Merge pull request #67 from sandstreamdev/add_isBoolean_method

Add is/boolean function

Author: przemyslawzalewski

README.md

@@ -2651,6 +2651,34 @@ array({ a: 1 });
 
 - How to check if a given value is an array?
 
+#### boolean
+
+Checks if the given value is a boolean.
+
+##### Type signature
+
+<!-- prettier-ignore-start -->
+```typescript
+(x?: any) => boolean
+```
+<!-- prettier-ignore-end -->
+
+##### Examples
+
+<!-- prettier-ignore-start -->
+```javascript
+boolean(false); // ⇒ true
+```
+
+```javascript
+boolean(1); // ⇒ false
+```
+<!-- prettier-ignore-end -->
+
+##### Questions
+
+- How to check if a given value is a boolean?
+
 #### byte
 
 Checks if the given value is a byte.

is/README.md

@@ -28,6 +28,34 @@ array({ a: 1 });
 
 - How to check if a given value is an array?
 
+# boolean
+
+Checks if the given value is a boolean.
+
+## Type signature
+
+<!-- prettier-ignore-start -->
+```typescript
+(x?: any) => boolean
+```
+<!-- prettier-ignore-end -->
+
+## Examples
+
+<!-- prettier-ignore-start -->
+```javascript
+boolean(false); // ⇒ true
+```
+
+```javascript
+boolean(1); // ⇒ false
+```
+<!-- prettier-ignore-end -->
+
+## Questions
+
+- How to check if a given value is a boolean?
+
 # byte
 
 Checks if the given value is a byte.

is/boolean.js

@@ -0,0 +1 @@
+export default x => typeof x === "boolean";

is/boolean.json

@@ -0,0 +1,16 @@
+{
+  "name": "boolean",
+  "description": "Checks if the given value is a boolean.",
+  "signature": "(x?: any) => boolean",
+  "examples": [
+    {
+      "language": "javascript",
+      "content": "boolean(false); // ⇒ true"
+    },
+    {
+      "language": "javascript",
+      "content": "boolean(1); // ⇒ false"
+    }
+  ],
+  "questions": ["How to check if a given value is a boolean?"]
+}

is/boolean.md

@@ -0,0 +1,27 @@
+# boolean
+
+Checks if the given value is a boolean.
+
+## Type signature
+
+<!-- prettier-ignore-start -->
+```typescript
+(x?: any) => boolean
+```
+<!-- prettier-ignore-end -->
+
+## Examples
+
+<!-- prettier-ignore-start -->
+```javascript
+boolean(false); // ⇒ true
+```
+
+```javascript
+boolean(1); // ⇒ false
+```
+<!-- prettier-ignore-end -->
+
+## Questions
+
+- How to check if a given value is a boolean?

is/boolean.test.ts

@@ -0,0 +1,24 @@
+/* eslint-env jest */
+// @ts-ignore ambiguous import
+import boolean from "./boolean";
+
+describe("boolean", () => {
+  it("checks if the given value is a boolean", () => {
+    expect(boolean(true)).toBe(true);
+    expect(boolean(false)).toBe(true);
+
+    expect(boolean("true")).toBe(false);
+    expect(boolean("")).toBe(false);
+    expect(boolean(undefined)).toBe(false);
+    expect(boolean(null)).toBe(false);
+    expect(boolean(0)).toBe(false);
+    expect(boolean({})).toBe(false);
+    expect(boolean([])).toBe(false);
+    expect(boolean(NaN)).toBe(false);
+    expect(boolean(() => {})).toBe(false);
+    expect(boolean([1, 2, 3])).toBe(false);
+    expect(boolean({ a: 1, b: 2, c: 3 })).toBe(false);
+    expect(boolean(17.6)).toBe(false);
+    expect(boolean(Math.min)).toBe(false);
+  });
+});

is/boolean.ts

@@ -0,0 +1 @@
+export default (x?: any) => typeof x === "boolean";

is/index.js

@@ -1,4 +1,5 @@
 import array from "./array.js";
+import boolean from "./boolean.js";
 import byte from "./byte.js";
 import date from "./date.js";
 import defined from "./defined.js";
@@ -12,6 +13,7 @@ import string from "./string.js";
 
 export {
   array,
+  boolean,
   byte,
   date,
   defined,
@@ -26,6 +28,7 @@ export {
 
 export default {
   array,
+  boolean,
   byte,
   date,
   defined,

is/index.ts

@@ -1,4 +1,5 @@
 import array from "./array";
+import boolean from "./boolean";
 import byte from "./byte";
 import date from "./date";
 import defined from "./defined";
@@ -12,6 +13,7 @@ import string from "./string";
 
 export {
   array,
+  boolean,
   byte,
   date,
   defined,
@@ -26,6 +28,7 @@ export {
 
 export default {
   array,
+  boolean,
   byte,
   date,
   defined,