Random JS Array Element, Different than the Last One

random_diff_element.js

// via http://stackoverflow.com/questions/4550505/getting-random-value-from-an-array
// usage: var myRandomDiffElement = myArray.randomDiffElement(lastRandomElement);
Array.prototype.randomDiffElement = function(last) {
   if (this.length == 0) {
      return;
   } else if (this.length == 1) {
      return this[0];
   } else {
      var num = 0;
      do {
         num = Math.floor(Math.random() * this.length);
      } while (this[num] == last);
      return this[num];
   }
}