Dive Into JavaScript

JavaScript Array forEach

The JavaScript Array forEach method executes a user-defined function for each element of an array.

Syntax

array.forEach(callback [, contextObject])

Parameters

callback

The callback function to execute for each element

contextObject

Object to be used as a context for the callback function

Description

The JavaScript ArrayforEach method iterates over and applies the callback function to each element of an array.

The callback function is invoked with three arguments: the value of the element, the index of the element and the Array object being traversed.

Cross-browser Array forEach

For browsers that don't support the Array forEach method, here's an alternative implementation:

/**
 * Copyright (c) Mozilla Foundation http://www.mozilla.org/
 * This code is available under the terms of the MIT License
 */
if (!Array.prototype.forEach) {
    Array.prototype.forEach = function(fun /*, thisp*/) {
        var len = this.length >>> 0;
        if (typeof fun != "function") {
            throw new TypeError();
        }

        var thisp = arguments[1];
        for (var i = 0; i < len; i++) {
            if (i in this) {
                fun.call(thisp, this[i], i, this);
            }
        }
    };
}

See also

• The JavaScript Array Object
• JavaScript Array every
• JavaScript Array filter
• JavaScript Array map
• JavaScript Array reduce
• JavaScript Array reduceRight
• JavaScript Array some