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 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
Specification |
---|
ECMAScript (ECMA-262) The definition of 'String.prototype.includes' in that specification. |
Browser compatibility
BCD tables only load in the browser
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.