'callee');
+    };
 
     /**
-     * Generates a unique ID. If `prefix` is given, the ID is appended to it.
+     * Checks if `value` is classified as an `Array` object.
      *
      * @static
-     * @since 0.1.0
      * @memberOf _
-     * @category Util
-     * @param {string} [prefix=''] The value to prefix the ID with.
-     * @returns {string} Returns the unique ID.
+     * @since 0.1.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is an array, else `false`.
      * @example
      *
-     * _.uniqueId('contact_');
-     * // => 'contact_104'
+     * _.isArray([1, 2, 3]);
+     * // => true
      *
-     * _.uniqueId();
-     * // => '105'
+     * _.isArray(document.body.children);
+     * // => false
+     *
+     * _.isArray('abc');
+     * // => false
+     *
+     * _.isArray(_.noop);
+     * // => false
      */
-    function uniqueId(prefix) {
-      var id = ++idCounter;
-      return toString(prefix) + id;
-    }
-
-    /*------------------------------------------------------------------------*/
+    var isArray = Array.isArray;
 
     /**
-     * Adds two numbers.
+     * Checks if `value` is classified as an `ArrayBuffer` object.
      *
      * @static
      * @memberOf _
-     * @since 3.4.0
-     * @category Math
-     * @param {number} augend The first number in an addition.
-     * @param {number} addend The second number in an addition.
-     * @returns {number} Returns the total.
+     * @since 4.3.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is an array buffer, else `false`.
      * @example
      *
-     * _.add(6, 4);
-     * // => 10
+     * _.isArrayBuffer(new ArrayBuffer(2));
+     * // => true
+     *
+     * _.isArrayBuffer(new Array(2));
+     * // => false
      */
-    var add = createMathOperation(function(augend, addend) {
-      return augend + addend;
-    });
+    var isArrayBuffer = nodeIsArrayBuffer ? baseUnary(nodeIsArrayBuffer) : baseIsArrayBuffer;
 
     /**
-     * Computes `number` rounded up to `precision`.
+     * Checks if `value` is array-like. A value is considered array-like if it's
+     * not a function and has a `value.length` that's an integer greater than or
+     * equal to `0` and less than or equal to `Number.MAX_SAFE_INTEGER`.
      *
      * @static
      * @memberOf _
-     * @since 3.10.0
-     * @category Math
-     * @param {number} number The number to round up.
-     * @param {number} [precision=0] The precision to round up to.
-     * @returns {number} Returns the rounded up number.
+     * @since 4.0.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is array-like, else `false`.
      * @example
      *
-     * _.ceil(4.006);
-     * // => 5
+     * _.isArrayLike([1, 2, 3]);
+     * // => true
      *
-     * _.ceil(6.004, 2);
-     * // => 6.01
+     * _.isArrayLike(document.body.children);
+     * // => true
      *
-     * _.ceil(6040, -2);
-     * // => 6100
+     * _.isArrayLike('abc');
+     * // => true
+     *
+     * _.isArrayLike(_.noop);
+     * // => false
      */
-    var ceil = createRound('ceil');
+    function isArrayLike(value) {
+      return value != null && isLength(value.length) && !isFunction(value);
+    }
 
     /**
-     * Divide two numbers.
+     * This method is like `_.isArrayLike` except that it also checks if `value`
+     * is an object.
      *
      * @static
      * @memberOf _
-     * @since 4.7.0
-     * @category Math
-     * @param {number} dividend The first number in a division.
-     * @param {number} divisor The second number in a division.
-     * @returns {number} Returns the quotient.
+     * @since 4.0.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is an array-like object,
+     *  else `false`.
      * @example
      *
-     * _.divide(6, 4);
-     * // => 1.5
+     * _.isArrayLikeObject([1, 2, 3]);
+     * // => true
+     *
+     * _.isArrayLikeObject(document.body.children);
+     * // => true
+     *
+     * _.isArrayLikeObject('abc');
+     * // => false
+     *
+     * _.isArrayLikeObject(_.noop);
+     * // => false
      */
-    var divide = createMathOperation(function(dividend, divisor) {
-      return dividend / divisor;
-    });
+    function isArrayLikeObject(value) {
+      return isObjectLike(value) && isArrayLike(value);
+    }
 
     /**
-     * Computes `number` rounded down to `precision`.
+     * Checks if `value` is classified as a boolean primitive or object.
      *
      * @static
      * @memberOf _
-     * @since 3.10.0
-     * @category Math
-     * @param {number} number The number to round down.
-     * @param {number} [precision=0] The precision to round down to.
-     * @returns {number} Returns the rounded down number.
+     * @since 0.1.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a boolean, else `false`.
      * @example
      *
-     * _.floor(4.006);
-     * // => 4
-     *
-     * _.floor(0.046, 2);
-     * // => 0.04
+     * _.isBoolean(false);
+     * // => true
      *
-     * _.floor(4060, -2);
-     * // => 4000
+     * _.isBoolean(null);
+     * // => false
      */
-    var floor = createRound('floor');
+    function isBoolean(value) {
+      return value === true || value === false ||
+        (isObjectLike(value) && baseGetTag(value) == boolTag);
+    }
 
     /**
-     * Computes the maximum value of `array`. If `array` is empty or falsey,
-     * `undefined` is returned.
+     * Checks if `value` is a buffer.
      *
      * @static
-     * @since 0.1.0
      * @memberOf _
-     * @category Math
-     * @param {Array} array The array to iterate over.
-     * @returns {*} Returns the maximum value.
+     * @since 4.3.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a buffer, else `false`.
      * @example
      *
-     * _.max([4, 2, 8, 6]);
-     * // => 8
+     * _.isBuffer(new Buffer(2));
+     * // => true
      *
-     * _.max([]);
-     * // => undefined
+     * _.isBuffer(new Uint8Array(2));
+     * // => false
      */
-    function max(array) {
-      return (array && array.length)
-        ? baseExtremum(array, identity, baseGt)
-        : undefined;
-    }
+    var isBuffer = nativeIsBuffer || stubFalse;
 
     /**
-     * This method is like `_.max` except that it accepts `iteratee` which is
-     * invoked for each element in `array` to generate the criterion by which
-     * the value is ranked. The iteratee is invoked with one argument: (value).
+     * Checks if `value` is classified as a `Date` object.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category Math
-     * @param {Array} array The array to iterate over.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The iteratee invoked per element.
-     * @returns {*} Returns the maximum value.
+     * @since 0.1.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a date object, else `false`.
      * @example
      *
-     * var objects = [{ 'n': 1 }, { 'n': 2 }];
-     *
-     * _.maxBy(objects, function(o) { return o.n; });
-     * // => { 'n': 2 }
+     * _.isDate(new Date);
+     * // => true
      *
-     * // The `_.property` iteratee shorthand.
-     * _.maxBy(objects, 'n');
-     * // => { 'n': 2 }
+     * _.isDate('Mon April 23 2012');
+     * // => false
      */
-    function maxBy(array, iteratee) {
-      return (array && array.length)
-        ? baseExtremum(array, getIteratee(iteratee), baseGt)
-        : undefined;
-    }
+    var isDate = nodeIsDate ? baseUnary(nodeIsDate) : baseIsDate;
 
     /**
-     * Computes the mean of the values in `array`.
+     * Checks if `value` is likely a DOM element.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category Math
-     * @param {Array} array The array to iterate over.
-     * @returns {number} Returns the mean.
+     * @since 0.1.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a DOM element, else `false`.
      * @example
      *
-     * _.mean([4, 2, 8, 6]);
-     * // => 5
+     * _.isElement(document.body);
+     * // => true
+     *
+     * _.isElement('<body>');
+     * // => false
      */
-    function mean(array) {
-      return baseMean(array, identity);
+    function isElement(value) {
+      return isObjectLike(value) && value.nodeType === 1 && !isPlainObject(value);
     }
 
     /**
-     * This method is like `_.mean` except that it accepts `iteratee` which is
-     * invoked for each element in `array` to generate the value to be averaged.
-     * The iteratee is invoked with one argument: (value).
+     * Checks if `value` is an empty object, collection, map, or set.
+     *
+     * Objects are considered empty if they have no own enumerable string keyed
+     * properties.
+     *
+     * Array-like values such as `arguments` objects, arrays, buffers, strings, or
+     * jQuery-like collections are considered empty if they have a `length` of `0`.
+     * Similarly, maps and sets are considered empty if they have a `size` of `0`.
      *
      * @static
      * @memberOf _
-     * @since 4.7.0
-     * @category Math
-     * @param {Array} array The array to iterate over.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The iteratee invoked per element.
-     * @returns {number} Returns the mean.
+     * @since 0.1.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is empty, else `false`.
      * @example
      *
-     * var objects = [{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }];
+     * _.isEmpty(null);
+     * // => true
      *
-     * _.meanBy(objects, function(o) { return o.n; });
-     * // => 5
+     * _.isEmpty(true);
+     * // => true
      *
-     * // The `_.property` iteratee shorthand.
-     * _.meanBy(objects, 'n');
-     * // => 5
+     * _.isEmpty(1);
+     * // => true
+     *
+     * _.isEmpty([1, 2, 3]);
+     * // => false
+     *
+     * _.isEmpty({ 'a': 1 });
+     * // => false
      */
-    function meanBy(array, iteratee) {
-      return baseMean(array, getIteratee(iteratee));
+    function isEmpty(value) {
+      if (value == null) {
+        return true;
+      }
+      if (isArrayLike(value) &&
+          (isArray(value) || typeof value == 'string' || typeof value.splice == 'function' ||
+            isBuffer(value) || isTypedArray(value) || isArguments(value))) {
+        return !value.length;
+      }
+      var tag = getTag(value);
+      if (tag == mapTag || tag == setTag) {
+        return !value.size;
+      }
+      if (isPrototype(value)) {
+        return !baseKeys(value).length;
+      }
+      for (var key in value) {
+        if (hasOwnProperty.call(value, key)) {
+          return false;
+        }
+      }
+      return true;
     }
 
     /**
-     * Computes the minimum value of `array`. If `array` is empty or falsey,
-     * `undefined` is returned.
+     * Performs a deep comparison between two values to determine if they are
+     * equivalent.
+     *
+     * **Note:** This method supports comparing arrays, array buffers, booleans,
+     * date objects, error objects, maps, numbers, `Object` objects, regexes,
+     * sets, strings, symbols, and typed arrays. `Object` objects are compared
+     * by their own, not inherited, enumerable properties. Functions and DOM
+     * nodes are compared by strict equality, i.e. `===`.
      *
      * @static
-     * @since 0.1.0
      * @memberOf _
-     * @category Math
-     * @param {Array} array The array to iterate over.
-     * @returns {*} Returns the minimum value.
+     * @since 0.1.0
+     * @category Lang
+     * @param {*} value The value to compare.
+     * @param {*} other The other value to compare.
+     * @returns {boolean} Returns `true` if the values are equivalent, else `false`.
      * @example
      *
-     * _.min([4, 2, 8, 6]);
-     * // => 2
+     * var object = { 'a': 1 };
+     * var other = { 'a': 1 };
      *
-     * _.min([]);
-     * // => undefined
+     * _.isEqual(object, other);
+     * // => true
+     *
+     * object === other;
+     * // => false
      */
-    function min(array) {
-      return (array && array.length)
-        ? baseExtremum(array, identity, baseLt)
-        : undefined;
+    function isEqual(value, other) {
+      return baseIsEqual(value, other);
     }
 
     /**
-     * This method is like `_.min` except that it accepts `iteratee` which is
-     * invoked for each element in `array` to generate the criterion by which
-     * the value is ranked. The iteratee is invoked with one argument: (value).
+     * This method is like `_.isEqual` except that it accepts `customizer` which
+     * is invoked to compare values. If `customizer` returns `undefined`, comparisons
+     * are handled by the method instead. The `customizer` is invoked with up to
+     * six arguments: (objValue, othValue [, index|key, object, other, stack]).
      *
      * @static
      * @memberOf _
      * @since 4.0.0
-     * @category Math
-     * @param {Array} array The array to iterate over.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The iteratee invoked per element.
-     * @returns {*} Returns the minimum value.
+     * @category Lang
+     * @param {*} value The value to compare.
+     * @param {*} other The other value to compare.
+     * @param {Function} [customizer] The function to customize comparisons.
+     * @returns {boolean} Returns `true` if the values are equivalent, else `false`.
      * @example
      *
-     * var objects = [{ 'n': 1 }, { 'n': 2 }];
+     * function isGreeting(value) {
+     *   return /^h(?:i|ello)$/.test(value);
+     * }
      *
-     * _.minBy(objects, function(o) { return o.n; });
-     * // => { 'n': 1 }
+     * function customizer(objValue, othValue) {
+     *   if (isGreeting(objValue) && isGreeting(othValue)) {
+     *     return true;
+     *   }
+     * }
      *
-     * // The `_.property` iteratee shorthand.
-     * _.minBy(objects, 'n');
-     * // => { 'n': 1 }
+     * var array = ['hello', 'goodbye'];
+     * var other = ['hi', 'goodbye'];
+     *
+     * _.isEqualWith(array, other, customizer);
+     * // => true
      */
-    function minBy(array, iteratee) {
-      return (array && array.length)
-        ? baseExtremum(array, getIteratee(iteratee), baseLt)
-        : undefined;
+    function isEqualWith(value, other, customizer) {
+      customizer = typeof customizer == 'function' ? customizer : undefined;
+      var result = customizer ? customizer(value, other) : undefined;
+      return result === undefined ? baseIsEqual(value, other, undefined, customizer) : !!result;
     }
 
     /**
-     * Multiply two numbers.
+     * Checks if `value` is an `Error`, `EvalError`, `RangeError`, `ReferenceError`,
+     * `SyntaxError`, `TypeError`, or `URIError` object.
      *
      * @static
      * @memberOf _
-     * @since 4.7.0
-     * @category Math
-     * @param {number} multiplier The first number in a multiplication.
-     * @param {number} multiplicand The second number in a multiplication.
-     * @returns {number} Returns the product.
+     * @since 3.0.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is an error object, else `false`.
      * @example
      *
-     * _.multiply(6, 4);
-     * // => 24
+     * _.isError(new Error);
+     * // => true
+     *
+     * _.isError(Error);
+     * // => false
      */
-    var multiply = createMathOperation(function(multiplier, multiplicand) {
-      return multiplier * multiplicand;
-    });
+    function isError(value) {
+      if (!isObjectLike(value)) {
+        return false;
+      }
+      var tag = baseGetTag(value);
+      return tag == errorTag || tag == domExcTag ||
+        (typeof value.message == 'string' && typeof value.name == 'string' && !isPlainObject(value));
+    }
 
     /**
-     * Computes `number` rounded to `precision`.
+     * Checks if `value` is a finite primitive number.
+     *
+     * **Note:** This method is based on
+     * [`Number.isFinite`](https://mdn.io/Number/isFinite).
      *
      * @static
      * @memberOf _
-     * @since 3.10.0
-     * @category Math
-     * @param {number} number The number to round.
-     * @param {number} [precision=0] The precision to round to.
-     * @returns {number} Returns the rounded number.
+     * @since 0.1.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a finite number, else `false`.
      * @example
      *
-     * _.round(4.006);
-     * // => 4
+     * _.isFinite(3);
+     * // => true
      *
-     * _.round(4.006, 2);
-     * // => 4.01
+     * _.isFinite(Number.MIN_VALUE);
+     * // => true
      *
-     * _.round(4060, -2);
-     * // => 4100
+     * _.isFinite(Infinity);
+     * // => false
+     *
+     * _.isFinite('3');
+     * // => false
      */
-    var round = createRound('round');
+    function isFinite(value) {
+      return typeof value == 'number' && nativeIsFinite(value);
+    }
 
     /**
-     * Subtract two numbers.
+     * Checks if `value` is classified as a `Function` object.
      *
      * @static
      * @memberOf _
-     * @since 4.0.0
-     * @category Math
-     * @param {number} minuend The first number in a subtraction.
-     * @param {number} subtrahend The second number in a subtraction.
-     * @returns {number} Returns the difference.
+     * @since 0.1.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a function, else `false`.
      * @example
      *
-     * _.subtract(6, 4);
-     * // => 2
+     * _.isFunction(_);
+     * // => true
+     *
+     * _.isFunction(/abc/);
+     * // => false
      */
-    var subtract = createMathOperation(function(minuend, subtrahend) {
-      return minuend - subtrahend;
-    });
+    function isFunction(value) {
+      if (!isObject(value)) {
+        return false;
+      }
+      // The use of `Object#toString` avoids issues with the `typeof` operator
+      // in Safari 9 which returns 'object' for typed arrays and other constructors.
+      var tag = baseGetTag(value);
+      return tag == funcTag || tag == genTag || tag == asyncTag || tag == proxyTag;
+    }
 
     /**
-     * Computes the sum of the values in `array`.
+     * Checks if `value` is an integer.
+     *
+     * **Note:** This method is based on
+     * [`Number.isInteger`](https://mdn.io/Number/isInteger).
      *
      * @static
      * @memberOf _
-     * @since 3.4.0
-     * @category Math
-     * @param {Array} array The array to iterate over.
-     * @returns {number} Returns the sum.
+     * @since 4.0.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is an integer, else `false`.
      * @example
      *
-     * _.sum([4, 2, 8, 6]);
-     * // => 20
+     * _.isInteger(3);
+     * // => true
+     *
+     * _.isInteger(Number.MIN_VALUE);
+     * // => false
+     *
+     * _.isInteger(Infinity);
+     * // => false
+     *
+     * _.isInteger('3');
+     * // => false
      */
-    function sum(array) {
-      return (array && array.length)
-        ? baseSum(array, identity)
-        : 0;
+    function isInteger(value) {
+      return typeof value == 'number' && value == toInteger(value);
     }
 
     /**
-     * This method is like `_.sum` except that it accepts `iteratee` which is
-     * invoked for each element in `array` to generate the value to be summed.
-     * The iteratee is invoked with one argument: (value).
+     * Checks if `value` is a valid array-like length.
+     *
+     * **Note:** This method is loosely based on
+     * [`ToLength`](http://ecma-international.org/ecma-262/7.0/#sec-tolength).
      *
      * @static
      * @memberOf _
      * @since 4.0.0
-     * @category Math
-     * @param {Array} array The array to iterate over.
-     * @param {Array|Function|Object|string} [iteratee=_.identity]
-     *  The iteratee invoked per element.
-     * @returns {number} Returns the sum.
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a valid length, else `false`.
      * @example
      *
-     * var objects = [{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }];
+     * _.isLength(3);
+     * // => true
      *
-     * _.sumBy(objects, function(o) { return o.n; });
-     * // => 20
+     * _.isLength(Number.MIN_VALUE);
+     * // => false
      *
-     * // The `_.property` iteratee shorthand.
-     * _.sumBy(objects, 'n');
-     * // => 20
+     * _.isLength(Infinity);
+     * // => false
+     *
+     * _.isLength('3');
+     * // => false
      */
-    function sumBy(array, iteratee) {
-      return (array && array.length)
-        ? baseSum(array, getIteratee(iteratee))
-        : 0;
+    function isLength(value) {
+      return typeof value == 'number' &&
+        value > -1 && value % 1 == 0 && value <= MAX_SAFE_INTEGER;
     }
 
-    /*------------------------------------------------------------------------*/
-
-    // Add methods that return wrapped values in chain sequences.
-    lodash.after = after;
-    lodash.ary = ary;
-    lodash.assign = assign;
-    lodash.assignIn = assignIn;
-    lodash.assignInWith = assignInWith;
-    lodash.assignWith = assignWith;
-    lodash.at = at;
-    lodash.before = before;
-    lodash.bind = bind;
-    lodash.bindAll = bindAll;
-    lodash.bindKey = bindKey;
-    lodash.castArray = castArray;
-    lodash.chain = chain;
-    lodash.chunk = chunk;
-    lodash.compact = compact;
-    lodash.concat = concat;
-    lodash.cond = cond;
-    lodash.conforms = conforms;
-    lodash.constant = constant;
-    lodash.countBy = countBy;
-    lodash.create = create;
-    lodash.curry = curry;
-    lodash.curryRight = curryRight;
-    lodash.debounce = debounce;
-    lodash.defaults = defaults;
-    lodash.defaultsDeep = defaultsDeep;
-    lodash.defer = defer;
-    lodash.delay = delay;
-    lodash.difference = difference;
-    lodash.differenceBy = differenceBy;
-    lodash.differenceWith = differenceWith;
-    lodash.drop = drop;
-    lodash.dropRight = dropRight;
-    lodash.dropRightWhile = dropRightWhile;
-    lodash.dropWhile = dropWhile;
-    lodash.fill = fill;
-    lodash.filter = filter;
-    lodash.flatMap = flatMap;
-    lodash.flatMapDeep = flatMapDeep;
-    lodash.flatMapDepth = flatMapDepth;
-    lodash.flatten = flatten;
-    lodash.flattenDeep = flattenDeep;
-    lodash.flattenDepth = flattenDepth;
-    lodash.flip = flip;
-    lodash.flow = flow;
-    lodash.flowRight = flowRight;
-    lodash.fromPairs = fromPairs;
-    lodash.functions = functions;
-    lodash.functionsIn = functionsIn;
-    lodash.groupBy = groupBy;
-    lodash.initial = initial;
-    lodash.intersection = intersection;
-    lodash.intersectionBy = intersectionBy;
-    lodash.intersectionWith = intersectionWith;
-    lodash.invert = invert;
-    lodash.invertBy = invertBy;
-    lodash.invokeMap = invokeMap;
-    lodash.iteratee = iteratee;
-    lodash.keyBy = keyBy;
-    lodash.keys = keys;
-    lodash.keysIn = keysIn;
-    lodash.map = map;
-    lodash.mapKeys = mapKeys;
-    lodash.mapValues = mapValues;
-    lodash.matches = matches;
-    lodash.matchesProperty = matchesProperty;
-    lodash.memoize = memoize;
-    lodash.merge = merge;
-    lodash.mergeWith = mergeWith;
-    lodash.method = method;
-    lodash.methodOf = methodOf;
-    lodash.mixin = mixin;
-    lodash.negate = negate;
-    lodash.nthArg = nthArg;
-    lodash.omit = omit;
-    lodash.omitBy = omitBy;
-    lodash.once = once;
-    lodash.orderBy = orderBy;
-    lodash.over = over;
-    lodash.overArgs = overArgs;
-    lodash.overEvery = overEvery;
-    lodash.overSome = overSome;
-    lodash.partial = partial;
-    lodash.partialRight = partialRight;
-    lodash.partition = partition;
-    lodash.pick = pick;
-    lodash.pickBy = pickBy;
-    lodash.property = property;
-    lodash.propertyOf = propertyOf;
-    lodash.pull = pull;
-    lodash.pullAll = pullAll;
-    lodash.pullAllBy = pullAllBy;
-    lodash.pullAllWith = pullAllWith;
-    lodash.pullAt = pullAt;
-    lodash.range = range;
-    lodash.rangeRight = rangeRight;
-    lodash.rearg = rearg;
-    lodash.reject = reject;
-    lodash.remove = remove;
-    lodash.rest = rest;
-    lodash.reverse = reverse;
-    lodash.sampleSize = sampleSize;
-    lodash.set = set;
-    lodash.setWith = setWith;
-    lodash.shuffle = shuffle;
-    lodash.slice = slice;
-    lodash.sortBy = sortBy;
-    lodash.sortedUniq = sortedUniq;
-    lodash.sortedUniqBy = sortedUniqBy;
-    lodash.split = split;
-    lodash.spread = spread;
-    lodash.tail = tail;
-    lodash.take = take;
-    lodash.takeRight = takeRight;
-    lodash.takeRightWhile = takeRightWhile;
-    lodash.takeWhile = takeWhile;
-    lodash.tap = tap;
-    lodash.throttle = throttle;
-    lodash.thru = thru;
-    lodash.toArray = toArray;
-    lodash.toPairs = toPairs;
-    lodash.toPairsIn = toPairsIn;
-    lodash.toPath = toPath;
-    lodash.toPlainObject = toPlainObject;
-    lodash.transform = transform;
-    lodash.unary = unary;
-    lodash.union = union;
-    lodash.unionBy = unionBy;
-    lodash.unionWith = unionWith;
-    lodash.uniq = uniq;
-    lodash.uniqBy = uniqBy;
-    lodash.uniqWith = uniqWith;
-    lodash.unset = unset;
-    lodash.unzip = unzip;
-    lodash.unzipWith = unzipWith;
-    lodash.update = update;
-    lodash.updateWith = updateWith;
-    lodash.values = values;
-    lodash.valuesIn = valuesIn;
-    lodash.without = without;
-    lodash.words = words;
-    lodash.wrap = wrap;
-    lodash.xor = xor;
-    lodash.xorBy = xorBy;
-    lodash.xorWith = xorWith;
-    lodash.zip = zip;
-    lodash.zipObject = zipObject;
-    lodash.zipObjectDeep = zipObjectDeep;
-    lodash.zipWith = zipWith;
-
-    // Add aliases.
-    lodash.entries = toPairs;
-    lodash.entriesIn = toPairsIn;
-    lodash.extend = assignIn;
-    lodash.extendWith = assignInWith;
-
-    // Add methods to `lodash.prototype`.
-    mixin(lodash, lodash);
-
-    /*------------------------------------------------------------------------*/
-
-    // Add methods that return unwrapped values in chain sequences.
-    lodash.add = add;
-    lodash.attempt = attempt;
-    lodash.camelCase = camelCase;
-    lodash.capitalize = capitalize;
-    lodash.ceil = ceil;
-    lodash.clamp = clamp;
-    lodash.clone = clone;
-    lodash.cloneDeep = cloneDeep;
-    lodash.cloneDeepWith = cloneDeepWith;
-    lodash.cloneWith = cloneWith;
-    lodash.deburr = deburr;
-    lodash.divide = divide;
-    lodash.endsWith = endsWith;
-    lodash.eq = eq;
-    lodash.escape = escape;
-    lodash.escapeRegExp = escapeRegExp;
-    lodash.every = every;
-    lodash.find = find;
-    lodash.findIndex = findIndex;
-    lodash.findKey = findKey;
-    lodash.findLast = findLast;
-    lodash.findLastIndex = findLastIndex;
-    lodash.findLastKey = findLastKey;
-    lodash.floor = floor;
-    lodash.forEach = forEach;
-    lodash.forEachRight = forEachRight;
-    lodash.forIn = forIn;
-    lodash.forInRight = forInRight;
-    lodash.forOwn = forOwn;
-    lodash.forOwnRight = forOwnRight;
-    lodash.get = get;
-    lodash.gt = gt;
-    lodash.gte = gte;
-    lodash.has = has;
-    lodash.hasIn = hasIn;
-    lodash.head = head;
-    lodash.identity = identity;
-    lodash.includes = includes;
-    lodash.indexOf = indexOf;
-    lodash.inRange = inRange;
-    lodash.invoke = invoke;
-    lodash.isArguments = isArguments;
-    lodash.isArray = isArray;
-    lodash.isArrayBuffer = isArrayBuffer;
-    lodash.isArrayLike = isArrayLike;
-    lodash.isArrayLikeObject = isArrayLikeObject;
-    lodash.isBoolean = isBoolean;
-    lodash.isBuffer = isBuffer;
-    lodash.isDate = isDate;
-    lodash.isElement = isElement;
-    lodash.isEmpty = isEmpty;
-    lodash.isEqual = isEqual;
-    lodash.isEqualWith = isEqualWith;
-    lodash.isError = isError;
-    lodash.isFinite = isFinite;
-    lodash.isFunction = isFunction;
-    lodash.isInteger = isInteger;
-    lodash.isLength = isLength;
-    lodash.isMap = isMap;
-    lodash.isMatch = isMatch;
-    lodash.isMatchWith = isMatchWith;
-    lodash.isNaN = isNaN;
-    lodash.isNative = isNative;
-    lodash.isNil = isNil;
-    lodash.isNull = isNull;
-    lodash.isNumber = isNumber;
-    lodash.isObject = isObject;
-    lodash.isObjectLike = isObjectLike;
-    lodash.isPlainObject = isPlainObject;
-    lodash.isRegExp = isRegExp;
-    lodash.isSafeInteger = isSafeInteger;
-    lodash.isSet = isSet;
-    lodash.isString = isString;
-    lodash.isSymbol = isSymbol;
-    lodash.isTypedArray = isTypedArray;
-    lodash.isUndefined = isUndefined;
-    lodash.isWeakMap = isWeakMap;
-    lodash.isWeakSet = isWeakSet;
-    lodash.join = join;
-    lodash.kebabCase = kebabCase;
-    lodash.last = last;
-    lodash.lastIndexOf = lastIndexOf;
-    lodash.lowerCase = lowerCase;
-    lodash.lowerFirst = lowerFirst;
-    lodash.lt = lt;
-    lodash.lte = lte;
-    lodash.max = max;
-    lodash.maxBy = maxBy;
-    lodash.mean = mean;
-    lodash.meanBy = meanBy;
-    lodash.min = min;
-    lodash.minBy = minBy;
-    lodash.stubArray = stubArray;
-    lodash.stubFalse = stubFalse;
-    lodash.stubObject = stubObject;
-    lodash.stubString = stubString;
-    lodash.stubTrue = stubTrue;
-    lodash.multiply = multiply;
-    lodash.nth = nth;
-    lodash.noConflict = noConflict;
-    lodash.noop = noop;
-    lodash.now = now;
-    lodash.pad = pad;
-    lodash.padEnd = padEnd;
-    lodash.padStart = padStart;
-    lodash.parseInt = parseInt;
-    lodash.random = random;
-    lodash.reduce = reduce;
-    lodash.reduceRight = reduceRight;
-    lodash.repeat = repeat;
-    lodash.replace = replace;
-    lodash.result = result;
-    lodash.round = round;
-    lodash.runInContext = runInContext;
-    lodash.sample = sample;
-    lodash.size = size;
-    lodash.snakeCase = snakeCase;
-    lodash.some = some;
-    lodash.sortedIndex = sortedIndex;
-    lodash.sortedIndexBy = sortedIndexBy;
-    lodash.sortedIndexOf = sortedIndexOf;
-    lodash.sortedLastIndex = sortedLastIndex;
-    lodash.sortedLastIndexBy = sortedLastIndexBy;
-    lodash.sortedLastIndexOf = sortedLastIndexOf;
-    lodash.startCase = startCase;
-    lodash.startsWith = startsWith;
-    lodash.subtract = subtract;
-    lodash.sum = sum;
-    lodash.sumBy = sumBy;
-    lodash.template = template;
-    lodash.times = times;
-    lodash.toFinite = toFinite;
-    lodash.toInteger = toInteger;
-    lodash.toLength = toLength;
-    lodash.toLower = toLower;
-    lodash.toNumber = toNumber;
-    lodash.toSafeInteger = toSafeInteger;
-    lodash.toString = toString;
-    lodash.toUpper = toUpper;
-    lodash.trim = trim;
-    lodash.trimEnd = trimEnd;
-    lodash.trimStart = trimStart;
-    lodash.truncate = truncate;
-    lodash.unescape = unescape;
-    lodash.uniqueId = uniqueId;
-    lodash.upperCase = upperCase;
-    lodash.upperFirst = upperFirst;
-
-    // Add aliases.
-    lodash.each = forEach;
-    lodash.eachRight = forEachRight;
-    lodash.first = head;
-
-    mixin(lodash, (function() {
-      var source = {};
-      baseForOwn(lodash, function(func, methodName) {
-        if (!hasOwnProperty.call(lodash.prototype, methodName)) {
-          source[methodName] = func;
-        }
-      });
-      return source;
-    }()), { 'chain': false });
-
-    /*------------------------------------------------------------------------*/
+    /**
+     * Checks if `value` is the
+     * [language type](http://www.ecma-international.org/ecma-262/7.0/#sec-ecmascript-language-types)
+     * of `Object`. (e.g. arrays, functions, objects, regexes, `new Number(0)`, and `new String('')`)
+     *
+     * @static
+     * @memberOf _
+     * @since 0.1.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is an object, else `false`.
+     * @example
+     *
+     * _.isObject({});
+     * // => true
+     *
+     * _.isObject([1, 2, 3]);
+     * // => true
+     *
+     * _.isObject(_.noop);
+     * // => true
+     *
+     * _.isObject(null);
+     * // => false
+     */
+    function isObject(value) {
+      var type = typeof value;
+      return value != null && (type == 'object' || type == 'function');
+    }
 
     /**
-     * The semantic version number.
+     * Checks if `value` is object-like. A value is object-like if it's not `null`
+     * and has a `typeof` result of "object".
      *
      * @static
      * @memberOf _
-     * @type {string}
+     * @since 4.0.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is object-like, else `false`.
+     * @example
+     *
+     * _.isObjectLike({});
+     * // => true
+     *
+     * _.isObjectLike([1, 2, 3]);
+     * // => true
+     *
+     * _.isObjectLike(_.noop);
+     * // => false
+     *
+     * _.isObjectLike(null);
+     * // => false
      */
-    lodash.VERSION = VERSION;
-
-    // Assign default placeholders.
-    arrayEach(['bind', 'bindKey', 'curry', 'curryRight', 'partial', 'partialRight'], function(methodName) {
-      lodash[methodName].placeholder = lodash;
-    });
-
-    // Add `LazyWrapper` methods for `_.drop` and `_.take` variants.
-    arrayEach(['drop', 'take'], function(methodName, index) {
-      LazyWrapper.prototype[methodName] = function(n) {
-        var filtered = this.__filtered__;
-        if (filtered && !index) {
-          return new LazyWrapper(this);
-        }
-        n = n === undefined ? 1 : nativeMax(toInteger(n), 0);
-
-        var result = this.clone();
-        if (filtered) {
-          result.__takeCount__ = nativeMin(n, result.__takeCount__);
-        } else {
-          result.__views__.push({
-            'size': nativeMin(n, MAX_ARRAY_LENGTH),
-            'type': methodName + (result.__dir__ < 0 ? 'Right' : '')
-          });
-        }
-        return result;
-      };
+    function isObjectLike(value) {
+      return value != null && typeof value == 'object';
+    }
 
-      LazyWrapper.prototype[methodName + 'Right'] = function(n) {
-        return this.reverse()[methodName](n).reverse();
-      };
-    });
+    /**
+     * Checks if `value` is classified as a `Map` object.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.3.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a map, else `false`.
+     * @example
+     *
+     * _.isMap(new Map);
+     * // => true
+     *
+     * _.isMap(new WeakMap);
+     * // => false
+     */
+    var isMap = nodeIsMap ? baseUnary(nodeIsMap) : baseIsMap;
 
-    // Add `LazyWrapper` methods that accept an `iteratee` value.
-    arrayEach(['filter', 'map', 'takeWhile'], function(methodName, index) {
-      var type = index + 1,
-          isFilter = type == LAZY_FILTER_FLAG || type == LAZY_WHILE_FLAG;
+    /**
+     * Performs a partial deep comparison between `object` and `source` to
+     * determine if `object` contains equivalent property values.
+     *
+     * **Note:** This method is equivalent to `_.matches` when `source` is
+     * partially applied.
+     *
+     * Partial comparisons will match empty array and empty object `source`
+     * values against any array or object value, respectively. See `_.isEqual`
+     * for a list of supported value comparisons.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category Lang
+     * @param {Object} object The object to inspect.
+     * @param {Object} source The object of property values to match.
+     * @returns {boolean} Returns `true` if `object` is a match, else `false`.
+     * @example
+     *
+     * var object = { 'a': 1, 'b': 2 };
+     *
+     * _.isMatch(object, { 'b': 2 });
+     * // => true
+     *
+     * _.isMatch(object, { 'b': 1 });
+     * // => false
+     */
+    function isMatch(object, source) {
+      return object === source || baseIsMatch(object, source, getMatchData(source));
+    }
 
-      LazyWrapper.prototype[methodName] = function(iteratee) {
-        var result = this.clone();
-        result.__iteratees__.push({
-          'iteratee': getIteratee(iteratee, 3),
-          'type': type
-        });
-        result.__filtered__ = result.__filtered__ || isFilter;
-        return result;
-      };
-    });
-
-    // Add `LazyWrapper` methods for `_.head` and `_.last`.
-    arrayEach(['head', 'last'], function(methodName, index) {
-      var takeName = 'take' + (index ? 'Right' : '');
-
-      LazyWrapper.prototype[methodName] = function() {
-        return this[takeName](1).value()[0];
-      };
-    });
-
-    // Add `LazyWrapper` methods for `_.initial` and `_.tail`.
-    arrayEach(['initial', 'tail'], function(methodName, index) {
-      var dropName = 'drop' + (index ? '' : 'Right');
-
-      LazyWrapper.prototype[methodName] = function() {
-        return this.__filtered__ ? new LazyWrapper(this) : this[dropName](1);
-      };
-    });
-
-    LazyWrapper.prototype.compact = function() {
-      return this.filter(identity);
-    };
-
-    LazyWrapper.prototype.find = function(predicate) {
-      return this.filter(predicate).head();
-    };
+    /**
+     * This method is like `_.isMatch` except that it accepts `customizer` which
+     * is invoked to compare values. If `customizer` returns `undefined`, comparisons
+     * are handled by the method instead. The `customizer` is invoked with five
+     * arguments: (objValue, srcValue, index|key, object, source).
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Lang
+     * @param {Object} object The object to inspect.
+     * @param {Object} source The object of property values to match.
+     * @param {Function} [customizer] The function to customize comparisons.
+     * @returns {boolean} Returns `true` if `object` is a match, else `false`.
+     * @example
+     *
+     * function isGreeting(value) {
+     *   return /^h(?:i|ello)$/.test(value);
+     * }
+     *
+     * function customizer(objValue, srcValue) {
+     *   if (isGreeting(objValue) && isGreeting(srcValue)) {
+     *     return true;
+     *   }
+     * }
+     *
+     * var object = { 'greeting': 'hello' };
+     * var source = { 'greeting': 'hi' };
+     *
+     * _.isMatchWith(object, source, customizer);
+     * // => true
+     */
+    function isMatchWith(object, source, customizer) {
+      customizer = typeof customizer == 'function' ? customizer : undefined;
+      return baseIsMatch(object, source, getMatchData(source), customizer);
+    }
 
-    LazyWrapper.prototype.findLast = function(predicate) {
-      return this.reverse().find(predicate);
-    };
+    /**
+     * Checks if `value` is `NaN`.
+     *
+     * **Note:** This method is based on
+     * [`Number.isNaN`](https://mdn.io/Number/isNaN) and is not the same as
+     * global [`isNaN`](https://mdn.io/isNaN) which returns `true` for
+     * `undefined` and other non-number values.
+     *
+     * @static
+     * @memberOf _
+     * @since 0.1.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is `NaN`, else `false`.
+     * @example
+     *
+     * _.isNaN(NaN);
+     * // => true
+     *
+     * _.isNaN(new Number(NaN));
+     * // => true
+     *
+     * isNaN(undefined);
+     * // => true
+     *
+     * _.isNaN(undefined);
+     * // => false
+     */
+    function isNaN(value) {
+      // An `NaN` primitive is the only value that is not equal to itself.
+      // Perform the `toStringTag` check first to avoid errors with some
+      // ActiveX objects in IE.
+      return isNumber(value) && value != +value;
+    }
 
