An extension to the Array class that returns a shuffled version of an array

array_shuffle.js

/*
 * Array.shuffle
 *
 * Usage:
 *   const arr1 = [1, 2, 3, 4, 5];
 *   const arr2 = Array.shuffle(arr1);
 *   const arr3 = arr1.shuffle();
 *
 * @TODO:
 * - Add callback functionality to Array.prototype.shuffle
 */

if (!Array.shuffle) {
  Array.shuffle = function(items) {
    var currentIndex = items.length, temporaryValue, randomIndex;

    while (0 !== currentIndex) {
      randomIndex = Math.floor(Math.random() * currentIndex);
      currentIndex -= 1;

      temporaryValue = items[currentIndex];
      items[currentIndex] = items[randomIndex];
      items[randomIndex] = temporaryValue;
    }

    return items;
  }
}

if(!Array.prototype.shuffle) {
  Array.prototype.shuffle = function() {
    return Array.shuffle(this);
  }
}