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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
5Please consider following this project's author, [Jon Schlinkert](https://github.com/jonschlinkert), and consider starring the project to show your :heart: and support.
6
7## Install
8
9Install with [npm](https://www.npmjs.com/):
10
11```sh
12$ npm install --save kind-of
13```
14
15Install with [bower](https://bower.io/)
16
17```sh
18$ bower install kind-of --save
19```
20
21## Why use this?
22
231. [it's fast](#benchmarks) | [optimizations](#optimizations)
242. [better type checking](#better-type-checking)
25
26## Usage
27
28> es5, es6, and browser ready
29
30```js
31var kindOf = require('kind-of');
32
33kindOf(undefined);
34//=> 'undefined'
35
36kindOf(null);
37//=> 'null'
38
39kindOf(true);
40//=> 'boolean'
41
42kindOf(false);
43//=> 'boolean'
44
45kindOf(new Buffer(''));
46//=> 'buffer'
47
48kindOf(42);
49//=> 'number'
50
51kindOf('str');
52//=> 'string'
53
54kindOf(arguments);
55//=> 'arguments'
56
57kindOf({});
58//=> 'object'
59
60kindOf(Object.create(null));
61//=> 'object'
62
63kindOf(new Test());
64//=> 'object'
65
66kindOf(new Date());
67//=> 'date'
68
69kindOf([1, 2, 3]);
70//=> 'array'
71
72kindOf(/foo/);
73//=> 'regexp'
74
75kindOf(new RegExp('foo'));
76//=> 'regexp'
77
78kindOf(new Error('error'));
79//=> 'error'
80
81kindOf(function () {});
82//=> 'function'
83
84kindOf(function * () {});
85//=> 'generatorfunction'
86
87kindOf(Symbol('str'));
88//=> 'symbol'
89
90kindOf(new Map());
91//=> 'map'
92
93kindOf(new WeakMap());
94//=> 'weakmap'
95
96kindOf(new Set());
97//=> 'set'
98
99kindOf(new WeakSet());
100//=> 'weakset'
101
102kindOf(new Int8Array());
103//=> 'int8array'
104
105kindOf(new Uint8Array());
106//=> 'uint8array'
107
108kindOf(new Uint8ClampedArray());
109//=> 'uint8clampedarray'
110
111kindOf(new Int16Array());
112//=> 'int16array'
113
114kindOf(new Uint16Array());
115//=> 'uint16array'
116
117kindOf(new Int32Array());
118//=> 'int32array'
119
120kindOf(new Uint32Array());
121//=> 'uint32array'
122
123kindOf(new Float32Array());
124//=> 'float32array'
125
126kindOf(new Float64Array());
127//=> 'float64array'
128```
129
130## Benchmarks
131
132Benchmarked against [typeof](http://github.com/CodingFu/typeof) and [type-of](https://github.com/ForbesLindesay/type-of).
133
134```bash
135# arguments (32 bytes)
136 kind-of x 17,024,098 ops/sec ±1.90% (86 runs sampled)
137 lib-type-of x 11,926,235 ops/sec ±1.34% (83 runs sampled)
138 lib-typeof x 9,245,257 ops/sec ±1.22% (87 runs sampled)
139
140 fastest is kind-of (by 161% avg)
141
142# array (22 bytes)
143 kind-of x 17,196,492 ops/sec ±1.07% (88 runs sampled)
144 lib-type-of x 8,838,283 ops/sec ±1.02% (87 runs sampled)
145 lib-typeof x 8,677,848 ops/sec ±0.87% (87 runs sampled)
146
147 fastest is kind-of (by 196% avg)
148
149# boolean (24 bytes)
150 kind-of x 16,841,600 ops/sec ±1.10% (86 runs sampled)
151 lib-type-of x 8,096,787 ops/sec ±0.95% (87 runs sampled)
152 lib-typeof x 8,423,345 ops/sec ±1.15% (86 runs sampled)
153
154 fastest is kind-of (by 204% avg)
155
156# buffer (38 bytes)
