kind-of
    DefinitelyTyped icon, indicating that this package has TypeScript declarations provided by the separate @types/kind-of package

    2.0.1 • Public • Published

    kind-of NPM version Build Status

    Get the native type of a value.

    What makes this so fast?

    Install

    Install with npm

    $ npm i kind-of --save

    Install with bower

    $ bower install kind-of --save

    Usage

    es5, browser and es6 ready

    var kindOf = require('kind-of');
     
    kindOf(undefined);
    //=> 'undefined'
     
    kindOf(null);
    //=> 'null'
     
    kindOf(true);
    //=> 'boolean'
     
    kindOf(false);
    //=> 'boolean'
     
    kindOf(new Boolean(true));
    //=> 'boolean'
     
    kindOf(new Buffer(''));
    //=> 'buffer'
     
    kindOf(42);
    //=> 'number'
     
    kindOf(new Number(42));
    //=> 'number'
     
    kindOf('str');
    //=> 'string'
     
    kindOf(new String('str'));
    //=> 'string'
     
    kindOf(arguments);
    //=> 'arguments'
     
    kindOf({});
    //=> 'object'
     
    kindOf(Object.create(null));
    //=> 'object'
     
    kindOf(new Test());
    //=> 'object'
     
    kindOf(new Date());
    //=> 'date'
     
    kindOf([]);
    //=> 'array'
     
    kindOf([1, 2, 3]);
    //=> 'array'
     
    kindOf(new Array());
    //=> 'array'
     
    kindOf(/[\s\S]+/);
    //=> 'regexp'
     
    kindOf(new RegExp('^' + 'foo$'));
    //=> 'regexp'
     
    kindOf(function () {});
    //=> 'function'
     
    kindOf(function * () {});
    //=> 'function'
     
    kindOf(new Function());
    //=> 'function'
     
    kindOf(new Map());
    //=> 'map'
     
    kindOf(new WeakMap());
    //=> 'weakmap'
     
    kindOf(new Set());
    //=> 'set'
     
    kindOf(new WeakSet());
    //=> 'weakset'
     
    kindOf(Symbol('str'));
    //=> 'symbol'

    Related projects

    • is-number: Returns true if the value is a number. comprehensive tests.
    • isobject: Returns true if the value is an object and not an array or null.
    • is-primitive: Returns true if the value is a primitive.
    • is-plain-object: Returns true if an object was created by the Object constructor.
    • is-match: Create a matching function from a glob pattern, regex, string, array or function.

    Benchmarks

    Benchmarked against typeof and type-of. Note that performaces is slower for es6 features Map, WeakMap, Set and WeakSet.

    #1: array 
      current x 23,329,397 ops/sec ±0.82% (94 runs sampled)
      lib-type-of x 4,170,273 ops/sec ±0.55% (94 runs sampled)
      lib-typeof x 9,686,935 ops/sec ±0.59% (98 runs sampled)
     
    #2: boolean 
      current x 27,197,115 ops/sec ±0.85% (94 runs sampled)
      lib-type-of x 3,145,791 ops/sec ±0.73% (97 runs sampled)
      lib-typeof x 9,199,562 ops/sec ±0.44% (99 runs sampled)
     
    #3: date 
      current x 20,190,117 ops/sec ±0.86% (92 runs sampled)
      lib-type-of x 5,166,970 ops/sec ±0.74% (94 runs sampled)
      lib-typeof x 9,610,821 ops/sec ±0.50% (96 runs sampled)
     
    #4: function 
      current x 23,855,460 ops/sec ±0.60% (97 runs sampled)
      lib-type-of x 5,667,740 ops/sec ±0.54% (100 runs sampled)
      lib-typeof x 10,010,644 ops/sec ±0.44% (100 runs sampled)
     
    #5: null 
      current x 27,061,047 ops/sec ±0.97% (96 runs sampled)
      lib-type-of x 13,965,573 ops/sec ±0.62% (97 runs sampled)
      lib-typeof x 8,460,194 ops/sec ±0.61% (97 runs sampled)
     
    #6: number 
      current x 25,075,682 ops/sec ±0.53% (99 runs sampled)
      lib-type-of x 2,266,405 ops/sec ±0.41% (98 runs sampled)
      lib-typeof x 9,821,481 ops/sec ±0.45% (99 runs sampled)
     
    #7: object 
      current x 3,348,980 ops/sec ±0.49% (99 runs sampled)
      lib-type-of x 3,245,138 ops/sec ±0.60% (94 runs sampled)
      lib-typeof x 9,262,952 ops/sec ±0.59% (99 runs sampled)
     
    #8: regex 
      current x 21,284,827 ops/sec ±0.72% (96 runs sampled)
      lib-type-of x 4,689,241 ops/sec ±0.43% (100 runs sampled)
      lib-typeof x 8,957,593 ops/sec ±0.62% (98 runs sampled)
     
    #9: string 
      current x 25,379,234 ops/sec ±0.58% (96 runs sampled)
      lib-type-of x 3,635,148 ops/sec ±0.76% (93 runs sampled)
      lib-typeof x 9,494,134 ops/sec ±0.49% (98 runs sampled)
     
    #10: undef 
      current x 27,459,221 ops/sec ±1.01% (93 runs sampled)
      lib-type-of x 14,360,433 ops/sec ±0.52% (99 runs sampled)
      lib-typeof x 23,202,868 ops/sec ±0.59% (94 runs sampled)

    Optimizations

    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:

    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.
    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.
    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'

    Running tests

    Install dev dependencies:

    $ npm i -d && npm test

    Contributing

    Pull requests and stars are always welcome. For bugs and feature requests, please create an issue

    Author

    Jon Schlinkert

    License

    Copyright © 2014-2015 Jon Schlinkert Released under the MIT license.


    This file was generated by verb-cli on May 31, 2015.

    Install

    npm i kind-of@2.0.1

    Version

    2.0.1

    License

    MIT

    Last publish

    Collaborators

    • doowb
    • jonschlinkert