-    LazyWrapper.prototype.invokeMap = rest(function(path, args) {
-      if (typeof path == 'function') {
-        return new LazyWrapper(this);
+    /**
+     * Checks if `value` is a pristine native function.
+     *
+     * **Note:** This method can't reliably detect native functions in the presence
+     * of the core-js package because core-js circumvents this kind of detection.
+     * Despite multiple requests, the core-js maintainer has made it clear: any
+     * attempt to fix the detection will be obstructed. As a result, we're left
+     * with little choice but to throw an error. Unfortunately, this also affects
+     * packages, like [babel-polyfill](https://www.npmjs.com/package/babel-polyfill),
+     * which rely on core-js.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a native function,
+     *  else `false`.
+     * @example
+     *
+     * _.isNative(Array.prototype.push);
+     * // => true
+     *
+     * _.isNative(_);
+     * // => false
+     */
+    function isNative(value) {
+      if (isMaskable(value)) {
+        throw new Error(CORE_ERROR_TEXT);
       }
-      return this.map(function(value) {
-        return baseInvoke(value, path, args);
-      });
-    });
+      return baseIsNative(value);
+    }
 
-    LazyWrapper.prototype.reject = function(predicate) {
-      predicate = getIteratee(predicate, 3);
-      return this.filter(function(value) {
-        return !predicate(value);
-      });
-    };
+    /**
+     * Checks if `value` is `null`.
+     *
+     * @static
+     * @memberOf _
+     * @since 0.1.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is `null`, else `false`.
+     * @example
+     *
+     * _.isNull(null);
+     * // => true
+     *
+     * _.isNull(void 0);
+     * // => false
+     */
+    function isNull(value) {
+      return value === null;
+    }
 
-    LazyWrapper.prototype.slice = function(start, end) {
-      start = toInteger(start);
+    /**
+     * Checks if `value` is `null` or `undefined`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is nullish, else `false`.
+     * @example
+     *
+     * _.isNil(null);
+     * // => true
+     *
+     * _.isNil(void 0);
+     * // => true
+     *
+     * _.isNil(NaN);
+     * // => false
+     */
+    function isNil(value) {
+      return value == null;
+    }
 
-      var result = this;
-      if (result.__filtered__ && (start > 0 || end < 0)) {
-        return new LazyWrapper(result);
+    /**
+     * Checks if `value` is classified as a `Number` primitive or object.
+     *
+     * **Note:** To exclude `Infinity`, `-Infinity`, and `NaN`, which are
+     * classified as numbers, use the `_.isFinite` method.
+     *
+     * @static
+     * @memberOf _
+     * @since 0.1.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a number, else `false`.
+     * @example
+     *
+     * _.isNumber(3);
+     * // => true
+     *
+     * _.isNumber(Number.MIN_VALUE);
+     * // => true
+     *
+     * _.isNumber(Infinity);
+     * // => true
+     *
+     * _.isNumber('3');
+     * // => false
+     */
+    function isNumber(value) {
+      return typeof value == 'number' ||
+        (isObjectLike(value) && baseGetTag(value) == numberTag);
+    }
+
+    /**
+     * Checks if `value` is a plain object, that is, an object created by the
+     * `Object` constructor or one with a `[[Prototype]]` of `null`.
+     *
+     * @static
+     * @memberOf _
+     * @since 0.8.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a plain object, else `false`.
+     * @example
+     *
+     * function Foo() {
+     *   this.a = 1;
+     * }
+     *
+     * _.isPlainObject(new Foo);
+     * // => false
+     *
+     * _.isPlainObject([1, 2, 3]);
+     * // => false
+     *
+     * _.isPlainObject({ 'x': 0, 'y': 0 });
+     * // => true
+     *
+     * _.isPlainObject(Object.create(null));
+     * // => true
+     */
+    function isPlainObject(value) {
+      if (!isObjectLike(value) || baseGetTag(value) != objectTag) {
+        return false;
       }
-      if (start < 0) {
-        result = result.takeRight(-start);
-      } else if (start) {
-        result = result.drop(start);
+      var proto = getPrototype(value);
+      if (proto === null) {
+        return true;
       }
-      if (end !== undefined) {
-        end = toInteger(end);
-        result = end < 0 ? result.dropRight(-end) : result.take(end - start);
-      }
-      return result;
-    };
-
-    LazyWrapper.prototype.takeRightWhile = function(predicate) {
-      return this.reverse().takeWhile(predicate).reverse();
-    };
-
-    LazyWrapper.prototype.toArray = function() {
-      return this.take(MAX_ARRAY_LENGTH);
-    };
-
-    // Add `LazyWrapper` methods to `lodash.prototype`.
-    baseForOwn(LazyWrapper.prototype, function(func, methodName) {
-      var checkIteratee = /^(?:filter|find|map|reject)|While$/.test(methodName),
-          isTaker = /^(?:head|last)$/.test(methodName),
-          lodashFunc = lodash[isTaker ? ('take' + (methodName == 'last' ? 'Right' : '')) : methodName],
-          retUnwrapped = isTaker || /^find/.test(methodName);
-
-      if (!lodashFunc) {
-        return;
-      }
-      lodash.prototype[methodName] = function() {
-        var value = this.__wrapped__,
-            args = isTaker ? [1] : arguments,
-            isLazy = value instanceof LazyWrapper,
-            iteratee = args[0],
-            useLazy = isLazy || isArray(value);
-
-        var interceptor = function(value) {
-          var result = lodashFunc.apply(lodash, arrayPush([value], args));
-          return (isTaker && chainAll) ? result[0] : result;
-        };
-
-        if (useLazy && checkIteratee && typeof iteratee == 'function' && iteratee.length != 1) {
-          // Avoid lazy use if the iteratee has a "length" value other than `1`.
-          isLazy = useLazy = false;
-        }
-        var chainAll = this.__chain__,
-            isHybrid = !!this.__actions__.length,
-            isUnwrapped = retUnwrapped && !chainAll,
-            onlyLazy = isLazy && !isHybrid;
-
-        if (!retUnwrapped && useLazy) {
-          value = onlyLazy ? value : new LazyWrapper(this);
-          var result = func.apply(value, args);
-          result.__actions__.push({ 'func': thru, 'args': [interceptor], 'thisArg': undefined });
-          return new LodashWrapper(result, chainAll);
-        }
-        if (isUnwrapped && onlyLazy) {
-          return func.apply(this, args);
-        }
-        result = this.thru(interceptor);
-        return isUnwrapped ? (isTaker ? result.value()[0] : result.value()) : result;
-      };
-    });
-
-    // Add `Array` methods to `lodash.prototype`.
-    arrayEach(['pop', 'push', 'shift', 'sort', 'splice', 'unshift'], function(methodName) {
-      var func = arrayProto[methodName],
-          chainName = /^(?:push|sort|unshift)$/.test(methodName) ? 'tap' : 'thru',
-          retUnwrapped = /^(?:pop|shift)$/.test(methodName);
+      var Ctor = hasOwnProperty.call(proto, 'constructor') && proto.constructor;
+      return typeof Ctor == 'function' && Ctor instanceof Ctor &&
+        funcToString.call(Ctor) == objectCtorString;
+    }
 
-      lodash.prototype[methodName] = function() {
-        var args = arguments;
-        if (retUnwrapped && !this.__chain__) {
-          var value = this.value();
-          return func.apply(isArray(value) ? value : [], args);
-        }
-        return this[chainName](function(value) {
-          return func.apply(isArray(value) ? value : [], args);
-        });
-      };
-    });
+    /**
+     * Checks if `value` is classified as a `RegExp` object.
+     *
+     * @static
+     * @memberOf _
+     * @since 0.1.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a regexp, else `false`.
+     * @example
+     *
+     * _.isRegExp(/abc/);
+     * // => true
+     *
+     * _.isRegExp('/abc/');
+     * // => false
+     */
+    var isRegExp = nodeIsRegExp ? baseUnary(nodeIsRegExp) : baseIsRegExp;
 
-    // Map minified method names to their real names.
-    baseForOwn(LazyWrapper.prototype, function(func, methodName) {
-      var lodashFunc = lodash[methodName];
-      if (lodashFunc) {
-        var key = (lodashFunc.name + ''),
-            names = realNames[key] || (realNames[key] = []);
+    /**
+     * Checks if `value` is a safe integer. An integer is safe if it's an IEEE-754
+     * double precision number which isn't the result of a rounded unsafe integer.
+     *
+     * **Note:** This method is based on
+     * [`Number.isSafeInteger`](https://mdn.io/Number/isSafeInteger).
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a safe integer, else `false`.
+     * @example
+     *
+     * _.isSafeInteger(3);
+     * // => true
+     *
+     * _.isSafeInteger(Number.MIN_VALUE);
+     * // => false
+     *
+     * _.isSafeInteger(Infinity);
+     * // => false
+     *
+     * _.isSafeInteger('3');
+     * // => false
+     */
+    function isSafeInteger(value) {
+      return isInteger(value) && value >= -MAX_SAFE_INTEGER && value <= MAX_SAFE_INTEGER;
+    }
 
-        names.push({ 'name': methodName, 'func': lodashFunc });
-      }
-    });
+    /**
+     * Checks if `value` is classified as a `Set` object.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.3.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a set, else `false`.
+     * @example
+     *
+     * _.isSet(new Set);
+     * // => true
+     *
+     * _.isSet(new WeakSet);
+     * // => false
+     */
+    var isSet = nodeIsSet ? baseUnary(nodeIsSet) : baseIsSet;
 
-    realNames[createHybridWrapper(undefined, BIND_KEY_FLAG).name] = [{
-      'name': 'wrapper',
-      'func': undefined
-    }];
+    /**
+     * Checks if `value` is classified as a `String` primitive or object.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a string, else `false`.
+     * @example
+     *
+     * _.isString('abc');
+     * // => true
+     *
+     * _.isString(1);
+     * // => false
+     */
+    function isString(value) {
+      return typeof value == 'string' ||
+        (!isArray(value) && isObjectLike(value) && baseGetTag(value) == stringTag);
+    }
 
-    // Add methods to `LazyWrapper`.
-    LazyWrapper.prototype.clone = lazyClone;
-    LazyWrapper.prototype.reverse = lazyReverse;
-    LazyWrapper.prototype.value = lazyValue;
+    /**
+     * Checks if `value` is classified as a `Symbol` primitive or object.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a symbol, else `false`.
+     * @example
+     *
+     * _.isSymbol(Symbol.iterator);
+     * // => true
+     *
+     * _.isSymbol('abc');
+     * // => false
+     */
+    function isSymbol(value) {
+      return typeof value == 'symbol' ||
+        (isObjectLike(value) && baseGetTag(value) == symbolTag);
+    }
 
-    // Add chain sequence methods to the `lodash` wrapper.
-    lodash.prototype.at = wrapperAt;
-    lodash.prototype.chain = wrapperChain;
-    lodash.prototype.commit = wrapperCommit;
-    lodash.prototype.next = wrapperNext;
-    lodash.prototype.plant = wrapperPlant;
-    lodash.prototype.reverse = wrapperReverse;
-    lodash.prototype.toJSON = lodash.prototype.valueOf = lodash.prototype.value = wrapperValue;
+    /**
+     * Checks if `value` is classified as a typed array.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a typed array, else `false`.
+     * @example
+     *
+     * _.isTypedArray(new Uint8Array);
+     * // => true
+     *
+     * _.isTypedArray([]);
+     * // => false
+     */
+    var isTypedArray = nodeIsTypedArray ? baseUnary(nodeIsTypedArray) : baseIsTypedArray;
 
-    if (iteratorSymbol) {
-      lodash.prototype[iteratorSymbol] = wrapperToIterator;
+    /**
+     * Checks if `value` is `undefined`.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is `undefined`, else `false`.
+     * @example
+     *
+     * _.isUndefined(void 0);
+     * // => true
+     *
+     * _.isUndefined(null);
+     * // => false
+     */
+    function isUndefined(value) {
+      return value === undefined;
     }
-    return lodash;
-  }
 
-  /*--------------------------------------------------------------------------*/
+    /**
+     * Checks if `value` is classified as a `WeakMap` object.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.3.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a weak map, else `false`.
+     * @example
+     *
+     * _.isWeakMap(new WeakMap);
+     * // => true
+     *
+     * _.isWeakMap(new Map);
+     * // => false
+     */
+    function isWeakMap(value) {
+      return isObjectLike(value) && getTag(value) == weakMapTag;
+    }
 
-  // Export lodash.
-  var _ = runInContext();
+    /**
+     * Checks if `value` is classified as a `WeakSet` object.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.3.0
+     * @category Lang
+     * @param {*} value The value to check.
+     * @returns {boolean} Returns `true` if `value` is a weak set, else `false`.
+     * @example
+     *
+     * _.isWeakSet(new WeakSet);
+     * // => true
+     *
+     * _.isWeakSet(new Set);
+     * // => false
+     */
+    function isWeakSet(value) {
+      return isObjectLike(value) && baseGetTag(value) == weakSetTag;
+    }
 
-  // Expose Lodash on the free variable `window` or `self` when available so it's
-  // globally accessible, even when bundled with Browserify, Webpack, etc. This
-  // also prevents errors in cases where Lodash is loaded by a script tag in the
-  // presence of an AMD loader. See http://requirejs.org/docs/errors.html#mismatch
-  // for more details. Use `_.noConflict` to remove Lodash from the global object.
-  (freeSelf || {})._ = _;
+    /**
+     * Checks if `value` is less than `other`.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.9.0
+     * @category Lang
+     * @param {*} value The value to compare.
+     * @param {*} other The other value to compare.
+     * @returns {boolean} Returns `true` if `value` is less than `other`,
+     *  else `false`.
+     * @see _.gt
+     * @example
+     *
+     * _.lt(1, 3);
+     * // => true
+     *
+     * _.lt(3, 3);
+     * // => false
+     *
+     * _.lt(3, 1);
+     * // => false
+     */
+    var lt = createRelationalOperation(baseLt);
 
-  // Some AMD build optimizers like r.js check for condition patterns like the following:
-  if (typeof define == 'function' && typeof define.amd == 'object' && define.amd) {
-    // Define as an anonymous module so, through path mapping, it can be
-    // referenced as the "underscore" module.
-    define(function() {
-      return _;
+    /**
+     * Checks if `value` is less than or equal to `other`.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.9.0
+     * @category Lang
+     * @param {*} value The value to compare.
+     * @param {*} other The other value to compare.
+     * @returns {boolean} Returns `true` if `value` is less than or equal to
+     *  `other`, else `false`.
+     * @see _.gte
+     * @example
+     *
+     * _.lte(1, 3);
+     * // => true
+     *
+     * _.lte(3, 3);
+     * // => true
+     *
+     * _.lte(3, 1);
+     * // => false
+     */
+    var lte = createRelationalOperation(function(value, other) {
+      return value <= other;
     });
-  }
-  // Check for `exports` after `define` in case a build optimizer adds an `exports` object.
-  else if (freeModule) {
-    // Export for Node.js.
-    (freeModule.exports = _)._ = _;
-    // Export for CommonJS support.
-    freeExports._ = _;
-  }
-  else {
-    // Export to the global object.
-    root._ = _;
-  }
-}.call(this));
-
-}).call(this,typeof global !== "undefined" ? global : typeof self !== "undefined" ? self : typeof window !== "undefined" ? window : {})
-},{}],7:[function(require,module,exports){
-/**
- * MicroEvent - to make any js object an event emitter (server or browser)
- * 
- * - pure javascript - server compatible, browser compatible
- * - dont rely on the browser doms
- * - super simple - you get it immediatly, no mistery, no magic involved
- *
- * - create a MicroEventDebug with goodies to debug
- *   - make it safer to use
-*/
-
-var MicroEvent	= function(){}
-MicroEvent.prototype	= {
-	bind	: function(event, fct){
-		this._events = this._events || {};
-		this._events[event] = this._events[event]	|| [];
-		this._events[event].push(fct);
-	},
-	unbind	: function(event, fct){
-		this._events = this._events || {};
-		if( event in this._events === false  )	return;
-		this._events[event].splice(this._events[event].indexOf(fct), 1);
-	},
-	trigger	: function(event /* , args... */){
-		this._events = this._events || {};
-		if( event in this._events === false  )	return;
-		for(var i = 0; i < this._events[event].length; i++){
-			this._events[event][i].apply(this, Array.prototype.slice.call(arguments, 1))
-		}
-	}
-};
-
-/**
- * mixin will delegate all MicroEvent.js function in the destination object
- *
- * - require('MicroEvent').mixin(Foobar) will make Foobar able to use MicroEvent
- *
- * @param {Object} the object which will support MicroEvent
-*/
-MicroEvent.mixin	= function(destObject){
-	var props	= ['bind', 'unbind', 'trigger'];
-	for(var i = 0; i < props.length; i ++){
-		destObject.prototype[props[i]]	= MicroEvent.prototype[props[i]];
-	}
-}
 
-// export in common js
-if( typeof module !== "undefined" && ('exports' in module)){
-	module.exports	= MicroEvent
-}
+    /**
+     * Converts `value` to an array.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Lang
+     * @param {*} value The value to convert.
+     * @returns {Array} Returns the converted array.
+     * @example
+     *
+     * _.toArray({ 'a': 1, 'b': 2 });
+     * // => [1, 2]
+     *
+     * _.toArray('abc');
+     * // => ['a', 'b', 'c']
+     *
+     * _.toArray(1);
+     * // => []
+     *
+     * _.toArray(null);
+     * // => []
+     */
+    function toArray(value) {
+      if (!value) {
+        return [];
+      }
+      if (isArrayLike(value)) {
+        return isString(value) ? stringToArray(value) : copyArray(value);
+      }
+      if (symIterator && value[symIterator]) {
+        return iteratorToArray(value[symIterator]());
+      }
+      var tag = getTag(value),
+          func = tag == mapTag ? mapToArray : (tag == setTag ? setToArray : values);
 
-},{}],8:[function(require,module,exports){
- /* eslint-env node */
-'use strict';
+      return func(value);
+    }
 
-// SDP helpers.
-var SDPUtils = {};
+    /**
+     * Converts `value` to a finite number.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.12.0
+     * @category Lang
+     * @param {*} value The value to convert.
+     * @returns {number} Returns the converted number.
+     * @example
+     *
+     * _.toFinite(3.2);
+     * // => 3.2
+     *
+     * _.toFinite(Number.MIN_VALUE);
+     * // => 5e-324
+     *
+     * _.toFinite(Infinity);
+     * // => 1.7976931348623157e+308
+     *
+     * _.toFinite('3.2');
+     * // => 3.2
+     */
+    function toFinite(value) {
+      if (!value) {
+        return value === 0 ? value : 0;
+      }
+      value = toNumber(value);
+      if (value === INFINITY || value === -INFINITY) {
+        var sign = (value < 0 ? -1 : 1);
+        return sign * MAX_INTEGER;
+      }
+      return value === value ? value : 0;
+    }
 
-// Generate an alphanumeric identifier for cname or mids.
-// TODO: use UUIDs instead? https://gist.github.com/jed/982883
-SDPUtils.generateIdentifier = function() {
-  return Math.random().toString(36).substr(2, 10);
-};
+    /**
+     * Converts `value` to an integer.
+     *
+     * **Note:** This method is loosely based on
+     * [`ToInteger`](http://www.ecma-international.org/ecma-262/7.0/#sec-tointeger).
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Lang
+     * @param {*} value The value to convert.
+     * @returns {number} Returns the converted integer.
+     * @example
+     *
+     * _.toInteger(3.2);
+     * // => 3
+     *
+     * _.toInteger(Number.MIN_VALUE);
+     * // => 0
+     *
+     * _.toInteger(Infinity);
+     * // => 1.7976931348623157e+308
+     *
+     * _.toInteger('3.2');
+     * // => 3
+     */
+    function toInteger(value) {
+      var result = toFinite(value),
+          remainder = result % 1;
 
-// The RTCP CNAME used by all peerconnections from the same JS.
-SDPUtils.localCName = SDPUtils.generateIdentifier();
+      return result === result ? (remainder ? result - remainder : result) : 0;
+    }
 
-// Splits SDP into lines, dealing with both CRLF and LF.
-SDPUtils.splitLines = function(blob) {
-  return blob.trim().split('\n').map(function(line) {
-    return line.trim();
-  });
-};
-// Splits SDP into sessionpart and mediasections. Ensures CRLF.
-SDPUtils.splitSections = function(blob) {
-  var parts = blob.split('\nm=');
-  return parts.map(function(part, index) {
-    return (index > 0 ? 'm=' + part : part).trim() + '\r\n';
-  });
-};
-
-// Returns lines that start with a certain prefix.
-SDPUtils.matchPrefix = function(blob, prefix) {
-  return SDPUtils.splitLines(blob).filter(function(line) {
-    return line.indexOf(prefix) === 0;
-  });
-};
-
-// Parses an ICE candidate line. Sample input:
-// candidate:702786350 2 udp 41819902 8.8.8.8 60769 typ relay raddr 8.8.8.8
-// rport 55996"
-SDPUtils.parseCandidate = function(line) {
-  var parts;
-  // Parse both variants.
-  if (line.indexOf('a=candidate:') === 0) {
-    parts = line.substring(12).split(' ');
-  } else {
-    parts = line.substring(10).split(' ');
-  }
-
-  var candidate = {
-    foundation: parts[0],
-    component: parts[1],
-    protocol: parts[2].toLowerCase(),
-    priority: parseInt(parts[3], 10),
-    ip: parts[4],
-    port: parseInt(parts[5], 10),
-    // skip parts[6] == 'typ'
-    type: parts[7]
-  };
-
-  for (var i = 8; i < parts.length; i += 2) {
-    switch (parts[i]) {
-      case 'raddr':
-        candidate.relatedAddress = parts[i + 1];
-        break;
-      case 'rport':
-        candidate.relatedPort = parseInt(parts[i + 1], 10);
-        break;
-      case 'tcptype':
-        candidate.tcpType = parts[i + 1];
-        break;
-      default: // Unknown extensions are silently ignored.
-        break;
+    /**
+     * Converts `value` to an integer suitable for use as the length of an
+     * array-like object.
+     *
+     * **Note:** This method is based on
+     * [`ToLength`](http://ecma-international.org/ecma-262/7.0/#sec-tolength).
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Lang
+     * @param {*} value The value to convert.
+     * @returns {number} Returns the converted integer.
+     * @example
+     *
+     * _.toLength(3.2);
+     * // => 3
+     *
+     * _.toLength(Number.MIN_VALUE);
+     * // => 0
+     *
+     * _.toLength(Infinity);
+     * // => 4294967295
+     *
+     * _.toLength('3.2');
+     * // => 3
+     */
+    function toLength(value) {
+      return value ? baseClamp(toInteger(value), 0, MAX_ARRAY_LENGTH) : 0;
     }
-  }
-  return candidate;
-};
-
-// Translates a candidate object into SDP candidate attribute.
-SDPUtils.writeCandidate = function(candidate) {
-  var sdp = [];
-  sdp.push(candidate.foundation);
-  sdp.push(candidate.component);
-  sdp.push(candidate.protocol.toUpperCase());
-  sdp.push(candidate.priority);
-  sdp.push(candidate.ip);
-  sdp.push(candidate.port);
 
-  var type = candidate.type;
-  sdp.push('typ');
-  sdp.push(type);
-  if (type !== 'host' && candidate.relatedAddress &&
-      candidate.relatedPort) {
-    sdp.push('raddr');
-    sdp.push(candidate.relatedAddress); // was: relAddr
-    sdp.push('rport');
-    sdp.push(candidate.relatedPort); // was: relPort
-  }
-  if (candidate.tcpType && candidate.protocol.toLowerCase() === 'tcp') {
-    sdp.push('tcptype');
-    sdp.push(candidate.tcpType);
-  }
-  return 'candidate:' + sdp.join(' ');
-};
+    /**
+     * Converts `value` to a number.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Lang
+     * @param {*} value The value to process.
+     * @returns {number} Returns the number.
+     * @example
+     *
+     * _.toNumber(3.2);
+     * // => 3.2
+     *
+     * _.toNumber(Number.MIN_VALUE);
+     * // => 5e-324
+     *
+     * _.toNumber(Infinity);
+     * // => Infinity
+     *
+     * _.toNumber('3.2');
+     * // => 3.2
+     */
+    function toNumber(value) {
+      if (typeof value == 'number') {
+        return value;
+      }
+      if (isSymbol(value)) {
+        return NAN;
+      }
+      if (isObject(value)) {
+        var other = typeof value.valueOf == 'function' ? value.valueOf() : value;
+        value = isObject(other) ? (other + '') : other;
+      }
+      if (typeof value != 'string') {
+        return value === 0 ? value : +value;
+      }
+      value = value.replace(reTrim, '');
+      var isBinary = reIsBinary.test(value);
+      return (isBinary || reIsOctal.test(value))
+        ? freeParseInt(value.slice(2), isBinary ? 2 : 8)
+        : (reIsBadHex.test(value) ? NAN : +value);
+    }
 
-// Parses an rtpmap line, returns RTCRtpCoddecParameters. Sample input:
-// a=rtpmap:111 opus/48000/2
-SDPUtils.parseRtpMap = function(line) {
-  var parts = line.substr(9).split(' ');
-  var parsed = {
-    payloadType: parseInt(parts.shift(), 10) // was: id
-  };
+    /**
+     * Converts `value` to a plain object flattening inherited enumerable string
+     * keyed properties of `value` to own properties of the plain object.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category Lang
+     * @param {*} value The value to convert.
+     * @returns {Object} Returns the converted plain object.
+     * @example
+     *
+     * function Foo() {
+     *   this.b = 2;
+     * }
+     *
+     * Foo.prototype.c = 3;
+     *
+     * _.assign({ 'a': 1 }, new Foo);
+     * // => { 'a': 1, 'b': 2 }
+     *
+     * _.assign({ 'a': 1 }, _.toPlainObject(new Foo));
+     * // => { 'a': 1, 'b': 2, 'c': 3 }
+     */
+    function toPlainObject(value) {
+      return copyObject(value, keysIn(value));
+    }
 
-  parts = parts[0].split('/');
+    /**
+     * Converts `value` to a safe integer. A safe integer can be compared and
+     * represented correctly.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Lang
+     * @param {*} value The value to convert.
+     * @returns {number} Returns the converted integer.
+     * @example
+     *
+     * _.toSafeInteger(3.2);
+     * // => 3
+     *
+     * _.toSafeInteger(Number.MIN_VALUE);
+     * // => 0
+     *
+     * _.toSafeInteger(Infinity);
+     * // => 9007199254740991
+     *
+     * _.toSafeInteger('3.2');
+     * // => 3
+     */
+    function toSafeInteger(value) {
+      return value
+        ? baseClamp(toInteger(value), -MAX_SAFE_INTEGER, MAX_SAFE_INTEGER)
+        : (value === 0 ? value : 0);
+    }
 
-  parsed.name = parts[0];
-  parsed.clockRate = parseInt(parts[1], 10); // was: clockrate
-  // was: channels
-  parsed.numChannels = parts.length === 3 ? parseInt(parts[2], 10) : 1;
-  return parsed;
-};
+    /**
+     * Converts `value` to a string. An empty string is returned for `null`
+     * and `undefined` values. The sign of `-0` is preserved.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Lang
+     * @param {*} value The value to convert.
+     * @returns {string} Returns the converted string.
+     * @example
+     *
+     * _.toString(null);
+     * // => ''
+     *
+     * _.toString(-0);
+     * // => '-0'
+     *
+     * _.toString([1, 2, 3]);
+     * // => '1,2,3'
+     */
+    function toString(value) {
+      return value == null ? '' : baseToString(value);
+    }
 
-// Generate an a=rtpmap line from RTCRtpCodecCapability or
-// RTCRtpCodecParameters.
-SDPUtils.writeRtpMap = function(codec) {
-  var pt = codec.payloadType;
-  if (codec.preferredPayloadType !== undefined) {
-    pt = codec.preferredPayloadType;
-  }
-  return 'a=rtpmap:' + pt + ' ' + codec.name + '/' + codec.clockRate +
-      (codec.numChannels !== 1 ? '/' + codec.numChannels : '') + '\r\n';
-};
+    /*------------------------------------------------------------------------*/
 
-// Parses an a=extmap line (headerextension from RFC 5285). Sample input:
-// a=extmap:2 urn:ietf:params:rtp-hdrext:toffset
-SDPUtils.parseExtmap = function(line) {
-  var parts = line.substr(9).split(' ');
-  return {
-    id: parseInt(parts[0], 10),
-    uri: parts[1]
-  };
-};
-
-// Generates a=extmap line from RTCRtpHeaderExtensionParameters or
-// RTCRtpHeaderExtension.
-SDPUtils.writeExtmap = function(headerExtension) {
-  return 'a=extmap:' + (headerExtension.id || headerExtension.preferredId) +
-       ' ' + headerExtension.uri + '\r\n';
-};
-
-// Parses an ftmp line, returns dictionary. Sample input:
-// a=fmtp:96 vbr=on;cng=on
-// Also deals with vbr=on; cng=on
-SDPUtils.parseFmtp = function(line) {
-  var parsed = {};
-  var kv;
-  var parts = line.substr(line.indexOf(' ') + 1).split(';');
-  for (var j = 0; j < parts.length; j++) {
-    kv = parts[j].trim().split('=');
-    parsed[kv[0].trim()] = kv[1];
-  }
-  return parsed;
-};
+    /**
+     * Assigns own enumerable string keyed properties of source objects to the
+     * destination object. Source objects are applied from left to right.
+     * Subsequent sources overwrite property assignments of previous sources.
+     *
+     * **Note:** This method mutates `object` and is loosely based on
+     * [`Object.assign`](https://mdn.io/Object/assign).
+     *
+     * @static
+     * @memberOf _
+     * @since 0.10.0
+     * @category Object
+     * @param {Object} object The destination object.
+     * @param {...Object} [sources] The source objects.
+     * @returns {Object} Returns `object`.
+     * @see _.assignIn
+     * @example
+     *
+     * function Foo() {
+     *   this.a = 1;
+     * }
+     *
+     * function Bar() {
+     *   this.c = 3;
+     * }
+     *
+     * Foo.prototype.b = 2;
+     * Bar.prototype.d = 4;
+     *
+     * _.assign({ 'a': 0 }, new Foo, new Bar);
+     * // => { 'a': 1, 'c': 3 }
+     */
+    var assign = createAssigner(function(object, source) {
+      if (isPrototype(source) || isArrayLike(source)) {
+        copyObject(source, keys(source), object);
+        return;
+      }
+      for (var key in source) {
+        if (hasOwnProperty.call(source, key)) {
+          assignValue(object, key, source[key]);
+        }
+      }
+    });
 
-// Generates an a=ftmp line from RTCRtpCodecCapability or RTCRtpCodecParameters.
-SDPUtils.writeFmtp = function(codec) {
-  var line = '';
-  var pt = codec.payloadType;
-  if (codec.preferredPayloadType !== undefined) {
-    pt = codec.preferredPayloadType;
-  }
-  if (codec.parameters && Object.keys(codec.parameters).length) {
-    var params = [];
-    Object.keys(codec.parameters).forEach(function(param) {
-      params.push(param + '=' + codec.parameters[param]);
+    /**
+     * This method is like `_.assign` except that it iterates over own and
+     * inherited source properties.
+     *
+     * **Note:** This method mutates `object`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @alias extend
+     * @category Object
+     * @param {Object} object The destination object.
+     * @param {...Object} [sources] The source objects.
+     * @returns {Object} Returns `object`.
+     * @see _.assign
+     * @example
+     *
+     * function Foo() {
+     *   this.a = 1;
+     * }
+     *
+     * function Bar() {
+     *   this.c = 3;
+     * }
+     *
+     * Foo.prototype.b = 2;
+     * Bar.prototype.d = 4;
+     *
+     * _.assignIn({ 'a': 0 }, new Foo, new Bar);
+     * // => { 'a': 1, 'b': 2, 'c': 3, 'd': 4 }
+     */
+    var assignIn = createAssigner(function(object, source) {
+      copyObject(source, keysIn(source), object);
     });
-    line += 'a=fmtp:' + pt + ' ' + params.join(';') + '\r\n';
-  }
-  return line;
-};
 
-// Parses an rtcp-fb line, returns RTCPRtcpFeedback object. Sample input:
-// a=rtcp-fb:98 nack rpsi
-SDPUtils.parseRtcpFb = function(line) {
-  var parts = line.substr(line.indexOf(' ') + 1).split(' ');
-  return {
-    type: parts.shift(),
-    parameter: parts.join(' ')
-  };
-};
-// Generate a=rtcp-fb lines from RTCRtpCodecCapability or RTCRtpCodecParameters.
-SDPUtils.writeRtcpFb = function(codec) {
-  var lines = '';
-  var pt = codec.payloadType;
-  if (codec.preferredPayloadType !== undefined) {
-    pt = codec.preferredPayloadType;
-  }
-  if (codec.rtcpFeedback && codec.rtcpFeedback.length) {
-    // FIXME: special handling for trr-int?
-    codec.rtcpFeedback.forEach(function(fb) {
-      lines += 'a=rtcp-fb:' + pt + ' ' + fb.type +
-      (fb.parameter && fb.parameter.length ? ' ' + fb.parameter : '') +
-          '\r\n';
+    /**
+     * This method is like `_.assignIn` except that it accepts `customizer`
+     * which is invoked to produce the assigned values. If `customizer` returns
+     * `undefined`, assignment is handled by the method instead. The `customizer`
+     * is invoked with five arguments: (objValue, srcValue, key, object, source).
+     *
+     * **Note:** This method mutates `object`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @alias extendWith
+     * @category Object
+     * @param {Object} object The destination object.
+     * @param {...Object} sources The source objects.
+     * @param {Function} [customizer] The function to customize assigned values.
+     * @returns {Object} Returns `object`.
+     * @see _.assignWith
+     * @example
+     *
+     * function customizer(objValue, srcValue) {
+     *   return _.isUndefined(objValue) ? srcValue : objValue;
+     * }
+     *
+     * var defaults = _.partialRight(_.assignInWith, customizer);
+     *
+     * defaults({ 'a': 1 }, { 'b': 2 }, { 'a': 3 });
+     * // => { 'a': 1, 'b': 2 }
+     */
+    var assignInWith = createAssigner(function(object, source, srcIndex, customizer) {
+      copyObject(source, keysIn(source), object, customizer);
     });
-  }
-  return lines;
-};
 
-// Parses an RFC 5576 ssrc media attribute. Sample input:
-// a=ssrc:3735928559 cname:something
-SDPUtils.parseSsrcMedia = function(line) {
-  var sp = line.indexOf(' ');
-  var parts = {
-    ssrc: parseInt(line.substr(7, sp - 7), 10)
-  };
-  var colon = line.indexOf(':', sp);
-  if (colon > -1) {
-    parts.attribute = line.substr(sp + 1, colon - sp - 1);
-    parts.value = line.substr(colon + 1);
-  } else {
-    parts.attribute = line.substr(sp + 1);
-  }
-  return parts;
-};
+    /**
+     * This method is like `_.assign` except that it accepts `customizer`
+     * which is invoked to produce the assigned values. If `customizer` returns
+     * `undefined`, assignment is handled by the method instead. The `customizer`
+     * is invoked with five arguments: (objValue, srcValue, key, object, source).
+     *
+     * **Note:** This method mutates `object`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Object
+     * @param {Object} object The destination object.
+     * @param {...Object} sources The source objects.
+     * @param {Function} [customizer] The function to customize assigned values.
+     * @returns {Object} Returns `object`.
+     * @see _.assignInWith
+     * @example
+     *
+     * function customizer(objValue, srcValue) {
+     *   return _.isUndefined(objValue) ? srcValue : objValue;
+     * }
+     *
+     * var defaults = _.partialRight(_.assignWith, customizer);
+     *
+     * defaults({ 'a': 1 }, { 'b': 2 }, { 'a': 3 });
+     * // => { 'a': 1, 'b': 2 }
+     */
+    var assignWith = createAssigner(function(object, source, srcIndex, customizer) {
+      copyObject(source, keys(source), object, customizer);
+    });
 
-// Extracts DTLS parameters from SDP media section or sessionpart.
-// FIXME: for consistency with other functions this should only
-//   get the fingerprint line as input. See also getIceParameters.
-SDPUtils.getDtlsParameters = function(mediaSection, sessionpart) {
-  var lines = SDPUtils.splitLines(mediaSection);
-  // Search in session part, too.
-  lines = lines.concat(SDPUtils.splitLines(sessionpart));
-  var fpLine = lines.filter(function(line) {
-    return line.indexOf('a=fingerprint:') === 0;
-  })[0].substr(14);
-  // Note: a=setup line is ignored since we use the 'auto' role.
-  var dtlsParameters = {
-    role: 'auto',
-    fingerprints: [{
-      algorithm: fpLine.split(' ')[0],
-      value: fpLine.split(' ')[1]
-    }]
-  };
-  return dtlsParameters;
-};
+    /**
+     * Creates an array of values corresponding to `paths` of `object`.
+     *
+     * @static
+     * @memberOf _
+     * @since 1.0.0
+     * @category Object
+     * @param {Object} object The object to iterate over.
+     * @param {...(string|string[])} [paths] The property paths to pick.
+     * @returns {Array} Returns the picked values.
+     * @example
+     *
+     * var object = { 'a': [{ 'b': { 'c': 3 } }, 4] };
+     *
+     * _.at(object, ['a[0].b.c', 'a[1]']);
+     * // => [3, 4]
+     */
+    var at = flatRest(baseAt);
 
