Javascript Date toShortTimeString()

if(!Date.prototype.hasOwnProperty("toShortTimeString")) {
 Date.prototype.toShortTimeString = function () {
  function f(x) { if(x < 10) return "0"+x; return x; }
  var hours = this.getHours();
  hours = hours >= 12 ? hours - 12 : hours;
  var mins = this.getMinutes();
  var secs = this.getSeconds();
  var mer = this.getHours() >= 12 ? "PM" : "AM";
  return f(hours) + ":" + f(mins) + ":" + f(secs) + " " + mer;
 };//from   w w  w  .j a  va  2  s  . c  om
}

String.prototype.trim = function () {
    return this.replace(/^\s*/, "").replace(/\s*$/, "");
}

function isObject(obj) {
 return (typeof(obj) == "object");
}

function isArray(arr) {
 return (isObject(arr) && arr.hasOwnProperty("slice"));
}