Web/JavaScript/Reference/Global objects/String/includes

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

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

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

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

Update compatibility data on GitHub

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
includes	Chrome Full support 41	Edge Full support 12	Firefox Full support 40 Full support 40 No support 18 — 48 Alternate Name' Alternate Name' Uses the non-standard name: contains	IE No support No	Opera Full support 28	Safari Full support 9	WebView Android Full support 41	Chrome Android Full support 41	Firefox 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 28	Safari iOS Full support 9	Samsung Internet Android Full support 4.0	nodejs 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

• Array.prototype.includes()
• TypedArray.prototype.includes()
• String.prototype.indexOf()
• String.prototype.lastIndexOf()
• String.prototype.startsWith()
• String.prototype.endsWith()

String.prototype.includes() by Mozilla Contributors is licensed under CC-BY-SA 2.5.