1# kind-of [![NPM version](https://img.shields.io/npm/v/kind-of.svg?style=flat)](https://www.npmjs.com/package/kind-of) [![NPM monthly downloads](https://img.shields.io/npm/dm/kind-of.svg?style=flat)](https://npmjs.org/package/kind-of) [![NPM total downloads](https://img.shields.io/npm/dt/kind-of.svg?style=flat)](https://npmjs.org/package/kind-of) [![Linux Build Status](https://img.shields.io/travis/jonschlinkert/kind-of.svg?style=flat&label=Travis)](https://travis-ci.org/jonschlinkert/kind-of)
2
3> Get the native type of a value.
4
5## Install
6
7Install with [npm](https://www.npmjs.com/):
8
9```sh
10$ npm install --save kind-of
11```
12
13## Install
14
15Install with [bower](https://bower.io/)
16
17```sh
18$ bower install kind-of --save
19```
20
21## Usage
22
23> es5, browser and es6 ready
24
25```js
26var kindOf = require('kind-of');
27
28kindOf(undefined);
29//=> 'undefined'
30
31kindOf(null);
32//=> 'null'
33
34kindOf(true);
35//=> 'boolean'
36
37kindOf(false);
38//=> 'boolean'
39
40kindOf(new Boolean(true));
41//=> 'boolean'
42
43kindOf(new Buffer(''));
44//=> 'buffer'
45
46kindOf(42);
47//=> 'number'
48
49kindOf(new Number(42));
50//=> 'number'
51
52kindOf('str');
53//=> 'string'
54
55kindOf(new String('str'));
56//=> 'string'
57
58kindOf(arguments);
59//=> 'arguments'
60
61kindOf({});
62//=> 'object'
63
64kindOf(Object.create(null));
65//=> 'object'
66
67kindOf(new Test());
68//=> 'object'
69
70kindOf(new Date());
71//=> 'date'
72
73kindOf([]);
74//=> 'array'
75
76kindOf([1, 2, 3]);
77//=> 'array'
78
79kindOf(new Array());
80//=> 'array'
81
82kindOf(/foo/);
83//=> 'regexp'
84
85kindOf(new RegExp('foo'));
86//=> 'regexp'
87
88kindOf(function () {});
89//=> 'function'
90
91kindOf(function * () {});
92//=> 'function'
93
94kindOf(new Function());
95//=> 'function'
96
97kindOf(new Map());
98//=> 'map'
99
100kindOf(new WeakMap());
101//=> 'weakmap'
102
103kindOf(new Set());
104//=> 'set'
105
106kindOf(new WeakSet());
107//=> 'weakset'
108
109kindOf(Symbol('str'));
110//=> 'symbol'
111
112kindOf(new Int8Array());
113//=> 'int8array'
114
115kindOf(new Uint8Array());
116//=> 'uint8array'
117
118kindOf(new Uint8ClampedArray());
119//=> 'uint8clampedarray'
120
121kindOf(new Int16Array());
122//=> 'int16array'
123
124kindOf(new Uint16Array());
125//=> 'uint16array'
126
127kindOf(new Int32Array());
128//=> 'int32array'
129
130kindOf(new Uint32Array());
131//=> 'uint32array'
132
133kindOf(new Float32Array());
134//=> 'float32array'
135
136kindOf(new Float64Array());
137//=> 'float64array'
138```
139
140## Benchmarks
141
142Benchmarked against [typeof](http://github.com/CodingFu/typeof) and [type-of](https://github.com/ForbesLindesay/type-of).
143Note that performaces is slower for es6 features `Map`, `WeakMap`, `Set` and `WeakSet`.
