/**

 * Format a date using PHP date shorthand

 * @param {Date} date - A Javascript Date object

 * @param {String} format - The format of the outputted date

 * @returns {String} - The formatted date

 */

function formatDate(date, format) {

  if (isNaN(date.getTime())) return "Invalid Date";

  var months = ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];

  var days = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"];

​

  var buffer = []; 

  for(var i=0; i<format.length; i++){

    switch(format[i]){

      // If the current char is a "\" then skip it and add then next literal char

      case "\\": buffer.push(format[++i]); break;

​

      // Symbols that represent numbers

      case "Y": buffer.push("" + date.getFullYear()); break;

      case "y": buffer.push(("" + date.getFullYear()).substring(2)); break;

      case "m": buffer.push(("0" + (date.getMonth() + 1)).substr(-2, 2)); break;

      case "n": buffer.push("" + (date.getMonth() + 1)); break;

      case "t": buffer.push("" + new Date(date.getFullYear(), date.getMonth() - 1, 0).getDate()); break; 

      case "d": buffer.push(("0" + date.getDate()).substr(-2, 2)); break;

      case "j": buffer.push(date.getDate() + ""); break;

      case "w": buffer.push(date.getDay()); break;

      case "g": buffer.push("" + (date.getHours() > 12 ? date.getHours() - 12 : date.getHours())); break;

      case "G": buffer.push("" + (date.getHours() + 1)); break;

      case "h": buffer.push(("0" + (date.getHours() > 12 ? date.getHours() - 12 : date.getHours())).substr(-2, 2)); break;

      case "H": buffer.push(("0" + (date.getHours() + 1)).substr(-2, 2)); break;

      case "i": buffer.push(("0" + date.getMinutes()).substr(-2, 2)); break;

      case "s": buffer.push(("0" + date.getSeconds()).substr(-2, 2)); break;

​

      // Symbols that represent text

      case "a": buffer.push(date.getHours() > 11 ? "pm" : "am"); break;

      case "A": buffer.push(date.getHours() > 11 ? "PM" : "AM"); break;

      case "l": buffer.push(days[date.getDay()]); break;

      case "D": buffer.push(days[date.getDay()].substr(0, 3)); break;

      case "F": buffer.push(months[date.getMonth()]); break;

      case "M": buffer.push(months[date.getMonth()].substring(0, 3)); break;

      default: buffer.push(format[i]); break;

    }

  }

  return buffer.join('');

}

​

// Use it as a helper function

alert(formatDate(new Date(), 'l, F j g:i A'));

​

// Or add it to the Date object for convenience 

Date.prototype.format = function(format){

  return formatDate(this, format);

};

alert(new Date().format('\\T\\o\\d\\a\\y \\i\\s m/d/y g:i:s a'));