-// Serializes DTLS parameters to SDP.
-SDPUtils.writeDtlsParameters = function(params, setupType) {
-  var sdp = 'a=setup:' + setupType + '\r\n';
-  params.fingerprints.forEach(function(fp) {
-    sdp += 'a=fingerprint:' + fp.algorithm + ' ' + fp.value + '\r\n';
-  });
-  return sdp;
-};
-// Parses ICE information from SDP media section or sessionpart.
-// FIXME: for consistency with other functions this should only
-//   get the ice-ufrag and ice-pwd lines as input.
-SDPUtils.getIceParameters = function(mediaSection, sessionpart) {
-  var lines = SDPUtils.splitLines(mediaSection);
-  // Search in session part, too.
-  lines = lines.concat(SDPUtils.splitLines(sessionpart));
-  var iceParameters = {
-    usernameFragment: lines.filter(function(line) {
-      return line.indexOf('a=ice-ufrag:') === 0;
-    })[0].substr(12),
-    password: lines.filter(function(line) {
-      return line.indexOf('a=ice-pwd:') === 0;
-    })[0].substr(10)
-  };
-  return iceParameters;
-};
-
-// Serializes ICE parameters to SDP.
-SDPUtils.writeIceParameters = function(params) {
-  return 'a=ice-ufrag:' + params.usernameFragment + '\r\n' +
-      'a=ice-pwd:' + params.password + '\r\n';
-};
-
-// Parses the SDP media section and returns RTCRtpParameters.
-SDPUtils.parseRtpParameters = function(mediaSection) {
-  var description = {
-    codecs: [],
-    headerExtensions: [],
-    fecMechanisms: [],
-    rtcp: []
-  };
-  var lines = SDPUtils.splitLines(mediaSection);
-  var mline = lines[0].split(' ');
-  for (var i = 3; i < mline.length; i++) { // find all codecs from mline[3..]
-    var pt = mline[i];
-    var rtpmapline = SDPUtils.matchPrefix(
-        mediaSection, 'a=rtpmap:' + pt + ' ')[0];
-    if (rtpmapline) {
-      var codec = SDPUtils.parseRtpMap(rtpmapline);
-      var fmtps = SDPUtils.matchPrefix(
-          mediaSection, 'a=fmtp:' + pt + ' ');
-      // Only the first a=fmtp:<pt> is considered.
-      codec.parameters = fmtps.length ? SDPUtils.parseFmtp(fmtps[0]) : {};
-      codec.rtcpFeedback = SDPUtils.matchPrefix(
-          mediaSection, 'a=rtcp-fb:' + pt + ' ')
-        .map(SDPUtils.parseRtcpFb);
-      description.codecs.push(codec);
-      // parse FEC mechanisms from rtpmap lines.
-      switch (codec.name.toUpperCase()) {
-        case 'RED':
-        case 'ULPFEC':
-          description.fecMechanisms.push(codec.name.toUpperCase());
-          break;
-        default: // only RED and ULPFEC are recognized as FEC mechanisms.
-          break;
-      }
-    }
-  }
-  SDPUtils.matchPrefix(mediaSection, 'a=extmap:').forEach(function(line) {
-    description.headerExtensions.push(SDPUtils.parseExtmap(line));
-  });
-  // FIXME: parse rtcp.
-  return description;
-};
-
-// Generates parts of the SDP media section describing the capabilities /
-// parameters.
-SDPUtils.writeRtpDescription = function(kind, caps) {
-  var sdp = '';
-
-  // Build the mline.
-  sdp += 'm=' + kind + ' ';
-  sdp += caps.codecs.length > 0 ? '9' : '0'; // reject if no codecs.
-  sdp += ' UDP/TLS/RTP/SAVPF ';
-  sdp += caps.codecs.map(function(codec) {
-    if (codec.preferredPayloadType !== undefined) {
-      return codec.preferredPayloadType;
+    /**
+     * Creates an object that inherits from the `prototype` object. If a
+     * `properties` object is given, its own enumerable string keyed properties
+     * are assigned to the created object.
+     *
+     * @static
+     * @memberOf _
+     * @since 2.3.0
+     * @category Object
+     * @param {Object} prototype The object to inherit from.
+     * @param {Object} [properties] The properties to assign to the object.
+     * @returns {Object} Returns the new object.
+     * @example
+     *
+     * function Shape() {
+     *   this.x = 0;
+     *   this.y = 0;
+     * }
+     *
+     * function Circle() {
+     *   Shape.call(this);
+     * }
+     *
+     * Circle.prototype = _.create(Shape.prototype, {
+     *   'constructor': Circle
+     * });
+     *
+     * var circle = new Circle;
+     * circle instanceof Circle;
+     * // => true
+     *
+     * circle instanceof Shape;
+     * // => true
+     */
+    function create(prototype, properties) {
+      var result = baseCreate(prototype);
+      return properties == null ? result : baseAssign(result, properties);
     }
-    return codec.payloadType;
-  }).join(' ') + '\r\n';
 
-  sdp += 'c=IN IP4 0.0.0.0\r\n';
-  sdp += 'a=rtcp:9 IN IP4 0.0.0.0\r\n';
+    /**
+     * Assigns own and inherited enumerable string keyed properties of source
+     * objects to the destination object for all destination properties that
+     * resolve to `undefined`. Source objects are applied from left to right.
+     * Once a property is set, additional values of the same property are ignored.
+     *
+     * **Note:** This method mutates `object`.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Object
+     * @param {Object} object The destination object.
+     * @param {...Object} [sources] The source objects.
+     * @returns {Object} Returns `object`.
+     * @see _.defaultsDeep
+     * @example
+     *
+     * _.defaults({ 'a': 1 }, { 'b': 2 }, { 'a': 3 });
+     * // => { 'a': 1, 'b': 2 }
+     */
+    var defaults = baseRest(function(object, sources) {
+      object = Object(object);
 
-  // Add a=rtpmap lines for each codec. Also fmtp and rtcp-fb.
-  caps.codecs.forEach(function(codec) {
-    sdp += SDPUtils.writeRtpMap(codec);
-    sdp += SDPUtils.writeFmtp(codec);
-    sdp += SDPUtils.writeRtcpFb(codec);
-  });
-  // FIXME: add headerExtensions, fecMechanismş and rtcp.
-  sdp += 'a=rtcp-mux\r\n';
-  return sdp;
-};
+      var index = -1;
+      var length = sources.length;
+      var guard = length > 2 ? sources[2] : undefined;
 
-// Parses the SDP media section and returns an array of
-// RTCRtpEncodingParameters.
-SDPUtils.parseRtpEncodingParameters = function(mediaSection) {
-  var encodingParameters = [];
-  var description = SDPUtils.parseRtpParameters(mediaSection);
-  var hasRed = description.fecMechanisms.indexOf('RED') !== -1;
-  var hasUlpfec = description.fecMechanisms.indexOf('ULPFEC') !== -1;
+      if (guard && isIterateeCall(sources[0], sources[1], guard)) {
+        length = 1;
+      }
 
-  // filter a=ssrc:... cname:, ignore PlanB-msid
-  var ssrcs = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
-  .map(function(line) {
-    return SDPUtils.parseSsrcMedia(line);
-  })
-  .filter(function(parts) {
-    return parts.attribute === 'cname';
-  });
-  var primarySsrc = ssrcs.length > 0 && ssrcs[0].ssrc;
-  var secondarySsrc;
+      while (++index < length) {
+        var source = sources[index];
+        var props = keysIn(source);
+        var propsIndex = -1;
+        var propsLength = props.length;
 
-  var flows = SDPUtils.matchPrefix(mediaSection, 'a=ssrc-group:FID')
-  .map(function(line) {
-    var parts = line.split(' ');
-    parts.shift();
-    return parts.map(function(part) {
-      return parseInt(part, 10);
-    });
-  });
-  if (flows.length > 0 && flows[0].length > 1 && flows[0][0] === primarySsrc) {
-    secondarySsrc = flows[0][1];
-  }
+        while (++propsIndex < propsLength) {
+          var key = props[propsIndex];
+          var value = object[key];
 
-  description.codecs.forEach(function(codec) {
-    if (codec.name.toUpperCase() === 'RTX' && codec.parameters.apt) {
-      var encParam = {
-        ssrc: primarySsrc,
-        codecPayloadType: parseInt(codec.parameters.apt, 10),
-        rtx: {
-          payloadType: codec.payloadType,
-          ssrc: secondarySsrc
+          if (value === undefined ||
+              (eq(value, objectProto[key]) && !hasOwnProperty.call(object, key))) {
+            object[key] = source[key];
+          }
         }
-      };
-      encodingParameters.push(encParam);
-      if (hasRed) {
-        encParam = JSON.parse(JSON.stringify(encParam));
-        encParam.fec = {
-          ssrc: secondarySsrc,
-          mechanism: hasUlpfec ? 'red+ulpfec' : 'red'
-        };
-        encodingParameters.push(encParam);
       }
-    }
-  });
-  if (encodingParameters.length === 0 && primarySsrc) {
-    encodingParameters.push({
-      ssrc: primarySsrc
-    });
-  }
 
-  // we support both b=AS and b=TIAS but interpret AS as TIAS.
-  var bandwidth = SDPUtils.matchPrefix(mediaSection, 'b=');
-  if (bandwidth.length) {
-    if (bandwidth[0].indexOf('b=TIAS:') === 0) {
-      bandwidth = parseInt(bandwidth[0].substr(7), 10);
-    } else if (bandwidth[0].indexOf('b=AS:') === 0) {
-      bandwidth = parseInt(bandwidth[0].substr(5), 10);
-    }
-    encodingParameters.forEach(function(params) {
-      params.maxBitrate = bandwidth;
+      return object;
     });
-  }
-  return encodingParameters;
-};
-
-SDPUtils.writeSessionBoilerplate = function() {
-  // FIXME: sess-id should be an NTP timestamp.
-  return 'v=0\r\n' +
-      'o=thisisadapterortc 8169639915646943137 2 IN IP4 127.0.0.1\r\n' +
-      's=-\r\n' +
-      't=0 0\r\n';
-};
-
-SDPUtils.writeMediaSection = function(transceiver, caps, type, stream) {
-  var sdp = SDPUtils.writeRtpDescription(transceiver.kind, caps);
-
-  // Map ICE parameters (ufrag, pwd) to SDP.
-  sdp += SDPUtils.writeIceParameters(
-      transceiver.iceGatherer.getLocalParameters());
-
-  // Map DTLS parameters to SDP.
-  sdp += SDPUtils.writeDtlsParameters(
-      transceiver.dtlsTransport.getLocalParameters(),
-      type === 'offer' ? 'actpass' : 'active');
-
-  sdp += 'a=mid:' + transceiver.mid + '\r\n';
 
-  if (transceiver.rtpSender && transceiver.rtpReceiver) {
-    sdp += 'a=sendrecv\r\n';
-  } else if (transceiver.rtpSender) {
-    sdp += 'a=sendonly\r\n';
-  } else if (transceiver.rtpReceiver) {
-    sdp += 'a=recvonly\r\n';
-  } else {
-    sdp += 'a=inactive\r\n';
-  }
+    /**
+     * This method is like `_.defaults` except that it recursively assigns
+     * default properties.
+     *
+     * **Note:** This method mutates `object`.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.10.0
+     * @category Object
+     * @param {Object} object The destination object.
+     * @param {...Object} [sources] The source objects.
+     * @returns {Object} Returns `object`.
+     * @see _.defaults
+     * @example
+     *
+     * _.defaultsDeep({ 'a': { 'b': 2 } }, { 'a': { 'b': 1, 'c': 3 } });
+     * // => { 'a': { 'b': 2, 'c': 3 } }
+     */
+    var defaultsDeep = baseRest(function(args) {
+      args.push(undefined, customDefaultsMerge);
+      return apply(mergeWith, undefined, args);
+    });
 
-  // FIXME: for RTX there might be multiple SSRCs. Not implemented in Edge yet.
-  if (transceiver.rtpSender) {
-    var msid = 'msid:' + stream.id + ' ' +
-        transceiver.rtpSender.track.id + '\r\n';
-    sdp += 'a=' + msid;
-    sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
-        ' ' + msid;
-  }
-  // FIXME: this should be written by writeRtpDescription.
-  sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
-      ' cname:' + SDPUtils.localCName + '\r\n';
-  return sdp;
-};
-
-// Gets the direction from the mediaSection or the sessionpart.
-SDPUtils.getDirection = function(mediaSection, sessionpart) {
-  // Look for sendrecv, sendonly, recvonly, inactive, default to sendrecv.
-  var lines = SDPUtils.splitLines(mediaSection);
-  for (var i = 0; i < lines.length; i++) {
-    switch (lines[i]) {
-      case 'a=sendrecv':
-      case 'a=sendonly':
-      case 'a=recvonly':
-      case 'a=inactive':
-        return lines[i].substr(2);
-      default:
-        // FIXME: What should happen here?
+    /**
+     * This method is like `_.find` except that it returns the key of the first
+     * element `predicate` returns truthy for instead of the element itself.
+     *
+     * @static
+     * @memberOf _
+     * @since 1.1.0
+     * @category Object
+     * @param {Object} object The object to inspect.
+     * @param {Function} [predicate=_.identity] The function invoked per iteration.
+     * @returns {string|undefined} Returns the key of the matched element,
+     *  else `undefined`.
+     * @example
+     *
+     * var users = {
+     *   'barney':  { 'age': 36, 'active': true },
+     *   'fred':    { 'age': 40, 'active': false },
+     *   'pebbles': { 'age': 1,  'active': true }
+     * };
+     *
+     * _.findKey(users, function(o) { return o.age < 40; });
+     * // => 'barney' (iteration order is not guaranteed)
+     *
+     * // The `_.matches` iteratee shorthand.
+     * _.findKey(users, { 'age': 1, 'active': true });
+     * // => 'pebbles'
+     *
+     * // The `_.matchesProperty` iteratee shorthand.
+     * _.findKey(users, ['active', false]);
+     * // => 'fred'
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.findKey(users, 'active');
+     * // => 'barney'
+     */
+    function findKey(object, predicate) {
+      return baseFindKey(object, getIteratee(predicate, 3), baseForOwn);
     }
-  }
-  if (sessionpart) {
-    return SDPUtils.getDirection(sessionpart);
-  }
-  return 'sendrecv';
-};
-
-// Expose public methods.
-module.exports = SDPUtils;
-
-},{}],9:[function(require,module,exports){
-const microevent = require('microevent')
-const _ = require('lodash')
-
-// get audio context
-const AudioContextType = window.webkitAudioContext || window.AudioContext
-
-// f_1 band for (most) human voice range
-var LOW_FREQ_CUT = 85
-var HIGH_FREQ_CUT = 583
-var bandPassMiddleFrequency = ((HIGH_FREQ_CUT - LOW_FREQ_CUT) / 2) + LOW_FREQ_CUT
-var bandPassFrequencyRange = HIGH_FREQ_CUT - bandPassMiddleFrequency
-
-// bandpass filter from AudioContext
-function bandPassFilterNode (audioContext) {
-  var bandpass = audioContext.createBiquadFilter()
-  bandpass.type = 'bandpass'
-  bandpass.frequency.value = bandPassMiddleFrequency
-  bandpass.Q = bandPassFrequencyRange
-  return bandpass
-}
-
-function speakingDetectionNode (audioContext, analyser, threshold, emitter) {
-  var javascriptNode = audioContext.createScriptProcessor(2048, 1, 1)
-  var speakingTimes = []
-  var quietHistory = [] // only contains continuous 'quiet' times
-  var currentVolume = -Infinity
 
-  var hasStoppedSpeaking = function () {
-    return (_.max(quietHistory) - _.min(quietHistory) > 500)
-  }
+    /**
+     * This method is like `_.findKey` except that it iterates over elements of
+     * a collection in the opposite order.
+     *
+     * @static
+     * @memberOf _
+     * @since 2.0.0
+     * @category Object
+     * @param {Object} object The object to inspect.
+     * @param {Function} [predicate=_.identity] The function invoked per iteration.
+     * @returns {string|undefined} Returns the key of the matched element,
+     *  else `undefined`.
+     * @example
+     *
+     * var users = {
+     *   'barney':  { 'age': 36, 'active': true },
+     *   'fred':    { 'age': 40, 'active': false },
+     *   'pebbles': { 'age': 1,  'active': true }
+     * };
+     *
+     * _.findLastKey(users, function(o) { return o.age < 40; });
+     * // => returns 'pebbles' assuming `_.findKey` returns 'barney'
+     *
+     * // The `_.matches` iteratee shorthand.
+     * _.findLastKey(users, { 'age': 36, 'active': true });
+     * // => 'barney'
+     *
+     * // The `_.matchesProperty` iteratee shorthand.
+     * _.findLastKey(users, ['active', false]);
+     * // => 'fred'
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.findLastKey(users, 'active');
+     * // => 'pebbles'
+     */
+    function findLastKey(object, predicate) {
+      return baseFindKey(object, getIteratee(predicate, 3), baseForOwnRight);
+    }
 
-  javascriptNode.onaudioprocess = function () {
-    var fftBins = new Float32Array(analyser.frequencyBinCount)
-    analyser.getFloatFrequencyData(fftBins)
-    var maxVolume = _.max(_.filter(fftBins, function (v) { return v < 0 }))
-    currentVolume = maxVolume
-    emitter.trigger('volumeChange', currentVolume)
-    // speaking, add the date to the stack, clear quiet record
-    if (currentVolume > threshold) {
-      emitter.trigger('speaking')
-      speakingTimes.push(new Date())
-      quietHistory = []
-    } else if (speakingTimes.length > 0) {
-      if (hasStoppedSpeaking()) {
-        emitter.trigger('stoppedSpeaking', {'start': _.min(speakingTimes), 'end': _.max(speakingTimes)})
-        speakingTimes = []
-      } else {
-        quietHistory.push(new Date())
-      }
+    /**
+     * Iterates over own and inherited enumerable string keyed properties of an
+     * object and invokes `iteratee` for each property. The iteratee is invoked
+     * with three arguments: (value, key, object). Iteratee functions may exit
+     * iteration early by explicitly returning `false`.
+     *
+     * @static
+     * @memberOf _
+     * @since 0.3.0
+     * @category Object
+     * @param {Object} object The object to iterate over.
+     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
+     * @returns {Object} Returns `object`.
+     * @see _.forInRight
+     * @example
+     *
+     * function Foo() {
+     *   this.a = 1;
+     *   this.b = 2;
+     * }
+     *
+     * Foo.prototype.c = 3;
+     *
+     * _.forIn(new Foo, function(value, key) {
+     *   console.log(key);
+     * });
+     * // => Logs 'a', 'b', then 'c' (iteration order is not guaranteed).
+     */
+    function forIn(object, iteratee) {
+      return object == null
+        ? object
+        : baseFor(object, getIteratee(iteratee, 3), keysIn);
     }
-  }
-  return javascriptNode
-}
 
-var Sibilant = function (element, options) {
-  options = options || {}
-  var self = this
-  // var useBandPass = (options.useBandPass || true)
-  var fftSize = (options.fftSize || 512)
-  var threshold = (options.threshold || -40)
-  var smoothing = (options.smoothing || 0.2)
-  var passThrough = (options.passThrough || false)
-  var audioContext = new AudioContextType()
-
-  var analyser = audioContext.createAnalyser()
-  analyser.fftSize = fftSize
-  analyser.smoothingTimeConstant = smoothing
-
-  var audioSource = null
-  // assume webRTC for now
-  if (element instanceof HTMLAudioElement || element instanceof HTMLVideoElement) {
-    audioSource = audioContext.createMediaElementSource(element)
-  } else {
-    audioSource = audioContext.createMediaStreamSource(element)
-  }
-  var speakingNode = speakingDetectionNode(audioContext, analyser, threshold, self)
-  var bandPassNode = bandPassFilterNode(audioContext)
-  audioSource.connect(analyser)
-  if (passThrough) {
-    console.log('passing through', element)
-    analyser.connect(audioContext.destination)
-  }
-  analyser.connect(bandPassNode)
-  bandPassNode.connect(speakingNode)
-}
+    /**
+     * This method is like `_.forIn` except that it iterates over properties of
+     * `object` in the opposite order.
+     *
+     * @static
+     * @memberOf _
+     * @since 2.0.0
+     * @category Object
+     * @param {Object} object The object to iterate over.
+     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
+     * @returns {Object} Returns `object`.
+     * @see _.forIn
+     * @example
+     *
+     * function Foo() {
+     *   this.a = 1;
+     *   this.b = 2;
+     * }
+     *
+     * Foo.prototype.c = 3;
+     *
+     * _.forInRight(new Foo, function(value, key) {
+     *   console.log(key);
+     * });
+     * // => Logs 'c', 'b', then 'a' assuming `_.forIn` logs 'a', 'b', then 'c'.
+     */
+    function forInRight(object, iteratee) {
+      return object == null
+        ? object
+        : baseForRight(object, getIteratee(iteratee, 3), keysIn);
+    }
 
-microevent.mixin(Sibilant)
+    /**
+     * Iterates over own enumerable string keyed properties of an object and
+     * invokes `iteratee` for each property. The iteratee is invoked with three
+     * arguments: (value, key, object). Iteratee functions may exit iteration
+     * early by explicitly returning `false`.
+     *
+     * @static
+     * @memberOf _
+     * @since 0.3.0
+     * @category Object
+     * @param {Object} object The object to iterate over.
+     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
+     * @returns {Object} Returns `object`.
+     * @see _.forOwnRight
+     * @example
+     *
+     * function Foo() {
+     *   this.a = 1;
+     *   this.b = 2;
+     * }
+     *
+     * Foo.prototype.c = 3;
+     *
+     * _.forOwn(new Foo, function(value, key) {
+     *   console.log(key);
+     * });
+     * // => Logs 'a' then 'b' (iteration order is not guaranteed).
+     */
+    function forOwn(object, iteratee) {
+      return object && baseForOwn(object, getIteratee(iteratee, 3));
+    }
 
-module.exports = Sibilant
+    /**
+     * This method is like `_.forOwn` except that it iterates over properties of
+     * `object` in the opposite order.
+     *
+     * @static
+     * @memberOf _
+     * @since 2.0.0
+     * @category Object
+     * @param {Object} object The object to iterate over.
+     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
+     * @returns {Object} Returns `object`.
+     * @see _.forOwn
+     * @example
+     *
+     * function Foo() {
+     *   this.a = 1;
+     *   this.b = 2;
+     * }
+     *
+     * Foo.prototype.c = 3;
+     *
+     * _.forOwnRight(new Foo, function(value, key) {
+     *   console.log(key);
+     * });
+     * // => Logs 'b' then 'a' assuming `_.forOwn` logs 'a' then 'b'.
+     */
+    function forOwnRight(object, iteratee) {
+      return object && baseForOwnRight(object, getIteratee(iteratee, 3));
+    }
 
-},{"lodash":6,"microevent":7}],10:[function(require,module,exports){
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
- /* eslint-env node */
+    /**
+     * Creates an array of function property names from own enumerable properties
+     * of `object`.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Object
+     * @param {Object} object The object to inspect.
+     * @returns {Array} Returns the function names.
+     * @see _.functionsIn
+     * @example
+     *
+     * function Foo() {
+     *   this.a = _.constant('a');
+     *   this.b = _.constant('b');
+     * }
+     *
+     * Foo.prototype.c = _.constant('c');
+     *
+     * _.functions(new Foo);
+     * // => ['a', 'b']
+     */
+    function functions(object) {
+      return object == null ? [] : baseFunctions(object, keys(object));
+    }
 
-'use strict';
+    /**
+     * Creates an array of function property names from own and inherited
+     * enumerable properties of `object`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Object
+     * @param {Object} object The object to inspect.
+     * @returns {Array} Returns the function names.
+     * @see _.functions
+     * @example
+     *
+     * function Foo() {
+     *   this.a = _.constant('a');
+     *   this.b = _.constant('b');
+     * }
+     *
+     * Foo.prototype.c = _.constant('c');
+     *
+     * _.functionsIn(new Foo);
+     * // => ['a', 'b', 'c']
+     */
+    function functionsIn(object) {
+      return object == null ? [] : baseFunctions(object, keysIn(object));
+    }
 
-// Shimming starts here.
-(function() {
-  // Utils.
-  var logging = require('./utils').log;
-  var browserDetails = require('./utils').browserDetails;
-  // Export to the adapter global object visible in the browser.
-  module.exports.browserDetails = browserDetails;
-  module.exports.extractVersion = require('./utils').extractVersion;
-  module.exports.disableLog = require('./utils').disableLog;
+    /**
+     * Gets the value at `path` of `object`. If the resolved value is
+     * `undefined`, the `defaultValue` is returned in its place.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.7.0
+     * @category Object
+     * @param {Object} object The object to query.
+     * @param {Array|string} path The path of the property to get.
+     * @param {*} [defaultValue] The value returned for `undefined` resolved values.
+     * @returns {*} Returns the resolved value.
+     * @example
+     *
+     * var object = { 'a': [{ 'b': { 'c': 3 } }] };
+     *
+     * _.get(object, 'a[0].b.c');
+     * // => 3
+     *
+     * _.get(object, ['a', '0', 'b', 'c']);
+     * // => 3
+     *
+     * _.get(object, 'a.b.c', 'default');
+     * // => 'default'
+     */
+    function get(object, path, defaultValue) {
+      var result = object == null ? undefined : baseGet(object, path);
+      return result === undefined ? defaultValue : result;
+    }
 
-  // Uncomment the line below if you want logging to occur, including logging
-  // for the switch statement below. Can also be turned on in the browser via
-  // adapter.disableLog(false), but then logging from the switch statement below
-  // will not appear.
-  // require('./utils').disableLog(false);
+    /**
+     * Checks if `path` is a direct property of `object`.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Object
+     * @param {Object} object The object to query.
+     * @param {Array|string} path The path to check.
+     * @returns {boolean} Returns `true` if `path` exists, else `false`.
+     * @example
+     *
+     * var object = { 'a': { 'b': 2 } };
+     * var other = _.create({ 'a': _.create({ 'b': 2 }) });
+     *
+     * _.has(object, 'a');
+     * // => true
+     *
+     * _.has(object, 'a.b');
+     * // => true
+     *
+     * _.has(object, ['a', 'b']);
+     * // => true
+     *
+     * _.has(other, 'a');
+     * // => false
+     */
+    function has(object, path) {
+      return object != null && hasPath(object, path, baseHas);
+    }
 
-  // Browser shims.
-  var chromeShim = require('./chrome/chrome_shim') || null;
-  var edgeShim = require('./edge/edge_shim') || null;
-  var firefoxShim = require('./firefox/firefox_shim') || null;
-  var safariShim = require('./safari/safari_shim') || null;
+    /**
+     * Checks if `path` is a direct or inherited property of `object`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Object
+     * @param {Object} object The object to query.
+     * @param {Array|string} path The path to check.
+     * @returns {boolean} Returns `true` if `path` exists, else `false`.
+     * @example
+     *
+     * var object = _.create({ 'a': _.create({ 'b': 2 }) });
+     *
+     * _.hasIn(object, 'a');
+     * // => true
+     *
+     * _.hasIn(object, 'a.b');
+     * // => true
+     *
+     * _.hasIn(object, ['a', 'b']);
+     * // => true
+     *
+     * _.hasIn(object, 'b');
+     * // => false
+     */
+    function hasIn(object, path) {
+      return object != null && hasPath(object, path, baseHasIn);
+    }
 
-  // Shim browser if found.
-  switch (browserDetails.browser) {
-    case 'opera': // fallthrough as it uses chrome shims
-    case 'chrome':
-      if (!chromeShim || !chromeShim.shimPeerConnection) {
-        logging('Chrome shim is not included in this adapter release.');
-        return;
+    /**
+     * Creates an object composed of the inverted keys and values of `object`.
+     * If `object` contains duplicate values, subsequent values overwrite
+     * property assignments of previous values.
+     *
+     * @static
+     * @memberOf _
+     * @since 0.7.0
+     * @category Object
+     * @param {Object} object The object to invert.
+     * @returns {Object} Returns the new inverted object.
+     * @example
+     *
+     * var object = { 'a': 1, 'b': 2, 'c': 1 };
+     *
+     * _.invert(object);
+     * // => { '1': 'c', '2': 'b' }
+     */
+    var invert = createInverter(function(result, value, key) {
+      if (value != null &&
+          typeof value.toString != 'function') {
+        value = nativeObjectToString.call(value);
       }
-      logging('adapter.js shimming chrome.');
-      // Export to the adapter global object visible in the browser.
-      module.exports.browserShim = chromeShim;
 
-      chromeShim.shimGetUserMedia();
-      chromeShim.shimMediaStream();
-      chromeShim.shimSourceObject();
-      chromeShim.shimPeerConnection();
-      chromeShim.shimOnTrack();
-      break;
-    case 'firefox':
-      if (!firefoxShim || !firefoxShim.shimPeerConnection) {
-        logging('Firefox shim is not included in this adapter release.');
-        return;
+      result[value] = key;
+    }, constant(identity));
+
+    /**
+     * This method is like `_.invert` except that the inverted object is generated
+     * from the results of running each element of `object` thru `iteratee`. The
+     * corresponding inverted value of each inverted key is an array of keys
+     * responsible for generating the inverted value. The iteratee is invoked
+     * with one argument: (value).
+     *
+     * @static
+     * @memberOf _
+     * @since 4.1.0
+     * @category Object
+     * @param {Object} object The object to invert.
+     * @param {Function} [iteratee=_.identity] The iteratee invoked per element.
+     * @returns {Object} Returns the new inverted object.
+     * @example
+     *
+     * var object = { 'a': 1, 'b': 2, 'c': 1 };
+     *
+     * _.invertBy(object);
+     * // => { '1': ['a', 'c'], '2': ['b'] }
+     *
+     * _.invertBy(object, function(value) {
+     *   return 'group' + value;
+     * });
+     * // => { 'group1': ['a', 'c'], 'group2': ['b'] }
+     */
+    var invertBy = createInverter(function(result, value, key) {
+      if (value != null &&
+          typeof value.toString != 'function') {
+        value = nativeObjectToString.call(value);
       }
-      logging('adapter.js shimming firefox.');
-      // Export to the adapter global object visible in the browser.
-      module.exports.browserShim = firefoxShim;
 
-      firefoxShim.shimGetUserMedia();
-      firefoxShim.shimSourceObject();
-      firefoxShim.shimPeerConnection();
-      firefoxShim.shimOnTrack();
-      break;
-    case 'edge':
-      if (!edgeShim || !edgeShim.shimPeerConnection) {
-        logging('MS edge shim is not included in this adapter release.');
-        return;
+      if (hasOwnProperty.call(result, value)) {
+        result[value].push(key);
+      } else {
+        result[value] = [key];
       }
-      logging('adapter.js shimming edge.');
-      // Export to the adapter global object visible in the browser.
-      module.exports.browserShim = edgeShim;
+    }, getIteratee);
 
-      edgeShim.shimGetUserMedia();
-      edgeShim.shimPeerConnection();
-      break;
-    case 'safari':
-      if (!safariShim) {
-        logging('Safari shim is not included in this adapter release.');
-        return;
-      }
-      logging('adapter.js shimming safari.');
-      // Export to the adapter global object visible in the browser.
-      module.exports.browserShim = safariShim;
-
-      safariShim.shimGetUserMedia();
-      break;
-    default:
-      logging('Unsupported browser!');
-  }
-})();
+    /**
+     * Invokes the method at `path` of `object`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Object
+     * @param {Object} object The object to query.
+     * @param {Array|string} path The path of the method to invoke.
+     * @param {...*} [args] The arguments to invoke the method with.
+     * @returns {*} Returns the result of the invoked method.
+     * @example
+     *
+     * var object = { 'a': [{ 'b': { 'c': [1, 2, 3, 4] } }] };
+     *
+     * _.invoke(object, 'a[0].b.c.slice', 1, 3);
+     * // => [2, 3]
+     */
+    var invoke = baseRest(baseInvoke);
 
-},{"./chrome/chrome_shim":11,"./edge/edge_shim":13,"./firefox/firefox_shim":15,"./safari/safari_shim":17,"./utils":18}],11:[function(require,module,exports){
+    /**
+     * Creates an array of the own enumerable property names of `object`.
+     *
+     * **Note:** Non-object values are coerced to objects. See the
+     * [ES spec](http://ecma-international.org/ecma-262/7.0/#sec-object.keys)
+     * for more details.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Object
+     * @param {Object} object The object to query.
+     * @returns {Array} Returns the array of property names.
+     * @example
+     *
+     * function Foo() {
+     *   this.a = 1;
+     *   this.b = 2;
+     * }
+     *
+     * Foo.prototype.c = 3;
+     *
+     * _.keys(new Foo);
+     * // => ['a', 'b'] (iteration order is not guaranteed)
+     *
+     * _.keys('hi');
+     * // => ['0', '1']
+     */
+    function keys(object) {
+      return isArrayLike(object) ? arrayLikeKeys(object) : baseKeys(object);
+    }
 
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
- /* eslint-env node */
-'use strict';
-var logging = require('../utils.js').log;
-var browserDetails = require('../utils.js').browserDetails;
+    /**
+     * Creates an array of the own and inherited enumerable property names of `object`.
+     *
+     * **Note:** Non-object values are coerced to objects.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category Object
+     * @param {Object} object The object to query.
+     * @returns {Array} Returns the array of property names.
+     * @example
+     *
+     * function Foo() {
+     *   this.a = 1;
+     *   this.b = 2;
+     * }
+     *
+     * Foo.prototype.c = 3;
+     *
+     * _.keysIn(new Foo);
+     * // => ['a', 'b', 'c'] (iteration order is not guaranteed)
+     */
+    function keysIn(object) {
+      return isArrayLike(object) ? arrayLikeKeys(object, true) : baseKeysIn(object);
+    }
 
-var chromeShim = {
-  shimMediaStream: function() {
-    window.MediaStream = window.MediaStream || window.webkitMediaStream;
-  },
+    /**
+     * The opposite of `_.mapValues`; this method creates an object with the
+     * same values as `object` and keys generated by running each own enumerable
+     * string keyed property of `object` thru `iteratee`. The iteratee is invoked
+     * with three arguments: (value, key, object).
+     *
+     * @static
+     * @memberOf _
+     * @since 3.8.0
+     * @category Object
+     * @param {Object} object The object to iterate over.
+     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
+     * @returns {Object} Returns the new mapped object.
+     * @see _.mapValues
+     * @example
+     *
+     * _.mapKeys({ 'a': 1, 'b': 2 }, function(value, key) {
+     *   return key + value;
+     * });
+     * // => { 'a1': 1, 'b2': 2 }
+     */
+    function mapKeys(object, iteratee) {
+      var result = {};
+      iteratee = getIteratee(iteratee, 3);
 
-  shimOnTrack: function() {
-    if (typeof window === 'object' && window.RTCPeerConnection && !('ontrack' in
-        window.RTCPeerConnection.prototype)) {
-      Object.defineProperty(window.RTCPeerConnection.prototype, 'ontrack', {
-        get: function() {
-          return this._ontrack;
-        },
-        set: function(f) {
-          var self = this;
-          if (this._ontrack) {
-            this.removeEventListener('track', this._ontrack);
-            this.removeEventListener('addstream', this._ontrackpoly);
-          }
-          this.addEventListener('track', this._ontrack = f);
-          this.addEventListener('addstream', this._ontrackpoly = function(e) {
-            // onaddstream does not fire when a track is added to an existing
-            // stream. But stream.onaddtrack is implemented so we use that.
-            e.stream.addEventListener('addtrack', function(te) {
-              var event = new Event('track');
-              event.track = te.track;
-              event.receiver = {track: te.track};
-              event.streams = [e.stream];
-              self.dispatchEvent(event);
-            });
-            e.stream.getTracks().forEach(function(track) {
-              var event = new Event('track');
-              event.track = track;
-              event.receiver = {track: track};
-              event.streams = [e.stream];
-              this.dispatchEvent(event);
-            }.bind(this));
-          }.bind(this));
-        }
+      baseForOwn(object, function(value, key, object) {
+        baseAssignValue(result, iteratee(value, key, object), value);
       });
+      return result;
     }
-  },
 
-  shimSourceObject: function() {
-    if (typeof window === 'object') {
-      if (window.HTMLMediaElement &&
-        !('srcObject' in window.HTMLMediaElement.prototype)) {
-        // Shim the srcObject property, once, when HTMLMediaElement is found.
-        Object.defineProperty(window.HTMLMediaElement.prototype, 'srcObject', {
-          get: function() {
-            return this._srcObject;
-          },
-          set: function(stream) {
-            var self = this;
-            // Use _srcObject as a private property for this shim
-            this._srcObject = stream;
-            if (this.src) {
-              URL.revokeObjectURL(this.src);
-            }
+    /**
+     * Creates an object with the same keys as `object` and values generated
+     * by running each own enumerable string keyed property of `object` thru
+     * `iteratee`. The iteratee is invoked with three arguments:
+     * (value, key, object).
+     *
+     * @static
+     * @memberOf _
+     * @since 2.4.0
+     * @category Object
+     * @param {Object} object The object to iterate over.
+     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
+     * @returns {Object} Returns the new mapped object.
+     * @see _.mapKeys
+     * @example
+     *
+     * var users = {
+     *   'fred':    { 'user': 'fred',    'age': 40 },
+     *   'pebbles': { 'user': 'pebbles', 'age': 1 }
+     * };
+     *
+     * _.mapValues(users, function(o) { return o.age; });
+     * // => { 'fred': 40, 'pebbles': 1 } (iteration order is not guaranteed)
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.mapValues(users, 'age');
+     * // => { 'fred': 40, 'pebbles': 1 } (iteration order is not guaranteed)
+     */
+    function mapValues(object, iteratee) {
+      var result = {};
+      iteratee = getIteratee(iteratee, 3);
 
-            if (!stream) {
-              this.src = '';
-              return;
-            }
-            this.src = URL.createObjectURL(stream);
-            // We need to recreate the blob url when a track is added or
-            // removed. Doing it manually since we want to avoid a recursion.
-            stream.addEventListener('addtrack', function() {
-              if (self.src) {
-                URL.revokeObjectURL(self.src);
-              }
-              self.src = URL.createObjectURL(stream);
-            });
-            stream.addEventListener('removetrack', function() {
-              if (self.src) {
-                URL.revokeObjectURL(self.src);
-              }
-              self.src = URL.createObjectURL(stream);
-            });
-          }
-        });
-      }
+      baseForOwn(object, function(value, key, object) {
+        baseAssignValue(result, key, iteratee(value, key, object));
+      });
+      return result;
     }
-  },
-
-  shimPeerConnection: function() {
-    // The RTCPeerConnection object.
-    window.RTCPeerConnection = function(pcConfig, pcConstraints) {
-      // Translate iceTransportPolicy to iceTransports,
-      // see https://code.google.com/p/webrtc/issues/detail?id=4869
-      logging('PeerConnection');
-      if (pcConfig && pcConfig.iceTransportPolicy) {
-        pcConfig.iceTransports = pcConfig.iceTransportPolicy;
-      }
-
-      var pc = new webkitRTCPeerConnection(pcConfig, pcConstraints);
-      var origGetStats = pc.getStats.bind(pc);
-      pc.getStats = function(selector, successCallback, errorCallback) {
-        var self = this;
-        var args = arguments;
 
