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 this string.
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

Examples

Using includes()

var 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

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) {
  Object.defineProperty(String.prototype, 'includes', {
    value: function(search, start) {
      if (typeof start !== 'number') {
        start = 0
      }
      
      if (start + search.length > this.length) {
        return false
      } else {
        return this.indexOf(search, start) !== -1
      }
    }
  })
}

Specifications

Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'String.prototype.includes' in that specification.
Standard Initial definition.
ECMAScript Latest Draft (ECMA-262)
The definition of 'String.prototype.includes' in that specification.
Draft  

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung InternetNode.js
Basic supportChrome Full support 41Edge Full support YesFirefox 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 YesSafari Full support 9WebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox 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 YesSafari iOS Full support 9Samsung Internet Android Full support Yesnodejs Full support 4.0.0

Legend

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

String.prototype.contains

In Firefox 18 - 39, the name of this method was contains(). It was renamed to includes() in bug 1102219 due to the following reason:

It's been reported that some websites using MooTools 1.2 broke on Firefox 17. This version of MooTools checks whether String.prototype.contains() exists and, if it doesn't,  MooTools adds its own function. With the introduction of this function in Firefox 17, the behavior of that check changed in a way that causes code based on MooTools' String.prototype.contains() implementation to break. As a result, the implementation was disabled in Firefox 17 and String.prototype.contains() was available one version later, in Firefox 18, when outreach to MooTools was leading to the release of MooTools version 1.2.6.

MooTools 1.3 forces its own version of String.prototype.contains(), so websites relying on it should not break. However, you should note that MooTools 1.3 signature and ECMAScript 2015 signatures for this method differ (on the second argument). Later, MooTools 1.5+ changed the signature to match the ES2015 standard.

In Firefox 48, String.prototype.contains() has been removed. Use String.prototype.includes() only.

See also