157 kind-of x 14,848,060 ops/sec ±1.05% (86 runs sampled)
158 lib-type-of x 3,671,577 ops/sec ±1.49% (87 runs sampled)
159 lib-typeof x 8,360,236 ops/sec ±1.24% (86 runs sampled)
160
161 fastest is kind-of (by 247% avg)
162
163# date (30 bytes)
164 kind-of x 16,067,761 ops/sec ±1.58% (86 runs sampled)
165 lib-type-of x 8,954,436 ops/sec ±1.40% (87 runs sampled)
166 lib-typeof x 8,488,307 ops/sec ±1.51% (84 runs sampled)
167
168 fastest is kind-of (by 184% avg)
169
170# error (36 bytes)
171 kind-of x 9,634,090 ops/sec ±1.12% (89 runs sampled)
172 lib-type-of x 7,735,624 ops/sec ±1.32% (86 runs sampled)
173 lib-typeof x 7,442,160 ops/sec ±1.11% (90 runs sampled)
174
175 fastest is kind-of (by 127% avg)
176
177# function (34 bytes)
178 kind-of x 10,031,494 ops/sec ±1.27% (86 runs sampled)
179 lib-type-of x 9,502,757 ops/sec ±1.17% (89 runs sampled)
180 lib-typeof x 8,278,985 ops/sec ±1.08% (88 runs sampled)
181
182 fastest is kind-of (by 113% avg)
183
184# null (24 bytes)
185 kind-of x 18,159,808 ops/sec ±1.92% (86 runs sampled)
186 lib-type-of x 12,927,635 ops/sec ±1.01% (88 runs sampled)
187 lib-typeof x 7,958,234 ops/sec ±1.21% (89 runs sampled)
188
189 fastest is kind-of (by 174% avg)
190
191# number (22 bytes)
192 kind-of x 17,846,779 ops/sec ±0.91% (85 runs sampled)
193 lib-type-of x 3,316,636 ops/sec ±1.19% (86 runs sampled)
194 lib-typeof x 2,329,477 ops/sec ±2.21% (85 runs sampled)
195
196 fastest is kind-of (by 632% avg)
197
198# object-plain (47 bytes)
199 kind-of x 7,085,155 ops/sec ±1.05% (88 runs sampled)
200 lib-type-of x 8,870,930 ops/sec ±1.06% (83 runs sampled)
201 lib-typeof x 8,716,024 ops/sec ±1.05% (87 runs sampled)
202
203 fastest is lib-type-of (by 112% avg)
204
205# regex (25 bytes)
206 kind-of x 14,196,052 ops/sec ±1.65% (84 runs sampled)
207 lib-type-of x 9,554,164 ops/sec ±1.25% (88 runs sampled)
208 lib-typeof x 8,359,691 ops/sec ±1.07% (87 runs sampled)
209
210 fastest is kind-of (by 158% avg)
211
212# string (33 bytes)
213 kind-of x 16,131,428 ops/sec ±1.41% (85 runs sampled)
214 lib-type-of x 7,273,172 ops/sec ±1.05% (87 runs sampled)
215 lib-typeof x 7,382,635 ops/sec ±1.17% (85 runs sampled)
216
217 fastest is kind-of (by 220% avg)
218
219# symbol (34 bytes)
220 kind-of x 17,011,537 ops/sec ±1.24% (86 runs sampled)
221 lib-type-of x 3,492,454 ops/sec ±1.23% (89 runs sampled)
222 lib-typeof x 7,471,235 ops/sec ±2.48% (87 runs sampled)
223
224 fastest is kind-of (by 310% avg)
225
226# template-strings (36 bytes)
227 kind-of x 15,434,250 ops/sec ±1.46% (83 runs sampled)
228 lib-type-of x 7,157,907 ops/sec ±0.97% (87 runs sampled)
229 lib-typeof x 7,517,986 ops/sec ±0.92% (86 runs sampled)
230
231 fastest is kind-of (by 210% avg)
232
233# undefined (29 bytes)
234 kind-of x 19,167,115 ops/sec ±1.71% (87 runs sampled)
235 lib-type-of x 15,477,740 ops/sec ±1.63% (85 runs sampled)
236 lib-typeof x 19,075,495 ops/sec ±1.17% (83 runs sampled)
237
238 fastest is lib-typeof,kind-of
239
240```
241
242## Optimizations
243
244In 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:
245
2461. 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.
