Array.prototype.in_array = function(search_term) {

  var i = this.length;

	do {

		if (this[i] === search_term) return true;

	} while (i--);

  return false;

}



// Returns all the elements of second_array that are not in this array.

Array.prototype.diff = function(second_array) {

  var return_array = Array();

	var i = second_array.length;

	var j = 0;

	do {

		if (!this.in_array(second_array[i])) {

			return_array[j++] = second_array[i];

		}

	} while (i--);

	return return_array;

}