Timers with Pause/Resume/Reset

timer.js

window.Timer = function(callback, duration = 500) {
  if (!callback) return;
  this.callback = callback;
  this.duration = duration;
  this.remaining = duration;
  this.resume();
};

Timer.prototype.resume = function() {
  this.start = new Date();
  this.timerId = setTimeout(this.callback, this.remaining);
};

Timer.prototype.pause = function() {
  window.clearTimeout(this.timerId);
  delete this.timerId;
  this.remaining -= new Date() - this.start;
};

Timer.prototype.reset = function() {
  this.pause();
  this.remaining = this.duration;
};

Timer.prototype.clone = function () {
  return new Timer(this);
};

Timer.prototype.toJSON = function () {
  var ownData = {};
  Object.keys(this).forEach(function (pn) {
    ownData[pn] = clone(this[pn]);
  }, this);
  return JSON.reviveWrapper('new Timer($ReviveData$)', ownData);
};