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is-number

Contributing

> Returns true if the value is a finite number.

Please consider following this project's author, Jon Schlinkert, and consider starring the project to show your :heart: and support.

# Install

Install with npm:

$ 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:

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

const isNumber = require('is-number');

See the tests for more examples.

## true

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:

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 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>

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

</details>

<details>

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:

$ npm install && npm test

</details>

<details>

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:

$ npm install -g verbose/verb#dev verb-generate-readme && verb

</details>

## Related projects

You might also be interested in these projects:

- is-plain-object: Returns true if an object was created by the `Object` constructor. | homepage
- is-primitive: Returns `true` if the value is a primitive. | homepage
- isobject: Returns true if the value is an object and not an array or null. | homepage
- kind-of: Get the native type of a value. | homepage

## Contributors

Commits | Contributor
--- | ---
49 | jonschlinkert
5 | charlike-old
1 | benaadams
1 | realityking

## Author

Jon Schlinkert

- LinkedIn Profile
- GitHub Profile
- Twitter Profile

## License

Copyright © 2018, Jon Schlinkert. Released under the [MIT License](LICENSE).

This file was generated by verb-generate-readme, v0.6.0, on June 15, 2018.