This is my `Array.prototype.map` polyfill.

map-polyfill.js

/**
 * Author: Alex Chao(alexchao1990@gmail.com)
 * Date: 2014-08-01
 */

/**
 * Note: You can choose the other polyfill which is compatible with ECMA-262, 5th edition
 * Url: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map
 */

// test
// Array.prototype.map = void 0;
 
// For array and array-like objects
if (typeof Array.prototype.map != 'function') {
    Array.prototype.map = function(callback, thisArg) {
        if (typeof this.length != 'number') return;
        if (typeof callback != 'function') return;
 
        var newArr = [];
 
        if (typeof this == 'object') {

            for (var i = 0; i < this.length; i++) {
                if (i in this) {
                    newArr[i] = callback.call(thisArg || this, this[i], i, this);
                } else {
                    return;
                }
            }
        }
 
        return newArr;
    };
}