String.prototype.includes()

The includes() method determines whether one string may be found within another string, returning true or false as appropriate.

Syntax

str.includes(searchString[, position])

Parameters

searchString
A string to be searched for within str.
position Optional
The position within the string at which to begin searching for searchString. (Defaults to 0.)

Return value

true if the search string is found anywhere within the given string; otherwise, false if not.

Description

This method lets you determine whether or not a string includes another string.

Case-sensitivity

The includes() method is case sensitive. For example, the following expression returns false:

'Blue Whale'.includes('blue')  // returns false

Polyfill

This method has been added to the ECMAScript 2015 specification and may not be available in all JavaScript implementations yet.

However, you can easily polyfill this method:

if (!String.prototype.includes) {
  String.prototype.includes = function(search, start) {
    'use strict';

    if (search instanceof RegExp) {
      throw TypeError('first argument must not be a RegExp');
    } 
    if (start === undefined) { start = 0; }
    return this.indexOf(search, start) !== -1;
  };
}

Examples

Using includes()

const str = 'To be, or not to be, that is the question.' 

console.log(str.includes('To be'))        // true
console.log(str.includes('question'))     // true
console.log(str.includes('nonexistent'))  // false
console.log(str.includes('To be', 1))     // false
console.log(str.includes('TO BE'))        // false
console.log(str.includes(''))             // true

Specifications

Specification
ECMAScript (ECMA-262)
The definition of 'String.prototype.includes' in that specification.

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
includesChrome Full support 41Edge Full support 12Firefox Full support 40
Full support 40
No support 18¬†— 48
Alternate Name
Alternate Name Uses the non-standard name: contains
IE No support NoOpera Full support 28Safari Full support 9WebView Android Full support 41Chrome Android Full support 41Firefox Android Full support 40
Full support 40
No support 18¬†— 48
Alternate Name
Alternate Name Uses the non-standard name: contains
Opera Android Full support 28Safari iOS Full support 9Samsung Internet Android Full support 4.0nodejs Full support 4.0.0

Legend

Full support  
Full support
No support  
No support
Uses a non-standard name.
Uses a non-standard name.

See also