-        // If selector is a function then we are in the old style stats so just
-        // pass back the original getStats format to avoid breaking old users.
-        if (arguments.length > 0 && typeof selector === 'function') {
-          return origGetStats(selector, successCallback);
-        }
-
-        var fixChromeStats_ = function(response) {
-          var standardReport = {};
-          var reports = response.result();
-          reports.forEach(function(report) {
-            var standardStats = {
-              id: report.id,
-              timestamp: report.timestamp,
-              type: report.type
-            };
-            report.names().forEach(function(name) {
-              standardStats[name] = report.stat(name);
-            });
-            standardReport[standardStats.id] = standardStats;
-          });
-
-          return standardReport;
-        };
-
-        // shim getStats with maplike support
-        var makeMapStats = function(stats, legacyStats) {
-          var map = new Map(Object.keys(stats).map(function(key) {
-            return[key, stats[key]];
-          }));
-          legacyStats = legacyStats || stats;
-          Object.keys(legacyStats).forEach(function(key) {
-            map[key] = legacyStats[key];
-          });
-          return map;
-        };
-
-        if (arguments.length >= 2) {
-          var successCallbackWrapper_ = function(response) {
-            args[1](makeMapStats(fixChromeStats_(response)));
-          };
-
-          return origGetStats.apply(this, [successCallbackWrapper_,
-              arguments[0]]);
-        }
-
-        // promise-support
-        return new Promise(function(resolve, reject) {
-          if (args.length === 1 && typeof selector === 'object') {
-            origGetStats.apply(self, [
-              function(response) {
-                resolve(makeMapStats(fixChromeStats_(response)));
-              }, reject]);
-          } else {
-            // Preserve legacy chrome stats only on legacy access of stats obj
-            origGetStats.apply(self, [
-              function(response) {
-                resolve(makeMapStats(fixChromeStats_(response),
-                    response.result()));
-              }, reject]);
-          }
-        }).then(successCallback, errorCallback);
-      };
+    /**
+     * This method is like `_.assign` except that it recursively merges own and
+     * inherited enumerable string keyed properties of source objects into the
+     * destination object. Source properties that resolve to `undefined` are
+     * skipped if a destination value exists. Array and plain object properties
+     * are merged recursively. Other objects and value types are overridden by
+     * assignment. Source objects are applied from left to right. Subsequent
+     * sources overwrite property assignments of previous sources.
+     *
+     * **Note:** This method mutates `object`.
+     *
+     * @static
+     * @memberOf _
+     * @since 0.5.0
+     * @category Object
+     * @param {Object} object The destination object.
+     * @param {...Object} [sources] The source objects.
+     * @returns {Object} Returns `object`.
+     * @example
+     *
+     * var object = {
+     *   'a': [{ 'b': 2 }, { 'd': 4 }]
+     * };
+     *
+     * var other = {
+     *   'a': [{ 'c': 3 }, { 'e': 5 }]
+     * };
+     *
+     * _.merge(object, other);
+     * // => { 'a': [{ 'b': 2, 'c': 3 }, { 'd': 4, 'e': 5 }] }
+     */
+    var merge = createAssigner(function(object, source, srcIndex) {
+      baseMerge(object, source, srcIndex);
+    });
 
-      return pc;
-    };
-    window.RTCPeerConnection.prototype = webkitRTCPeerConnection.prototype;
+    /**
+     * This method is like `_.merge` except that it accepts `customizer` which
+     * is invoked to produce the merged values of the destination and source
+     * properties. If `customizer` returns `undefined`, merging is handled by the
+     * method instead. The `customizer` is invoked with six arguments:
+     * (objValue, srcValue, key, object, source, stack).
+     *
+     * **Note:** This method mutates `object`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Object
+     * @param {Object} object The destination object.
+     * @param {...Object} sources The source objects.
+     * @param {Function} customizer The function to customize assigned values.
+     * @returns {Object} Returns `object`.
+     * @example
+     *
+     * function customizer(objValue, srcValue) {
+     *   if (_.isArray(objValue)) {
+     *     return objValue.concat(srcValue);
+     *   }
+     * }
+     *
+     * var object = { 'a': [1], 'b': [2] };
+     * var other = { 'a': [3], 'b': [4] };
+     *
+     * _.mergeWith(object, other, customizer);
+     * // => { 'a': [1, 3], 'b': [2, 4] }
+     */
+    var mergeWith = createAssigner(function(object, source, srcIndex, customizer) {
+      baseMerge(object, source, srcIndex, customizer);
+    });
 
-    // wrap static methods. Currently just generateCertificate.
-    if (webkitRTCPeerConnection.generateCertificate) {
-      Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
-        get: function() {
-          return webkitRTCPeerConnection.generateCertificate;
-        }
+    /**
+     * The opposite of `_.pick`; this method creates an object composed of the
+     * own and inherited enumerable property paths of `object` that are not omitted.
+     *
+     * **Note:** This method is considerably slower than `_.pick`.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Object
+     * @param {Object} object The source object.
+     * @param {...(string|string[])} [paths] The property paths to omit.
+     * @returns {Object} Returns the new object.
+     * @example
+     *
+     * var object = { 'a': 1, 'b': '2', 'c': 3 };
+     *
+     * _.omit(object, ['a', 'c']);
+     * // => { 'b': '2' }
+     */
+    var omit = flatRest(function(object, paths) {
+      var result = {};
+      if (object == null) {
+        return result;
+      }
+      var isDeep = false;
+      paths = arrayMap(paths, function(path) {
+        path = castPath(path, object);
+        isDeep || (isDeep = path.length > 1);
+        return path;
       });
+      copyObject(object, getAllKeysIn(object), result);
+      if (isDeep) {
+        result = baseClone(result, CLONE_DEEP_FLAG | CLONE_FLAT_FLAG | CLONE_SYMBOLS_FLAG, customOmitClone);
+      }
+      var length = paths.length;
+      while (length--) {
+        baseUnset(result, paths[length]);
+      }
+      return result;
+    });
+
+    /**
+     * The opposite of `_.pickBy`; this method creates an object composed of
+     * the own and inherited enumerable string keyed properties of `object` that
+     * `predicate` doesn't return truthy for. The predicate is invoked with two
+     * arguments: (value, key).
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Object
+     * @param {Object} object The source object.
+     * @param {Function} [predicate=_.identity] The function invoked per property.
+     * @returns {Object} Returns the new object.
+     * @example
+     *
+     * var object = { 'a': 1, 'b': '2', 'c': 3 };
+     *
+     * _.omitBy(object, _.isNumber);
+     * // => { 'b': '2' }
+     */
+    function omitBy(object, predicate) {
+      return pickBy(object, negate(getIteratee(predicate)));
     }
 
-    ['createOffer', 'createAnswer'].forEach(function(method) {
-      var nativeMethod = webkitRTCPeerConnection.prototype[method];
-      webkitRTCPeerConnection.prototype[method] = function() {
-        var self = this;
-        if (arguments.length < 1 || (arguments.length === 1 &&
-            typeof arguments[0] === 'object')) {
-          var opts = arguments.length === 1 ? arguments[0] : undefined;
-          return new Promise(function(resolve, reject) {
-            nativeMethod.apply(self, [resolve, reject, opts]);
-          });
-        }
-        return nativeMethod.apply(this, arguments);
-      };
+    /**
+     * Creates an object composed of the picked `object` properties.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Object
+     * @param {Object} object The source object.
+     * @param {...(string|string[])} [paths] The property paths to pick.
+     * @returns {Object} Returns the new object.
+     * @example
+     *
+     * var object = { 'a': 1, 'b': '2', 'c': 3 };
+     *
+     * _.pick(object, ['a', 'c']);
+     * // => { 'a': 1, 'c': 3 }
+     */
+    var pick = flatRest(function(object, paths) {
+      return object == null ? {} : basePick(object, paths);
     });
 
-    // add promise support -- natively available in Chrome 51
-    if (browserDetails.version < 51) {
-      ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate']
-          .forEach(function(method) {
-            var nativeMethod = webkitRTCPeerConnection.prototype[method];
-            webkitRTCPeerConnection.prototype[method] = function() {
-              var args = arguments;
-              var self = this;
-              var promise = new Promise(function(resolve, reject) {
-                nativeMethod.apply(self, [args[0], resolve, reject]);
-              });
-              if (args.length < 2) {
-                return promise;
-              }
-              return promise.then(function() {
-                args[1].apply(null, []);
-              },
-              function(err) {
-                if (args.length >= 3) {
-                  args[2].apply(null, [err]);
-                }
-              });
-            };
-          });
+    /**
+     * Creates an object composed of the `object` properties `predicate` returns
+     * truthy for. The predicate is invoked with two arguments: (value, key).
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Object
+     * @param {Object} object The source object.
+     * @param {Function} [predicate=_.identity] The function invoked per property.
+     * @returns {Object} Returns the new object.
+     * @example
+     *
+     * var object = { 'a': 1, 'b': '2', 'c': 3 };
+     *
+     * _.pickBy(object, _.isNumber);
+     * // => { 'a': 1, 'c': 3 }
+     */
+    function pickBy(object, predicate) {
+      if (object == null) {
+        return {};
+      }
+      var props = arrayMap(getAllKeysIn(object), function(prop) {
+        return [prop];
+      });
+      predicate = getIteratee(predicate);
+      return basePickBy(object, props, function(value, path) {
+        return predicate(value, path[0]);
+      });
     }
 
-    // support for addIceCandidate(null)
-    var nativeAddIceCandidate =
-        RTCPeerConnection.prototype.addIceCandidate;
-    RTCPeerConnection.prototype.addIceCandidate = function() {
-      return arguments[0] === null ? Promise.resolve()
-          : nativeAddIceCandidate.apply(this, arguments);
-    };
+    /**
+     * This method is like `_.get` except that if the resolved value is a
+     * function it's invoked with the `this` binding of its parent object and
+     * its result is returned.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Object
+     * @param {Object} object The object to query.
+     * @param {Array|string} path The path of the property to resolve.
+     * @param {*} [defaultValue] The value returned for `undefined` resolved values.
+     * @returns {*} Returns the resolved value.
+     * @example
+     *
+     * var object = { 'a': [{ 'b': { 'c1': 3, 'c2': _.constant(4) } }] };
+     *
+     * _.result(object, 'a[0].b.c1');
+     * // => 3
+     *
+     * _.result(object, 'a[0].b.c2');
+     * // => 4
+     *
+     * _.result(object, 'a[0].b.c3', 'default');
+     * // => 'default'
+     *
+     * _.result(object, 'a[0].b.c3', _.constant('default'));
+     * // => 'default'
+     */
+    function result(object, path, defaultValue) {
+      path = castPath(path, object);
 
-    // shim implicit creation of RTCSessionDescription/RTCIceCandidate
-    ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate']
-        .forEach(function(method) {
-          var nativeMethod = webkitRTCPeerConnection.prototype[method];
-          webkitRTCPeerConnection.prototype[method] = function() {
-            arguments[0] = new ((method === 'addIceCandidate') ?
-                RTCIceCandidate : RTCSessionDescription)(arguments[0]);
-            return nativeMethod.apply(this, arguments);
-          };
-        });
-  },
+      var index = -1,
+          length = path.length;
 
-  // Attach a media stream to an element.
-  attachMediaStream: function(element, stream) {
-    logging('DEPRECATED, attachMediaStream will soon be removed.');
-    if (browserDetails.version >= 43) {
-      element.srcObject = stream;
-    } else if (typeof element.src !== 'undefined') {
-      element.src = URL.createObjectURL(stream);
-    } else {
-      logging('Error attaching stream to element.');
+      // Ensure the loop is entered when path is empty.
+      if (!length) {
+        length = 1;
+        object = undefined;
+      }
+      while (++index < length) {
+        var value = object == null ? undefined : object[toKey(path[index])];
+        if (value === undefined) {
+          index = length;
+          value = defaultValue;
+        }
+        object = isFunction(value) ? value.call(object) : value;
+      }
+      return object;
     }
-  },
 
-  reattachMediaStream: function(to, from) {
-    logging('DEPRECATED, reattachMediaStream will soon be removed.');
-    if (browserDetails.version >= 43) {
-      to.srcObject = from.srcObject;
-    } else {
-      to.src = from.src;
+    /**
+     * Sets the value at `path` of `object`. If a portion of `path` doesn't exist,
+     * it's created. Arrays are created for missing index properties while objects
+     * are created for all other missing properties. Use `_.setWith` to customize
+     * `path` creation.
+     *
+     * **Note:** This method mutates `object`.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.7.0
+     * @category Object
+     * @param {Object} object The object to modify.
+     * @param {Array|string} path The path of the property to set.
+     * @param {*} value The value to set.
+     * @returns {Object} Returns `object`.
+     * @example
+     *
+     * var object = { 'a': [{ 'b': { 'c': 3 } }] };
+     *
+     * _.set(object, 'a[0].b.c', 4);
+     * console.log(object.a[0].b.c);
+     * // => 4
+     *
+     * _.set(object, ['x', '0', 'y', 'z'], 5);
+     * console.log(object.x[0].y.z);
+     * // => 5
+     */
+    function set(object, path, value) {
+      return object == null ? object : baseSet(object, path, value);
     }
-  }
-};
 
+    /**
+     * This method is like `_.set` except that it accepts `customizer` which is
+     * invoked to produce the objects of `path`.  If `customizer` returns `undefined`
+     * path creation is handled by the method instead. The `customizer` is invoked
+     * with three arguments: (nsValue, key, nsObject).
+     *
+     * **Note:** This method mutates `object`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Object
+     * @param {Object} object The object to modify.
+     * @param {Array|string} path The path of the property to set.
+     * @param {*} value The value to set.
+     * @param {Function} [customizer] The function to customize assigned values.
+     * @returns {Object} Returns `object`.
+     * @example
+     *
+     * var object = {};
+     *
+     * _.setWith(object, '[0][1]', 'a', Object);
+     * // => { '0': { '1': 'a' } }
+     */
+    function setWith(object, path, value, customizer) {
+      customizer = typeof customizer == 'function' ? customizer : undefined;
+      return object == null ? object : baseSet(object, path, value, customizer);
+    }
 
-// Expose public methods.
-module.exports = {
-  shimMediaStream: chromeShim.shimMediaStream,
-  shimOnTrack: chromeShim.shimOnTrack,
-  shimSourceObject: chromeShim.shimSourceObject,
-  shimPeerConnection: chromeShim.shimPeerConnection,
-  shimGetUserMedia: require('./getusermedia'),
-  attachMediaStream: chromeShim.attachMediaStream,
-  reattachMediaStream: chromeShim.reattachMediaStream
-};
+    /**
+     * Creates an array of own enumerable string keyed-value pairs for `object`
+     * which can be consumed by `_.fromPairs`. If `object` is a map or set, its
+     * entries are returned.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @alias entries
+     * @category Object
+     * @param {Object} object The object to query.
+     * @returns {Array} Returns the key-value pairs.
+     * @example
+     *
+     * function Foo() {
+     *   this.a = 1;
+     *   this.b = 2;
+     * }
+     *
+     * Foo.prototype.c = 3;
+     *
+     * _.toPairs(new Foo);
+     * // => [['a', 1], ['b', 2]] (iteration order is not guaranteed)
+     */
+    var toPairs = createToPairs(keys);
 
-},{"../utils.js":18,"./getusermedia":12}],12:[function(require,module,exports){
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
- /* eslint-env node */
-'use strict';
-var logging = require('../utils.js').log;
+    /**
+     * Creates an array of own and inherited enumerable string keyed-value pairs
+     * for `object` which can be consumed by `_.fromPairs`. If `object` is a map
+     * or set, its entries are returned.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @alias entriesIn
+     * @category Object
+     * @param {Object} object The object to query.
+     * @returns {Array} Returns the key-value pairs.
+     * @example
+     *
+     * function Foo() {
+     *   this.a = 1;
+     *   this.b = 2;
+     * }
+     *
+     * Foo.prototype.c = 3;
+     *
+     * _.toPairsIn(new Foo);
+     * // => [['a', 1], ['b', 2], ['c', 3]] (iteration order is not guaranteed)
+     */
+    var toPairsIn = createToPairs(keysIn);
 
-// Expose public methods.
-module.exports = function() {
-  var constraintsToChrome_ = function(c) {
-    if (typeof c !== 'object' || c.mandatory || c.optional) {
-      return c;
-    }
-    var cc = {};
-    Object.keys(c).forEach(function(key) {
-      if (key === 'require' || key === 'advanced' || key === 'mediaSource') {
-        return;
-      }
-      var r = (typeof c[key] === 'object') ? c[key] : {ideal: c[key]};
-      if (r.exact !== undefined && typeof r.exact === 'number') {
-        r.min = r.max = r.exact;
-      }
-      var oldname_ = function(prefix, name) {
-        if (prefix) {
-          return prefix + name.charAt(0).toUpperCase() + name.slice(1);
+    /**
+     * An alternative to `_.reduce`; this method transforms `object` to a new
+     * `accumulator` object which is the result of running each of its own
+     * enumerable string keyed properties thru `iteratee`, with each invocation
+     * potentially mutating the `accumulator` object. If `accumulator` is not
+     * provided, a new object with the same `[[Prototype]]` will be used. The
+     * iteratee is invoked with four arguments: (accumulator, value, key, object).
+     * Iteratee functions may exit iteration early by explicitly returning `false`.
+     *
+     * @static
+     * @memberOf _
+     * @since 1.3.0
+     * @category Object
+     * @param {Object} object The object to iterate over.
+     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
+     * @param {*} [accumulator] The custom accumulator value.
+     * @returns {*} Returns the accumulated value.
+     * @example
+     *
+     * _.transform([2, 3, 4], function(result, n) {
+     *   result.push(n *= n);
+     *   return n % 2 == 0;
+     * }, []);
+     * // => [4, 9]
+     *
+     * _.transform({ 'a': 1, 'b': 2, 'c': 1 }, function(result, value, key) {
+     *   (result[value] || (result[value] = [])).push(key);
+     * }, {});
+     * // => { '1': ['a', 'c'], '2': ['b'] }
+     */
+    function transform(object, iteratee, accumulator) {
+      var isArr = isArray(object),
+          isArrLike = isArr || isBuffer(object) || isTypedArray(object);
+
+      iteratee = getIteratee(iteratee, 4);
+      if (accumulator == null) {
+        var Ctor = object && object.constructor;
+        if (isArrLike) {
+          accumulator = isArr ? new Ctor : [];
         }
-        return (name === 'deviceId') ? 'sourceId' : name;
-      };
-      if (r.ideal !== undefined) {
-        cc.optional = cc.optional || [];
-        var oc = {};
-        if (typeof r.ideal === 'number') {
-          oc[oldname_('min', key)] = r.ideal;
-          cc.optional.push(oc);
-          oc = {};
-          oc[oldname_('max', key)] = r.ideal;
-          cc.optional.push(oc);
-        } else {
-          oc[oldname_('', key)] = r.ideal;
-          cc.optional.push(oc);
+        else if (isObject(object)) {
+          accumulator = isFunction(Ctor) ? baseCreate(getPrototype(object)) : {};
+        }
+        else {
+          accumulator = {};
         }
       }
-      if (r.exact !== undefined && typeof r.exact !== 'number') {
-        cc.mandatory = cc.mandatory || {};
-        cc.mandatory[oldname_('', key)] = r.exact;
-      } else {
-        ['min', 'max'].forEach(function(mix) {
-          if (r[mix] !== undefined) {
-            cc.mandatory = cc.mandatory || {};
-            cc.mandatory[oldname_(mix, key)] = r[mix];
-          }
-        });
-      }
-    });
-    if (c.advanced) {
-      cc.optional = (cc.optional || []).concat(c.advanced);
+      (isArrLike ? arrayEach : baseForOwn)(object, function(value, index, object) {
+        return iteratee(accumulator, value, index, object);
+      });
+      return accumulator;
     }
-    return cc;
-  };
 
-  var shimConstraints_ = function(constraints, func) {
-    constraints = JSON.parse(JSON.stringify(constraints));
-    if (constraints && constraints.audio) {
-      constraints.audio = constraintsToChrome_(constraints.audio);
+    /**
+     * Removes the property at `path` of `object`.
+     *
+     * **Note:** This method mutates `object`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Object
+     * @param {Object} object The object to modify.
+     * @param {Array|string} path The path of the property to unset.
+     * @returns {boolean} Returns `true` if the property is deleted, else `false`.
+     * @example
+     *
+     * var object = { 'a': [{ 'b': { 'c': 7 } }] };
+     * _.unset(object, 'a[0].b.c');
+     * // => true
+     *
+     * console.log(object);
+     * // => { 'a': [{ 'b': {} }] };
+     *
+     * _.unset(object, ['a', '0', 'b', 'c']);
+     * // => true
+     *
+     * console.log(object);
+     * // => { 'a': [{ 'b': {} }] };
+     */
+    function unset(object, path) {
+      return object == null ? true : baseUnset(object, path);
     }
-    if (constraints && typeof constraints.video === 'object') {
-      // Shim facingMode for mobile, where it defaults to "user".
-      var face = constraints.video.facingMode;
-      face = face && ((typeof face === 'object') ? face : {ideal: face});
 
-      if ((face && (face.exact === 'user' || face.exact === 'environment' ||
-                    face.ideal === 'user' || face.ideal === 'environment')) &&
-          !(navigator.mediaDevices.getSupportedConstraints &&
-            navigator.mediaDevices.getSupportedConstraints().facingMode)) {
-        delete constraints.video.facingMode;
-        if (face.exact === 'environment' || face.ideal === 'environment') {
-          // Look for "back" in label, or use last cam (typically back cam).
-          return navigator.mediaDevices.enumerateDevices()
-          .then(function(devices) {
-            devices = devices.filter(function(d) {
-              return d.kind === 'videoinput';
-            });
-            var back = devices.find(function(d) {
-              return d.label.toLowerCase().indexOf('back') !== -1;
-            }) || (devices.length && devices[devices.length - 1]);
-            if (back) {
-              constraints.video.deviceId = face.exact ? {exact: back.deviceId} :
-                                                        {ideal: back.deviceId};
-            }
-            constraints.video = constraintsToChrome_(constraints.video);
-            logging('chrome: ' + JSON.stringify(constraints));
-            return func(constraints);
-          });
-        }
-      }
-      constraints.video = constraintsToChrome_(constraints.video);
+    /**
+     * This method is like `_.set` except that accepts `updater` to produce the
+     * value to set. Use `_.updateWith` to customize `path` creation. The `updater`
+     * is invoked with one argument: (value).
+     *
+     * **Note:** This method mutates `object`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.6.0
+     * @category Object
+     * @param {Object} object The object to modify.
+     * @param {Array|string} path The path of the property to set.
+     * @param {Function} updater The function to produce the updated value.
+     * @returns {Object} Returns `object`.
+     * @example
+     *
+     * var object = { 'a': [{ 'b': { 'c': 3 } }] };
+     *
+     * _.update(object, 'a[0].b.c', function(n) { return n * n; });
+     * console.log(object.a[0].b.c);
+     * // => 9
+     *
+     * _.update(object, 'x[0].y.z', function(n) { return n ? n + 1 : 0; });
+     * console.log(object.x[0].y.z);
+     * // => 0
+     */
+    function update(object, path, updater) {
+      return object == null ? object : baseUpdate(object, path, castFunction(updater));
     }
-    logging('chrome: ' + JSON.stringify(constraints));
-    return func(constraints);
-  };
-
-  var shimError_ = function(e) {
-    return {
-      name: {
-        PermissionDeniedError: 'NotAllowedError',
-        ConstraintNotSatisfiedError: 'OverconstrainedError'
-      }[e.name] || e.name,
-      message: e.message,
-      constraint: e.constraintName,
-      toString: function() {
-        return this.name + (this.message && ': ') + this.message;
-      }
-    };
-  };
 
-  var getUserMedia_ = function(constraints, onSuccess, onError) {
-    shimConstraints_(constraints, function(c) {
-      navigator.webkitGetUserMedia(c, onSuccess, function(e) {
-        onError(shimError_(e));
-      });
-    });
-  };
+    /**
+     * This method is like `_.update` except that it accepts `customizer` which is
+     * invoked to produce the objects of `path`.  If `customizer` returns `undefined`
+     * path creation is handled by the method instead. The `customizer` is invoked
+     * with three arguments: (nsValue, key, nsObject).
+     *
+     * **Note:** This method mutates `object`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.6.0
+     * @category Object
+     * @param {Object} object The object to modify.
+     * @param {Array|string} path The path of the property to set.
+     * @param {Function} updater The function to produce the updated value.
+     * @param {Function} [customizer] The function to customize assigned values.
+     * @returns {Object} Returns `object`.
+     * @example
+     *
+     * var object = {};
+     *
+     * _.updateWith(object, '[0][1]', _.constant('a'), Object);
+     * // => { '0': { '1': 'a' } }
+     */
+    function updateWith(object, path, updater, customizer) {
+      customizer = typeof customizer == 'function' ? customizer : undefined;
+      return object == null ? object : baseUpdate(object, path, castFunction(updater), customizer);
+    }
 
-  navigator.getUserMedia = getUserMedia_;
+    /**
+     * Creates an array of the own enumerable string keyed property values of `object`.
+     *
+     * **Note:** Non-object values are coerced to objects.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Object
+     * @param {Object} object The object to query.
+     * @returns {Array} Returns the array of property values.
+     * @example
+     *
+     * function Foo() {
+     *   this.a = 1;
+     *   this.b = 2;
+     * }
+     *
+     * Foo.prototype.c = 3;
+     *
+     * _.values(new Foo);
+     * // => [1, 2] (iteration order is not guaranteed)
+     *
+     * _.values('hi');
+     * // => ['h', 'i']
+     */
+    function values(object) {
+      return object == null ? [] : baseValues(object, keys(object));
+    }
 
-  // Returns the result of getUserMedia as a Promise.
-  var getUserMediaPromise_ = function(constraints) {
-    return new Promise(function(resolve, reject) {
-      navigator.getUserMedia(constraints, resolve, reject);
-    });
-  };
+    /**
+     * Creates an array of the own and inherited enumerable string keyed property
+     * values of `object`.
+     *
+     * **Note:** Non-object values are coerced to objects.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category Object
+     * @param {Object} object The object to query.
+     * @returns {Array} Returns the array of property values.
+     * @example
+     *
+     * function Foo() {
+     *   this.a = 1;
+     *   this.b = 2;
+     * }
+     *
+     * Foo.prototype.c = 3;
+     *
+     * _.valuesIn(new Foo);
+     * // => [1, 2, 3] (iteration order is not guaranteed)
+     */
+    function valuesIn(object) {
+      return object == null ? [] : baseValues(object, keysIn(object));
+    }
 
-  if (!navigator.mediaDevices) {
-    navigator.mediaDevices = {
-      getUserMedia: getUserMediaPromise_,
-      enumerateDevices: function() {
-        return new Promise(function(resolve) {
-          var kinds = {audio: 'audioinput', video: 'videoinput'};
-          return MediaStreamTrack.getSources(function(devices) {
-            resolve(devices.map(function(device) {
-              return {label: device.label,
-                      kind: kinds[device.kind],
-                      deviceId: device.id,
-                      groupId: ''};
-            }));
-          });
-        });
-      }
-    };
-  }
+    /*------------------------------------------------------------------------*/
 
-  // A shim for getUserMedia method on the mediaDevices object.
-  // TODO(KaptenJansson) remove once implemented in Chrome stable.
-  if (!navigator.mediaDevices.getUserMedia) {
-    navigator.mediaDevices.getUserMedia = function(constraints) {
-      return getUserMediaPromise_(constraints);
-    };
-  } else {
-    // Even though Chrome 45 has navigator.mediaDevices and a getUserMedia
-    // function which returns a Promise, it does not accept spec-style
-    // constraints.
-    var origGetUserMedia = navigator.mediaDevices.getUserMedia.
-        bind(navigator.mediaDevices);
-    navigator.mediaDevices.getUserMedia = function(cs) {
-      return shimConstraints_(cs, function(c) {
-        return origGetUserMedia(c).catch(function(e) {
-          return Promise.reject(shimError_(e));
-        });
-      });
-    };
-  }
-
-  // Dummy devicechange event methods.
-  // TODO(KaptenJansson) remove once implemented in Chrome stable.
-  if (typeof navigator.mediaDevices.addEventListener === 'undefined') {
-    navigator.mediaDevices.addEventListener = function() {
-      logging('Dummy mediaDevices.addEventListener called.');
-    };
-  }
-  if (typeof navigator.mediaDevices.removeEventListener === 'undefined') {
-    navigator.mediaDevices.removeEventListener = function() {
-      logging('Dummy mediaDevices.removeEventListener called.');
-    };
-  }
-};
-
-},{"../utils.js":18}],13:[function(require,module,exports){
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
- /* eslint-env node */
-'use strict';
+    /**
+     * Clamps `number` within the inclusive `lower` and `upper` bounds.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Number
+     * @param {number} number The number to clamp.
+     * @param {number} [lower] The lower bound.
+     * @param {number} upper The upper bound.
+     * @returns {number} Returns the clamped number.
+     * @example
+     *
+     * _.clamp(-10, -5, 5);
+     * // => -5
+     *
+     * _.clamp(10, -5, 5);
+     * // => 5
+     */
+    function clamp(number, lower, upper) {
+      if (upper === undefined) {
+        upper = lower;
+        lower = undefined;
+      }
+      if (upper !== undefined) {
+        upper = toNumber(upper);
+        upper = upper === upper ? upper : 0;
+      }
+      if (lower !== undefined) {
+        lower = toNumber(lower);
+        lower = lower === lower ? lower : 0;
+      }
+      return baseClamp(toNumber(number), lower, upper);
+    }
 
-var SDPUtils = require('sdp');
-var logging = require('../utils').log;
+    /**
+     * Checks if `n` is between `start` and up to, but not including, `end`. If
+     * `end` is not specified, it's set to `start` with `start` then set to `0`.
+     * If `start` is greater than `end` the params are swapped to support
+     * negative ranges.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.3.0
+     * @category Number
+     * @param {number} number The number to check.
+     * @param {number} [start=0] The start of the range.
+     * @param {number} end The end of the range.
+     * @returns {boolean} Returns `true` if `number` is in the range, else `false`.
+     * @see _.range, _.rangeRight
+     * @example
+     *
+     * _.inRange(3, 2, 4);
+     * // => true
+     *
+     * _.inRange(4, 8);
+     * // => true
+     *
+     * _.inRange(4, 2);
+     * // => false
+     *
+     * _.inRange(2, 2);
+     * // => false
+     *
+     * _.inRange(1.2, 2);
+     * // => true
+     *
+     * _.inRange(5.2, 4);
+     * // => false
+     *
+     * _.inRange(-3, -2, -6);
+     * // => true
+     */
+    function inRange(number, start, end) {
+      start = toFinite(start);
+      if (end === undefined) {
+        end = start;
+        start = 0;
+      } else {
+        end = toFinite(end);
+      }
+      number = toNumber(number);
+      return baseInRange(number, start, end);
+    }
 
-var edgeShim = {
-  shimPeerConnection: function() {
-    if (window.RTCIceGatherer) {
-      // ORTC defines an RTCIceCandidate object but no constructor.
-      // Not implemented in Edge.
-      if (!window.RTCIceCandidate) {
-        window.RTCIceCandidate = function(args) {
-          return args;
-        };
+    /**
+     * Produces a random number between the inclusive `lower` and `upper` bounds.
+     * If only one argument is provided a number between `0` and the given number
+     * is returned. If `floating` is `true`, or either `lower` or `upper` are
+     * floats, a floating-point number is returned instead of an integer.
+     *
+     * **Note:** JavaScript follows the IEEE-754 standard for resolving
+     * floating-point values which can produce unexpected results.
+     *
+     * @static
+     * @memberOf _
+     * @since 0.7.0
+     * @category Number
+     * @param {number} [lower=0] The lower bound.
+     * @param {number} [upper=1] The upper bound.
+     * @param {boolean} [floating] Specify returning a floating-point number.
+     * @returns {number} Returns the random number.
+     * @example
+     *
+     * _.random(0, 5);
+     * // => an integer between 0 and 5
+     *
+     * _.random(5);
+     * // => also an integer between 0 and 5
+     *
+     * _.random(5, true);
+     * // => a floating-point number between 0 and 5
+     *
+     * _.random(1.2, 5.2);
+     * // => a floating-point number between 1.2 and 5.2
+     */
+    function random(lower, upper, floating) {
+      if (floating && typeof floating != 'boolean' && isIterateeCall(lower, upper, floating)) {
+        upper = floating = undefined;
       }
-      // ORTC does not have a session description object but
-      // other browsers (i.e. Chrome) that will support both PC and ORTC
-      // in the future might have this defined already.
-      if (!window.RTCSessionDescription) {
-        window.RTCSessionDescription = function(args) {
-          return args;
-        };
+      if (floating === undefined) {
+        if (typeof upper == 'boolean') {
+          floating = upper;
+          upper = undefined;
+        }
+        else if (typeof lower == 'boolean') {
+          floating = lower;
+          lower = undefined;
+        }
+      }
+      if (lower === undefined && upper === undefined) {
+        lower = 0;
+        upper = 1;
+      }
+      else {
+        lower = toFinite(lower);
+        if (upper === undefined) {
+          upper = lower;
+          lower = 0;
+        } else {
+          upper = toFinite(upper);
+        }
+      }
+      if (lower > upper) {
+        var temp = lower;
+        lower = upper;
+        upper = temp;
+      }
+      if (floating || lower % 1 || upper % 1) {
+        var rand = nativeRandom();
+        return nativeMin(lower + (rand * (upper - lower + freeParseFloat('1e-' + ((rand + '').length - 1)))), upper);
       }
+      return baseRandom(lower, upper);
     }
 
-    window.RTCPeerConnection = function(config) {
-      var self = this;
+    /*------------------------------------------------------------------------*/
 
-      var _eventTarget = document.createDocumentFragment();
-      ['addEventListener', 'removeEventListener', 'dispatchEvent']
-          .forEach(function(method) {
-            self[method] = _eventTarget[method].bind(_eventTarget);
-          });
+    /**
+     * Converts `string` to [camel case](https://en.wikipedia.org/wiki/CamelCase).
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category String
+     * @param {string} [string=''] The string to convert.
+     * @returns {string} Returns the camel cased string.
+     * @example
+     *
+     * _.camelCase('Foo Bar');
+     * // => 'fooBar'
+     *
+     * _.camelCase('--foo-bar--');
+     * // => 'fooBar'
+     *
+     * _.camelCase('__FOO_BAR__');
+     * // => 'fooBar'
+     */
+    var camelCase = createCompounder(function(result, word, index) {
+      word = word.toLowerCase();
+      return result + (index ? capitalize(word) : word);
+    });
 
-      this.onicecandidate = null;
-      this.onaddstream = null;
-      this.ontrack = null;
-      this.onremovestream = null;
-      this.onsignalingstatechange = null;
-      this.oniceconnectionstatechange = null;
-      this.onnegotiationneeded = null;
-      this.ondatachannel = null;
+    /**
+     * Converts the first character of `string` to upper case and the remaining
+     * to lower case.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category String
+     * @param {string} [string=''] The string to capitalize.
+     * @returns {string} Returns the capitalized string.
+     * @example
+     *
+     * _.capitalize('FRED');
+     * // => 'Fred'
+     */
+    function capitalize(string) {
+      return upperFirst(toString(string).toLowerCase());
+    }
 
-      this.localStreams = [];
-      this.remoteStreams = [];
-      this.getLocalStreams = function() {
-        return self.localStreams;
-      };
-      this.getRemoteStreams = function() {
-        return self.remoteStreams;
-      };
+    /**
+     * Deburrs `string` by converting
+     * [Latin-1 Supplement](https://en.wikipedia.org/wiki/Latin-1_Supplement_(Unicode_block)#Character_table)
+     * and [Latin Extended-A](https://en.wikipedia.org/wiki/Latin_Extended-A)
+     * letters to basic Latin letters and removing
+     * [combining diacritical marks](https://en.wikipedia.org/wiki/Combining_Diacritical_Marks).
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category String
+     * @param {string} [string=''] The string to deburr.
+     * @returns {string} Returns the deburred string.
+     * @example
+     *
+     * _.deburr('déjà vu');
+     * // => 'deja vu'
+     */
+    function deburr(string) {
+      string = toString(string);
+      return string && string.replace(reLatin, deburrLetter).replace(reComboMark, '');
+    }
 
-      this.localDescription = new RTCSessionDescription({
-        type: '',
-        sdp: ''
-      });
-      this.remoteDescription = new RTCSessionDescription({
-        type: '',
-        sdp: ''
-      });
-      this.signalingState = 'stable';
-      this.iceConnectionState = 'new';
-      this.iceGatheringState = 'new';
+    /**
+     * Checks if `string` ends with the given target string.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category String
+     * @param {string} [string=''] The string to inspect.
+     * @param {string} [target] The string to search for.
+     * @param {number} [position=string.length] The position to search up to.
+     * @returns {boolean} Returns `true` if `string` ends with `target`,
+     *  else `false`.
+     * @example
+     *
+     * _.endsWith('abc', 'c');
+     * // => true
+     *
+     * _.endsWith('abc', 'b');
+     * // => false
+     *
+     * _.endsWith('abc', 'b', 2);
+     * // => true
+     */
+    function endsWith(string, target, position) {
+      string = toString(string);
+      target = baseToString(target);
 
-      this.iceOptions = {
-        gatherPolicy: 'all',
-        iceServers: []
-      };
-      if (config && config.iceTransportPolicy) {
-        switch (config.iceTransportPolicy) {
-          case 'all':
-          case 'relay':
-            this.iceOptions.gatherPolicy = config.iceTransportPolicy;
-            break;
-          case 'none':
-            // FIXME: remove once implementation and spec have added this.
-            throw new TypeError('iceTransportPolicy "none" not supported');
-          default:
-            // don't set iceTransportPolicy.
-            break;
-        }
-      }
-      this.usingBundle = config && config.bundlePolicy === 'max-bundle';
+      var length = string.length;
+      position = position === undefined
+        ? length
+        : baseClamp(toInteger(position), 0, length);
 
-      if (config && config.iceServers) {
-        // Edge does not like
-        // 1) stun:
-        // 2) turn: that does not have all of turn:host:port?transport=udp
-        var iceServers = JSON.parse(JSON.stringify(config.iceServers));
-        this.iceOptions.iceServers = iceServers.filter(function(server) {
-          if (server && server.urls) {
-            var urls = server.urls;
-            if (typeof urls === 'string') {
-              urls = [urls];
-            }
-            urls = urls.filter(function(url) {
-              return url.indexOf('turn:') === 0 &&
-                  url.indexOf('transport=udp') !== -1;
-            })[0];
-            return !!urls;
-          }
-          return false;
-        });
-      }
+      var end = position;
+      position -= target.length;
+      return position >= 0 && string.slice(position, end) == target;
+    }
 
-      // per-track iceGathers, iceTransports, dtlsTransports, rtpSenders, ...
-      // everything that is needed to describe a SDP m-line.
-      this.transceivers = [];
+    /**
+     * Converts the characters "&", "<", ">", '"', and "'" in `string` to their
+     * corresponding HTML entities.
+     *
+     * **Note:** No other characters are escaped. To escape additional
+     * characters use a third-party library like [_he_](https://mths.be/he).
+     *
+     * Though the ">" character is escaped for symmetry, characters like
+     * ">" and "/" don't need escaping in HTML and have no special meaning
+     * unless they're part of a tag or unquoted attribute value. See
+     * [Mathias Bynens's article](https://mathiasbynens.be/notes/ambiguous-ampersands)
+     * (under "semi-related fun fact") for more details.
+     *
+     * When working with HTML you should always
+     * [quote attribute values](http://wonko.com/post/html-escaping) to reduce
+     * XSS vectors.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category String
+     * @param {string} [string=''] The string to escape.
+     * @returns {string} Returns the escaped string.
+     * @example
+     *
+     * _.escape('fred, barney, & pebbles');
+     * // => 'fred, barney, &amp; pebbles'
+     */
+    function escape(string) {
+      string = toString(string);
+      return (string && reHasUnescapedHtml.test(string))
+        ? string.replace(reUnescapedHtml, escapeHtmlChar)
+        : string;
+    }
 
-      // since the iceGatherer is currently created in createOffer but we
-      // must not emit candidates until after setLocalDescription we buffer
-      // them in this array.
-      this._localIceCandidatesBuffer = [];
-    };
+    /**
+     * Escapes the `RegExp` special characters "^", "$", "\", ".", "*", "+",
+     * "?", "(", ")", "[", "]", "{", "}", and "|" in `string`.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category String
+     * @param {string} [string=''] The string to escape.
+     * @returns {string} Returns the escaped string.
+     * @example
+     *
+     * _.escapeRegExp('[lodash](https://lodash.com/)');
+     * // => '\[lodash\]\(https://lodash\.com/\)'
+     */
+    function escapeRegExp(string) {
+      string = toString(string);
+      return (string && reHasRegExpChar.test(string))
+        ? string.replace(reRegExpChar, '\\$&')
+        : string;
+    }
 
