# 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 number. comprehensive tests.
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?
This library provides a fast, simple way of checking whether a value is a number, whether defined as a string or number by the user.
It's easy to check for a number in JavaScript, all we need to do is `typeof value === 'number'`. But sometimes that's not enough. For example, `typeof NaN` returns `number`, and there are many use cases where it's possible or necessary for a numerical value to be defined as a string, like in parsers or regex matches where it's not possible for the value to be defined as a number.
## Usage
To understand some of the rationale behind the decisions made in this library (and to learn about some oddities of number evaluation in JavaScript), [see this gist](https://gist.github.com/jonschlinkert/e30c70c713da325d0e81).
```js
const isNumber = require('is-number');
```
### true
See the [tests](./test.js) for more examples.
```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
See the [tests](./test.js) for more examples.
```js
isNumber('foo'); // false
isNumber([1]); // false
isNumber([]); // false
isNumber(function () {}); // false
isNumber(Infinity); // false
isNumber(NaN); // false
isNumber(new Buffer('abc')); // false
isNumber(null); // false
isNumber(undefined); // false
isNumber({abc: 'abc'}); // false
```
## Release history
### 6.0.0
* optimizations, thanks to @benaadams.
### 5.0.0
**Breaking changes**
* removed support for `instanceof Number` and `instanceof String`
## About
Contributing
Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](../../issues/new).
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:
```sh
$ npm install && npm test
```
Building docs
_(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
```
### 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** |
| --- | --- |
| 47 | [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 March 31, 2018._