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kind-of

Get the native type of a value.

Install

Install with npm:

$ npm install --save kind-of

Install

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(/foo/);
//=> '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'

kindOf(new Int8Array());
//=> 'int8array'

kindOf(new Uint8Array());
//=> 'uint8array'

kindOf(new Uint8ClampedArray());
//=> 'uint8clampedarray'

kindOf(new Int16Array());
//=> 'int16array'

kindOf(new Uint16Array());
//=> 'uint16array'

kindOf(new Int32Array());
//=> 'int32array'

kindOf(new Uint32Array());
//=> 'uint32array'

kindOf(new Float32Array());
//=> 'float32array'

kindOf(new Float64Array());
//=> 'float64array'

Benchmarks

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

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'

About

Related projects

Contributing

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

Contributors

Commits

Contributor

59

jonschlinkert

2

miguelmota

1

dtothefp

1

ksheedlo

1

pdehaan

1

laggingreflex

Building docs

(This project's readme.md is generated by verb, please don't edit the readme directly. Any changes to the readme must be made in the .verb.md readme template.)

To generate the readme, run the following command:

Running tests

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:

Author

Jon Schlinkert

License

Copyright © 2017, Jon Schlinkert. Released under the MIT License.

This file was generated by verb-generate-readme, v0.6.0, on May 16, 2017.

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