README.md
1 # kind-of [](https://www.npmjs.com/package/kind-of) [](https://npmjs.org/package/kind-of) [](https://npmjs.org/package/kind-of) [](https://travis-ci.org/jonschlinkert/kind-of) 2 3 > Get the native type of a value. 4 5 ## Install 6 7 Install with [npm](https://www.npmjs.com/): 8 9 ```sh 10 $ npm install --save kind-of 11 ``` 12 13 ## Install 14 15 Install 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 26 var kindOf = require('kind-of'); 27 28 kindOf(undefined); 29 //=> 'undefined' 30 31 kindOf(null); 32 //=> 'null' 33 34 kindOf(true); 35 //=> 'boolean' 36 37 kindOf(false); 38 //=> 'boolean' 39 40 kindOf(new Boolean(true)); 41 //=> 'boolean' 42 43 kindOf(new Buffer('')); 44 //=> 'buffer' 45 46 kindOf(42); 47 //=> 'number' 48 49 kindOf(new Number(42)); 50 //=> 'number' 51 52 kindOf('str'); 53 //=> 'string' 54 55 kindOf(new String('str')); 56 //=> 'string' 57 58 kindOf(arguments); 59 //=> 'arguments' 60 61 kindOf({}); 62 //=> 'object' 63 64 kindOf(Object.create(null)); 65 //=> 'object' 66 67 kindOf(new Test()); 68 //=> 'object' 69 70 kindOf(new Date()); 71 //=> 'date' 72 73 kindOf([]); 74 //=> 'array' 75 76 kindOf([1, 2, 3]); 77 //=> 'array' 78 79 kindOf(new Array()); 80 //=> 'array' 81 82 kindOf(/foo/); 83 //=> 'regexp' 84 85 kindOf(new RegExp('foo')); 86 //=> 'regexp' 87 88 kindOf(function () {}); 89 //=> 'function' 90 91 kindOf(function * () {}); 92 //=> 'function' 93 94 kindOf(new Function()); 95 //=> 'function' 96 97 kindOf(new Map()); 98 //=> 'map' 99 100 kindOf(new WeakMap()); 101 //=> 'weakmap' 102 103 kindOf(new Set()); 104 //=> 'set' 105 106 kindOf(new WeakSet()); 107 //=> 'weakset' 108 109 kindOf(Symbol('str')); 110 //=> 'symbol' 111 112 kindOf(new Int8Array()); 113 //=> 'int8array' 114 115 kindOf(new Uint8Array()); 116 //=> 'uint8array' 117 118 kindOf(new Uint8ClampedArray()); 119 //=> 'uint8clampedarray' 120 121 kindOf(new Int16Array()); 122 //=> 'int16array' 123 124 kindOf(new Uint16Array()); 125 //=> 'uint16array' 126 127 kindOf(new Int32Array()); 128 //=> 'int32array' 129 130 kindOf(new Uint32Array()); 131 //=> 'uint32array' 132 133 kindOf(new Float32Array()); 134 //=> 'float32array' 135 136 kindOf(new Float64Array()); 137 //=> 'float64array' 138 ``` 139 140 ## Benchmarks 141 142 Benchmarked against [typeof](http://github.com/CodingFu/typeof) and [type-of](https://github.com/ForbesLindesay/type-of). 143 Note 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 199 200 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: 201 202 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. 203 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. 204 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'` 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 215 216 Pull 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.)_ 232 233 To 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 240 241 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: 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 255 256 Copyright © 2017, [Jon Schlinkert](https://github.com/jonschlinkert). 257 Released 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._