-    window.RTCPeerConnection.prototype._emitBufferedCandidates = function() {
-      var self = this;
-      var sections = SDPUtils.splitSections(self.localDescription.sdp);
-      // FIXME: need to apply ice candidates in a way which is async but
-      // in-order
-      this._localIceCandidatesBuffer.forEach(function(event) {
-        var end = !event.candidate || Object.keys(event.candidate).length === 0;
-        if (end) {
-          for (var j = 1; j < sections.length; j++) {
-            if (sections[j].indexOf('\r\na=end-of-candidates\r\n') === -1) {
-              sections[j] += 'a=end-of-candidates\r\n';
-            }
-          }
-        } else if (event.candidate.candidate.indexOf('typ endOfCandidates')
-            === -1) {
-          sections[event.candidate.sdpMLineIndex + 1] +=
-              'a=' + event.candidate.candidate + '\r\n';
-        }
-        self.localDescription.sdp = sections.join('');
-        self.dispatchEvent(event);
-        if (self.onicecandidate !== null) {
-          self.onicecandidate(event);
-        }
-        if (!event.candidate && self.iceGatheringState !== 'complete') {
-          var complete = self.transceivers.every(function(transceiver) {
-            return transceiver.iceGatherer &&
-                transceiver.iceGatherer.state === 'completed';
-          });
-          if (complete) {
-            self.iceGatheringState = 'complete';
-          }
-        }
-      });
-      this._localIceCandidatesBuffer = [];
-    };
+    /**
+     * Converts `string` to
+     * [kebab case](https://en.wikipedia.org/wiki/Letter_case#Special_case_styles).
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category String
+     * @param {string} [string=''] The string to convert.
+     * @returns {string} Returns the kebab cased string.
+     * @example
+     *
+     * _.kebabCase('Foo Bar');
+     * // => 'foo-bar'
+     *
+     * _.kebabCase('fooBar');
+     * // => 'foo-bar'
+     *
+     * _.kebabCase('__FOO_BAR__');
+     * // => 'foo-bar'
+     */
+    var kebabCase = createCompounder(function(result, word, index) {
+      return result + (index ? '-' : '') + word.toLowerCase();
+    });
 
-    window.RTCPeerConnection.prototype.addStream = function(stream) {
-      // Clone is necessary for local demos mostly, attaching directly
-      // to two different senders does not work (build 10547).
-      this.localStreams.push(stream.clone());
-      this._maybeFireNegotiationNeeded();
-    };
+    /**
+     * Converts `string`, as space separated words, to lower case.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category String
+     * @param {string} [string=''] The string to convert.
+     * @returns {string} Returns the lower cased string.
+     * @example
+     *
+     * _.lowerCase('--Foo-Bar--');
+     * // => 'foo bar'
+     *
+     * _.lowerCase('fooBar');
+     * // => 'foo bar'
+     *
+     * _.lowerCase('__FOO_BAR__');
+     * // => 'foo bar'
+     */
+    var lowerCase = createCompounder(function(result, word, index) {
+      return result + (index ? ' ' : '') + word.toLowerCase();
+    });
 
-    window.RTCPeerConnection.prototype.removeStream = function(stream) {
-      var idx = this.localStreams.indexOf(stream);
-      if (idx > -1) {
-        this.localStreams.splice(idx, 1);
-        this._maybeFireNegotiationNeeded();
-      }
-    };
+    /**
+     * Converts the first character of `string` to lower case.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category String
+     * @param {string} [string=''] The string to convert.
+     * @returns {string} Returns the converted string.
+     * @example
+     *
+     * _.lowerFirst('Fred');
+     * // => 'fred'
+     *
+     * _.lowerFirst('FRED');
+     * // => 'fRED'
+     */
+    var lowerFirst = createCaseFirst('toLowerCase');
 
-    window.RTCPeerConnection.prototype.getSenders = function() {
-      return this.transceivers.filter(function(transceiver) {
-        return !!transceiver.rtpSender;
-      })
-      .map(function(transceiver) {
-        return transceiver.rtpSender;
-      });
-    };
+    /**
+     * Pads `string` on the left and right sides if it's shorter than `length`.
+     * Padding characters are truncated if they can't be evenly divided by `length`.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category String
+     * @param {string} [string=''] The string to pad.
+     * @param {number} [length=0] The padding length.
+     * @param {string} [chars=' '] The string used as padding.
+     * @returns {string} Returns the padded string.
+     * @example
+     *
+     * _.pad('abc', 8);
+     * // => '  abc   '
+     *
+     * _.pad('abc', 8, '_-');
+     * // => '_-abc_-_'
+     *
+     * _.pad('abc', 3);
+     * // => 'abc'
+     */
+    function pad(string, length, chars) {
+      string = toString(string);
+      length = toInteger(length);
 
-    window.RTCPeerConnection.prototype.getReceivers = function() {
-      return this.transceivers.filter(function(transceiver) {
-        return !!transceiver.rtpReceiver;
-      })
-      .map(function(transceiver) {
-        return transceiver.rtpReceiver;
-      });
-    };
+      var strLength = length ? stringSize(string) : 0;
+      if (!length || strLength >= length) {
+        return string;
+      }
+      var mid = (length - strLength) / 2;
+      return (
+        createPadding(nativeFloor(mid), chars) +
+        string +
+        createPadding(nativeCeil(mid), chars)
+      );
+    }
 
-    // Determines the intersection of local and remote capabilities.
-    window.RTCPeerConnection.prototype._getCommonCapabilities =
-        function(localCapabilities, remoteCapabilities) {
-          var commonCapabilities = {
-            codecs: [],
-            headerExtensions: [],
-            fecMechanisms: []
-          };
-          localCapabilities.codecs.forEach(function(lCodec) {
-            for (var i = 0; i < remoteCapabilities.codecs.length; i++) {
-              var rCodec = remoteCapabilities.codecs[i];
-              if (lCodec.name.toLowerCase() === rCodec.name.toLowerCase() &&
-                  lCodec.clockRate === rCodec.clockRate &&
-                  lCodec.numChannels === rCodec.numChannels) {
-                // push rCodec so we reply with offerer payload type
-                commonCapabilities.codecs.push(rCodec);
+    /**
+     * Pads `string` on the right side if it's shorter than `length`. Padding
+     * characters are truncated if they exceed `length`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category String
+     * @param {string} [string=''] The string to pad.
+     * @param {number} [length=0] The padding length.
+     * @param {string} [chars=' '] The string used as padding.
+     * @returns {string} Returns the padded string.
+     * @example
+     *
+     * _.padEnd('abc', 6);
+     * // => 'abc   '
+     *
+     * _.padEnd('abc', 6, '_-');
+     * // => 'abc_-_'
+     *
+     * _.padEnd('abc', 3);
+     * // => 'abc'
+     */
+    function padEnd(string, length, chars) {
+      string = toString(string);
+      length = toInteger(length);
 
-                // FIXME: also need to determine intersection between
-                // .rtcpFeedback and .parameters
-                break;
-              }
-            }
-          });
+      var strLength = length ? stringSize(string) : 0;
+      return (length && strLength < length)
+        ? (string + createPadding(length - strLength, chars))
+        : string;
+    }
 
-          localCapabilities.headerExtensions
-              .forEach(function(lHeaderExtension) {
-                for (var i = 0; i < remoteCapabilities.headerExtensions.length;
-                     i++) {
-                  var rHeaderExtension = remoteCapabilities.headerExtensions[i];
-                  if (lHeaderExtension.uri === rHeaderExtension.uri) {
-                    commonCapabilities.headerExtensions.push(rHeaderExtension);
-                    break;
-                  }
-                }
-              });
+    /**
+     * Pads `string` on the left side if it's shorter than `length`. Padding
+     * characters are truncated if they exceed `length`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category String
+     * @param {string} [string=''] The string to pad.
+     * @param {number} [length=0] The padding length.
+     * @param {string} [chars=' '] The string used as padding.
+     * @returns {string} Returns the padded string.
+     * @example
+     *
+     * _.padStart('abc', 6);
+     * // => '   abc'
+     *
+     * _.padStart('abc', 6, '_-');
+     * // => '_-_abc'
+     *
+     * _.padStart('abc', 3);
+     * // => 'abc'
+     */
+    function padStart(string, length, chars) {
+      string = toString(string);
+      length = toInteger(length);
 
-          // FIXME: fecMechanisms
-          return commonCapabilities;
-        };
+      var strLength = length ? stringSize(string) : 0;
+      return (length && strLength < length)
+        ? (createPadding(length - strLength, chars) + string)
+        : string;
+    }
 
-    // Create ICE gatherer, ICE transport and DTLS transport.
-    window.RTCPeerConnection.prototype._createIceAndDtlsTransports =
-        function(mid, sdpMLineIndex) {
-          var self = this;
-          var iceGatherer = new RTCIceGatherer(self.iceOptions);
-          var iceTransport = new RTCIceTransport(iceGatherer);
-          iceGatherer.onlocalcandidate = function(evt) {
-            var event = new Event('icecandidate');
-            event.candidate = {sdpMid: mid, sdpMLineIndex: sdpMLineIndex};
+    /**
+     * Converts `string` to an integer of the specified radix. If `radix` is
+     * `undefined` or `0`, a `radix` of `10` is used unless `value` is a
+     * hexadecimal, in which case a `radix` of `16` is used.
+     *
+     * **Note:** This method aligns with the
+     * [ES5 implementation](https://es5.github.io/#x15.1.2.2) of `parseInt`.
+     *
+     * @static
+     * @memberOf _
+     * @since 1.1.0
+     * @category String
+     * @param {string} string The string to convert.
+     * @param {number} [radix=10] The radix to interpret `value` by.
+     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
+     * @returns {number} Returns the converted integer.
+     * @example
+     *
+     * _.parseInt('08');
+     * // => 8
+     *
+     * _.map(['6', '08', '10'], _.parseInt);
+     * // => [6, 8, 10]
+     */
+    function parseInt(string, radix, guard) {
+      if (guard || radix == null) {
+        radix = 0;
+      } else if (radix) {
+        radix = +radix;
+      }
+      return nativeParseInt(toString(string).replace(reTrimStart, ''), radix || 0);
+    }
 
-            var cand = evt.candidate;
-            var end = !cand || Object.keys(cand).length === 0;
-            // Edge emits an empty object for RTCIceCandidateComplete‥
-            if (end) {
-              // polyfill since RTCIceGatherer.state is not implemented in
-              // Edge 10547 yet.
-              if (iceGatherer.state === undefined) {
-                iceGatherer.state = 'completed';
-              }
+    /**
+     * Repeats the given string `n` times.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category String
+     * @param {string} [string=''] The string to repeat.
+     * @param {number} [n=1] The number of times to repeat the string.
+     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
+     * @returns {string} Returns the repeated string.
+     * @example
+     *
+     * _.repeat('*', 3);
+     * // => '***'
+     *
+     * _.repeat('abc', 2);
+     * // => 'abcabc'
+     *
+     * _.repeat('abc', 0);
+     * // => ''
+     */
+    function repeat(string, n, guard) {
+      if ((guard ? isIterateeCall(string, n, guard) : n === undefined)) {
+        n = 1;
+      } else {
+        n = toInteger(n);
+      }
+      return baseRepeat(toString(string), n);
+    }
 
-              // Emit a candidate with type endOfCandidates to make the samples
-              // work. Edge requires addIceCandidate with this empty candidate
-              // to start checking. The real solution is to signal
-              // end-of-candidates to the other side when getting the null
-              // candidate but some apps (like the samples) don't do that.
-              event.candidate.candidate =
-                  'candidate:1 1 udp 1 0.0.0.0 9 typ endOfCandidates';
-            } else {
-              // RTCIceCandidate doesn't have a component, needs to be added
-              cand.component = iceTransport.component === 'RTCP' ? 2 : 1;
-              event.candidate.candidate = SDPUtils.writeCandidate(cand);
-            }
-
-            // update local description.
-            var sections = SDPUtils.splitSections(self.localDescription.sdp);
-            if (event.candidate.candidate.indexOf('typ endOfCandidates')
-                === -1) {
-              sections[event.candidate.sdpMLineIndex + 1] +=
-                  'a=' + event.candidate.candidate + '\r\n';
-            } else {
-              sections[event.candidate.sdpMLineIndex + 1] +=
-                  'a=end-of-candidates\r\n';
-            }
-            self.localDescription.sdp = sections.join('');
-
-            var complete = self.transceivers.every(function(transceiver) {
-              return transceiver.iceGatherer &&
-                  transceiver.iceGatherer.state === 'completed';
-            });
-
-            // Emit candidate if localDescription is set.
-            // Also emits null candidate when all gatherers are complete.
-            switch (self.iceGatheringState) {
-              case 'new':
-                self._localIceCandidatesBuffer.push(event);
-                if (end && complete) {
-                  self._localIceCandidatesBuffer.push(
-                      new Event('icecandidate'));
-                }
-                break;
-              case 'gathering':
-                self._emitBufferedCandidates();
-                self.dispatchEvent(event);
-                if (self.onicecandidate !== null) {
-                  self.onicecandidate(event);
-                }
-                if (complete) {
-                  self.dispatchEvent(new Event('icecandidate'));
-                  if (self.onicecandidate !== null) {
-                    self.onicecandidate(new Event('icecandidate'));
-                  }
-                  self.iceGatheringState = 'complete';
-                }
-                break;
-              case 'complete':
-                // should not happen... currently!
-                break;
-              default: // no-op.
-                break;
-            }
-          };
-          iceTransport.onicestatechange = function() {
-            self._updateConnectionState();
-          };
+    /**
+     * Replaces matches for `pattern` in `string` with `replacement`.
+     *
+     * **Note:** This method is based on
+     * [`String#replace`](https://mdn.io/String/replace).
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category String
+     * @param {string} [string=''] The string to modify.
+     * @param {RegExp|string} pattern The pattern to replace.
+     * @param {Function|string} replacement The match replacement.
+     * @returns {string} Returns the modified string.
+     * @example
+     *
+     * _.replace('Hi Fred', 'Fred', 'Barney');
+     * // => 'Hi Barney'
+     */
+    function replace() {
+      var args = arguments,
+          string = toString(args[0]);
 
-          var dtlsTransport = new RTCDtlsTransport(iceTransport);
-          dtlsTransport.ondtlsstatechange = function() {
-            self._updateConnectionState();
-          };
-          dtlsTransport.onerror = function() {
-            // onerror does not set state to failed by itself.
-            dtlsTransport.state = 'failed';
-            self._updateConnectionState();
-          };
+      return args.length < 3 ? string : string.replace(args[1], args[2]);
+    }
 
-          return {
-            iceGatherer: iceGatherer,
-            iceTransport: iceTransport,
-            dtlsTransport: dtlsTransport
-          };
-        };
+    /**
+     * Converts `string` to
+     * [snake case](https://en.wikipedia.org/wiki/Snake_case).
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category String
+     * @param {string} [string=''] The string to convert.
+     * @returns {string} Returns the snake cased string.
+     * @example
+     *
+     * _.snakeCase('Foo Bar');
+     * // => 'foo_bar'
+     *
+     * _.snakeCase('fooBar');
+     * // => 'foo_bar'
+     *
+     * _.snakeCase('--FOO-BAR--');
+     * // => 'foo_bar'
+     */
+    var snakeCase = createCompounder(function(result, word, index) {
+      return result + (index ? '_' : '') + word.toLowerCase();
+    });
 
-    // Start the RTP Sender and Receiver for a transceiver.
-    window.RTCPeerConnection.prototype._transceive = function(transceiver,
-        send, recv) {
-      var params = this._getCommonCapabilities(transceiver.localCapabilities,
-          transceiver.remoteCapabilities);
-      if (send && transceiver.rtpSender) {
-        params.encodings = transceiver.sendEncodingParameters;
-        params.rtcp = {
-          cname: SDPUtils.localCName
-        };
-        if (transceiver.recvEncodingParameters.length) {
-          params.rtcp.ssrc = transceiver.recvEncodingParameters[0].ssrc;
-        }
-        transceiver.rtpSender.send(params);
+    /**
+     * Splits `string` by `separator`.
+     *
+     * **Note:** This method is based on
+     * [`String#split`](https://mdn.io/String/split).
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category String
+     * @param {string} [string=''] The string to split.
+     * @param {RegExp|string} separator The separator pattern to split by.
+     * @param {number} [limit] The length to truncate results to.
+     * @returns {Array} Returns the string segments.
+     * @example
+     *
+     * _.split('a-b-c', '-', 2);
+     * // => ['a', 'b']
+     */
+    function split(string, separator, limit) {
+      if (limit && typeof limit != 'number' && isIterateeCall(string, separator, limit)) {
+        separator = limit = undefined;
       }
-      if (recv && transceiver.rtpReceiver) {
-        params.encodings = transceiver.recvEncodingParameters;
-        params.rtcp = {
-          cname: transceiver.cname
-        };
-        if (transceiver.sendEncodingParameters.length) {
-          params.rtcp.ssrc = transceiver.sendEncodingParameters[0].ssrc;
+      limit = limit === undefined ? MAX_ARRAY_LENGTH : limit >>> 0;
+      if (!limit) {
+        return [];
+      }
+      string = toString(string);
+      if (string && (
+            typeof separator == 'string' ||
+            (separator != null && !isRegExp(separator))
+          )) {
+        separator = baseToString(separator);
+        if (!separator && hasUnicode(string)) {
+          return castSlice(stringToArray(string), 0, limit);
         }
-        transceiver.rtpReceiver.receive(params);
       }
-    };
-
-    window.RTCPeerConnection.prototype.setLocalDescription =
-        function(description) {
-          var self = this;
-          var sections;
-          var sessionpart;
-          if (description.type === 'offer') {
-            // FIXME: What was the purpose of this empty if statement?
-            // if (!this._pendingOffer) {
-            // } else {
-            if (this._pendingOffer) {
-              // VERY limited support for SDP munging. Limited to:
-              // * changing the order of codecs
-              sections = SDPUtils.splitSections(description.sdp);
-              sessionpart = sections.shift();
-              sections.forEach(function(mediaSection, sdpMLineIndex) {
-                var caps = SDPUtils.parseRtpParameters(mediaSection);
-                self._pendingOffer[sdpMLineIndex].localCapabilities = caps;
-              });
-              this.transceivers = this._pendingOffer;
-              delete this._pendingOffer;
-            }
-          } else if (description.type === 'answer') {
-            sections = SDPUtils.splitSections(self.remoteDescription.sdp);
-            sessionpart = sections.shift();
-            var isIceLite = SDPUtils.matchPrefix(sessionpart,
-                'a=ice-lite').length > 0;
-            sections.forEach(function(mediaSection, sdpMLineIndex) {
-              var transceiver = self.transceivers[sdpMLineIndex];
-              var iceGatherer = transceiver.iceGatherer;
-              var iceTransport = transceiver.iceTransport;
-              var dtlsTransport = transceiver.dtlsTransport;
-              var localCapabilities = transceiver.localCapabilities;
-              var remoteCapabilities = transceiver.remoteCapabilities;
-              var rejected = mediaSection.split('\n', 1)[0]
-                  .split(' ', 2)[1] === '0';
+      return string.split(separator, limit);
+    }
 
-              if (!rejected) {
-                var remoteIceParameters = SDPUtils.getIceParameters(
-                    mediaSection, sessionpart);
-                if (isIceLite) {
-                  var cands = SDPUtils.matchPrefix(mediaSection, 'a=candidate:')
-                  .map(function(cand) {
-                    return SDPUtils.parseCandidate(cand);
-                  })
-                  .filter(function(cand) {
-                    return cand.component === '1';
-                  });
-                  // ice-lite only includes host candidates in the SDP so we can
-                  // use setRemoteCandidates (which implies an
-                  // RTCIceCandidateComplete)
-                  if (cands.length) {
-                    iceTransport.setRemoteCandidates(cands);
-                  }
-                }
-                var remoteDtlsParameters = SDPUtils.getDtlsParameters(
-                    mediaSection, sessionpart);
-                if (isIceLite) {
-                  remoteDtlsParameters.role = 'server';
-                }
+    /**
+     * Converts `string` to
+     * [start case](https://en.wikipedia.org/wiki/Letter_case#Stylistic_or_specialised_usage).
+     *
+     * @static
+     * @memberOf _
+     * @since 3.1.0
+     * @category String
+     * @param {string} [string=''] The string to convert.
+     * @returns {string} Returns the start cased string.
+     * @example
+     *
+     * _.startCase('--foo-bar--');
+     * // => 'Foo Bar'
+     *
+     * _.startCase('fooBar');
+     * // => 'Foo Bar'
+     *
+     * _.startCase('__FOO_BAR__');
+     * // => 'FOO BAR'
+     */
+    var startCase = createCompounder(function(result, word, index) {
+      return result + (index ? ' ' : '') + upperFirst(word);
+    });
 
-                if (!self.usingBundle || sdpMLineIndex === 0) {
-                  iceTransport.start(iceGatherer, remoteIceParameters,
-                      isIceLite ? 'controlling' : 'controlled');
-                  dtlsTransport.start(remoteDtlsParameters);
-                }
+    /**
+     * Checks if `string` starts with the given target string.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category String
+     * @param {string} [string=''] The string to inspect.
+     * @param {string} [target] The string to search for.
+     * @param {number} [position=0] The position to search from.
+     * @returns {boolean} Returns `true` if `string` starts with `target`,
+     *  else `false`.
+     * @example
+     *
+     * _.startsWith('abc', 'a');
+     * // => true
+     *
+     * _.startsWith('abc', 'b');
+     * // => false
+     *
+     * _.startsWith('abc', 'b', 1);
+     * // => true
+     */
+    function startsWith(string, target, position) {
+      string = toString(string);
+      position = position == null
+        ? 0
+        : baseClamp(toInteger(position), 0, string.length);
 
-                // Calculate intersection of capabilities.
-                var params = self._getCommonCapabilities(localCapabilities,
-                    remoteCapabilities);
+      target = baseToString(target);
+      return string.slice(position, position + target.length) == target;
+    }
 
-                // Start the RTCRtpSender. The RTCRtpReceiver for this
-                // transceiver has already been started in setRemoteDescription.
-                self._transceive(transceiver,
-                    params.codecs.length > 0,
-                    false);
-              }
-            });
-          }
+    /**
+     * Creates a compiled template function that can interpolate data properties
+     * in "interpolate" delimiters, HTML-escape interpolated data properties in
+     * "escape" delimiters, and execute JavaScript in "evaluate" delimiters. Data
+     * properties may be accessed as free variables in the template. If a setting
+     * object is given, it takes precedence over `_.templateSettings` values.
+     *
+     * **Note:** In the development build `_.template` utilizes
+     * [sourceURLs](http://www.html5rocks.com/en/tutorials/developertools/sourcemaps/#toc-sourceurl)
+     * for easier debugging.
+     *
+     * For more information on precompiling templates see
+     * [lodash's custom builds documentation](https://lodash.com/custom-builds).
+     *
+     * For more information on Chrome extension sandboxes see
+     * [Chrome's extensions documentation](https://developer.chrome.com/extensions/sandboxingEval).
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category String
+     * @param {string} [string=''] The template string.
+     * @param {Object} [options={}] The options object.
+     * @param {RegExp} [options.escape=_.templateSettings.escape]
+     *  The HTML "escape" delimiter.
+     * @param {RegExp} [options.evaluate=_.templateSettings.evaluate]
+     *  The "evaluate" delimiter.
+     * @param {Object} [options.imports=_.templateSettings.imports]
+     *  An object to import into the template as free variables.
+     * @param {RegExp} [options.interpolate=_.templateSettings.interpolate]
+     *  The "interpolate" delimiter.
+     * @param {string} [options.sourceURL='lodash.templateSources[n]']
+     *  The sourceURL of the compiled template.
+     * @param {string} [options.variable='obj']
+     *  The data object variable name.
+     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
+     * @returns {Function} Returns the compiled template function.
+     * @example
+     *
+     * // Use the "interpolate" delimiter to create a compiled template.
+     * var compiled = _.template('hello <%= user %>!');
+     * compiled({ 'user': 'fred' });
+     * // => 'hello fred!'
+     *
+     * // Use the HTML "escape" delimiter to escape data property values.
+     * var compiled = _.template('<b><%- value %></b>');
+     * compiled({ 'value': '<script>' });
+     * // => '<b>&lt;script&gt;</b>'
+     *
+     * // Use the "evaluate" delimiter to execute JavaScript and generate HTML.
+     * var compiled = _.template('<% _.forEach(users, function(user) { %><li><%- user %></li><% }); %>');
+     * compiled({ 'users': ['fred', 'barney'] });
+     * // => '<li>fred</li><li>barney</li>'
+     *
+     * // Use the internal `print` function in "evaluate" delimiters.
+     * var compiled = _.template('<% print("hello " + user); %>!');
+     * compiled({ 'user': 'barney' });
+     * // => 'hello barney!'
+     *
+     * // Use the ES template literal delimiter as an "interpolate" delimiter.
+     * // Disable support by replacing the "interpolate" delimiter.
+     * var compiled = _.template('hello ${ user }!');
+     * compiled({ 'user': 'pebbles' });
+     * // => 'hello pebbles!'
+     *
+     * // Use backslashes to treat delimiters as plain text.
+     * var compiled = _.template('<%= "\\<%- value %\\>" %>');
+     * compiled({ 'value': 'ignored' });
+     * // => '<%- value %>'
+     *
+     * // Use the `imports` option to import `jQuery` as `jq`.
+     * var text = '<% jq.each(users, function(user) { %><li><%- user %></li><% }); %>';
+     * var compiled = _.template(text, { 'imports': { 'jq': jQuery } });
+     * compiled({ 'users': ['fred', 'barney'] });
+     * // => '<li>fred</li><li>barney</li>'
+     *
+     * // Use the `sourceURL` option to specify a custom sourceURL for the template.
+     * var compiled = _.template('hello <%= user %>!', { 'sourceURL': '/basic/greeting.jst' });
+     * compiled(data);
+     * // => Find the source of "greeting.jst" under the Sources tab or Resources panel of the web inspector.
+     *
+     * // Use the `variable` option to ensure a with-statement isn't used in the compiled template.
+     * var compiled = _.template('hi <%= data.user %>!', { 'variable': 'data' });
+     * compiled.source;
+     * // => function(data) {
+     * //   var __t, __p = '';
+     * //   __p += 'hi ' + ((__t = ( data.user )) == null ? '' : __t) + '!';
+     * //   return __p;
+     * // }
+     *
+     * // Use custom template delimiters.
+     * _.templateSettings.interpolate = /{{([\s\S]+?)}}/g;
+     * var compiled = _.template('hello {{ user }}!');
+     * compiled({ 'user': 'mustache' });
+     * // => 'hello mustache!'
+     *
+     * // Use the `source` property to inline compiled templates for meaningful
+     * // line numbers in error messages and stack traces.
+     * fs.writeFileSync(path.join(process.cwd(), 'jst.js'), '\
+     *   var JST = {\
+     *     "main": ' + _.template(mainText).source + '\
+     *   };\
+     * ');
+     */
+    function template(string, options, guard) {
+      // Based on John Resig's `tmpl` implementation
+      // (http://ejohn.org/blog/javascript-micro-templating/)
+      // and Laura Doktorova's doT.js (https://github.com/olado/doT).
+      var settings = lodash.templateSettings;
 
-          this.localDescription = {
-            type: description.type,
-            sdp: description.sdp
-          };
-          switch (description.type) {
-            case 'offer':
-              this._updateSignalingState('have-local-offer');
-              break;
-            case 'answer':
-              this._updateSignalingState('stable');
-              break;
-            default:
-              throw new TypeError('unsupported type "' + description.type +
-                  '"');
-          }
+      if (guard && isIterateeCall(string, options, guard)) {
+        options = undefined;
+      }
+      string = toString(string);
+      options = assignInWith({}, options, settings, customDefaultsAssignIn);
 
-          // If a success callback was provided, emit ICE candidates after it
-          // has been executed. Otherwise, emit callback after the Promise is
-          // resolved.
-          var hasCallback = arguments.length > 1 &&
-            typeof arguments[1] === 'function';
-          if (hasCallback) {
-            var cb = arguments[1];
-            window.setTimeout(function() {
-              cb();
-              if (self.iceGatheringState === 'new') {
-                self.iceGatheringState = 'gathering';
-              }
-              self._emitBufferedCandidates();
-            }, 0);
-          }
-          var p = Promise.resolve();
-          p.then(function() {
-            if (!hasCallback) {
-              if (self.iceGatheringState === 'new') {
-                self.iceGatheringState = 'gathering';
-              }
-              // Usually candidates will be emitted earlier.
-              window.setTimeout(self._emitBufferedCandidates.bind(self), 500);
-            }
-          });
-          return p;
-        };
+      var imports = assignInWith({}, options.imports, settings.imports, customDefaultsAssignIn),
+          importsKeys = keys(imports),
+          importsValues = baseValues(imports, importsKeys);
 
-    window.RTCPeerConnection.prototype.setRemoteDescription =
-        function(description) {
-          var self = this;
-          var stream = new MediaStream();
-          var receiverList = [];
-          var sections = SDPUtils.splitSections(description.sdp);
-          var sessionpart = sections.shift();
-          var isIceLite = SDPUtils.matchPrefix(sessionpart,
-              'a=ice-lite').length > 0;
-          this.usingBundle = SDPUtils.matchPrefix(sessionpart,
-              'a=group:BUNDLE ').length > 0;
-          sections.forEach(function(mediaSection, sdpMLineIndex) {
-            var lines = SDPUtils.splitLines(mediaSection);
-            var mline = lines[0].substr(2).split(' ');
-            var kind = mline[0];
-            var rejected = mline[1] === '0';
-            var direction = SDPUtils.getDirection(mediaSection, sessionpart);
+      var isEscaping,
+          isEvaluating,
+          index = 0,
+          interpolate = options.interpolate || reNoMatch,
+          source = "__p += '";
 
-            var transceiver;
-            var iceGatherer;
-            var iceTransport;
-            var dtlsTransport;
-            var rtpSender;
-            var rtpReceiver;
-            var sendEncodingParameters;
-            var recvEncodingParameters;
-            var localCapabilities;
+      // Compile the regexp to match each delimiter.
+      var reDelimiters = RegExp(
+        (options.escape || reNoMatch).source + '|' +
+        interpolate.source + '|' +
+        (interpolate === reInterpolate ? reEsTemplate : reNoMatch).source + '|' +
+        (options.evaluate || reNoMatch).source + '|$'
+      , 'g');
 
-            var track;
-            // FIXME: ensure the mediaSection has rtcp-mux set.
-            var remoteCapabilities = SDPUtils.parseRtpParameters(mediaSection);
-            var remoteIceParameters;
-            var remoteDtlsParameters;
-            if (!rejected) {
-              remoteIceParameters = SDPUtils.getIceParameters(mediaSection,
-                  sessionpart);
-              remoteDtlsParameters = SDPUtils.getDtlsParameters(mediaSection,
-                  sessionpart);
-              remoteDtlsParameters.role = 'client';
-            }
-            recvEncodingParameters =
-                SDPUtils.parseRtpEncodingParameters(mediaSection);
+      // Use a sourceURL for easier debugging.
+      var sourceURL = '//# sourceURL=' +
+        ('sourceURL' in options
+          ? options.sourceURL
+          : ('lodash.templateSources[' + (++templateCounter) + ']')
+        ) + '\n';
 
-            var mid = SDPUtils.matchPrefix(mediaSection, 'a=mid:');
-            if (mid.length) {
-              mid = mid[0].substr(6);
-            } else {
-              mid = SDPUtils.generateIdentifier();
-            }
+      string.replace(reDelimiters, function(match, escapeValue, interpolateValue, esTemplateValue, evaluateValue, offset) {
+        interpolateValue || (interpolateValue = esTemplateValue);
 
-            var cname;
-            // Gets the first SSRC. Note that with RTX there might be multiple
-            // SSRCs.
-            var remoteSsrc = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
-                .map(function(line) {
-                  return SDPUtils.parseSsrcMedia(line);
-                })
-                .filter(function(obj) {
-                  return obj.attribute === 'cname';
-                })[0];
-            if (remoteSsrc) {
-              cname = remoteSsrc.value;
-            }
+        // Escape characters that can't be included in string literals.
+        source += string.slice(index, offset).replace(reUnescapedString, escapeStringChar);
 
-            var isComplete = SDPUtils.matchPrefix(mediaSection,
-                'a=end-of-candidates').length > 0;
-            var cands = SDPUtils.matchPrefix(mediaSection, 'a=candidate:')
-                .map(function(cand) {
-                  return SDPUtils.parseCandidate(cand);
-                })
-                .filter(function(cand) {
-                  return cand.component === '1';
-                });
-            if (description.type === 'offer' && !rejected) {
-              var transports = self.usingBundle && sdpMLineIndex > 0 ? {
-                iceGatherer: self.transceivers[0].iceGatherer,
-                iceTransport: self.transceivers[0].iceTransport,
-                dtlsTransport: self.transceivers[0].dtlsTransport
-              } : self._createIceAndDtlsTransports(mid, sdpMLineIndex);
+        // Replace delimiters with snippets.
+        if (escapeValue) {
+          isEscaping = true;
+          source += "' +\n__e(" + escapeValue + ") +\n'";
+        }
+        if (evaluateValue) {
+          isEvaluating = true;
+          source += "';\n" + evaluateValue + ";\n__p += '";
+        }
+        if (interpolateValue) {
+          source += "' +\n((__t = (" + interpolateValue + ")) == null ? '' : __t) +\n'";
+        }
+        index = offset + match.length;
 
-              if (isComplete) {
-                transports.iceTransport.setRemoteCandidates(cands);
-              }
+        // The JS engine embedded in Adobe products needs `match` returned in
+        // order to produce the correct `offset` value.
+        return match;
+      });
 
-              localCapabilities = RTCRtpReceiver.getCapabilities(kind);
-              sendEncodingParameters = [{
-                ssrc: (2 * sdpMLineIndex + 2) * 1001
-              }];
+      source += "';\n";
 
-              rtpReceiver = new RTCRtpReceiver(transports.dtlsTransport, kind);
+      // If `variable` is not specified wrap a with-statement around the generated
+      // code to add the data object to the top of the scope chain.
+      var variable = options.variable;
+      if (!variable) {
+        source = 'with (obj) {\n' + source + '\n}\n';
+      }
+      // Cleanup code by stripping empty strings.
+      source = (isEvaluating ? source.replace(reEmptyStringLeading, '') : source)
+        .replace(reEmptyStringMiddle, '$1')
+        .replace(reEmptyStringTrailing, '$1;');
 
-              track = rtpReceiver.track;
-              receiverList.push([track, rtpReceiver]);
-              // FIXME: not correct when there are multiple streams but that is
-              // not currently supported in this shim.
-              stream.addTrack(track);
+      // Frame code as the function body.
+      source = 'function(' + (variable || 'obj') + ') {\n' +
+        (variable
+          ? ''
+          : 'obj || (obj = {});\n'
+        ) +
+        "var __t, __p = ''" +
+        (isEscaping
+           ? ', __e = _.escape'
+           : ''
+        ) +
+        (isEvaluating
+          ? ', __j = Array.prototype.join;\n' +
+            "function print() { __p += __j.call(arguments, '') }\n"
+          : ';\n'
+        ) +
+        source +
+        'return __p\n}';
 
-              // FIXME: look at direction.
-              if (self.localStreams.length > 0 &&
-                  self.localStreams[0].getTracks().length >= sdpMLineIndex) {
-                // FIXME: actually more complicated, needs to match types etc
-                var localtrack = self.localStreams[0]
-                    .getTracks()[sdpMLineIndex];
-                rtpSender = new RTCRtpSender(localtrack,
-                    transports.dtlsTransport);
-              }
+      var result = attempt(function() {
+        return Function(importsKeys, sourceURL + 'return ' + source)
+          .apply(undefined, importsValues);
+      });
 
-              self.transceivers[sdpMLineIndex] = {
-                iceGatherer: transports.iceGatherer,
-                iceTransport: transports.iceTransport,
-                dtlsTransport: transports.dtlsTransport,
-                localCapabilities: localCapabilities,
-                remoteCapabilities: remoteCapabilities,
-                rtpSender: rtpSender,
-                rtpReceiver: rtpReceiver,
-                kind: kind,
-                mid: mid,
-                cname: cname,
-                sendEncodingParameters: sendEncodingParameters,
-                recvEncodingParameters: recvEncodingParameters
-              };
-              // Start the RTCRtpReceiver now. The RTPSender is started in
-              // setLocalDescription.
-              self._transceive(self.transceivers[sdpMLineIndex],
-                  false,
-                  direction === 'sendrecv' || direction === 'sendonly');
-            } else if (description.type === 'answer' && !rejected) {
-              transceiver = self.transceivers[sdpMLineIndex];
-              iceGatherer = transceiver.iceGatherer;
-              iceTransport = transceiver.iceTransport;
-              dtlsTransport = transceiver.dtlsTransport;
-              rtpSender = transceiver.rtpSender;
-              rtpReceiver = transceiver.rtpReceiver;
-              sendEncodingParameters = transceiver.sendEncodingParameters;
-              localCapabilities = transceiver.localCapabilities;
+      // Provide the compiled function's source by its `toString` method or
+      // the `source` property as a convenience for inlining compiled templates.
+      result.source = source;
+      if (isError(result)) {
+        throw result;
+      }
+      return result;
+    }
 
-              self.transceivers[sdpMLineIndex].recvEncodingParameters =
-                  recvEncodingParameters;
-              self.transceivers[sdpMLineIndex].remoteCapabilities =
-                  remoteCapabilities;
-              self.transceivers[sdpMLineIndex].cname = cname;
+    /**
+     * Converts `string`, as a whole, to lower case just like
+     * [String#toLowerCase](https://mdn.io/toLowerCase).
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category String
+     * @param {string} [string=''] The string to convert.
+     * @returns {string} Returns the lower cased string.
+     * @example
+     *
+     * _.toLower('--Foo-Bar--');
+     * // => '--foo-bar--'
+     *
+     * _.toLower('fooBar');
+     * // => 'foobar'
+     *
+     * _.toLower('__FOO_BAR__');
+     * // => '__foo_bar__'
+     */
+    function toLower(value) {
+      return toString(value).toLowerCase();
+    }
 
-              if ((isIceLite || isComplete) && cands.length) {
-                iceTransport.setRemoteCandidates(cands);
-              }
-              if (!self.usingBundle || sdpMLineIndex === 0) {
-                iceTransport.start(iceGatherer, remoteIceParameters,
-                    'controlling');
-                dtlsTransport.start(remoteDtlsParameters);
-              }
+    /**
+     * Converts `string`, as a whole, to upper case just like
+     * [String#toUpperCase](https://mdn.io/toUpperCase).
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category String
+     * @param {string} [string=''] The string to convert.
+     * @returns {string} Returns the upper cased string.
+     * @example
+     *
+     * _.toUpper('--foo-bar--');
+     * // => '--FOO-BAR--'
+     *
+     * _.toUpper('fooBar');
+     * // => 'FOOBAR'
+     *
+     * _.toUpper('__foo_bar__');
+     * // => '__FOO_BAR__'
+     */
+    function toUpper(value) {
+      return toString(value).toUpperCase();
+    }
 
