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# is-number [![NPM version](https://img.shields.io/npm/v/is-number.svg?style=flat)](https://www.npmjs.com/package/is-number) [![NPM monthly downloads](https://img.shields.io/npm/dm/is-number.svg?style=flat)](https://npmjs.org/package/is-number) [![NPM total downloads](https://img.shields.io/npm/dt/is-number.svg?style=flat)](https://npmjs.org/package/is-number) [![Linux Build Status](https://img.shields.io/travis/jonschlinkert/is-number.svg?style=flat&label=Travis)](https://travis-ci.org/jonschlinkert/is-number)
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> 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.
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## Install
Install with [npm ](https://www.npmjs.com/ ):
```sh
$ npm install --save is-number
```
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## Why is this needed?
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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:
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```js
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console.log(+[]); //=> 0
console.log(+''); //=> 0
console.log(+' '); //=> 0
console.log(typeof NaN); //=> 'number'
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```
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This library offers a performant way to smooth out edge cases like these.
## Usage
```js
const isNumber = require('is-number');
```
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See the [tests ](./test.js ) for more examples.
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### true
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```js
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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
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```
### False
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Everything else is false, as you would expect:
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```js
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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
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```
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## Release history
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### 7.0.0
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* 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**
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* 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 >
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Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue ](../../issues/new ).
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< / details >
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< details >
< summary > < strong > Running Tests< / strong > < / summary >
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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:
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```sh
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$ npm install & & npm test
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```
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< / 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.)_
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To generate the readme, run the following command:
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```sh
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$ npm install -g verbose/verb#dev verb-generate-readme & & verb
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```
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< / 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 ) |
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### Author
**Jon Schlinkert**
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* [LinkedIn Profile ](https://linkedin.com/in/jonschlinkert )
* [GitHub Profile ](https://github.com/jonschlinkert )
* [Twitter Profile ](https://twitter.com/jonschlinkert )
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### License
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Copyright © 2018, [Jon Schlinkert ](https://github.com/jonschlinkert ).
Released under the [MIT License ](LICENSE ).
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***
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_This file was generated by [verb-generate-readme ](https://github.com/verbose/verb-generate-readme ), v0.6.0, on June 15, 2018._