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)
3 > Get the native type of a value.
5 Please consider following this project's author, [Jon Schlinkert](https://github.com/jonschlinkert), and consider starring the project to show your :heart: and support.
9 Install with [npm](https://www.npmjs.com/):
12 $ npm install --save kind-of
15 Install with [bower](https://bower.io/)
18 $ bower install kind-of --save
23 1. [it's fast](#benchmarks) | [optimizations](#optimizations)
24 2. [better type checking](#better-type-checking)
28 > es5, es6, and browser ready
31 var kindOf = require('kind-of');
45 kindOf(new Buffer(''));
60 kindOf(Object.create(null));
75 kindOf(new RegExp('foo'));
78 kindOf(new Error('error'));
81 kindOf(function () {});
84 kindOf(function * () {});
85 //=> 'generatorfunction'
87 kindOf(Symbol('str'));
93 kindOf(new WeakMap());
99 kindOf(new WeakSet());
102 kindOf(new Int8Array());
105 kindOf(new Uint8Array());
108 kindOf(new Uint8ClampedArray());
109 //=> 'uint8clampedarray'
111 kindOf(new Int16Array());
114 kindOf(new Uint16Array());
117 kindOf(new Int32Array());
120 kindOf(new Uint32Array());
123 kindOf(new Float32Array());
126 kindOf(new Float64Array());
132 Benchmarked against [typeof](http://github.com/CodingFu/typeof) and [type-of](https://github.com/ForbesLindesay/type-of).
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)
140 fastest is kind-of (by 161% avg)
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)
147 fastest is kind-of (by 196% avg)
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)
154 fastest is kind-of (by 204% avg)
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)
161 fastest is kind-of (by 247% avg)
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)
168 fastest is kind-of (by 184% avg)
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)
175 fastest is kind-of (by 127% avg)
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)
182 fastest is kind-of (by 113% avg)
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)
189 fastest is kind-of (by 174% avg)
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)
196 fastest is kind-of (by 632% avg)
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)
203 fastest is lib-type-of (by 112% avg)
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)
210 fastest is kind-of (by 158% avg)
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)
217 fastest is kind-of (by 220% avg)
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)
224 fastest is kind-of (by 310% avg)
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)
231 fastest is kind-of (by 210% avg)
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)
238 fastest is lib-typeof,kind-of
244 In 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:
246 1. 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.
247 2. 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.
248 3. 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'`
249 4. 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.
251 ## Better type checking
253 kind-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:
255 ### [typeof](https://github.com/CodingFu/typeof) lib
257 Incorrectly identifies instances of custom constructors (pretty common):
260 var typeOf = require('typeof');
262 console.log(typeOf(new Test()));
266 Returns `object` instead of `arguments`:
270 console.log(typeOf(arguments)) //=> 'object'
275 ### [type-of](https://github.com/ForbesLindesay/type-of) lib
277 Incorrectly returns `object` for generator functions, buffers, `Map`, `Set`, `WeakMap` and `WeakSet`:
281 console.log(typeOf(foo));
283 console.log(typeOf(new Buffer('')));
285 console.log(typeOf(new Map()));
287 console.log(typeOf(new Set()));
289 console.log(typeOf(new WeakMap()));
291 console.log(typeOf(new WeakSet()));
298 <summary><strong>Contributing</strong></summary>
300 Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](../../issues/new).
305 <summary><strong>Running Tests</strong></summary>
307 Running 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:
310 $ npm install && npm test
316 <summary><strong>Building docs</strong></summary>
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.)_
320 To generate the readme, run the following command:
323 $ npm install -g verbose/verb#dev verb-generate-readme && verb
330 You might also be interested in these projects:
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. ")
338 | **Commits** | **Contributor** |
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) |
356 * [GitHub Profile](https://github.com/jonschlinkert)
357 * [Twitter Profile](https://twitter.com/jonschlinkert)
358 * [LinkedIn Profile](https://linkedin.com/in/jonschlinkert)
362 Copyright © 2020, [Jon Schlinkert](https://github.com/jonschlinkert).
363 Released under the [MIT License](LICENSE).
367 _This file was generated by [verb-generate-readme](https://github.com/verbose/verb-generate-readme), v0.8.0, on January 16, 2020._