Write executeInSequence and create shared.js to put it in

Author: skilldrick

_layouts/default.html

@@ -34,6 +34,7 @@ <h1>Easy Forth</h1>
     <script src="javascripts/jquery-2.1.4.js"></script>
     <script src="javascripts/toc.js"></script>
     <script src="javascripts/scale.fix.js"></script>
+    <script src="javascripts/shared.js"></script>
     <script src="javascripts/stack.js"></script>
     <script src="javascripts/dictionary.js"></script>
     <script src="javascripts/memory.js"></script>

javascripts/forth.js

@@ -1,8 +1,5 @@
 'use strict';
 
-var FALSE = 0;
-var TRUE = -1;
-
 function Forth() {
   // Core structures
   var context = {
@@ -168,13 +165,14 @@ function Forth() {
   }
 
   function readLines(codeLines, callbacks) {
-    // Use reduce to execute promises in sequence
-    return codeLines.reduce(function (promise, codeLine) {
-      return promise.then(function () {
+    var promiseFunctions = codeLines.map(function (codeLine) {
+      return function () {
         callbacks && callbacks.lineCallback(codeLine);
         return readLine(codeLine, callbacks && callbacks.outputCallback);
-      });
-    }, Promise.resolve());
+      };
+    });
+
+    return executeInSequence(promiseFunctions); // defined in shared.js
   }
 
   // because readLines is async, addPredefinedWords is async too

javascripts/shared.js

@@ -0,0 +1,21 @@
+var FALSE = 0;
+var TRUE = -1;
+
+// Takes an array of nullary functions that return promises and executes them in series,
+// collecting the output from each, and finally resolving with the combined output
+function executeInSequence(promiseFunctions) {
+  var output = [];
+
+  function addOutput(promise) {
+    return promise.then(function (o) {
+      output.push(o);
+      return output.join("");
+    });
+  }
+
+  return promiseFunctions.reduce(function (promise, promiseFunction) {
+    return promise.then(function () {
+      return addOutput(promiseFunction());
+    });
+  }, Promise.resolve());
+}

test/index.html

@@ -12,6 +12,7 @@
   <script src="lib/jasmine-2.3.4/boot.js"></script>
 
   <!-- include source files here... -->
+  <script src="../javascripts/shared.js"></script>
   <script src="../javascripts/stack.js"></script>
   <script src="../javascripts/dictionary.js"></script>
   <script src="../javascripts/memory.js"></script>