Returns true if the value is a number. comprehensive tests.

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

Install with npm:

$ npm install --save is-number

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.

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

See the tests for more examples.

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'

See the tests for more examples.

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'

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.

In JavaScript, can easily test for a number by doing 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 (I personally use this library to check for numbers when parsing a string. Clearly, this is a case where it's not possible for the value to be defined as a number).

Breaking changes

• removed support for instanceof Number and instanceof String

$ npm install && npm test

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

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

Jon Schlinkert

• linkedin/in/jonschlinkert
• github/jonschlinkert
• twitter/jonschlinkert

Copyright © 2018, Jon Schlinkert. Released under the MIT License.

This file was generated by verb-generate-readme, v0.6.0, on January 28, 2018.