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# is-number [](https://www.npmjs.com/package/is-number) [](https://npmjs.org/package/is-number) [](https://npmjs.org/package/is-number) [](https://travis-ci.org/jonschlinkert/is-number) > Returns true if the value is a finite number. Please consider following this project's author, [Jon Schlinkert](https://github.com/jonschlinkert), and consider starring the project to show your :heart: and support. ## Install Install with [npm](https://www.npmjs.com/): ```sh $ npm install --save is-number ``` ## Why is this needed? In JavaScript, it's not always as straightforward as it should be to reliably check if a value is a number. It's common for devs to use `+`, `-`, or `Number()` to cast a string value to a number (for example, when values are returned from user input, regex matches, parsers, etc). But there are many non-intuitive edge cases that yield unexpected results: ```js console.log(+[]); //=> 0 console.log(+''); //=> 0 console.log(+' '); //=> 0 console.log(typeof NaN); //=> 'number' ``` This library offers a performant way to smooth out edge cases like these. ## Usage ```js const isNumber = require('is-number'); ``` See the [tests](./test.js) for more examples. ### true ```js isNumber(5e3); // true isNumber(0xff); // true isNumber(-1.1); // true isNumber(0); // true isNumber(1); // true isNumber(1.1); // true isNumber(10); // true isNumber(10.10); // true isNumber(100); // true isNumber('-1.1'); // true isNumber('0'); // true isNumber('012'); // true isNumber('0xff'); // true isNumber('1'); // true isNumber('1.1'); // true isNumber('10'); // true isNumber('10.10'); // true isNumber('100'); // true isNumber('5e3'); // true isNumber(parseInt('012')); // true isNumber(parseFloat('012')); // true ``` ### False Everything else is false, as you would expect: ```js isNumber(Infinity); // false isNumber(NaN); // false isNumber(null); // false isNumber(undefined); // false isNumber(''); // false isNumber(' '); // false isNumber('foo'); // false isNumber([1]); // false isNumber([]); // false isNumber(function () {}); // false isNumber({}); // false ``` ## Release history ### 7.0.0 * Refactor. Now uses `.isFinite` if it exists. * Performance is about the same as v6.0 when the value is a string or number. But it's now 3x-4x faster when the value is not a string or number. ### 6.0.0 * Optimizations, thanks to @benaadams. ### 5.0.0 **Breaking changes** * removed support for `instanceof Number` and `instanceof String` ## Benchmarks As with all benchmarks, take these with a grain of salt. See the [benchmarks](./benchmark/index.js) for more detail. ``` # all v7.0 x 413,222 ops/sec ±2.02% (86 runs sampled) v6.0 x 111,061 ops/sec ±1.29% (85 runs sampled) parseFloat x 317,596 ops/sec ±1.36% (86 runs sampled) fastest is 'v7.0' # string v7.0 x 3,054,496 ops/sec ±1.05% (89 runs sampled) v6.0 x 2,957,781 ops/sec ±0.98% (88 runs sampled) parseFloat x 3,071,060 ops/sec ±1.13% (88 runs sampled) fastest is 'parseFloat,v7.0' # number v7.0 x 3,146,895 ops/sec ±0.89% (89 runs sampled) v6.0 x 3,214,038 ops/sec ±1.07% (89 runs sampled) parseFloat x 3,077,588 ops/sec ±1.07% (87 runs sampled) fastest is 'v6.0' ``` ## About <details> <summary><strong>Contributing</strong></summary> Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](../../issues/new). </details> <details> <summary><strong>Running Tests</strong></summary> 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: ```sh $ npm install && npm test ``` </details> <details> <summary><strong>Building docs</strong></summary> _(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.)_ To generate the readme, run the following command: ```sh $ npm install -g verbose/verb#dev verb-generate-readme && verb ``` </details> ### Related projects You might also be interested in these projects: * [is-plain-object](https://www.npmjs.com/package/is-plain-object): Returns true if an object was created by the `Object` constructor. | [homepage](https://github.com/jonschlinkert/is-plain-object "Returns true if an object was created by the `Object` constructor.") * [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. ") * [isobject](https://www.npmjs.com/package/isobject): Returns true if the value is an object and not an array or null. | [homepage](https://github.com/jonschlinkert/isobject "Returns true if the value is an object and not an array or null.") * [kind-of](https://www.npmjs.com/package/kind-of): Get the native type of a value. | [homepage](https://github.com/jonschlinkert/kind-of "Get the native type of a value.") ### Contributors | **Commits** | **Contributor** | | --- | --- | | 49 | [jonschlinkert](https://github.com/jonschlinkert) | | 5 | [charlike-old](https://github.com/charlike-old) | | 1 | [benaadams](https://github.com/benaadams) | | 1 | [realityking](https://github.com/realityking) | ### Author **Jon Schlinkert** * [LinkedIn Profile](https://linkedin.com/in/jonschlinkert) * [GitHub Profile](https://github.com/jonschlinkert) * [Twitter Profile](https://twitter.com/jonschlinkert) ### License Copyright © 2018, [Jon Schlinkert](https://github.com/jonschlinkert). Released under the [MIT License](LICENSE). *** _This file was generated by [verb-generate-readme](https://github.com/verbose/verb-generate-readme), v0.6.0, on June 15, 2018._