Javascript Array reduce_a_fraction()

Array.prototype.reduce_a_fraction = function () {
 var m = this[0];
 var n = this[1];
 var a = (m < n) ? m : n;
 while (true) {/*from   www .  j  a va2 s . c o  m*/
  if (m % a == 0 && n % a == 0) break;
  a--;
 }
 return [m / a, n / a];
}

NodeList.prototype.map = function (callback) {
 for (var i = 0; i < this.length; i++) callback(this[i]);
}