-              self._transceive(transceiver,
-                  direction === 'sendrecv' || direction === 'recvonly',
-                  direction === 'sendrecv' || direction === 'sendonly');
+    /**
+     * Removes leading and trailing whitespace or specified characters from `string`.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category String
+     * @param {string} [string=''] The string to trim.
+     * @param {string} [chars=whitespace] The characters to trim.
+     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
+     * @returns {string} Returns the trimmed string.
+     * @example
+     *
+     * _.trim('  abc  ');
+     * // => 'abc'
+     *
+     * _.trim('-_-abc-_-', '_-');
+     * // => 'abc'
+     *
+     * _.map(['  foo  ', '  bar  '], _.trim);
+     * // => ['foo', 'bar']
+     */
+    function trim(string, chars, guard) {
+      string = toString(string);
+      if (string && (guard || chars === undefined)) {
+        return string.replace(reTrim, '');
+      }
+      if (!string || !(chars = baseToString(chars))) {
+        return string;
+      }
+      var strSymbols = stringToArray(string),
+          chrSymbols = stringToArray(chars),
+          start = charsStartIndex(strSymbols, chrSymbols),
+          end = charsEndIndex(strSymbols, chrSymbols) + 1;
 
-              if (rtpReceiver &&
-                  (direction === 'sendrecv' || direction === 'sendonly')) {
-                track = rtpReceiver.track;
-                receiverList.push([track, rtpReceiver]);
-                stream.addTrack(track);
-              } else {
-                // FIXME: actually the receiver should be created later.
-                delete transceiver.rtpReceiver;
-              }
-            }
-          });
+      return castSlice(strSymbols, start, end).join('');
+    }
 
-          this.remoteDescription = {
-            type: description.type,
-            sdp: description.sdp
-          };
-          switch (description.type) {
-            case 'offer':
-              this._updateSignalingState('have-remote-offer');
-              break;
-            case 'answer':
-              this._updateSignalingState('stable');
-              break;
-            default:
-              throw new TypeError('unsupported type "' + description.type +
-                  '"');
-          }
-          if (stream.getTracks().length) {
-            self.remoteStreams.push(stream);
-            window.setTimeout(function() {
-              var event = new Event('addstream');
-              event.stream = stream;
-              self.dispatchEvent(event);
-              if (self.onaddstream !== null) {
-                window.setTimeout(function() {
-                  self.onaddstream(event);
-                }, 0);
-              }
-
-              receiverList.forEach(function(item) {
-                var track = item[0];
-                var receiver = item[1];
-                var trackEvent = new Event('track');
-                trackEvent.track = track;
-                trackEvent.receiver = receiver;
-                trackEvent.streams = [stream];
-                self.dispatchEvent(event);
-                if (self.ontrack !== null) {
-                  window.setTimeout(function() {
-                    self.ontrack(trackEvent);
-                  }, 0);
-                }
-              });
-            }, 0);
-          }
-          if (arguments.length > 1 && typeof arguments[1] === 'function') {
-            window.setTimeout(arguments[1], 0);
-          }
-          return Promise.resolve();
-        };
+    /**
+     * Removes trailing whitespace or specified characters from `string`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category String
+     * @param {string} [string=''] The string to trim.
+     * @param {string} [chars=whitespace] The characters to trim.
+     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
+     * @returns {string} Returns the trimmed string.
+     * @example
+     *
+     * _.trimEnd('  abc  ');
+     * // => '  abc'
+     *
+     * _.trimEnd('-_-abc-_-', '_-');
+     * // => '-_-abc'
+     */
+    function trimEnd(string, chars, guard) {
+      string = toString(string);
+      if (string && (guard || chars === undefined)) {
+        return string.replace(reTrimEnd, '');
+      }
+      if (!string || !(chars = baseToString(chars))) {
+        return string;
+      }
+      var strSymbols = stringToArray(string),
+          end = charsEndIndex(strSymbols, stringToArray(chars)) + 1;
 
-    window.RTCPeerConnection.prototype.close = function() {
-      this.transceivers.forEach(function(transceiver) {
-        /* not yet
-        if (transceiver.iceGatherer) {
-          transceiver.iceGatherer.close();
-        }
-        */
-        if (transceiver.iceTransport) {
-          transceiver.iceTransport.stop();
-        }
-        if (transceiver.dtlsTransport) {
-          transceiver.dtlsTransport.stop();
-        }
-        if (transceiver.rtpSender) {
-          transceiver.rtpSender.stop();
-        }
-        if (transceiver.rtpReceiver) {
-          transceiver.rtpReceiver.stop();
-        }
-      });
-      // FIXME: clean up tracks, local streams, remote streams, etc
-      this._updateSignalingState('closed');
-    };
+      return castSlice(strSymbols, 0, end).join('');
+    }
 
-    // Update the signaling state.
-    window.RTCPeerConnection.prototype._updateSignalingState =
-        function(newState) {
-          this.signalingState = newState;
-          var event = new Event('signalingstatechange');
-          this.dispatchEvent(event);
-          if (this.onsignalingstatechange !== null) {
-            this.onsignalingstatechange(event);
-          }
-        };
+    /**
+     * Removes leading whitespace or specified characters from `string`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category String
+     * @param {string} [string=''] The string to trim.
+     * @param {string} [chars=whitespace] The characters to trim.
+     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
+     * @returns {string} Returns the trimmed string.
+     * @example
+     *
+     * _.trimStart('  abc  ');
+     * // => 'abc  '
+     *
+     * _.trimStart('-_-abc-_-', '_-');
+     * // => 'abc-_-'
+     */
+    function trimStart(string, chars, guard) {
+      string = toString(string);
+      if (string && (guard || chars === undefined)) {
+        return string.replace(reTrimStart, '');
+      }
+      if (!string || !(chars = baseToString(chars))) {
+        return string;
+      }
+      var strSymbols = stringToArray(string),
+          start = charsStartIndex(strSymbols, stringToArray(chars));
 
-    // Determine whether to fire the negotiationneeded event.
-    window.RTCPeerConnection.prototype._maybeFireNegotiationNeeded =
-        function() {
-          // Fire away (for now).
-          var event = new Event('negotiationneeded');
-          this.dispatchEvent(event);
-          if (this.onnegotiationneeded !== null) {
-            this.onnegotiationneeded(event);
-          }
-        };
+      return castSlice(strSymbols, start).join('');
+    }
 
-    // Update the connection state.
-    window.RTCPeerConnection.prototype._updateConnectionState = function() {
-      var self = this;
-      var newState;
-      var states = {
-        'new': 0,
-        closed: 0,
-        connecting: 0,
-        checking: 0,
-        connected: 0,
-        completed: 0,
-        failed: 0
-      };
-      this.transceivers.forEach(function(transceiver) {
-        states[transceiver.iceTransport.state]++;
-        states[transceiver.dtlsTransport.state]++;
-      });
-      // ICETransport.completed and connected are the same for this purpose.
-      states.connected += states.completed;
+    /**
+     * Truncates `string` if it's longer than the given maximum string length.
+     * The last characters of the truncated string are replaced with the omission
+     * string which defaults to "...".
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category String
+     * @param {string} [string=''] The string to truncate.
+     * @param {Object} [options={}] The options object.
+     * @param {number} [options.length=30] The maximum string length.
+     * @param {string} [options.omission='...'] The string to indicate text is omitted.
+     * @param {RegExp|string} [options.separator] The separator pattern to truncate to.
+     * @returns {string} Returns the truncated string.
+     * @example
+     *
+     * _.truncate('hi-diddly-ho there, neighborino');
+     * // => 'hi-diddly-ho there, neighbo...'
+     *
+     * _.truncate('hi-diddly-ho there, neighborino', {
+     *   'length': 24,
+     *   'separator': ' '
+     * });
+     * // => 'hi-diddly-ho there,...'
+     *
+     * _.truncate('hi-diddly-ho there, neighborino', {
+     *   'length': 24,
+     *   'separator': /,? +/
+     * });
+     * // => 'hi-diddly-ho there...'
+     *
+     * _.truncate('hi-diddly-ho there, neighborino', {
+     *   'omission': ' [...]'
+     * });
+     * // => 'hi-diddly-ho there, neig [...]'
+     */
+    function truncate(string, options) {
+      var length = DEFAULT_TRUNC_LENGTH,
+          omission = DEFAULT_TRUNC_OMISSION;
 
-      newState = 'new';
-      if (states.failed > 0) {
-        newState = 'failed';
-      } else if (states.connecting > 0 || states.checking > 0) {
-        newState = 'connecting';
-      } else if (states.disconnected > 0) {
-        newState = 'disconnected';
-      } else if (states.new > 0) {
-        newState = 'new';
-      } else if (states.connected > 0 || states.completed > 0) {
-        newState = 'connected';
+      if (isObject(options)) {
+        var separator = 'separator' in options ? options.separator : separator;
+        length = 'length' in options ? toInteger(options.length) : length;
+        omission = 'omission' in options ? baseToString(options.omission) : omission;
       }
+      string = toString(string);
 
-      if (newState !== self.iceConnectionState) {
-        self.iceConnectionState = newState;
-        var event = new Event('iceconnectionstatechange');
-        this.dispatchEvent(event);
-        if (this.oniceconnectionstatechange !== null) {
-          this.oniceconnectionstatechange(event);
-        }
+      var strLength = string.length;
+      if (hasUnicode(string)) {
+        var strSymbols = stringToArray(string);
+        strLength = strSymbols.length;
       }
-    };
-
-    window.RTCPeerConnection.prototype.createOffer = function() {
-      var self = this;
-      if (this._pendingOffer) {
-        throw new Error('createOffer called while there is a pending offer.');
+      if (length >= strLength) {
+        return string;
       }
-      var offerOptions;
-      if (arguments.length === 1 && typeof arguments[0] !== 'function') {
-        offerOptions = arguments[0];
-      } else if (arguments.length === 3) {
-        offerOptions = arguments[2];
+      var end = length - stringSize(omission);
+      if (end < 1) {
+        return omission;
       }
+      var result = strSymbols
+        ? castSlice(strSymbols, 0, end).join('')
+        : string.slice(0, end);
 
-      var tracks = [];
-      var numAudioTracks = 0;
-      var numVideoTracks = 0;
-      // Default to sendrecv.
-      if (this.localStreams.length) {
-        numAudioTracks = this.localStreams[0].getAudioTracks().length;
-        numVideoTracks = this.localStreams[0].getVideoTracks().length;
+      if (separator === undefined) {
+        return result + omission;
       }
-      // Determine number of audio and video tracks we need to send/recv.
-      if (offerOptions) {
-        // Reject Chrome legacy constraints.
-        if (offerOptions.mandatory || offerOptions.optional) {
-          throw new TypeError(
-              'Legacy mandatory/optional constraints not supported.');
-        }
-        if (offerOptions.offerToReceiveAudio !== undefined) {
-          numAudioTracks = offerOptions.offerToReceiveAudio;
-        }
-        if (offerOptions.offerToReceiveVideo !== undefined) {
-          numVideoTracks = offerOptions.offerToReceiveVideo;
-        }
+      if (strSymbols) {
+        end += (result.length - end);
       }
-      if (this.localStreams.length) {
-        // Push local streams.
-        this.localStreams[0].getTracks().forEach(function(track) {
-          tracks.push({
-            kind: track.kind,
-            track: track,
-            wantReceive: track.kind === 'audio' ?
-                numAudioTracks > 0 : numVideoTracks > 0
-          });
-          if (track.kind === 'audio') {
-            numAudioTracks--;
-          } else if (track.kind === 'video') {
-            numVideoTracks--;
+      if (isRegExp(separator)) {
+        if (string.slice(end).search(separator)) {
+          var match,
+              substring = result;
+
+          if (!separator.global) {
+            separator = RegExp(separator.source, toString(reFlags.exec(separator)) + 'g');
           }
-        });
-      }
-      // Create M-lines for recvonly streams.
-      while (numAudioTracks > 0 || numVideoTracks > 0) {
-        if (numAudioTracks > 0) {
-          tracks.push({
-            kind: 'audio',
-            wantReceive: true
-          });
-          numAudioTracks--;
+          separator.lastIndex = 0;
+          while ((match = separator.exec(substring))) {
+            var newEnd = match.index;
+          }
+          result = result.slice(0, newEnd === undefined ? end : newEnd);
         }
-        if (numVideoTracks > 0) {
-          tracks.push({
-            kind: 'video',
-            wantReceive: true
-          });
-          numVideoTracks--;
+      } else if (string.indexOf(baseToString(separator), end) != end) {
+        var index = result.lastIndexOf(separator);
+        if (index > -1) {
+          result = result.slice(0, index);
         }
       }
+      return result + omission;
+    }
 
-      var sdp = SDPUtils.writeSessionBoilerplate();
-      var transceivers = [];
-      tracks.forEach(function(mline, sdpMLineIndex) {
-        // For each track, create an ice gatherer, ice transport,
-        // dtls transport, potentially rtpsender and rtpreceiver.
-        var track = mline.track;
-        var kind = mline.kind;
-        var mid = SDPUtils.generateIdentifier();
-
-        var transports = self.usingBundle && sdpMLineIndex > 0 ? {
-          iceGatherer: transceivers[0].iceGatherer,
-          iceTransport: transceivers[0].iceTransport,
-          dtlsTransport: transceivers[0].dtlsTransport
-        } : self._createIceAndDtlsTransports(mid, sdpMLineIndex);
-
-        var localCapabilities = RTCRtpSender.getCapabilities(kind);
-        var rtpSender;
-        var rtpReceiver;
+    /**
+     * The inverse of `_.escape`; this method converts the HTML entities
+     * `&amp;`, `&lt;`, `&gt;`, `&quot;`, and `&#39;` in `string` to
+     * their corresponding characters.
+     *
+     * **Note:** No other HTML entities are unescaped. To unescape additional
+     * HTML entities use a third-party library like [_he_](https://mths.be/he).
+     *
+     * @static
+     * @memberOf _
+     * @since 0.6.0
+     * @category String
+     * @param {string} [string=''] The string to unescape.
+     * @returns {string} Returns the unescaped string.
+     * @example
+     *
+     * _.unescape('fred, barney, &amp; pebbles');
+     * // => 'fred, barney, & pebbles'
+     */
+    function unescape(string) {
+      string = toString(string);
+      return (string && reHasEscapedHtml.test(string))
+        ? string.replace(reEscapedHtml, unescapeHtmlChar)
+        : string;
+    }
 
-        // generate an ssrc now, to be used later in rtpSender.send
-        var sendEncodingParameters = [{
-          ssrc: (2 * sdpMLineIndex + 1) * 1001
-        }];
-        if (track) {
-          rtpSender = new RTCRtpSender(track, transports.dtlsTransport);
-        }
+    /**
+     * Converts `string`, as space separated words, to upper case.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category String
+     * @param {string} [string=''] The string to convert.
+     * @returns {string} Returns the upper cased string.
+     * @example
+     *
+     * _.upperCase('--foo-bar');
+     * // => 'FOO BAR'
+     *
+     * _.upperCase('fooBar');
+     * // => 'FOO BAR'
+     *
+     * _.upperCase('__foo_bar__');
+     * // => 'FOO BAR'
+     */
+    var upperCase = createCompounder(function(result, word, index) {
+      return result + (index ? ' ' : '') + word.toUpperCase();
+    });
 
-        if (mline.wantReceive) {
-          rtpReceiver = new RTCRtpReceiver(transports.dtlsTransport, kind);
-        }
+    /**
+     * Converts the first character of `string` to upper case.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category String
+     * @param {string} [string=''] The string to convert.
+     * @returns {string} Returns the converted string.
+     * @example
+     *
+     * _.upperFirst('fred');
+     * // => 'Fred'
+     *
+     * _.upperFirst('FRED');
+     * // => 'FRED'
+     */
+    var upperFirst = createCaseFirst('toUpperCase');
 
-        transceivers[sdpMLineIndex] = {
-          iceGatherer: transports.iceGatherer,
-          iceTransport: transports.iceTransport,
-          dtlsTransport: transports.dtlsTransport,
-          localCapabilities: localCapabilities,
-          remoteCapabilities: null,
-          rtpSender: rtpSender,
-          rtpReceiver: rtpReceiver,
-          kind: kind,
-          mid: mid,
-          sendEncodingParameters: sendEncodingParameters,
-          recvEncodingParameters: null
-        };
-      });
-      if (this.usingBundle) {
-        sdp += 'a=group:BUNDLE ' + transceivers.map(function(t) {
-          return t.mid;
-        }).join(' ') + '\r\n';
-      }
-      tracks.forEach(function(mline, sdpMLineIndex) {
-        var transceiver = transceivers[sdpMLineIndex];
-        sdp += SDPUtils.writeMediaSection(transceiver,
-            transceiver.localCapabilities, 'offer', self.localStreams[0]);
-      });
+    /**
+     * Splits `string` into an array of its words.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category String
+     * @param {string} [string=''] The string to inspect.
+     * @param {RegExp|string} [pattern] The pattern to match words.
+     * @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
+     * @returns {Array} Returns the words of `string`.
+     * @example
+     *
+     * _.words('fred, barney, & pebbles');
+     * // => ['fred', 'barney', 'pebbles']
+     *
+     * _.words('fred, barney, & pebbles', /[^, ]+/g);
+     * // => ['fred', 'barney', '&', 'pebbles']
+     */
+    function words(string, pattern, guard) {
+      string = toString(string);
+      pattern = guard ? undefined : pattern;
 
-      this._pendingOffer = transceivers;
-      var desc = new RTCSessionDescription({
-        type: 'offer',
-        sdp: sdp
-      });
-      if (arguments.length && typeof arguments[0] === 'function') {
-        window.setTimeout(arguments[0], 0, desc);
+      if (pattern === undefined) {
+        return hasUnicodeWord(string) ? unicodeWords(string) : asciiWords(string);
       }
-      return Promise.resolve(desc);
-    };
+      return string.match(pattern) || [];
+    }
 
-    window.RTCPeerConnection.prototype.createAnswer = function() {
-      var self = this;
+    /*------------------------------------------------------------------------*/
 
-      var sdp = SDPUtils.writeSessionBoilerplate();
-      if (this.usingBundle) {
-        sdp += 'a=group:BUNDLE ' + this.transceivers.map(function(t) {
-          return t.mid;
-        }).join(' ') + '\r\n';
+    /**
+     * Attempts to invoke `func`, returning either the result or the caught error
+     * object. Any additional arguments are provided to `func` when it's invoked.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category Util
+     * @param {Function} func The function to attempt.
+     * @param {...*} [args] The arguments to invoke `func` with.
+     * @returns {*} Returns the `func` result or error object.
+     * @example
+     *
+     * // Avoid throwing errors for invalid selectors.
+     * var elements = _.attempt(function(selector) {
+     *   return document.querySelectorAll(selector);
+     * }, '>_>');
+     *
+     * if (_.isError(elements)) {
+     *   elements = [];
+     * }
+     */
+    var attempt = baseRest(function(func, args) {
+      try {
+        return apply(func, undefined, args);
+      } catch (e) {
+        return isError(e) ? e : new Error(e);
       }
-      this.transceivers.forEach(function(transceiver) {
-        // Calculate intersection of capabilities.
-        var commonCapabilities = self._getCommonCapabilities(
-            transceiver.localCapabilities,
-            transceiver.remoteCapabilities);
+    });
 
-        sdp += SDPUtils.writeMediaSection(transceiver, commonCapabilities,
-            'answer', self.localStreams[0]);
+    /**
+     * Binds methods of an object to the object itself, overwriting the existing
+     * method.
+     *
+     * **Note:** This method doesn't set the "length" property of bound functions.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Util
+     * @param {Object} object The object to bind and assign the bound methods to.
+     * @param {...(string|string[])} methodNames The object method names to bind.
+     * @returns {Object} Returns `object`.
+     * @example
+     *
+     * var view = {
+     *   'label': 'docs',
+     *   'click': function() {
+     *     console.log('clicked ' + this.label);
+     *   }
+     * };
+     *
+     * _.bindAll(view, ['click']);
+     * jQuery(element).on('click', view.click);
+     * // => Logs 'clicked docs' when clicked.
+     */
+    var bindAll = flatRest(function(object, methodNames) {
+      arrayEach(methodNames, function(key) {
+        key = toKey(key);
+        baseAssignValue(object, key, bind(object[key], object));
       });
+      return object;
+    });
 
-      var desc = new RTCSessionDescription({
-        type: 'answer',
-        sdp: sdp
+    /**
+     * Creates a function that iterates over `pairs` and invokes the corresponding
+     * function of the first predicate to return truthy. The predicate-function
+     * pairs are invoked with the `this` binding and arguments of the created
+     * function.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Util
+     * @param {Array} pairs The predicate-function pairs.
+     * @returns {Function} Returns the new composite function.
+     * @example
+     *
+     * var func = _.cond([
+     *   [_.matches({ 'a': 1 }),           _.constant('matches A')],
+     *   [_.conforms({ 'b': _.isNumber }), _.constant('matches B')],
+     *   [_.stubTrue,                      _.constant('no match')]
+     * ]);
+     *
+     * func({ 'a': 1, 'b': 2 });
+     * // => 'matches A'
+     *
+     * func({ 'a': 0, 'b': 1 });
+     * // => 'matches B'
+     *
+     * func({ 'a': '1', 'b': '2' });
+     * // => 'no match'
+     */
+    function cond(pairs) {
+      var length = pairs == null ? 0 : pairs.length,
+          toIteratee = getIteratee();
+
+      pairs = !length ? [] : arrayMap(pairs, function(pair) {
+        if (typeof pair[1] != 'function') {
+          throw new TypeError(FUNC_ERROR_TEXT);
+        }
+        return [toIteratee(pair[0]), pair[1]];
       });
-      if (arguments.length && typeof arguments[0] === 'function') {
-        window.setTimeout(arguments[0], 0, desc);
-      }
-      return Promise.resolve(desc);
-    };
 