144
145```bash
146#1: array
147  current x 23,329,397 ops/sec ±0.82% (94 runs sampled)
148  lib-type-of x 4,170,273 ops/sec ±0.55% (94 runs sampled)
149  lib-typeof x 9,686,935 ops/sec ±0.59% (98 runs sampled)
150
151#2: boolean
152  current x 27,197,115 ops/sec ±0.85% (94 runs sampled)
153  lib-type-of x 3,145,791 ops/sec ±0.73% (97 runs sampled)
154  lib-typeof x 9,199,562 ops/sec ±0.44% (99 runs sampled)
155
156#3: date
157  current x 20,190,117 ops/sec ±0.86% (92 runs sampled)
158  lib-type-of x 5,166,970 ops/sec ±0.74% (94 runs sampled)
159  lib-typeof x 9,610,821 ops/sec ±0.50% (96 runs sampled)
160
161#4: function
162  current x 23,855,460 ops/sec ±0.60% (97 runs sampled)
163  lib-type-of x 5,667,740 ops/sec ±0.54% (100 runs sampled)
164  lib-typeof x 10,010,644 ops/sec ±0.44% (100 runs sampled)
165
166#5: null
167  current x 27,061,047 ops/sec ±0.97% (96 runs sampled)
168  lib-type-of x 13,965,573 ops/sec ±0.62% (97 runs sampled)
169  lib-typeof x 8,460,194 ops/sec ±0.61% (97 runs sampled)
170
171#6: number
172  current x 25,075,682 ops/sec ±0.53% (99 runs sampled)
173  lib-type-of x 2,266,405 ops/sec ±0.41% (98 runs sampled)
174  lib-typeof x 9,821,481 ops/sec ±0.45% (99 runs sampled)
175
176#7: object
177  current x 3,348,980 ops/sec ±0.49% (99 runs sampled)
178  lib-type-of x 3,245,138 ops/sec ±0.60% (94 runs sampled)
179  lib-typeof x 9,262,952 ops/sec ±0.59% (99 runs sampled)
180
181#8: regex
182  current x 21,284,827 ops/sec ±0.72% (96 runs sampled)
183  lib-type-of x 4,689,241 ops/sec ±0.43% (100 runs sampled)
184  lib-typeof x 8,957,593 ops/sec ±0.62% (98 runs sampled)
185
186#9: string
187  current x 25,379,234 ops/sec ±0.58% (96 runs sampled)
188  lib-type-of x 3,635,148 ops/sec ±0.76% (93 runs sampled)
189  lib-typeof x 9,494,134 ops/sec ±0.49% (98 runs sampled)
190
191#10: undef
192  current x 27,459,221 ops/sec ±1.01% (93 runs sampled)
193  lib-type-of x 14,360,433 ops/sec ±0.52% (99 runs sampled)
194  lib-typeof x 23,202,868 ops/sec ±0.59% (94 runs sampled)
195
196```
197
198## Optimizations
199
200In 7 out of 8 cases, this library is 2x-10x faster than other top libraries included in the benchmarks. There are a few things that lead to this performance advantage, none of them hard and fast rules, but all of them simple and repeatable in almost any code library:
201
2021. Optimize around the fastest and most common use cases first. Of course, this will change from project-to-project, but I took some time to understand how and why `typeof` checks were being used in my own libraries and other libraries I use a lot.
2032. Optimize around bottlenecks - In other words, the order in which conditionals are implemented is significant, because each check is only as fast as the failing checks that came before it. Here, the biggest bottleneck by far is checking for plain objects (an object that was created by the `Object` constructor). I opted to make this check happen by process of elimination rather than brute force up front (e.g. by using something like `val.constructor.name`), so that every other type check would not be penalized it.
2043. Don't do uneccessary processing - why do `.slice(8, -1).toLowerCase();` just to get the word `regex`? It's much faster to do `if (type === '[object RegExp]') return 'regex'`
205
206## About
207
208### Related projects
209
210* [is-glob](https://www.npmjs.com/package/is-glob): Returns `true` if the given string looks like a glob pattern or an extglob pattern… [more](https://github.com/jonschlinkert/is-glob) | [homepage](https://github.com/jonschlinkert/is-glob "Returns `true` if the given string looks like a glob pattern or an extglob pattern. This makes it easy to create code that only uses external modules like node-glob when necessary, resulting in much faster code execution and initialization time, and a bet")
211* [is-number](https://www.npmjs.com/package/is-number): Returns true if the value is a number. comprehensive tests. | [homepage](https://github.com/jonschlinkert/is-number "Returns true if the value is a number. comprehensive tests.")
212* [is-primitive](https://www.npmjs.com/package/is-primitive): Returns `true` if the value is a primitive.  | [homepage](https://github.com/jonschlinkert/is-primitive "Returns `true` if the value is a primitive. ")
213
214### Contributing
215
216Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](../../issues/new).
217
218### Contributors
219
220| **Commits** | **Contributor** |
221| --- | --- |
222| 59 | [jonschlinkert](https://github.com/jonschlinkert) |
223| 2 | [miguelmota](https://github.com/miguelmota) |
224| 1 | [dtothefp](https://github.com/dtothefp) |
225| 1 | [ksheedlo](https://github.com/ksheedlo) |
226| 1 | [pdehaan](https://github.com/pdehaan) |
227| 1 | [laggingreflex](https://github.com/laggingreflex) |
228
229### Building docs
230
231_(This project's readme.md is generated by [verb](https://github.com/verbose/verb-generate-readme), please don't edit the readme directly. Any changes to the readme must be made in the [.verb.md](.verb.md) readme template.)_
232
233To generate the readme, run the following command:
234
235```sh
236$ npm install -g verbose/verb#dev verb-generate-readme && verb
237```
238
239### Running tests
240
241Running and reviewing unit tests is a great way to get familiarized with a library and its API. You can install dependencies and run tests with the following command:
242
243```sh
244$ npm install && npm test
245```
246
247### Author
248
249**Jon Schlinkert**
250
251* [github/jonschlinkert](https://github.com/jonschlinkert)
252* [twitter/jonschlinkert](https://twitter.com/jonschlinkert)
253
254### License
255
256Copyright © 2017, [Jon Schlinkert](https://github.com/jonschlinkert).
257Released under the [MIT License](LICENSE).
258
259***
260
261_This file was generated by [verb-generate-readme](https://github.com/verbose/verb-generate-readme), v0.6.0, on May 16, 2017._