1  # is-extendable [![NPM version](https://badge.fury.io/js/is-extendable.svg)](http://badge.fury.io/js/is-extendable)
 2  
 3  > Returns true if a value is any of the object types: array, regexp, plain object, function or date. This is useful for determining if a value can be extended, e.g. "can the value have keys?"
 4  
 5  ## Install
 6  
 7  Install with [npm](https://www.npmjs.com/)
 8  
 9  ```sh
10  $ npm i is-extendable --save
11  ```
12  
13  ## Usage
14  
15  ```js
16  var isExtendable = require('is-extendable');
17  ```
18  
19  Returns true if the value is any of the following:
20  
21  * `array`
22  * `regexp`
23  * `plain object`
24  * `function`
25  * `date`
26  * `error`
27  
28  ## Notes
29  
30  All objects in JavaScript can have keys, but it's a pain to check for this, since we ether need to verify that the value is not `null` or `undefined` and:
31  
32  * the value is not a primitive, or
33  * that the object is an `object`, `function`
34  
35  Also note that an `extendable` object is not the same as an [extensible object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isExtensible), which is one that (in es6) is not sealed, frozen, or marked as non-extensible using `preventExtensions`.
36  
37  ## Related projects
38  
39  * [assign-deep](https://github.com/jonschlinkert/assign-deep): Deeply assign the enumerable properties of source objects to a destination object.
40  * [extend-shallow](https://github.com/jonschlinkert/extend-shallow): Extend an object with the properties of additional objects. node.js/javascript util.
41  * [isobject](https://github.com/jonschlinkert/isobject): Returns true if the value is an object and not an array or null.
42  * [is-plain-object](https://github.com/jonschlinkert/is-plain-object): Returns true if an object was created by the `Object` constructor.
43  * [is-equal-shallow](https://github.com/jonschlinkert/is-equal-shallow): Does a shallow comparison of two objects, returning false if the keys or values differ.
44  * [kind-of](https://github.com/jonschlinkert/kind-of): Get the native type of a value.
45  
46  ## Running tests
47  
48  Install dev dependencies:
49  
50  ```sh
51  $ npm i -d && npm test
52  ```
53  
54  ## Contributing
55  
56  Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](https://github.com/jonschlinkert/is-extendable/issues/new)
57  
58  ## Author
59  
60  **Jon Schlinkert**
61  
62  + [github/jonschlinkert](https://github.com/jonschlinkert)
63  + [twitter/jonschlinkert](http://twitter.com/jonschlinkert)
64  
65  ## License
66  
67  Copyright © 2015 Jon Schlinkert
68  Released under the MIT license.
69  
70  ***
71  
72  _This file was generated by [verb-cli](https://github.com/assemble/verb-cli) on July 04, 2015._