-    window.RTCPeerConnection.prototype.addIceCandidate = function(candidate) {
-      if (candidate === null) {
-        this.transceivers.forEach(function(transceiver) {
-          transceiver.iceTransport.addRemoteCandidate({});
-        });
-      } else {
-        var mLineIndex = candidate.sdpMLineIndex;
-        if (candidate.sdpMid) {
-          for (var i = 0; i < this.transceivers.length; i++) {
-            if (this.transceivers[i].mid === candidate.sdpMid) {
-              mLineIndex = i;
-              break;
-            }
+      return baseRest(function(args) {
+        var index = -1;
+        while (++index < length) {
+          var pair = pairs[index];
+          if (apply(pair[0], this, args)) {
+            return apply(pair[1], this, args);
           }
         }
-        var transceiver = this.transceivers[mLineIndex];
-        if (transceiver) {
-          var cand = Object.keys(candidate.candidate).length > 0 ?
-              SDPUtils.parseCandidate(candidate.candidate) : {};
-          // Ignore Chrome's invalid candidates since Edge does not like them.
-          if (cand.protocol === 'tcp' && cand.port === 0) {
-            return;
-          }
-          // Ignore RTCP candidates, we assume RTCP-MUX.
-          if (cand.component !== '1') {
-            return;
-          }
-          // A dirty hack to make samples work.
-          if (cand.type === 'endOfCandidates') {
-            cand = {};
-          }
-          transceiver.iceTransport.addRemoteCandidate(cand);
+      });
+    }
+
+    /**
+     * Creates a function that invokes the predicate properties of `source` with
+     * the corresponding property values of a given object, returning `true` if
+     * all predicates return truthy, else `false`.
+     *
+     * **Note:** The created function is equivalent to `_.conformsTo` with
+     * `source` partially applied.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Util
+     * @param {Object} source The object of property predicates to conform to.
+     * @returns {Function} Returns the new spec function.
+     * @example
+     *
+     * var objects = [
+     *   { 'a': 2, 'b': 1 },
+     *   { 'a': 1, 'b': 2 }
+     * ];
+     *
+     * _.filter(objects, _.conforms({ 'b': function(n) { return n > 1; } }));
+     * // => [{ 'a': 1, 'b': 2 }]
+     */
+    function conforms(source) {
+      return baseConforms(baseClone(source, CLONE_DEEP_FLAG));
+    }
+
+    /**
+     * Creates a function that returns `value`.
+     *
+     * @static
+     * @memberOf _
+     * @since 2.4.0
+     * @category Util
+     * @param {*} value The value to return from the new function.
+     * @returns {Function} Returns the new constant function.
+     * @example
+     *
+     * var objects = _.times(2, _.constant({ 'a': 1 }));
+     *
+     * console.log(objects);
+     * // => [{ 'a': 1 }, { 'a': 1 }]
+     *
+     * console.log(objects[0] === objects[1]);
+     * // => true
+     */
+    function constant(value) {
+      return function() {
+        return value;
+      };
+    }
+
+    /**
+     * Checks `value` to determine whether a default value should be returned in
+     * its place. The `defaultValue` is returned if `value` is `NaN`, `null`,
+     * or `undefined`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.14.0
+     * @category Util
+     * @param {*} value The value to check.
+     * @param {*} defaultValue The default value.
+     * @returns {*} Returns the resolved value.
+     * @example
+     *
+     * _.defaultTo(1, 10);
+     * // => 1
+     *
+     * _.defaultTo(undefined, 10);
+     * // => 10
+     */
+    function defaultTo(value, defaultValue) {
+      return (value == null || value !== value) ? defaultValue : value;
+    }
+
+    /**
+     * Creates a function that returns the result of invoking the given functions
+     * with the `this` binding of the created function, where each successive
+     * invocation is supplied the return value of the previous.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category Util
+     * @param {...(Function|Function[])} [funcs] The functions to invoke.
+     * @returns {Function} Returns the new composite function.
+     * @see _.flowRight
+     * @example
+     *
+     * function square(n) {
+     *   return n * n;
+     * }
+     *
+     * var addSquare = _.flow([_.add, square]);
+     * addSquare(1, 2);
+     * // => 9
+     */
+    var flow = createFlow();
+
+    /**
+     * This method is like `_.flow` except that it creates a function that
+     * invokes the given functions from right to left.
+     *
+     * @static
+     * @since 3.0.0
+     * @memberOf _
+     * @category Util
+     * @param {...(Function|Function[])} [funcs] The functions to invoke.
+     * @returns {Function} Returns the new composite function.
+     * @see _.flow
+     * @example
+     *
+     * function square(n) {
+     *   return n * n;
+     * }
+     *
+     * var addSquare = _.flowRight([square, _.add]);
+     * addSquare(1, 2);
+     * // => 9
+     */
+    var flowRight = createFlow(true);
+
+    /**
+     * This method returns the first argument it receives.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Util
+     * @param {*} value Any value.
+     * @returns {*} Returns `value`.
+     * @example
+     *
+     * var object = { 'a': 1 };
+     *
+     * console.log(_.identity(object) === object);
+     * // => true
+     */
+    function identity(value) {
+      return value;
+    }
+
+    /**
+     * Creates a function that invokes `func` with the arguments of the created
+     * function. If `func` is a property name, the created function returns the
+     * property value for a given element. If `func` is an array or object, the
+     * created function returns `true` for elements that contain the equivalent
+     * source properties, otherwise it returns `false`.
+     *
+     * @static
+     * @since 4.0.0
+     * @memberOf _
+     * @category Util
+     * @param {*} [func=_.identity] The value to convert to a callback.
+     * @returns {Function} Returns the callback.
+     * @example
+     *
+     * var users = [
+     *   { 'user': 'barney', 'age': 36, 'active': true },
+     *   { 'user': 'fred',   'age': 40, 'active': false }
+     * ];
+     *
+     * // The `_.matches` iteratee shorthand.
+     * _.filter(users, _.iteratee({ 'user': 'barney', 'active': true }));
+     * // => [{ 'user': 'barney', 'age': 36, 'active': true }]
+     *
+     * // The `_.matchesProperty` iteratee shorthand.
+     * _.filter(users, _.iteratee(['user', 'fred']));
+     * // => [{ 'user': 'fred', 'age': 40 }]
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.map(users, _.iteratee('user'));
+     * // => ['barney', 'fred']
+     *
+     * // Create custom iteratee shorthands.
+     * _.iteratee = _.wrap(_.iteratee, function(iteratee, func) {
+     *   return !_.isRegExp(func) ? iteratee(func) : function(string) {
+     *     return func.test(string);
+     *   };
+     * });
+     *
+     * _.filter(['abc', 'def'], /ef/);
+     * // => ['def']
+     */
+    function iteratee(func) {
+      return baseIteratee(typeof func == 'function' ? func : baseClone(func, CLONE_DEEP_FLAG));
+    }
+
+    /**
+     * Creates a function that performs a partial deep comparison between a given
+     * object and `source`, returning `true` if the given object has equivalent
+     * property values, else `false`.
+     *
+     * **Note:** The created function is equivalent to `_.isMatch` with `source`
+     * partially applied.
+     *
+     * Partial comparisons will match empty array and empty object `source`
+     * values against any array or object value, respectively. See `_.isEqual`
+     * for a list of supported value comparisons.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category Util
+     * @param {Object} source The object of property values to match.
+     * @returns {Function} Returns the new spec function.
+     * @example
+     *
+     * var objects = [
+     *   { 'a': 1, 'b': 2, 'c': 3 },
+     *   { 'a': 4, 'b': 5, 'c': 6 }
+     * ];
+     *
+     * _.filter(objects, _.matches({ 'a': 4, 'c': 6 }));
+     * // => [{ 'a': 4, 'b': 5, 'c': 6 }]
+     */
+    function matches(source) {
+      return baseMatches(baseClone(source, CLONE_DEEP_FLAG));
+    }
+
+    /**
+     * Creates a function that performs a partial deep comparison between the
+     * value at `path` of a given object to `srcValue`, returning `true` if the
+     * object value is equivalent, else `false`.
+     *
+     * **Note:** Partial comparisons will match empty array and empty object
+     * `srcValue` values against any array or object value, respectively. See
+     * `_.isEqual` for a list of supported value comparisons.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.2.0
+     * @category Util
+     * @param {Array|string} path The path of the property to get.
+     * @param {*} srcValue The value to match.
+     * @returns {Function} Returns the new spec function.
+     * @example
+     *
+     * var objects = [
+     *   { 'a': 1, 'b': 2, 'c': 3 },
+     *   { 'a': 4, 'b': 5, 'c': 6 }
+     * ];
+     *
+     * _.find(objects, _.matchesProperty('a', 4));
+     * // => { 'a': 4, 'b': 5, 'c': 6 }
+     */
+    function matchesProperty(path, srcValue) {
+      return baseMatchesProperty(path, baseClone(srcValue, CLONE_DEEP_FLAG));
+    }
+
+    /**
+     * Creates a function that invokes the method at `path` of a given object.
+     * Any additional arguments are provided to the invoked method.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.7.0
+     * @category Util
+     * @param {Array|string} path The path of the method to invoke.
+     * @param {...*} [args] The arguments to invoke the method with.
+     * @returns {Function} Returns the new invoker function.
+     * @example
+     *
+     * var objects = [
+     *   { 'a': { 'b': _.constant(2) } },
+     *   { 'a': { 'b': _.constant(1) } }
+     * ];
+     *
+     * _.map(objects, _.method('a.b'));
+     * // => [2, 1]
+     *
+     * _.map(objects, _.method(['a', 'b']));
+     * // => [2, 1]
+     */
+    var method = baseRest(function(path, args) {
+      return function(object) {
+        return baseInvoke(object, path, args);
+      };
+    });
+
+    /**
+     * The opposite of `_.method`; this method creates a function that invokes
+     * the method at a given path of `object`. Any additional arguments are
+     * provided to the invoked method.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.7.0
+     * @category Util
+     * @param {Object} object The object to query.
+     * @param {...*} [args] The arguments to invoke the method with.
+     * @returns {Function} Returns the new invoker function.
+     * @example
+     *
+     * var array = _.times(3, _.constant),
+     *     object = { 'a': array, 'b': array, 'c': array };
+     *
+     * _.map(['a[2]', 'c[0]'], _.methodOf(object));
+     * // => [2, 0]
+     *
+     * _.map([['a', '2'], ['c', '0']], _.methodOf(object));
+     * // => [2, 0]
+     */
+    var methodOf = baseRest(function(object, args) {
+      return function(path) {
+        return baseInvoke(object, path, args);
+      };
+    });
+
+    /**
+     * Adds all own enumerable string keyed function properties of a source
+     * object to the destination object. If `object` is a function, then methods
+     * are added to its prototype as well.
+     *
+     * **Note:** Use `_.runInContext` to create a pristine `lodash` function to
+     * avoid conflicts caused by modifying the original.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Util
+     * @param {Function|Object} [object=lodash] The destination object.
+     * @param {Object} source The object of functions to add.
+     * @param {Object} [options={}] The options object.
+     * @param {boolean} [options.chain=true] Specify whether mixins are chainable.
+     * @returns {Function|Object} Returns `object`.
+     * @example
+     *
+     * function vowels(string) {
+     *   return _.filter(string, function(v) {
+     *     return /[aeiou]/i.test(v);
+     *   });
+     * }
+     *
+     * _.mixin({ 'vowels': vowels });
+     * _.vowels('fred');
+     * // => ['e']
+     *
+     * _('fred').vowels().value();
+     * // => ['e']
+     *
+     * _.mixin({ 'vowels': vowels }, { 'chain': false });
+     * _('fred').vowels();
+     * // => ['e']
+     */
+    function mixin(object, source, options) {
+      var props = keys(source),
+          methodNames = baseFunctions(source, props);
+
+      if (options == null &&
+          !(isObject(source) && (methodNames.length || !props.length))) {
+        options = source;
+        source = object;
+        object = this;
+        methodNames = baseFunctions(source, keys(source));
+      }
+      var chain = !(isObject(options) && 'chain' in options) || !!options.chain,
+          isFunc = isFunction(object);
+
+      arrayEach(methodNames, function(methodName) {
+        var func = source[methodName];
+        object[methodName] = func;
+        if (isFunc) {
+          object.prototype[methodName] = function() {
+            var chainAll = this.__chain__;
+            if (chain || chainAll) {
+              var result = object(this.__wrapped__),
+                  actions = result.__actions__ = copyArray(this.__actions__);
+
+              actions.push({ 'func': func, 'args': arguments, 'thisArg': object });
+              result.__chain__ = chainAll;
+              return result;
+            }
+            return func.apply(object, arrayPush([this.value()], arguments));
+          };
+        }
+      });
+
+      return object;
+    }
+
+    /**
+     * Reverts the `_` variable to its previous value and returns a reference to
+     * the `lodash` function.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Util
+     * @returns {Function} Returns the `lodash` function.
+     * @example
+     *
+     * var lodash = _.noConflict();
+     */
+    function noConflict() {
+      if (root._ === this) {
+        root._ = oldDash;
+      }
+      return this;
+    }
+
+    /**
+     * This method returns `undefined`.
+     *
+     * @static
+     * @memberOf _
+     * @since 2.3.0
+     * @category Util
+     * @example
+     *
+     * _.times(2, _.noop);
+     * // => [undefined, undefined]
+     */
+    function noop() {
+      // No operation performed.
+    }
+
+    /**
+     * Creates a function that gets the argument at index `n`. If `n` is negative,
+     * the nth argument from the end is returned.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Util
+     * @param {number} [n=0] The index of the argument to return.
+     * @returns {Function} Returns the new pass-thru function.
+     * @example
+     *
+     * var func = _.nthArg(1);
+     * func('a', 'b', 'c', 'd');
+     * // => 'b'
+     *
+     * var func = _.nthArg(-2);
+     * func('a', 'b', 'c', 'd');
+     * // => 'c'
+     */
+    function nthArg(n) {
+      n = toInteger(n);
+      return baseRest(function(args) {
+        return baseNth(args, n);
+      });
+    }
+
+    /**
+     * Creates a function that invokes `iteratees` with the arguments it receives
+     * and returns their results.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Util
+     * @param {...(Function|Function[])} [iteratees=[_.identity]]
+     *  The iteratees to invoke.
+     * @returns {Function} Returns the new function.
+     * @example
+     *
+     * var func = _.over([Math.max, Math.min]);
+     *
+     * func(1, 2, 3, 4);
+     * // => [4, 1]
+     */
+    var over = createOver(arrayMap);
+
+    /**
+     * Creates a function that checks if **all** of the `predicates` return
+     * truthy when invoked with the arguments it receives.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Util
+     * @param {...(Function|Function[])} [predicates=[_.identity]]
+     *  The predicates to check.
+     * @returns {Function} Returns the new function.
+     * @example
+     *
+     * var func = _.overEvery([Boolean, isFinite]);
+     *
+     * func('1');
+     * // => true
+     *
+     * func(null);
+     * // => false
+     *
+     * func(NaN);
+     * // => false
+     */
+    var overEvery = createOver(arrayEvery);
+
+    /**
+     * Creates a function that checks if **any** of the `predicates` return
+     * truthy when invoked with the arguments it receives.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Util
+     * @param {...(Function|Function[])} [predicates=[_.identity]]
+     *  The predicates to check.
+     * @returns {Function} Returns the new function.
+     * @example
+     *
+     * var func = _.overSome([Boolean, isFinite]);
+     *
+     * func('1');
+     * // => true
+     *
+     * func(null);
+     * // => true
+     *
+     * func(NaN);
+     * // => false
+     */
+    var overSome = createOver(arraySome);
+
+    /**
+     * Creates a function that returns the value at `path` of a given object.
+     *
+     * @static
+     * @memberOf _
+     * @since 2.4.0
+     * @category Util
+     * @param {Array|string} path The path of the property to get.
+     * @returns {Function} Returns the new accessor function.
+     * @example
+     *
+     * var objects = [
+     *   { 'a': { 'b': 2 } },
+     *   { 'a': { 'b': 1 } }
+     * ];
+     *
+     * _.map(objects, _.property('a.b'));
+     * // => [2, 1]
+     *
+     * _.map(_.sortBy(objects, _.property(['a', 'b'])), 'a.b');
+     * // => [1, 2]
+     */
+    function property(path) {
+      return isKey(path) ? baseProperty(toKey(path)) : basePropertyDeep(path);
+    }
+
+    /**
+     * The opposite of `_.property`; this method creates a function that returns
+     * the value at a given path of `object`.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.0.0
+     * @category Util
+     * @param {Object} object The object to query.
+     * @returns {Function} Returns the new accessor function.
+     * @example
+     *
+     * var array = [0, 1, 2],
+     *     object = { 'a': array, 'b': array, 'c': array };
+     *
+     * _.map(['a[2]', 'c[0]'], _.propertyOf(object));
+     * // => [2, 0]
+     *
+     * _.map([['a', '2'], ['c', '0']], _.propertyOf(object));
+     * // => [2, 0]
+     */
+    function propertyOf(object) {
+      return function(path) {
+        return object == null ? undefined : baseGet(object, path);
+      };
+    }
+
+    /**
+     * Creates an array of numbers (positive and/or negative) progressing from
+     * `start` up to, but not including, `end`. A step of `-1` is used if a negative
+     * `start` is specified without an `end` or `step`. If `end` is not specified,
+     * it's set to `start` with `start` then set to `0`.
+     *
+     * **Note:** JavaScript follows the IEEE-754 standard for resolving
+     * floating-point values which can produce unexpected results.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Util
+     * @param {number} [start=0] The start of the range.
+     * @param {number} end The end of the range.
+     * @param {number} [step=1] The value to increment or decrement by.
+     * @returns {Array} Returns the range of numbers.
+     * @see _.inRange, _.rangeRight
+     * @example
+     *
+     * _.range(4);
+     * // => [0, 1, 2, 3]
+     *
+     * _.range(-4);
+     * // => [0, -1, -2, -3]
+     *
+     * _.range(1, 5);
+     * // => [1, 2, 3, 4]
+     *
+     * _.range(0, 20, 5);
+     * // => [0, 5, 10, 15]
+     *
+     * _.range(0, -4, -1);
+     * // => [0, -1, -2, -3]
+     *
+     * _.range(1, 4, 0);
+     * // => [1, 1, 1]
+     *
+     * _.range(0);
+     * // => []
+     */
+    var range = createRange();
+
+    /**
+     * This method is like `_.range` except that it populates values in
+     * descending order.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Util
+     * @param {number} [start=0] The start of the range.
+     * @param {number} end The end of the range.
+     * @param {number} [step=1] The value to increment or decrement by.
+     * @returns {Array} Returns the range of numbers.
+     * @see _.inRange, _.range
+     * @example
+     *
+     * _.rangeRight(4);
+     * // => [3, 2, 1, 0]
+     *
+     * _.rangeRight(-4);
+     * // => [-3, -2, -1, 0]
+     *
+     * _.rangeRight(1, 5);
+     * // => [4, 3, 2, 1]
+     *
+     * _.rangeRight(0, 20, 5);
+     * // => [15, 10, 5, 0]
+     *
+     * _.rangeRight(0, -4, -1);
+     * // => [-3, -2, -1, 0]
+     *
+     * _.rangeRight(1, 4, 0);
+     * // => [1, 1, 1]
+     *
+     * _.rangeRight(0);
+     * // => []
+     */
+    var rangeRight = createRange(true);
+
+    /**
+     * This method returns a new empty array.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.13.0
+     * @category Util
+     * @returns {Array} Returns the new empty array.
+     * @example
+     *
+     * var arrays = _.times(2, _.stubArray);
+     *
+     * console.log(arrays);
+     * // => [[], []]
+     *
+     * console.log(arrays[0] === arrays[1]);
+     * // => false
+     */
+    function stubArray() {
+      return [];
+    }
+
+    /**
+     * This method returns `false`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.13.0
+     * @category Util
+     * @returns {boolean} Returns `false`.
+     * @example
+     *
+     * _.times(2, _.stubFalse);
+     * // => [false, false]
+     */
+    function stubFalse() {
+      return false;
+    }
+
+    /**
+     * This method returns a new empty object.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.13.0
+     * @category Util
+     * @returns {Object} Returns the new empty object.
+     * @example
+     *
+     * var objects = _.times(2, _.stubObject);
+     *
+     * console.log(objects);
+     * // => [{}, {}]
+     *
+     * console.log(objects[0] === objects[1]);
+     * // => false
+     */
+    function stubObject() {
+      return {};
+    }
+
+    /**
+     * This method returns an empty string.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.13.0
+     * @category Util
+     * @returns {string} Returns the empty string.
+     * @example
+     *
+     * _.times(2, _.stubString);
+     * // => ['', '']
+     */
+    function stubString() {
+      return '';
+    }
+
+    /**
+     * This method returns `true`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.13.0
+     * @category Util
+     * @returns {boolean} Returns `true`.
+     * @example
+     *
+     * _.times(2, _.stubTrue);
+     * // => [true, true]
+     */
+    function stubTrue() {
+      return true;
+    }
+
+    /**
+     * Invokes the iteratee `n` times, returning an array of the results of
+     * each invocation. The iteratee is invoked with one argument; (index).
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Util
+     * @param {number} n The number of times to invoke `iteratee`.
+     * @param {Function} [iteratee=_.identity] The function invoked per iteration.
+     * @returns {Array} Returns the array of results.
+     * @example
+     *
+     * _.times(3, String);
+     * // => ['0', '1', '2']
+     *
+     *  _.times(4, _.constant(0));
+     * // => [0, 0, 0, 0]
+     */
+    function times(n, iteratee) {
+      n = toInteger(n);
+      if (n < 1 || n > MAX_SAFE_INTEGER) {
+        return [];
+      }
+      var index = MAX_ARRAY_LENGTH,
+          length = nativeMin(n, MAX_ARRAY_LENGTH);
+
+      iteratee = getIteratee(iteratee);
+      n -= MAX_ARRAY_LENGTH;
+
+      var result = baseTimes(length, iteratee);
+      while (++index < n) {
+        iteratee(index);
+      }
+      return result;
+    }
+
+    /**
+     * Converts `value` to a property path array.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Util
+     * @param {*} value The value to convert.
+     * @returns {Array} Returns the new property path array.
+     * @example
+     *
+     * _.toPath('a.b.c');
+     * // => ['a', 'b', 'c']
+     *
+     * _.toPath('a[0].b.c');
+     * // => ['a', '0', 'b', 'c']
+     */
+    function toPath(value) {
+      if (isArray(value)) {
+        return arrayMap(value, toKey);
+      }
+      return isSymbol(value) ? [value] : copyArray(stringToPath(toString(value)));
+    }
+
+    /**
+     * Generates a unique ID. If `prefix` is given, the ID is appended to it.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Util
+     * @param {string} [prefix=''] The value to prefix the ID with.
+     * @returns {string} Returns the unique ID.
+     * @example
+     *
+     * _.uniqueId('contact_');
+     * // => 'contact_104'
+     *
+     * _.uniqueId();
+     * // => '105'
+     */
+    function uniqueId(prefix) {
+      var id = ++idCounter;
+      return toString(prefix) + id;
+    }
+
+    /*------------------------------------------------------------------------*/
+
+    /**
+     * Adds two numbers.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.4.0
+     * @category Math
+     * @param {number} augend The first number in an addition.
+     * @param {number} addend The second number in an addition.
+     * @returns {number} Returns the total.
+     * @example
+     *
+     * _.add(6, 4);
+     * // => 10
+     */
+    var add = createMathOperation(function(augend, addend) {
+      return augend + addend;
+    }, 0);
+
+    /**
+     * Computes `number` rounded up to `precision`.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.10.0
+     * @category Math
+     * @param {number} number The number to round up.
+     * @param {number} [precision=0] The precision to round up to.
+     * @returns {number} Returns the rounded up number.
+     * @example
+     *
+     * _.ceil(4.006);
+     * // => 5
+     *
+     * _.ceil(6.004, 2);
+     * // => 6.01
+     *
+     * _.ceil(6040, -2);
+     * // => 6100
+     */
+    var ceil = createRound('ceil');
+
+    /**
+     * Divide two numbers.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.7.0
+     * @category Math
+     * @param {number} dividend The first number in a division.
+     * @param {number} divisor The second number in a division.
+     * @returns {number} Returns the quotient.
+     * @example
+     *
+     * _.divide(6, 4);
+     * // => 1.5
+     */
+    var divide = createMathOperation(function(dividend, divisor) {
+      return dividend / divisor;
+    }, 1);
+
+    /**
+     * Computes `number` rounded down to `precision`.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.10.0
+     * @category Math
+     * @param {number} number The number to round down.
+     * @param {number} [precision=0] The precision to round down to.
+     * @returns {number} Returns the rounded down number.
+     * @example
+     *
+     * _.floor(4.006);
+     * // => 4
+     *
+     * _.floor(0.046, 2);
+     * // => 0.04
+     *
+     * _.floor(4060, -2);
+     * // => 4000
+     */
+    var floor = createRound('floor');
+
+    /**
+     * Computes the maximum value of `array`. If `array` is empty or falsey,
+     * `undefined` is returned.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Math
+     * @param {Array} array The array to iterate over.
+     * @returns {*} Returns the maximum value.
+     * @example
+     *
+     * _.max([4, 2, 8, 6]);
+     * // => 8
+     *
+     * _.max([]);
+     * // => undefined
+     */
+    function max(array) {
+      return (array && array.length)
+        ? baseExtremum(array, identity, baseGt)
+        : undefined;
+    }
+
+    /**
+     * This method is like `_.max` except that it accepts `iteratee` which is
+     * invoked for each element in `array` to generate the criterion by which
+     * the value is ranked. The iteratee is invoked with one argument: (value).
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Math
+     * @param {Array} array The array to iterate over.
+     * @param {Function} [iteratee=_.identity] The iteratee invoked per element.
+     * @returns {*} Returns the maximum value.
+     * @example
+     *
+     * var objects = [{ 'n': 1 }, { 'n': 2 }];
+     *
+     * _.maxBy(objects, function(o) { return o.n; });
+     * // => { 'n': 2 }
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.maxBy(objects, 'n');
+     * // => { 'n': 2 }
+     */
+    function maxBy(array, iteratee) {
+      return (array && array.length)
+        ? baseExtremum(array, getIteratee(iteratee, 2), baseGt)
+        : undefined;
+    }
+
+    /**
+     * Computes the mean of the values in `array`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Math
+     * @param {Array} array The array to iterate over.
+     * @returns {number} Returns the mean.
+     * @example
+     *
+     * _.mean([4, 2, 8, 6]);
+     * // => 5
+     */
+    function mean(array) {
+      return baseMean(array, identity);
+    }
+
+    /**
+     * This method is like `_.mean` except that it accepts `iteratee` which is
+     * invoked for each element in `array` to generate the value to be averaged.
+     * The iteratee is invoked with one argument: (value).
+     *
+     * @static
+     * @memberOf _
+     * @since 4.7.0
+     * @category Math
+     * @param {Array} array The array to iterate over.
+     * @param {Function} [iteratee=_.identity] The iteratee invoked per element.
+     * @returns {number} Returns the mean.
+     * @example
+     *
+     * var objects = [{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }];
+     *
+     * _.meanBy(objects, function(o) { return o.n; });
+     * // => 5
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.meanBy(objects, 'n');
+     * // => 5
+     */
+    function meanBy(array, iteratee) {
+      return baseMean(array, getIteratee(iteratee, 2));
+    }
+
+    /**
+     * Computes the minimum value of `array`. If `array` is empty or falsey,
+     * `undefined` is returned.
+     *
+     * @static
+     * @since 0.1.0
+     * @memberOf _
+     * @category Math
+     * @param {Array} array The array to iterate over.
+     * @returns {*} Returns the minimum value.
+     * @example
+     *
+     * _.min([4, 2, 8, 6]);
+     * // => 2
+     *
+     * _.min([]);
+     * // => undefined
+     */
+    function min(array) {
+      return (array && array.length)
+        ? baseExtremum(array, identity, baseLt)
+        : undefined;
+    }
+
+    /**
+     * This method is like `_.min` except that it accepts `iteratee` which is
+     * invoked for each element in `array` to generate the criterion by which
+     * the value is ranked. The iteratee is invoked with one argument: (value).
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Math
+     * @param {Array} array The array to iterate over.
+     * @param {Function} [iteratee=_.identity] The iteratee invoked per element.
+     * @returns {*} Returns the minimum value.
+     * @example
+     *
+     * var objects = [{ 'n': 1 }, { 'n': 2 }];
+     *
+     * _.minBy(objects, function(o) { return o.n; });
+     * // => { 'n': 1 }
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.minBy(objects, 'n');
+     * // => { 'n': 1 }
+     */
+    function minBy(array, iteratee) {
+      return (array && array.length)
+        ? baseExtremum(array, getIteratee(iteratee, 2), baseLt)
+        : undefined;
+    }
+
+    /**
+     * Multiply two numbers.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.7.0
+     * @category Math
+     * @param {number} multiplier The first number in a multiplication.
+     * @param {number} multiplicand The second number in a multiplication.
+     * @returns {number} Returns the product.
+     * @example
+     *
+     * _.multiply(6, 4);
+     * // => 24
+     */
+    var multiply = createMathOperation(function(multiplier, multiplicand) {
+      return multiplier * multiplicand;
+    }, 1);
+
+    /**
+     * Computes `number` rounded to `precision`.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.10.0
+     * @category Math
+     * @param {number} number The number to round.
+     * @param {number} [precision=0] The precision to round to.
+     * @returns {number} Returns the rounded number.
+     * @example
+     *
+     * _.round(4.006);
+     * // => 4
+     *
+     * _.round(4.006, 2);
+     * // => 4.01
+     *
+     * _.round(4060, -2);
+     * // => 4100
+     */
+    var round = createRound('round');
+
+    /**
+     * Subtract two numbers.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Math
+     * @param {number} minuend The first number in a subtraction.
+     * @param {number} subtrahend The second number in a subtraction.
+     * @returns {number} Returns the difference.
+     * @example
+     *
+     * _.subtract(6, 4);
+     * // => 2
+     */
+    var subtract = createMathOperation(function(minuend, subtrahend) {
+      return minuend - subtrahend;
+    }, 0);
+
+    /**
+     * Computes the sum of the values in `array`.
+     *
+     * @static
+     * @memberOf _
+     * @since 3.4.0
+     * @category Math
+     * @param {Array} array The array to iterate over.
+     * @returns {number} Returns the sum.
+     * @example
+     *
+     * _.sum([4, 2, 8, 6]);
+     * // => 20
+     */
+    function sum(array) {
+      return (array && array.length)
+        ? baseSum(array, identity)
+        : 0;
+    }
+
+    /**
+     * This method is like `_.sum` except that it accepts `iteratee` which is
+     * invoked for each element in `array` to generate the value to be summed.
+     * The iteratee is invoked with one argument: (value).
+     *
+     * @static
+     * @memberOf _
+     * @since 4.0.0
+     * @category Math
+     * @param {Array} array The array to iterate over.
+     * @param {Function} [iteratee=_.identity] The iteratee invoked per element.
+     * @returns {number} Returns the sum.
+     * @example
+     *
+     * var objects = [{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }];
+     *
+     * _.sumBy(objects, function(o) { return o.n; });
+     * // => 20
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.sumBy(objects, 'n');
+     * // => 20
+     */
+    function sumBy(array, iteratee) {
+      return (array && array.length)
+        ? baseSum(array, getIteratee(iteratee, 2))
+        : 0;
+    }
+
+    /*------------------------------------------------------------------------*/
+
+    // Add methods that return wrapped values in chain sequences.
+    lodash.after = after;
+    lodash.ary = ary;
+    lodash.assign = assign;
+    lodash.assignIn = assignIn;
+    lodash.assignInWith = assignInWith;
+    lodash.assignWith = assignWith;
+    lodash.at = at;
+    lodash.before = before;
+    lodash.bind = bind;
+    lodash.bindAll = bindAll;
+    lodash.bindKey = bindKey;
+    lodash.castArray = castArray;
+    lodash.chain = chain;
+    lodash.chunk = chunk;
+    lodash.compact = compact;
+    lodash.concat = concat;
+    lodash.cond = cond;
+    lodash.conforms = conforms;
+    lodash.constant = constant;
+    lodash.countBy = countBy;
+    lodash.create = create;
+    lodash.curry = curry;
+    lodash.curryRight = curryRight;
+    lodash.debounce = debounce;
+    lodash.defaults = defaults;
+    lodash.defaultsDeep = defaultsDeep;
+    lodash.defer = defer;
+    lodash.delay = delay;
+    lodash.difference = difference;
+    lodash.differenceBy = differenceBy;
+    lodash.differenceWith = differenceWith;
+    lodash.drop = drop;
+    lodash.dropRight = dropRight;
+    lodash.dropRightWhile = dropRightWhile;
+    lodash.dropWhile = dropWhile;
+    lodash.fill = fill;
+    lodash.filter = filter;
+    lodash.flatMap = flatMap;
+    lodash.flatMapDeep = flatMapDeep;
+    lodash.flatMapDepth = flatMapDepth;
+    lodash.flatten = flatten;
+    lodash.flattenDeep = flattenDeep;
+    lodash.flattenDepth = flattenDepth;
+    lodash.flip = flip;
+    lodash.flow = flow;
+    lodash.flowRight = flowRight;
+    lodash.fromPairs = fromPairs;
+    lodash.functions = functions;
+    lodash.functionsIn = functionsIn;
+    lodash.groupBy = groupBy;
+    lodash.initial = initial;
+    lodash.intersection = intersection;
+    lodash.intersectionBy = intersectionBy;
+    lodash.intersectionWith = intersectionWith;
+    lodash.invert = invert;
+    lodash.invertBy = invertBy;
+    lodash.invokeMap = invokeMap;
+    lodash.iteratee = iteratee;
+    lodash.keyBy = keyBy;
+    lodash.keys = keys;
+    lodash.keysIn = keysIn;
+    lodash.map = map;
+    lodash.mapKeys = mapKeys;
+    lodash.mapValues = mapValues;
+    lodash.matches = matches;
+    lodash.matchesProperty = matchesProperty;
+    lodash.memoize = memoize;
+    lodash.merge = merge;
+    lodash.mergeWith = mergeWith;
+    lodash.method = method;
+    lodash.methodOf = methodOf;
+    lodash.mixin = mixin;
+    lodash.negate = negate;
+    lodash.nthArg = nthArg;
+    lodash.omit = omit;
+    lodash.omitBy = omitBy;
+    lodash.once = once;
+    lodash.orderBy = orderBy;
+    lodash.over = over;
+    lodash.overArgs = overArgs;
+    lodash.overEvery = overEvery;
+    lodash.overSome = overSome;
+    lodash.partial = partial;
+    lodash.partialRight = partialRight;
+    lodash.partition = partition;
+    lodash.pick = pick;
+    lodash.pickBy = pickBy;
+    lodash.property = property;
+    lodash.propertyOf = propertyOf;
+    lodash.pull = pull;
+    lodash.pullAll = pullAll;
+    lodash.pullAllBy = pullAllBy;
+    lodash.pullAllWith = pullAllWith;
+    lodash.pullAt = pullAt;
+    lodash.range = range;
+    lodash.rangeRight = rangeRight;
+    lodash.rearg = rearg;
+    lodash.reject = reject;
+    lodash.remove = remove;
+    lodash.rest = rest;
+    lodash.reverse = reverse;
+    lodash.sampleSize = sampleSize;
+    lodash.set = set;
+    lodash.setWith = setWith;
+    lodash.shuffle = shuffle;
+    lodash.slice = slice;
+    lodash.sortBy = sortBy;
+    lodash.sortedUniq = sortedUniq;
+    lodash.sortedUniqBy = sortedUniqBy;
+    lodash.split = split;
+    lodash.spread = spread;
+    lodash.tail = tail;
+    lodash.take = take;
+    lodash.takeRight = takeRight;
+    lodash.takeRightWhile = takeRightWhile;
+    lodash.takeWhile = takeWhile;
+    lodash.tap = tap;
+    lodash.throttle = throttle;
+    lodash.thru = thru;
+    lodash.toArray = toArray;
+    lodash.toPairs = toPairs;
+    lodash.toPairsIn = toPairsIn;
+    lodash.toPath = toPath;
+    lodash.toPlainObject = toPlainObject;
+    lodash.transform = transform;
+    lodash.unary = unary;
+    lodash.union = union;
+    lodash.unionBy = unionBy;
+    lodash.unionWith = unionWith;
+    lodash.uniq = uniq;
+    lodash.uniqBy = uniqBy;
+    lodash.uniqWith = uniqWith;
+    lodash.unset = unset;
+    lodash.unzip = unzip;
+    lodash.unzipWith = unzipWith;
+    lodash.update = update;
+    lodash.updateWith = updateWith;
+    lodash.values = values;
+    lodash.valuesIn = valuesIn;
+    lodash.without = without;
+    lodash.words = words;
+    lodash.wrap = wrap;
+    lodash.xor = xor;
+    lodash.xorBy = xorBy;
+    lodash.xorWith = xorWith;
+    lodash.zip = zip;
+    lodash.zipObject = zipObject;
+    lodash.zipObjectDeep = zipObjectDeep;
+    lodash.zipWith = zipWith;
+
+    // Add aliases.
+    lodash.entries = toPairs;
+    lodash.entriesIn = toPairsIn;
+    lodash.extend = assignIn;
+    lodash.extendWith = assignInWith;
+
+    // Add methods to `lodash.prototype`.
+    mixin(lodash, lodash);
+
+    /*------------------------------------------------------------------------*/
+
+    // Add methods that return unwrapped values in chain sequences.
+    lodash.add = add;
+    lodash.attempt = attempt;
+    lodash.camelCase = camelCase;
+    lodash.capitalize = capitalize;
+    lodash.ceil = ceil;
+    lodash.clamp = clamp;
+    lodash.clone = clone;
+    lodash.cloneDeep = cloneDeep;
+    lodash.cloneDeepWith = cloneDeepWith;
+    lodash.cloneWith = cloneWith;
+    lodash.conformsTo = conformsTo;
+    lodash.deburr = deburr;
+    lodash.defaultTo = defaultTo;
+    lodash.divide = divide;
+    lodash.endsWith = endsWith;
+    lodash.eq = eq;
+    lodash.escape = escape;
+    lodash.escapeRegExp = escapeRegExp;
+    lodash.every = every;
+    lodash.find = find;
+    lodash.findIndex = findIndex;
+    lodash.findKey = findKey;
+    lodash.findLast = findLast;
+    lodash.findLastIndex = findLastIndex;
+    lodash.findLastKey = findLastKey;
+    lodash.floor = floor;
+    lodash.forEach = forEach;
+    lodash.forEachRight = forEachRight;
+    lodash.forIn = forIn;
+    lodash.forInRight = forInRight;
+    lodash.forOwn = forOwn;
+    lodash.forOwnRight = forOwnRight;
+    lodash.get = get;
+    lodash.gt = gt;
+    lodash.gte = gte;
+    lodash.has = has;
+    lodash.hasIn = hasIn;
+    lodash.head = head;
+    lodash.identity = identity;
+    lodash.includes = includes;
+    lodash.indexOf = indexOf;
+    lodash.inRange = inRange;
+    lodash.invoke = invoke;
+    lodash.isArguments = isArguments;
+    lodash.isArray = isArray;
+    lodash.isArrayBuffer = isArrayBuffer;
+    lodash.isArrayLike = isArrayLike;
+    lodash.isArrayLikeObject = isArrayLikeObject;
+    lodash.isBoolean = isBoolean;
+    lodash.isBuffer = isBuffer;
+    lodash.isDate = isDate;
+    lodash.isElement = isElement;
+    lodash.isEmpty = isEmpty;
+    lodash.isEqual = isEqual;
+    lodash.isEqualWith = isEqualWith;
+    lodash.isError = isError;
+    lodash.isFinite = isFinite;
+    lodash.isFunction = isFunction;
+    lodash.isInteger = isInteger;
+    lodash.isLength = isLength;
+    lodash.isMap = isMap;
+    lodash.isMatch = isMatch;
+    lodash.isMatchWith = isMatchWith;
+    lodash.isNaN = isNaN;
+    lodash.isNative = isNative;
+    lodash.isNil = isNil;
+    lodash.isNull = isNull;
+    lodash.isNumber = isNumber;
+    lodash.isObject = isObject;
+    lodash.isObjectLike = isObjectLike;
+    lodash.isPlainObject = isPlainObject;
+    lodash.isRegExp = isRegExp;
+    lodash.isSafeInteger = isSafeInteger;
+    lodash.isSet = isSet;
+    lodash.isString = isString;
+    lodash.isSymbol = isSymbol;
+    lodash.isTypedArray = isTypedArray;
+    lodash.isUndefined = isUndefined;
+    lodash.isWeakMap = isWeakMap;
+    lodash.isWeakSet = isWeakSet;
+    lodash.join = join;
+    lodash.kebabCase = kebabCase;
+    lodash.last = last;
+    lodash.lastIndexOf = lastIndexOf;
+    lodash.lowerCase = lowerCase;
+    lodash.lowerFirst = lowerFirst;
+    lodash.lt = lt;
+    lodash.lte = lte;
+    lodash.max = max;
+    lodash.maxBy = maxBy;
+    lodash.mean = mean;
+    lodash.meanBy = meanBy;
+    lodash.min = min;
+    lodash.minBy = minBy;
+    lodash.stubArray = stubArray;
+    lodash.stubFalse = stubFalse;
+    lodash.stubObject = stubObject;
+    lodash.stubString = stubString;
+    lodash.stubTrue = stubTrue;
+    lodash.multiply = multiply;
+    lodash.nth = nth;
+    lodash.noConflict = noConflict;
+    lodash.noop = noop;
+    lodash.now = now;
+    lodash.pad = pad;
+    lodash.padEnd = padEnd;
+    lodash.padStart = padStart;
+    lodash.parseInt = parseInt;
+    lodash.random = random;
+    lodash.reduce = reduce;
+    lodash.reduceRight = reduceRight;
+    lodash.repeat = repeat;
+    lodash.replace = replace;
+    lodash.result = result;
+    lodash.round = round;
+    lodash.runInContext = runInContext;
+    lodash.sample = sample;
+    lodash.size = size;
+    lodash.snakeCase = snakeCase;
+    lodash.some = some;
+    lodash.sortedIndex = sortedIndex;
+    lodash.sortedIndexBy = sortedIndexBy;
+    lodash.sortedIndexOf = sortedIndexOf;
+    lodash.sortedLastIndex = sortedLastIndex;
+    lodash.sortedLastIndexBy = sortedLastIndexBy;
+    lodash.sortedLastIndexOf = sortedLastIndexOf;
+    lodash.startCase = startCase;
+    lodash.startsWith = startsWith;
+    lodash.subtract = subtract;
+    lodash.sum = sum;
+    lodash.sumBy = sumBy;
+    lodash.template = template;
+    lodash.times = times;
+    lodash.toFinite = toFinite;
+    lodash.toInteger = toInteger;
+    lodash.toLength = toLength;
+    lodash.toLower = toLower;
+    lodash.toNumber = toNumber;
+    lodash.toSafeInteger = toSafeInteger;
+    lodash.toString = toString;
+    lodash.toUpper = toUpper;
+    lodash.trim = trim;
+    lodash.trimEnd = trimEnd;
+    lodash.trimStart = trimStart;
+    lodash.truncate = truncate;
+    lodash.unescape = unescape;
+    lodash.uniqueId = uniqueId;
+    lodash.upperCase = upperCase;
+    lodash.upperFirst = upperFirst;
+
+    // Add aliases.
+    lodash.each = forEach;
+    lodash.eachRight = forEachRight;
+    lodash.first = head;
 
-          // update the remoteDescription.
-          var sections = SDPUtils.splitSections(this.remoteDescription.sdp);
-          sections[mLineIndex + 1] += (cand.type ? candidate.candidate.trim()
-              : 'a=end-of-candidates') + '\r\n';
-          this.remoteDescription.sdp = sections.join('');
+    mixin(lodash, (function() {
+      var source = {};
+      baseForOwn(lodash, function(func, methodName) {
+        if (!hasOwnProperty.call(lodash.prototype, methodName)) {
+          source[methodName] = func;
         }
-      }
-      if (arguments.length > 1 && typeof arguments[1] === 'function') {
-        window.setTimeout(arguments[1], 0);
-      }
-      return Promise.resolve();
-    };
-
-    window.RTCPeerConnection.prototype.getStats = function() {
-      var promises = [];
-      this.transceivers.forEach(function(transceiver) {
-        ['rtpSender', 'rtpReceiver', 'iceGatherer', 'iceTransport',
-            'dtlsTransport'].forEach(function(method) {
-              if (transceiver[method]) {
-                promises.push(transceiver[method].getStats());
-              }
-            });
-      });
-      var cb = arguments.length > 1 && typeof arguments[1] === 'function' &&
-          arguments[1];
-      return new Promise(function(resolve) {
-        // shim getStats with maplike support
-        var results = new Map();
-        Promise.all(promises).then(function(res) {
-          res.forEach(function(result) {
-            Object.keys(result).forEach(function(id) {
-              results.set(id, result[id]);
-              results[id] = result[id];
-            });
-          });
-          if (cb) {
-            window.setTimeout(cb, 0, results);
-          }
-          resolve(results);
-        });
       });
-    };
-  },
-
-  // Attach a media stream to an element.
-  attachMediaStream: function(element, stream) {
-    logging('DEPRECATED, attachMediaStream will soon be removed.');
-    element.srcObject = stream;
-  },
-
-  reattachMediaStream: function(to, from) {
-    logging('DEPRECATED, reattachMediaStream will soon be removed.');
-    to.srcObject = from.srcObject;
-  }
-};
-
-// Expose public methods.
-module.exports = {
-  shimPeerConnection: edgeShim.shimPeerConnection,
-  shimGetUserMedia: require('./getusermedia'),
-  attachMediaStream: edgeShim.attachMediaStream,
-  reattachMediaStream: edgeShim.reattachMediaStream
-};
+      return source;
+    }()), { 'chain': false });
 
-},{"../utils":18,"./getusermedia":14,"sdp":8}],14:[function(require,module,exports){
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
- /* eslint-env node */
-'use strict';
+    /*------------------------------------------------------------------------*/
 
-// Expose public methods.
-module.exports = function() {
-  var shimError_ = function(e) {
-    return {
-      name: {PermissionDeniedError: 'NotAllowedError'}[e.name] || e.name,
-      message: e.message,
-      constraint: e.constraint,
-      toString: function() {
-        return this.name;
-      }
-    };
-  };
+    /**
+     * The semantic version number.
+     *
+     * @static
+     * @memberOf _
+     * @type {string}
+     */
+    lodash.VERSION = VERSION;
 
-  // getUserMedia error shim.
-  var origGetUserMedia = navigator.mediaDevices.getUserMedia.
-      bind(navigator.mediaDevices);
-  navigator.mediaDevices.getUserMedia = function(c) {
-    return origGetUserMedia(c).catch(function(e) {
-      return Promise.reject(shimError_(e));
+    // Assign default placeholders.
+    arrayEach(['bind', 'bindKey', 'curry', 'curryRight', 'partial', 'partialRight'], function(methodName) {
+      lodash[methodName].placeholder = lodash;
     });
-  };
-};
 
-},{}],15:[function(require,module,exports){
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
- /* eslint-env node */
-'use strict';
+    // Add `LazyWrapper` methods for `_.drop` and `_.take` variants.
+    arrayEach(['drop', 'take'], function(methodName, index) {
+      LazyWrapper.prototype[methodName] = function(n) {
+        n = n === undefined ? 1 : nativeMax(toInteger(n), 0);
 
-var logging = require('../utils').log;
-var browserDetails = require('../utils').browserDetails;
+        var result = (this.__filtered__ && !index)
+          ? new LazyWrapper(this)
+          : this.clone();
 
-var firefoxShim = {
-  shimOnTrack: function() {
-    if (typeof window === 'object' && window.RTCPeerConnection && !('ontrack' in
-        window.RTCPeerConnection.prototype)) {
-      Object.defineProperty(window.RTCPeerConnection.prototype, 'ontrack', {
-        get: function() {
-          return this._ontrack;
-        },
-        set: function(f) {
-          if (this._ontrack) {
-            this.removeEventListener('track', this._ontrack);
-            this.removeEventListener('addstream', this._ontrackpoly);
-          }
-          this.addEventListener('track', this._ontrack = f);
-          this.addEventListener('addstream', this._ontrackpoly = function(e) {
-            e.stream.getTracks().forEach(function(track) {
-              var event = new Event('track');
-              event.track = track;
-              event.receiver = {track: track};
-              event.streams = [e.stream];
-              this.dispatchEvent(event);
-            }.bind(this));
-          }.bind(this));
+        if (result.__filtered__) {
+          result.__takeCount__ = nativeMin(n, result.__takeCount__);
+        } else {
+          result.__views__.push({
+            'size': nativeMin(n, MAX_ARRAY_LENGTH),
+            'type': methodName + (result.__dir__ < 0 ? 'Right' : '')
+          });
         }
-      });
-    }
-  },
-
-  shimSourceObject: function() {
-    // Firefox has supported mozSrcObject since FF22, unprefixed in 42.
-    if (typeof window === 'object') {
-      if (window.HTMLMediaElement &&
-        !('srcObject' in window.HTMLMediaElement.prototype)) {
-        // Shim the srcObject property, once, when HTMLMediaElement is found.
-        Object.defineProperty(window.HTMLMediaElement.prototype, 'srcObject', {
-          get: function() {
-            return this.mozSrcObject;
-          },
-          set: function(stream) {
-            this.mozSrcObject = stream;
-          }
-        });
-      }
-    }
-  },
+        return result;
+      };
 
-  shimPeerConnection: function() {
-    if (typeof window !== 'object' || !(window.RTCPeerConnection ||
-        window.mozRTCPeerConnection)) {
-      return; // probably media.peerconnection.enabled=false in about:config
-    }
-    // The RTCPeerConnection object.
-    if (!window.RTCPeerConnection) {
-      window.RTCPeerConnection = function(pcConfig, pcConstraints) {
-        if (browserDetails.version < 38) {
-          // .urls is not supported in FF < 38.
-          // create RTCIceServers with a single url.
-          if (pcConfig && pcConfig.iceServers) {
-            var newIceServers = [];
-            for (var i = 0; i < pcConfig.iceServers.length; i++) {
-              var server = pcConfig.iceServers[i];
-              if (server.hasOwnProperty('urls')) {
-                for (var j = 0; j < server.urls.length; j++) {
-                  var newServer = {
-                    url: server.urls[j]
-                  };
-                  if (server.urls[j].indexOf('turn') === 0) {
-                    newServer.username = server.username;
-                    newServer.credential = server.credential;
-                  }
-                  newIceServers.push(newServer);
-                }
-              } else {
-                newIceServers.push(pcConfig.iceServers[i]);
-              }
-            }
-            pcConfig.iceServers = newIceServers;
-          }
-        }
-        return new mozRTCPeerConnection(pcConfig, pcConstraints);
+      LazyWrapper.prototype[methodName + 'Right'] = function(n) {
+        return this.reverse()[methodName](n).reverse();
       };
-      window.RTCPeerConnection.prototype = mozRTCPeerConnection.prototype;
+    });
 
-      // wrap static methods. Currently just generateCertificate.
-      if (mozRTCPeerConnection.generateCertificate) {
-        Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
-          get: function() {
-            return mozRTCPeerConnection.generateCertificate;
-          }
+    // Add `LazyWrapper` methods that accept an `iteratee` value.
+    arrayEach(['filter', 'map', 'takeWhile'], function(methodName, index) {
+      var type = index + 1,
+          isFilter = type == LAZY_FILTER_FLAG || type == LAZY_WHILE_FLAG;
+
+      LazyWrapper.prototype[methodName] = function(iteratee) {
+        var result = this.clone();
+        result.__iteratees__.push({
+          'iteratee': getIteratee(iteratee, 3),
+          'type': type
         });
-      }
+        result.__filtered__ = result.__filtered__ || isFilter;
+        return result;
+      };
+    });
 
-      window.RTCSessionDescription = mozRTCSessionDescription;
-      window.RTCIceCandidate = mozRTCIceCandidate;
-    }
+    // Add `LazyWrapper` methods for `_.head` and `_.last`.
+    arrayEach(['head', 'last'], function(methodName, index) {
+      var takeName = 'take' + (index ? 'Right' : '');
 
-    // shim away need for obsolete RTCIceCandidate/RTCSessionDescription.
-    ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate']
-        .forEach(function(method) {
-          var nativeMethod = RTCPeerConnection.prototype[method];
-          RTCPeerConnection.prototype[method] = function() {
-            arguments[0] = new ((method === 'addIceCandidate') ?
-                RTCIceCandidate : RTCSessionDescription)(arguments[0]);
-            return nativeMethod.apply(this, arguments);
-          };
-        });
+      LazyWrapper.prototype[methodName] = function() {
+        return this[takeName](1).value()[0];
+      };
+    });
+
+    // Add `LazyWrapper` methods for `_.initial` and `_.tail`.
+    arrayEach(['initial', 'tail'], function(methodName, index) {
+      var dropName = 'drop' + (index ? '' : 'Right');
+
+      LazyWrapper.prototype[methodName] = function() {
+        return this.__filtered__ ? new LazyWrapper(this) : this[dropName](1);
+      };
+    });
 
-    // support for addIceCandidate(null)
-    var nativeAddIceCandidate =
-        RTCPeerConnection.prototype.addIceCandidate;
-    RTCPeerConnection.prototype.addIceCandidate = function() {
-      return arguments[0] === null ? Promise.resolve()
-          : nativeAddIceCandidate.apply(this, arguments);
+    LazyWrapper.prototype.compact = function() {
+      return this.filter(identity);
     };
 
-    // shim getStats with maplike support
-    var makeMapStats = function(stats) {
-      var map = new Map();
-      Object.keys(stats).forEach(function(key) {
-        map.set(key, stats[key]);
-        map[key] = stats[key];
-      });
-      return map;
+    LazyWrapper.prototype.find = function(predicate) {
+      return this.filter(predicate).head();
     };
 
-    var nativeGetStats = RTCPeerConnection.prototype.getStats;
-    RTCPeerConnection.prototype.getStats = function(selector, onSucc, onErr) {
-      return nativeGetStats.apply(this, [selector || null])
-        .then(function(stats) {
-          return makeMapStats(stats);
-        })
-        .then(onSucc, onErr);
+    LazyWrapper.prototype.findLast = function(predicate) {
+      return this.reverse().find(predicate);
     };
-  },
 
-  // Attach a media stream to an element.
-  attachMediaStream: function(element, stream) {
-    logging('DEPRECATED, attachMediaStream will soon be removed.');
-    element.srcObject = stream;
-  },
+    LazyWrapper.prototype.invokeMap = baseRest(function(path, args) {
+      if (typeof path == 'function') {
+        return new LazyWrapper(this);
+      }
+      return this.map(function(value) {
+        return baseInvoke(value, path, args);
+      });
+    });
 
-  reattachMediaStream: function(to, from) {
-    logging('DEPRECATED, reattachMediaStream will soon be removed.');
-    to.srcObject = from.srcObject;
-  }
-};
+    LazyWrapper.prototype.reject = function(predicate) {
+      return this.filter(negate(getIteratee(predicate)));
+    };
 
-// Expose public methods.
-module.exports = {
-  shimOnTrack: firefoxShim.shimOnTrack,
-  shimSourceObject: firefoxShim.shimSourceObject,
-  shimPeerConnection: firefoxShim.shimPeerConnection,
-  shimGetUserMedia: require('./getusermedia'),
-  attachMediaStream: firefoxShim.attachMediaStream,
-  reattachMediaStream: firefoxShim.reattachMediaStream
-};
+    LazyWrapper.prototype.slice = function(start, end) {
+      start = toInteger(start);
 
-},{"../utils":18,"./getusermedia":16}],16:[function(require,module,exports){
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
- /* eslint-env node */
-'use strict';
+      var result = this;
+      if (result.__filtered__ && (start > 0 || end < 0)) {
+        return new LazyWrapper(result);
+      }
+      if (start < 0) {
+        result = result.takeRight(-start);
+      } else if (start) {
+        result = result.drop(start);
+      }
+      if (end !== undefined) {
+        end = toInteger(end);
+        result = end < 0 ? result.dropRight(-end) : result.take(end - start);
+      }
+      return result;
+    };
 
