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    String.prototype.includes()

    This is a new technology, part of the ECMAScript 2015 (ES6) standard .
    This technology's specification has been finalized, but check the compatibility table for usage and implementation status in various browsers.

    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 in this string at which to begin searching for searchString; defaults to 0.

    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 6 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() {'use strict';
        return String.prototype.indexOf.apply(this, arguments) !== -1;
      };
    }
    
    

    Specifications

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

    Browser compatibility

    Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
    Basic support 41 40 (40) Not supported Not supported Not supported
    Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
    Basic support Not supported Not supported 40.0 (40) Not supported Not supported Not supported

    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 behaviour of that check changed in a way that causes code based on MooTools' String.prototype.contains() implementation to break. As a result, this change was disabled in Firefox 17 and String.prototype.contains() was available one version later, in Firefox 18.

    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 6 signatures for this method differ (on the second argument). Later, MooTools 1.5+ changed the signature to match the ES6 standard.

    See also

    Document Tags and Contributors

    Last updated by: fscholz,
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