TimeCounter: jQuery plugin object to display count from certain time

timecounter.js

(function($) {
  function TimeCounter($clock, $start) {
    var that = this;
    this.$clock = $clock;
    this.$start = $start;
    this.since = new Date(this.$start.text());
    self.setTimeout(function() { that.init(); }, 200);
  }

  // FIXME Use DateDiff object instead.
  // SEE https://gist.github.com/1563963
  TimeCounter.prototype.convert = function(ms) {
    var d, h, m, s, t;
    s = Math.floor(ms / 1000);
    m = Math.floor(s / 60);
    s = s % 60;
    h = Math.floor(m / 60);
    m = m % 60;
    d = Math.floor(h / 24);
    h = h % 24;
    t = this.padLeft(d, 0, 3);
    t += ':' + this.padLeft(h, 0, 2);
    t += ':' + this.padLeft(m, 0, 2);
    t += ':' + this.padLeft(s, 0, 2);
    return t;
  };

  TimeCounter.prototype.init = function() {
    this.print();
  };

  TimeCounter.prototype.padLeft = function(str, chr, len) {
    var padding = '';
    str = str + '';
    for(var i = 0; i < len - str.length; i++) {
      padding += chr;
    }
    return padding + str;
  };

  TimeCounter.prototype.print = function() {
    var that = this;
    var clock = this.convert(new Date() - this.since);
    this.$clock.text(clock);
    self.setTimeout(function() { that.print(); }, 50);
  };

  $.fn.timeCounter = function($start) {
    if(!this.data('timeCounter'))
      this.data('timeCounter', new TimeCounter(this, $start));
    return this.data('timeCounter');
  };

  /* Usage example */
  // $(document).ready(function() {
  //   $('.post strong').timeCounter($('.post em'));
  // });
})(jQuery);