-var logging = require('../utils').log;
-var browserDetails = require('../utils').browserDetails;
+    LazyWrapper.prototype.takeRightWhile = function(predicate) {
+      return this.reverse().takeWhile(predicate).reverse();
+    };
 
-// Expose public methods.
-module.exports = function() {
-  var shimError_ = function(e) {
-    return {
-      name: {
-        SecurityError: 'NotAllowedError',
-        PermissionDeniedError: 'NotAllowedError'
-      }[e.name] || e.name,
-      message: {
-        'The operation is insecure.': 'The request is not allowed by the ' +
-        'user agent or the platform in the current context.'
-      }[e.message] || e.message,
-      constraint: e.constraint,
-      toString: function() {
-        return this.name + (this.message && ': ') + this.message;
-      }
+    LazyWrapper.prototype.toArray = function() {
+      return this.take(MAX_ARRAY_LENGTH);
     };
-  };
 
-  // getUserMedia constraints shim.
-  var getUserMedia_ = function(constraints, onSuccess, onError) {
-    var constraintsToFF37_ = function(c) {
-      if (typeof c !== 'object' || c.require) {
-        return c;
+    // Add `LazyWrapper` methods to `lodash.prototype`.
+    baseForOwn(LazyWrapper.prototype, function(func, methodName) {
+      var checkIteratee = /^(?:filter|find|map|reject)|While$/.test(methodName),
+          isTaker = /^(?:head|last)$/.test(methodName),
+          lodashFunc = lodash[isTaker ? ('take' + (methodName == 'last' ? 'Right' : '')) : methodName],
+          retUnwrapped = isTaker || /^find/.test(methodName);
+
+      if (!lodashFunc) {
+        return;
       }
-      var require = [];
-      Object.keys(c).forEach(function(key) {
-        if (key === 'require' || key === 'advanced' || key === 'mediaSource') {
-          return;
-        }
-        var r = c[key] = (typeof c[key] === 'object') ?
-            c[key] : {ideal: c[key]};
-        if (r.min !== undefined ||
-            r.max !== undefined || r.exact !== undefined) {
-          require.push(key);
+      lodash.prototype[methodName] = function() {
+        var value = this.__wrapped__,
+            args = isTaker ? [1] : arguments,
+            isLazy = value instanceof LazyWrapper,
+            iteratee = args[0],
+            useLazy = isLazy || isArray(value);
+
+        var interceptor = function(value) {
+          var result = lodashFunc.apply(lodash, arrayPush([value], args));
+          return (isTaker && chainAll) ? result[0] : result;
+        };
+
+        if (useLazy && checkIteratee && typeof iteratee == 'function' && iteratee.length != 1) {
+          // Avoid lazy use if the iteratee has a "length" value other than `1`.
+          isLazy = useLazy = false;
         }
-        if (r.exact !== undefined) {
-          if (typeof r.exact === 'number') {
-            r. min = r.max = r.exact;
-          } else {
-            c[key] = r.exact;
-          }
-          delete r.exact;
+        var chainAll = this.__chain__,
+            isHybrid = !!this.__actions__.length,
+            isUnwrapped = retUnwrapped && !chainAll,
+            onlyLazy = isLazy && !isHybrid;
+
+        if (!retUnwrapped && useLazy) {
+          value = onlyLazy ? value : new LazyWrapper(this);
+          var result = func.apply(value, args);
+          result.__actions__.push({ 'func': thru, 'args': [interceptor], 'thisArg': undefined });
+          return new LodashWrapper(result, chainAll);
         }
-        if (r.ideal !== undefined) {
-          c.advanced = c.advanced || [];
-          var oc = {};
-          if (typeof r.ideal === 'number') {
-            oc[key] = {min: r.ideal, max: r.ideal};
-          } else {
-            oc[key] = r.ideal;
-          }
-          c.advanced.push(oc);
-          delete r.ideal;
-          if (!Object.keys(r).length) {
-            delete c[key];
-          }
+        if (isUnwrapped && onlyLazy) {
+          return func.apply(this, args);
         }
-      });
-      if (require.length) {
-        c.require = require;
-      }
-      return c;
-    };
-    constraints = JSON.parse(JSON.stringify(constraints));
-    if (browserDetails.version < 38) {
-      logging('spec: ' + JSON.stringify(constraints));
-      if (constraints.audio) {
-        constraints.audio = constraintsToFF37_(constraints.audio);
-      }
-      if (constraints.video) {
-        constraints.video = constraintsToFF37_(constraints.video);
-      }
-      logging('ff37: ' + JSON.stringify(constraints));
-    }
-    return navigator.mozGetUserMedia(constraints, onSuccess, function(e) {
-      onError(shimError_(e));
+        result = this.thru(interceptor);
+        return isUnwrapped ? (isTaker ? result.value()[0] : result.value()) : result;
+      };
     });
-  };
 
-  // Returns the result of getUserMedia as a Promise.
-  var getUserMediaPromise_ = function(constraints) {
-    return new Promise(function(resolve, reject) {
-      getUserMedia_(constraints, resolve, reject);
-    });
-  };
+    // Add `Array` methods to `lodash.prototype`.
+    arrayEach(['pop', 'push', 'shift', 'sort', 'splice', 'unshift'], function(methodName) {
+      var func = arrayProto[methodName],
+          chainName = /^(?:push|sort|unshift)$/.test(methodName) ? 'tap' : 'thru',
+          retUnwrapped = /^(?:pop|shift)$/.test(methodName);
 
-  // Shim for mediaDevices on older versions.
-  if (!navigator.mediaDevices) {
-    navigator.mediaDevices = {getUserMedia: getUserMediaPromise_,
-      addEventListener: function() { },
-      removeEventListener: function() { }
-    };
-  }
-  navigator.mediaDevices.enumerateDevices =
-      navigator.mediaDevices.enumerateDevices || function() {
-        return new Promise(function(resolve) {
-          var infos = [
-            {kind: 'audioinput', deviceId: 'default', label: '', groupId: ''},
-            {kind: 'videoinput', deviceId: 'default', label: '', groupId: ''}
-          ];
-          resolve(infos);
+      lodash.prototype[methodName] = function() {
+        var args = arguments;
+        if (retUnwrapped && !this.__chain__) {
+          var value = this.value();
+          return func.apply(isArray(value) ? value : [], args);
+        }
+        return this[chainName](function(value) {
+          return func.apply(isArray(value) ? value : [], args);
         });
       };
+    });
 
-  if (browserDetails.version < 41) {
-    // Work around http://bugzil.la/1169665
-    var orgEnumerateDevices =
-        navigator.mediaDevices.enumerateDevices.bind(navigator.mediaDevices);
-    navigator.mediaDevices.enumerateDevices = function() {
-      return orgEnumerateDevices().then(undefined, function(e) {
-        if (e.name === 'NotFoundError') {
-          return [];
-        }
-        throw e;
-      });
-    };
-  }
-  if (browserDetails.version < 49) {
-    var origGetUserMedia = navigator.mediaDevices.getUserMedia.
-        bind(navigator.mediaDevices);
-    navigator.mediaDevices.getUserMedia = function(c) {
-      return origGetUserMedia(c).catch(function(e) {
-        return Promise.reject(shimError_(e));
-      });
-    };
-  }
-  navigator.getUserMedia = function(constraints, onSuccess, onError) {
-    if (browserDetails.version < 44) {
-      return getUserMedia_(constraints, onSuccess, onError);
+    // Map minified method names to their real names.
+    baseForOwn(LazyWrapper.prototype, function(func, methodName) {
+      var lodashFunc = lodash[methodName];
+      if (lodashFunc) {
+        var key = (lodashFunc.name + ''),
+            names = realNames[key] || (realNames[key] = []);
+
+        names.push({ 'name': methodName, 'func': lodashFunc });
+      }
+    });
+
+    realNames[createHybrid(undefined, WRAP_BIND_KEY_FLAG).name] = [{
+      'name': 'wrapper',
+      'func': undefined
+    }];
+
+    // Add methods to `LazyWrapper`.
+    LazyWrapper.prototype.clone = lazyClone;
+    LazyWrapper.prototype.reverse = lazyReverse;
+    LazyWrapper.prototype.value = lazyValue;
+
+    // Add chain sequence methods to the `lodash` wrapper.
+    lodash.prototype.at = wrapperAt;
+    lodash.prototype.chain = wrapperChain;
+    lodash.prototype.commit = wrapperCommit;
+    lodash.prototype.next = wrapperNext;
+    lodash.prototype.plant = wrapperPlant;
+    lodash.prototype.reverse = wrapperReverse;
+    lodash.prototype.toJSON = lodash.prototype.valueOf = lodash.prototype.value = wrapperValue;
+
+    // Add lazy aliases.
+    lodash.prototype.first = lodash.prototype.head;
+
+    if (symIterator) {
+      lodash.prototype[symIterator] = wrapperToIterator;
     }
-    // Replace Firefox 44+'s deprecation warning with unprefixed version.
-    console.warn('navigator.getUserMedia has been replaced by ' +
-                 'navigator.mediaDevices.getUserMedia');
-    navigator.mediaDevices.getUserMedia(constraints).then(onSuccess, onError);
-  };
-};
+    return lodash;
+  });
 
-},{"../utils":18}],17:[function(require,module,exports){
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
-'use strict';
-var safariShim = {
-  // TODO: DrAlex, should be here, double check against LayoutTests
-  // shimOnTrack: function() { },
+  /*--------------------------------------------------------------------------*/
 
-  // TODO: DrAlex
-  // attachMediaStream: function(element, stream) { },
-  // reattachMediaStream: function(to, from) { },
+  // Export lodash.
+  var _ = runInContext();
 
-  // TODO: once the back-end for the mac port is done, add.
-  // TODO: check for webkitGTK+
-  // shimPeerConnection: function() { },
+  // Some AMD build optimizers, like r.js, check for condition patterns like:
+  if (typeof define == 'function' && typeof define.amd == 'object' && define.amd) {
+    // Expose Lodash on the global object to prevent errors when Lodash is
+    // loaded by a script tag in the presence of an AMD loader.
+    // See http://requirejs.org/docs/errors.html#mismatch for more details.
+    // Use `_.noConflict` to remove Lodash from the global object.
+    root._ = _;
 
-  shimGetUserMedia: function() {
-    navigator.getUserMedia = navigator.webkitGetUserMedia;
+    // Define as an anonymous module so, through path mapping, it can be
+    // referenced as the "underscore" module.
+    define(function() {
+      return _;
+    });
   }
-};
+  // Check for `exports` after `define` in case a build optimizer adds it.
+  else if (freeModule) {
+    // Export for Node.js.
+    (freeModule.exports = _)._ = _;
+    // Export for CommonJS support.
+    freeExports._ = _;
+  }
+  else {
+    // Export to the global object.
+    root._ = _;
+  }
+}.call(this));
 
-// Expose public methods.
-module.exports = {
-  shimGetUserMedia: safariShim.shimGetUserMedia
-  // TODO
-  // shimOnTrack: safariShim.shimOnTrack,
-  // shimPeerConnection: safariShim.shimPeerConnection,
-  // attachMediaStream: safariShim.attachMediaStream,
-  // reattachMediaStream: safariShim.reattachMediaStream
+}).call(this,typeof global !== "undefined" ? global : typeof self !== "undefined" ? self : typeof window !== "undefined" ? window : {})
+},{}],17:[function(require,module,exports){
+/**
+ * MicroEvent - to make any js object an event emitter (server or browser)
+ * 
+ * - pure javascript - server compatible, browser compatible
+ * - dont rely on the browser doms
+ * - super simple - you get it immediatly, no mistery, no magic involved
+ *
+ * - create a MicroEventDebug with goodies to debug
+ *   - make it safer to use
+*/
+
+var MicroEvent	= function(){}
+MicroEvent.prototype	= {
+	bind	: function(event, fct){
+		this._events = this._events || {};
+		this._events[event] = this._events[event]	|| [];
+		this._events[event].push(fct);
+	},
+	unbind	: function(event, fct){
+		this._events = this._events || {};
+		if( event in this._events === false  )	return;
+		this._events[event].splice(this._events[event].indexOf(fct), 1);
+	},
+	trigger	: function(event /* , args... */){
+		this._events = this._events || {};
+		if( event in this._events === false  )	return;
+		for(var i = 0; i < this._events[event].length; i++){
+			this._events[event][i].apply(this, Array.prototype.slice.call(arguments, 1))
+		}
+	}
 };
 
-},{}],18:[function(require,module,exports){
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+/**
+ * mixin will delegate all MicroEvent.js function in the destination object
  *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
- /* eslint-env node */
-'use strict';
+ * - require('MicroEvent').mixin(Foobar) will make Foobar able to use MicroEvent
+ *
+ * @param {Object} the object which will support MicroEvent
+*/
+MicroEvent.mixin	= function(destObject){
+	var props	= ['bind', 'unbind', 'trigger'];
+	for(var i = 0; i < props.length; i ++){
+		destObject.prototype[props[i]]	= MicroEvent.prototype[props[i]];
+	}
+}
 
-var logDisabled_ = true;
+// export in common js
+if( typeof module !== "undefined" && ('exports' in module)){
+	module.exports	= MicroEvent
+}
 
-// Utility methods.
-var utils = {
-  disableLog: function(bool) {
-    if (typeof bool !== 'boolean') {
-      return new Error('Argument type: ' + typeof bool +
-          '. Please use a boolean.');
+},{}],18:[function(require,module,exports){
+const microevent = require('microevent');
+const _ = require('lodash');
+
+// get audio context
+const AudioContextType = window.AudioContext || window.webkitAudioContext;
+
+// f_1 band for (most) human voice range
+var LOW_FREQ_CUT = 85;
+var HIGH_FREQ_CUT = 583;
+var bandPassMiddleFrequency = ((HIGH_FREQ_CUT - LOW_FREQ_CUT) / 2) + LOW_FREQ_CUT;
+//var bandPassFrequencyRange = HIGH_FREQ_CUT - bandPassMiddleFrequency;
+var Q = bandPassMiddleFrequency / (HIGH_FREQ_CUT - LOW_FREQ_CUT);
+
+function getMaxVolume (analyser, fftBins) {
+  var maxVolume = -Infinity;
+  analyser.getFloatFrequencyData(fftBins);
+
+  for(var i=4, ii=fftBins.length; i < ii; i++) {
+    if (fftBins[i] > maxVolume && fftBins[i] < 0) {
+      maxVolume = fftBins[i];
     }
-    logDisabled_ = bool;
-    return (bool) ? 'adapter.js logging disabled' :
-        'adapter.js logging enabled';
-  },
+  };
 
-  log: function() {
-    if (typeof window === 'object') {
-      if (logDisabled_) {
-        return;
-      }
-      if (typeof console !== 'undefined' && typeof console.log === 'function') {
-        console.log.apply(console, arguments);
+  return maxVolume;
+}
+
+
+// bandpass filter from AudioContext
+function bandPassFilterNode (audioContext) {
+  var bandpass = audioContext.createBiquadFilter();
+  bandpass.type = 'bandpass';
+  bandpass.frequency.value = bandPassMiddleFrequency;
+  bandpass.Q = Q;
+  return bandpass;
+}
+
+function speakingDetectionNode (audioContext, analyser, threshold, emitter) {
+  var javascriptNode = audioContext.createScriptProcessor(2048, 1, 1);
+  var speakingTimes = [];
+  var quietHistory = []; // only contains continuous 'quiet' times
+  var currentVolume = -Infinity;
+  var volumes = [];
+
+  var hasStoppedSpeaking = function () {
+    return (_.max(quietHistory) - _.min(quietHistory) > 250);
+  };
+
+  javascriptNode.onaudioprocess = function () {
+    var fftBins = new Float32Array(analyser.frequencyBinCount);
+    analyser.getFloatFrequencyData(fftBins);
+    //var maxVolume = _.max(_.filter(fftBins, function (v) { return v < 0 }));
+    //currentVolume = maxVolume;
+    currentVolume = getMaxVolume(analyser, fftBins);
+    volumes.push({timestamp: Date.now(),
+                  vol: currentVolume});
+    emitter.trigger('volumeChange', currentVolume);
+    // speaking, add the date to the stack, clear quiet record
+    if (currentVolume > threshold) {
+      emitter.trigger('speaking');
+      speakingTimes.push(new Date());
+      quietHistory = [];
+    } else if (speakingTimes.length > 0) {
+      if (hasStoppedSpeaking()) {
+        emitter.trigger('stoppedSpeaking', {'start': _.min(speakingTimes), 'end': _.max(speakingTimes), 'volumes': volumes});
+        volumes = [];
+        speakingTimes = [];
+      } else {
+        quietHistory.push(new Date());
       }
     }
-  },
+  };
+  return javascriptNode;
+}
 
-  /**
-   * Extract browser version out of the provided user agent string.
-   *
-   * @param {!string} uastring userAgent string.
-   * @param {!string} expr Regular expression used as match criteria.
-   * @param {!number} pos position in the version string to be returned.
-   * @return {!number} browser version.
-   */
-  extractVersion: function(uastring, expr, pos) {
-    var match = uastring.match(expr);
-    return match && match.length >= pos && parseInt(match[pos], 10);
-  },
+var audioContext = null;
 
-  /**
-   * Browser detector.
-   *
-   * @return {object} result containing browser, version and minVersion
-   *     properties.
-   */
-  detectBrowser: function() {
-    // Returned result object.
-    var result = {};
-    result.browser = null;
-    result.version = null;
-    result.minVersion = null;
+class Sibilant {
+  constructor (stream, options) {
+    options = options || {};
+    var self = this;
+    // var useBandPass = (options.useBandPass || true)
+    this.fftSize = (options.fftSize || 512);
+    this.threshold = (options.threshold || -40);
+    this.smoothing = (options.smoothing || 0.2);
+    this.passThrough = (options.passThrough || false);
 
-    // Fail early if it's not a browser
-    if (typeof window === 'undefined' || !window.navigator) {
-      result.browser = 'Not a browser.';
-      return result;
-    }
 
-    // Firefox.
-    if (navigator.mozGetUserMedia) {
-      result.browser = 'firefox';
-      result.version = this.extractVersion(navigator.userAgent,
-          /Firefox\/([0-9]+)\./, 1);
-      result.minVersion = 31;
+    console.log("middle freq:", bandPassMiddleFrequency);
+    console.log("range / Q:", Q);
 
-    // all webkit-based browsers
-    } else if (navigator.webkitGetUserMedia) {
-      // Chrome, Chromium, Webview, Opera, all use the chrome shim for now
-      if (window.webkitRTCPeerConnection) {
-        result.browser = 'chrome';
-        result.version = this.extractVersion(navigator.userAgent,
-          /Chrom(e|ium)\/([0-9]+)\./, 2);
-        result.minVersion = 38;
+    // Ensure that just a single AudioContext is internally created
+    this.audioContext = options.audioContext || audioContext || new AudioContextType();
 
-      // Safari or unknown webkit-based
-      // for the time being Safari has support for MediaStreams but not webRTC
-      } else {
-        // Safari UA substrings of interest for reference:
-        // - webkit version:           AppleWebKit/602.1.25 (also used in Op,Cr)
-        // - safari UI version:        Version/9.0.3 (unique to Safari)
-        // - safari UI webkit version: Safari/601.4.4 (also used in Op,Cr)
-        //
-        // if the webkit version and safari UI webkit versions are equals,
-        // ... this is a stable version.
-        //
-        // only the internal webkit version is important today to know if
-        // media streams are supported
-        //
-        if (navigator.userAgent.match(/Version\/(\d+).(\d+)/)) {
-          result.browser = 'safari';
-          result.version = this.extractVersion(navigator.userAgent,
-            /AppleWebKit\/([0-9]+)\./, 1);
-          result.minVersion = 602;
+    this.sourceNode = null;
+    this.fftBins = null;
+    this.analyser = null;
 
-        // unknown webkit-based browser
-        } else {
-          result.browser = 'Unsupported webkit-based browser ' +
-              'with GUM support but no WebRTC support.';
-          return result;
-        }
-      }
+    this.getStream(stream);
 
-    // Edge.
-    } else if (navigator.mediaDevices &&
-        navigator.userAgent.match(/Edge\/(\d+).(\d+)$/)) {
-      result.browser = 'edge';
-      result.version = this.extractVersion(navigator.userAgent,
-          /Edge\/(\d+).(\d+)$/, 2);
-      result.minVersion = 10547;
+    this.analyser = this.audioContext.createAnalyser();
+    this.analyser.fftSize = this.fftSize;
+    this.analyser.smoothingTimeConstant = this.smoothing;
+    this.fftBins = new Float32Array(this.analyser.frequencyBinCount);
 
-    // Default fallthrough: not supported.
-    } else {
-      result.browser = 'Not a supported browser.';
-      return result;
+    this.audioSource = this.sourceNode;
+
+    var speakingNode = speakingDetectionNode(this.audioContext, this.analyser, this.threshold, this);
+    var bandPassNode = bandPassFilterNode(this.audioContext);
+    this.audioSource.connect(this.analyser);
+    if (this.passThrough) {
+      console.log('passing through', stream);
+      this.analyser.connect(this.audioContext.destination);
     }
+    this.analyser.connect(bandPassNode);
+    bandPassNode.connect(speakingNode);
+    // needed for chrome onprocessaudio compatibility
+    speakingNode.connect(this.audioContext.destination);
+  }
 
-    // Warn if version is less than minVersion.
-    if (result.version < result.minVersion) {
-      utils.log('Browser: ' + result.browser + ' Version: ' + result.version +
-          ' < minimum supported version: ' + result.minVersion +
-          '\n some things might not work!');
+  getStream (stream) {
+    if (stream.jquery) stream = stream[0];
+    if (stream instanceof HTMLAudioElement || stream instanceof HTMLVideoElement) {
+      //Audio Tag
+      this.sourceNode = this.audioContext.createMediaElementSource(stream);
+//      if (typeof play === 'undefined') play = true;
+      this.threshold = this.threshold || -50;
+    } else {
+      //WebRTC Stream
+      this.sourceNode = this.audioContext.createMediaStreamSource(stream);
+      this.threshold = this.threshold || -50;
     }
+  }
 
-    return result;
+  suspend () {
+    this.audioContext.suspend();
   }
-};
 
-// Export.
-module.exports = {
-  log: utils.log,
-  disableLog: utils.disableLog,
-  browserDetails: utils.detectBrowser(),
-  extractVersion: utils.extractVersion
-};
+  resume () {
+    this.audioContext.resume();
+  }
+}
+
+microevent.mixin(Sibilant);
+
+module.exports = Sibilant;
 
-},{}]},{},[1]);
+},{"lodash":16,"microevent":17}]},{},[1]);
diff --git a/demo/demo.js b/demo/demo.js
index fcaa8aa..05934d9 100644
--- a/demo/demo.js
+++ b/demo/demo.js
@@ -1,32 +1,57 @@
-const Sibilant = require('sibilant-webaudio')
-const alert = require('alerts')
-const getUserMedia = require('getusermedia')
-const attachmediastream = require('attachmediastream')
-const $ = require('jquery')
+const Sibilant = require("../")
+const alert = require('alerts');
+const getUserMedia = require('getusermedia');
+const attachmediastream = require('attachmediastream');
+const $ = require('jquery');
 
-getUserMedia(function (err, stream) {
-  if (err) {
-    console.log('couldnt get user media!', err)
-    alert('Sibilant couldnt get your user media. give it access to audio and try again!')
-    throw err
-  } else {
-    console.log('got a stream!')
 
-    attachmediastream(stream, document.querySelector('#vid video'))
-    document.querySelector('#vid video').muted = true
-    var speakingEvents = new Sibilant(stream, {passThrough: false})
-    speakingEvents.bind('speaking', function () {
-      document.querySelector('#vid video').style.border = '10px solid #27ae60'
-      console.log('speaking!')
-    })
+navigator.getUserMedia (
+    // constraints
+    {
+        video: true,
+        audio: true
+    },
 
-    speakingEvents.bind('stoppedSpeaking', function (data) {
-      console.log('speaking event recorded!', data.start)
-      var start = new Date(data.start)
-      var end = new Date(data.end)
-      var duration = end - start
-      $('#info').prepend('You spoke for ' + duration + ' ms! <br>')
-      document.querySelector('#vid video').style.border = '10px solid #555'
-    })
-  }
-})
+    // successCallback
+    function(stream) {
+      // var video = document.querySelector('video');
+      // video.src = window.URL.createObjectURL(localMediaStream);
+      // video.onloadedmetadata = function(e) {
+      //     // Do something with the video here.
+      // };
+      attachmediastream(stream, document.querySelector('#vid video'));
+      document.querySelector('#vid video').muted = true;
+      var speakingEvents = new Sibilant(stream, {passThrough: false});
+
+      console.log("whoa!", speakingEvents.volumes);
+
+      document.querySelector('#button').addEventListener('click', function() {
+        console.log("boooop")
+        speakingEvents.resumeContext().then(() => {
+          console.log('Playback resumed successfully');
+        });
+      });
+        speakingEvents.bind('speaking', function () {
+            document.querySelector('#vid video').style.border = '10px solid #27ae60';
+            console.log('speaking!');
+        });
+
+        speakingEvents.bind('stoppedSpeaking', function (data) {
+            console.log('speaking event recorded!', data.start);
+            var start = new Date(data.start);
+            var end = new Date(data.end);
+            var duration = end - start;
+            $('#info').prepend('You spoke for ' + duration + ' ms! <br>');
+            document.querySelector('#vid video').style.border = '10px solid #555';
+        });
+    },
+
+    // errorCallback
+    function(err) {
+        if(err === 'PERMISSION_DENIED') {
+            alert('Sibilant couldnt get your user media. give it access to audio and try again!', err);
+            console.log("error", err);
+            // Explain why you need permission and how to update the permission setting
+        }
+    }
+);
diff --git a/demo/index.html b/demo/index.html
index 764f98e..b275d05 100644
--- a/demo/index.html
+++ b/demo/index.html
@@ -44,7 +44,8 @@ <h1>sibilant demo</h1>
         <h2>It'll go green when you speak!</h2>
     </div>
     <div class='window' id='vid'>
-        <video width=480></video>
+      <video width=480></video>
+      <button id="button">Enable Mic</button>
     </div>
     <div class="console" s>
         <h2>Alerts</h2>
diff --git a/package.json b/package.json
index a4643c7..a646e30 100644
--- a/package.json
+++ b/package.json
@@ -18,6 +18,8 @@
     "microevent": "^1.0.0"
   },
   "devDependencies": {
-    "alerts": "^0.1.3"
+    "alerts": "^0.1.3",
+    "browserify": "^16.2.2",
+    "http-server": "^0.11.1"
   }
 }
diff --git a/sibilant.js b/sibilant.js
index 5c517e6..b937679 100644
--- a/sibilant.js
+++ b/sibilant.js
@@ -1,95 +1,145 @@
-const microevent = require('microevent')
-const _ = require('lodash')
+const microevent = require('microevent');
+const _ = require('lodash');
 
 // get audio context
-const AudioContextType = window.AudioContext || window.webkitAudioContext
+const AudioContextType = window.AudioContext || window.webkitAudioContext;
 
 // f_1 band for (most) human voice range
-var LOW_FREQ_CUT = 85
-var HIGH_FREQ_CUT = 583
-var bandPassMiddleFrequency = ((HIGH_FREQ_CUT - LOW_FREQ_CUT) / 2) + LOW_FREQ_CUT
-var bandPassFrequencyRange = HIGH_FREQ_CUT - bandPassMiddleFrequency
+var LOW_FREQ_CUT = 85;
+var HIGH_FREQ_CUT = 583;
+var bandPassMiddleFrequency = ((HIGH_FREQ_CUT - LOW_FREQ_CUT) / 2) + LOW_FREQ_CUT;
+//var bandPassFrequencyRange = HIGH_FREQ_CUT - bandPassMiddleFrequency;
+var Q = bandPassMiddleFrequency / (HIGH_FREQ_CUT - LOW_FREQ_CUT);
+
+function getMaxVolume (analyser, fftBins) {
+  var maxVolume = -Infinity;
+  analyser.getFloatFrequencyData(fftBins);
+
+  for(var i=4, ii=fftBins.length; i < ii; i++) {
+    if (fftBins[i] > maxVolume && fftBins[i] < 0) {
+      maxVolume = fftBins[i];
+    }
+  };
+
+  return maxVolume;
+}
+
 
 // bandpass filter from AudioContext
 function bandPassFilterNode (audioContext) {
-  var bandpass = audioContext.createBiquadFilter()
-  bandpass.type = 'bandpass'
-  bandpass.frequency.value = bandPassMiddleFrequency
-  bandpass.Q = bandPassFrequencyRange
-  return bandpass
+  var bandpass = audioContext.createBiquadFilter();
+  bandpass.type = 'bandpass';
+  bandpass.frequency.value = bandPassMiddleFrequency;
+  bandpass.Q = Q;
+  return bandpass;
 }
 
 function speakingDetectionNode (audioContext, analyser, threshold, emitter) {
-  var javascriptNode = audioContext.createScriptProcessor(2048, 1, 1)
-  var speakingTimes = []
-  var quietHistory = [] // only contains continuous 'quiet' times
-  var currentVolume = -Infinity
-  var volumes = []
+  var javascriptNode = audioContext.createScriptProcessor(2048, 1, 1);
+  var speakingTimes = [];
+  var quietHistory = []; // only contains continuous 'quiet' times
+  var currentVolume = -Infinity;
+  var volumes = [];
 
   var hasStoppedSpeaking = function () {
-    return (_.max(quietHistory) - _.min(quietHistory) > 500)
-  }
+    return (_.max(quietHistory) - _.min(quietHistory) > 250);
+  };
 
   javascriptNode.onaudioprocess = function () {
-    var fftBins = new Float32Array(analyser.frequencyBinCount)
-    analyser.getFloatFrequencyData(fftBins)
-    var maxVolume = _.max(_.filter(fftBins, function (v) { return v < 0 }))
-    currentVolume = maxVolume
+    var fftBins = new Float32Array(analyser.frequencyBinCount);
+    analyser.getFloatFrequencyData(fftBins);
+    //var maxVolume = _.max(_.filter(fftBins, function (v) { return v < 0 }));
+    //currentVolume = maxVolume;
+    currentVolume = getMaxVolume(analyser, fftBins);
     volumes.push({timestamp: Date.now(),
-                  vol: currentVolume})
-    emitter.trigger('volumeChange', currentVolume)
+                  vol: currentVolume});
+    emitter.trigger('volumeChange', currentVolume);
     // speaking, add the date to the stack, clear quiet record
     if (currentVolume > threshold) {
-      emitter.trigger('speaking')
-      speakingTimes.push(new Date())
-      quietHistory = []
+      emitter.trigger('speaking');
+      speakingTimes.push(new Date());
+      quietHistory = [];
     } else if (speakingTimes.length > 0) {
       if (hasStoppedSpeaking()) {
-        emitter.trigger('stoppedSpeaking', {'start': _.min(speakingTimes), 'end': _.max(speakingTimes), 'volumes': volumes})
-        volumes = []
-        speakingTimes = []
+        emitter.trigger('stoppedSpeaking', {'start': _.min(speakingTimes), 'end': _.max(speakingTimes), 'volumes': volumes});
+        volumes = [];
+        speakingTimes = [];
       } else {
-        quietHistory.push(new Date())
+        quietHistory.push(new Date());
       }
     }
-  }
-  return javascriptNode
+  };
+  return javascriptNode;
 }
 
-var Sibilant = function (element, options) {
-  options = options || {}
-  var self = this
-  // var useBandPass = (options.useBandPass || true)
-  var fftSize = (options.fftSize || 512)
-  var threshold = (options.threshold || -40)
-  var smoothing = (options.smoothing || 0.2)
-  var passThrough = (options.passThrough || false)
-  var audioContext = new AudioContextType()
-
-  var analyser = audioContext.createAnalyser()
-  analyser.fftSize = fftSize
-  analyser.smoothingTimeConstant = smoothing
-
-  var audioSource = null
-  // assume webRTC for now
-  if (element instanceof HTMLAudioElement || element instanceof HTMLVideoElement) {
-    audioSource = audioContext.createMediaElementSource(element)
-  } else {
-    audioSource = audioContext.createMediaStreamSource(element)
+var audioContext = null;
+
+class Sibilant {
+  constructor (stream, options) {
+    options = options || {};
+    var self = this;
+    // var useBandPass = (options.useBandPass || true)
+    this.fftSize = (options.fftSize || 512);
+    this.threshold = (options.threshold || -40);
+    this.smoothing = (options.smoothing || 0.2);
+    this.passThrough = (options.passThrough || false);
+
+
+    console.log("middle freq:", bandPassMiddleFrequency);
+    console.log("range / Q:", Q);
+
+    // Ensure that just a single AudioContext is internally created
+    this.audioContext = options.audioContext || audioContext || new AudioContextType();
+
+    this.sourceNode = null;
+    this.fftBins = null;
+    this.analyser = null;
+
+    this.getStream(stream);
+
+    this.analyser = this.audioContext.createAnalyser();
+    this.analyser.fftSize = this.fftSize;
+    this.analyser.smoothingTimeConstant = this.smoothing;
+    this.fftBins = new Float32Array(this.analyser.frequencyBinCount);
+
+    this.audioSource = this.sourceNode;
+
+    var speakingNode = speakingDetectionNode(this.audioContext, this.analyser, this.threshold, this);
+    var bandPassNode = bandPassFilterNode(this.audioContext);
+    this.audioSource.connect(this.analyser);
+    if (this.passThrough) {
+      console.log('passing through', stream);
+      this.analyser.connect(this.audioContext.destination);
+    }
+    this.analyser.connect(bandPassNode);
+    bandPassNode.connect(speakingNode);
+    // needed for chrome onprocessaudio compatibility
+    speakingNode.connect(this.audioContext.destination);
   }
-  var speakingNode = speakingDetectionNode(audioContext, analyser, threshold, self)
-  var bandPassNode = bandPassFilterNode(audioContext)
-  audioSource.connect(analyser)
-  if (passThrough) {
-    console.log('passing through', element)
-    analyser.connect(audioContext.destination)
+
+  getStream (stream) {
+    if (stream.jquery) stream = stream[0];
+    if (stream instanceof HTMLAudioElement || stream instanceof HTMLVideoElement) {
+      //Audio Tag
+      this.sourceNode = this.audioContext.createMediaElementSource(stream);
+//      if (typeof play === 'undefined') play = true;
+      this.threshold = this.threshold || -50;
+    } else {
+      //WebRTC Stream
+      this.sourceNode = this.audioContext.createMediaStreamSource(stream);
+      this.threshold = this.threshold || -50;
+    }
+  }
+
+  suspend () {
+    this.audioContext.suspend();
+  }
+
+  resume () {
+    this.audioContext.resume();
   }
-  analyser.connect(bandPassNode)
-  bandPassNode.connect(speakingNode)
-  // needed for chrome onprocessaudio compatibility
-  speakingNode.connect(audioContext.destination)
 }
 
-microevent.mixin(Sibilant)
+microevent.mixin(Sibilant);
 
-module.exports = Sibilant
+module.exports = Sibilant;

From b217bca2bbce3b9b813346858038187b2ae375c2 Mon Sep 17 00:00:00 2001
From: Dan Calacci <dan@dcalacci.net>
Date: Thu, 13 Sep 2018 15:58:34 -0400
Subject: [PATCH 08/10] bumped version

---
 package.json | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/package.json b/package.json
index a646e30..1ee900a 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "sibilant-webaudio",
-  "version": "0.1.4",
+  "version": "0.1.5",
   "description": "detect speaking events from webRTC audio",
   "main": "sibilant.js",
   "scripts": {

From 72f843e980fdcf2bacd77bbb499186875c144f91 Mon Sep 17 00:00:00 2001
From: Rajan Jain <jain.rajan91@gmail.com>
Date: Sun, 13 Feb 2022 15:24:11 +0100
Subject: [PATCH 09/10] #rajan #no-ticket setting BiquadFilter Q.value as Q is
 readonly

---
 sibilant.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sibilant.js b/sibilant.js
index b937679..a851558 100644
--- a/sibilant.js
+++ b/sibilant.js
@@ -30,7 +30,7 @@ function bandPassFilterNode (audioContext) {
   var bandpass = audioContext.createBiquadFilter();
   bandpass.type = 'bandpass';
   bandpass.frequency.value = bandPassMiddleFrequency;
-  bandpass.Q = Q;
+  bandpass.Q.value = Q;
   return bandpass;
 }
 

From d742689bb5ece27c8ec0d6f43db0dfdf87caf881 Mon Sep 17 00:00:00 2001
From: Henil Mehta <henilmehta@Henils-MacBook-Pro.local>
Date: Wed, 27 Sep 2023 17:07:51 +0530
Subject: [PATCH 10/10] Henil Mehta updated dependencies

---
 package-lock.json | 3857 +++++++++++++++++++++++++++++++++++++++++++++
 package.json      |    6 +-
 2 files changed, 3860 insertions(+), 3 deletions(-)
 create mode 100644 package-lock.json

diff --git a/package-lock.json b/package-lock.json
new file mode 100644
index 0000000..328df11
--- /dev/null
+++ b/package-lock.json
@@ -0,0 +1,3857 @@
+{
+  "name": "sibilant-webaudio",
+  "version": "0.1.5",
+  "lockfileVersion": 2,
+  "requires": true,
+  "packages": {
+    "": {
+      "name": "sibilant-webaudio",
+      "version": "0.1.5",
+      "license": "MIT",
+      "dependencies": {
+        "lodash": "^4.17.21",
+        "microevent": "^1.0.0"
+      },
+      "devDependencies": {
+        "alerts": "^0.1.3",
+        "browserify": "^17.0.0",
+        "http-server": "^14.1.1"
+      }
+    },
+    "node_modules/acorn": {
+      "version": "7.4.1",
+      "resolved": "https://registry.npmjs.org/acorn/-/acorn-7.4.1.tgz",
+      "integrity": "sha512-nQyp0o1/mNdbTO1PO6kHkwSrmgZ0MT/jCCpNiwbUjGoRN4dlBhqJtoQuCnEOKzgTVwg0ZWiCoQy6SxMebQVh8A==",
+      "dev": true,
+      "bin": {
+        "acorn": "bin/acorn"
+      },
+      "engines": {
+        "node": ">=0.4.0"
+      }
+    },
+    "node_modules/acorn-node": {
+      "version": "1.8.2",
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diff --git a/package.json b/package.json
index 1ee900a..965036a 100644
--- a/package.json
+++ b/package.json
@@ -14,12 +14,12 @@
   "author": "dcalacci@media.mit.edu",
   "license": "MIT",
   "dependencies": {
-    "lodash": "^4.13.1",
+    "lodash": "^4.17.21",
     "microevent": "^1.0.0"
   },
   "devDependencies": {
     "alerts": "^0.1.3",
-    "browserify": "^16.2.2",
-    "http-server": "^0.11.1"
+    "browserify": "^17.0.0",
+    "http-server": "^14.1.1"
   }
 }