2472. 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.
2483. 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'`
2494. There is no reason to make the code in a microlib as terse as possible, just to win points for making it shorter. It's always better to favor performant code over terse code. You will always only be using a single `require()` statement to use the library anyway, regardless of how the code is written.
250
251## Better type checking
252
253kind-of seems to be more consistently "correct" than other type checking libs I've looked at. For example, here are some differing results from other popular libs:
254
255### [typeof](https://github.com/CodingFu/typeof) lib
256
257Incorrectly identifies instances of custom constructors (pretty common):
258
259```js
260var typeOf = require('typeof');
261function Test() {}
262console.log(typeOf(new Test()));
263//=> 'test'
264```
265
266Returns `object` instead of `arguments`:
267
268```js
269function foo() {
270 console.log(typeOf(arguments)) //=> 'object'
271}
272foo();
273```
274
275### [type-of](https://github.com/ForbesLindesay/type-of) lib
276
277Incorrectly returns `object` for generator functions, buffers, `Map`, `Set`, `WeakMap` and `WeakSet`:
278
279```js
280function * foo() {}
281console.log(typeOf(foo));
282//=> 'object'
283console.log(typeOf(new Buffer('')));
284//=> 'object'
285console.log(typeOf(new Map()));
286//=> 'object'
287console.log(typeOf(new Set()));
288//=> 'object'
289console.log(typeOf(new WeakMap()));
290//=> 'object'
291console.log(typeOf(new WeakSet()));
292//=> 'object'
293```
294
295## About
296
297<details>
298<summary><strong>Contributing</strong></summary>
299
300Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](../../issues/new).
301
302</details>
303
304<details>
305<summary><strong>Running Tests</strong></summary>
306
307Running 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:
308
309```sh
310$ npm install && npm test
311```
312
313</details>
314
315<details>
316<summary><strong>Building docs</strong></summary>
317
318_(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.)_
319
320To generate the readme, run the following command:
321
322```sh
323$ npm install -g verbose/verb#dev verb-generate-readme && verb
324```
325
326</details>
327
328### Related projects
329
330You might also be interested in these projects:
331
332* [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/micromatch/is-glob) | [homepage](https://github.com/micromatch/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")
333* [is-number](https://www.npmjs.com/package/is-number): Returns true if a number or string value is a finite number. Useful for regex… [more](https://github.com/jonschlinkert/is-number) | [homepage](https://github.com/jonschlinkert/is-number "Returns true if a number or string value is a finite number. Useful for regex matches, parsing, user input, etc.")
334* [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. ")
335
336### Contributors
337
338| **Commits** | **Contributor** |
339| --- | --- |
340| 102 | [jonschlinkert](https://github.com/jonschlinkert) |
341| 3 | [aretecode](https://github.com/aretecode) |
342| 2 | [miguelmota](https://github.com/miguelmota) |
343| 1 | [doowb](https://github.com/doowb) |
344| 1 | [dtothefp](https://github.com/dtothefp) |
345| 1 | [ianstormtaylor](https://github.com/ianstormtaylor) |
346| 1 | [ksheedlo](https://github.com/ksheedlo) |
347| 1 | [pdehaan](https://github.com/pdehaan) |
348| 1 | [laggingreflex](https://github.com/laggingreflex) |
349| 1 | [tunnckoCore](https://github.com/tunnckoCore) |
350| 1 | [xiaofen9](https://github.com/xiaofen9) |
351
352### Author
353
354**Jon Schlinkert**
355
356* [GitHub Profile](https://github.com/jonschlinkert)
357* [Twitter Profile](https://twitter.com/jonschlinkert)
358* [LinkedIn Profile](https://linkedin.com/in/jonschlinkert)
359
360### License
361
362Copyright © 2020, [Jon Schlinkert](https://github.com/jonschlinkert).
363Released under the [MIT License](LICENSE).
364
365***
366
367_This file was generated by [verb-generate-readme](https://github.com/verbose/verb-generate-readme), v0.8.0, on January 16, 2020._
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