code: function Timer(timer, clear, duration, fn) {
            this.start = +(new Date());
            this.duration = duration;
            this.clear = clear;
            this.timer = timer;
            this.fns = [fn];
          }
docs: Timer instance.
  
  @constructor
  @param {Object} timer New timer instance.
  @param {Function} clear Clears the timer instance.
  @param {Function} duration Duration of the timer.
  @param {Function} fn The functions that need to be executed.
  @api private