The kind-of npm package is a utility library that allows developers to check the type of a given value in JavaScript. It provides a simple API to determine whether a value is a string, number, array, object, function, and other JavaScript types. This can be particularly useful for type checking and validation in applications where type safety is important.
Type checking for primitives
This feature allows you to check the type of primitive values such as numbers, strings, and booleans.
"use strict"; const kindOf = require('kind-of'); console.log(kindOf(1)); // 'number' console.log(kindOf('hello')); // 'string' console.log(kindOf(true)); // 'boolean'Type checking for objects
This feature allows you to check the type of object-based values such as plain objects, arrays, and regular expressions.
"use strict"; const kindOf = require('kind-of'); console.log(kindOf({})); // 'object' console.log(kindOf([])); // 'array' console.log(kindOf(/foo/)); // 'regexp'Type checking for functions and undefined
This feature allows you to check the type of functions and the undefined value.
"use strict"; const kindOf = require('kind-of'); console.log(kindOf(function () {})); // 'function' console.log(kindOf(undefined)); // 'undefined'Type checking for null and dates
This feature allows you to check the type of null values and date objects.
"use strict"; const kindOf = require('kind-of'); console.log(kindOf(null)); // 'null' console.log(kindOf(new Date())); // 'date'The 'type-check' package offers a similar functionality to 'kind-of' by allowing type assertions and checks. It provides a mini language to specify the types of values and can validate against those specifications.
The 'is' package is another utility library that provides type checking functions. It has a wider range of type checks available, including checks for specific JavaScript environments like the browser or Node.js.
The 'check-types' package provides a set of predicates for type checking. It has a fluent API and includes additional checks for min/max values, empty strings, and arrays, which are not directly available in 'kind-of'.
Get the native type of a value.
Install with npm:
$ npm install --save kind-of
Install with bower
$ bower install kind-of --save
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'
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)
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:
typeof checks were being used in my own libraries and other libraries I use a lot.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..slice(8, -1).toLowerCase(); just to get the word regex? It's much faster to do if (type === '[object RegExp]') return 'regex'true if the given string looks like a glob pattern or an extglob pattern… more | homepagetrue if the value is a primitive. | homepagePull requests and stars are always welcome. For bugs and feature requests, please create an issue.
| Commits | Contributor |
|---|---|
| 59 | jonschlinkert |
| 2 | miguelmota |
| 1 | dtothefp |
| 1 | ksheedlo |
| 1 | pdehaan |
| 1 | laggingreflex |
(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:
$ npm install -g verbose/verb#dev verb-generate-readme && verb
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:
$ npm install && npm test
Jon Schlinkert
Copyright © 2017, Jon Schlinkert. Released under the MIT License.
This file was generated by verb-generate-readme, v0.6.0, on May 16, 2017.
[3.2.2] - 2017-05-16
FAQs
Get the native type of a value.
The npm package kind-of receives a total of 141,487,951 weekly downloads. As such, kind-of popularity was classified as popular.
We found that kind-of demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 2 open source maintainers collaborating on the project.
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