example.js

$(function() {
  function render($el, timer, timestamp) {
    var seconds = Math.round((timestamp - timer.timestamp) / timer.delay);
    var minutes = (seconds - seconds % 60) / 60;
    seconds = seconds % 60;
    if (String(seconds).length == 1) {
      seconds = '0' + seconds;
    }
    var timeDisplay = minutes + ':' + seconds;
    if (minutes >= 60) {
      var hours = (minutes - minutes % 60) / 60;
      minutes = minutes % 60;
      if (String(minutes).length == 1) {
        minutes = '0' + minutes;
      }
      timeDisplay = hours + ':' + minutes + ':' + seconds;
    }
    $($el).text(timeDisplay);
  }
  $('.timer').each(function() {
    var $this = $(this);
    var timer = Timer({
      timestamp: Number($this.attr('data-timestamp')),
    });
    timer.afterTick = render.bind($this, $this, timer);
    $this.data('timer', timer.tick());
  });
});

extend.js

function extend() {
  var result = arguments[0];
  for(var i = 1; i < arguments.length; i++) {
    for(var key in arguments[i]) {
      result[key] = arguments[i][key];
    }
  }
  return result;
}

Timer.js

function Timer() {
  var _this = {};
  return extend.bind(this, _this, {
    timestamp: new Date().getTime(),
    timeout: -1,
    delay: 1000,
    tick: function(timestamp) {
      var timestamp = timestamp || this.now();
      this.timeout = setTimeout(function() {
      var timestamp = _this.now();
        _this.tick(timestamp);
        _this.afterTick(timestamp);
      }, this.nextTickDelay(timestamp));
      return this;
    },
    stop: function() {
      clearTimeout(this.timeout);
      return this;
    },
    nextTickDelay: function(timestamp) {
      return this.delay - ((timestamp - this.timestamp) % this.delay);
    },
    now: function() {
      return new Date().getTime();
    },
    afterTick: Function(),
  }).apply(this, arguments);
}