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


str.includes(searchString[, position])


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.


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


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

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


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


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


Browser compatibilityUpdate compatibility data on GitHub

Chrome Edge Firefox Internet Explorer Opera Safari
Basic support 41 Yes 40
18 — 48
Uses the non-standard name: contains
No Yes 9
Android webview Chrome for Android Edge Mobile Firefox for Android Opera for Android iOS Safari Samsung Internet
Basic support Yes Yes Yes 40
18 — 48
Uses the non-standard name: contains
Yes 9 Yes
Basic support 4.0.0


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

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