The includes()
method performs a case-sensitive search to determine whether one string may be found within another string, returning true
or false
as appropriate.
String.prototype.includes()
Try it
Syntax
includes(searchString) 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 to0
.)
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
Browser compatibility
Desktop | Mobile | Server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | Deno | Node.js | |
includes |
41
|
12
|
40
18-48
|
No
|
28
|
9
|
41
|
41
|
40
18-48
|
28
|
9
|
4.0
|
1.0
|
4.0.0
|
See also
© 2005–2022 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/includes