A timer class. Based on: require.js, extend.js https://github.com/amatiasq/ , EventEmitter https://github.com/otorras/basics

timer.js

define(['core/extend', 'core/emitter'], function(extend, EventEmitter) {
  'use strict';

  var Timer = extend(EventEmitter, {
    constructor: function(precision) {
      this.precision = precision;
      this.watchers = [];
      this.ticks = 0;
      this.tick = this.tick.bind(this);
    },

    start: function() {
      this.handler = setInterval(this.tick, this.precision);
      return this;
    },

    stop: function() {
      this.pause();
      this.emit('stop', this.ticks, this.precision);
      return this;
    },

    pause: function() {
      if (this.handler) {
        clearInterval(this.handler);
        delete this.handler;
      }
    },

    reset: function() {
      this.pause();
      this.watchers.length = 0;
      this.ticks = 0;
    },

    addWatcher: function(time, listener) {
      this.watchers[time] = listener;
    },

    tick: function() {
      ++this.ticks;
      this.emit('tick', this.ticks, this.precision);
      var stopWatch = this.watchers[this.ticks * this.precision];
      if (stopWatch) { stopWatch(); }
    }
  }, {
    second: 1000,
    minute: 60 * 1000,
    hour: 60 * 60 * 1000
  });

  return Timer;
});