timer.js

class Timer {
  
  static delay(delay) {
    return new Timer(
      (delay ? (fn) => { setTimeout(fn, delay) } : (fn) => { fn() }),
      (delay ? (id) => { clearTimeout(id) } : () => {})
    );
  }
  
  static interval(interval) {
    return new Timer(
      (fn) => { setInterval(fn, interval) },
      (id) => { clearInterval(id) }
    );
  }

  constructor(start, stop, tick = () => {}) {
    this._start = start;
    this._stop = stop;
    this._tick = tick;
  }
  
  timeout(duration) {
    const start = () => { this.start() };
    const stop = () => { this.stop() };
    return Timer.delay(duration).start(start).tick(stop).stop(stop);
  }

  start(fn) {
    if (fn) {
      return new Timer((tick) => { fn(tick); return this._start(tick); }, this._stop, this._tick);
    } else {
      this._id = this._start(() => { this._tick() });
      return this;
    }
  }
  
  stop(fn) {
    if (fn) {
      return new Timer(this._start, (id) => { this._stop(id); fn(id); }, this._tick);
    } else {
      this._stop(this._id);
      return this;
    }
  }
  
  tick(fn) {
    return fn ? new Timer(this._start, this._stop, () => { this.tick(); fn(); }) : this._tick();
  }
}