class Subscribable {
  constructor() {
    this.listeners = new Set();
    this.subscribe = this.subscribe.bind(this);
  }

  subscribe(listener) {
    const identity = {
      listener
    };
    this.listeners.add(identity);
    this.onSubscribe();
    return () => {
      this.listeners.delete(identity);
      this.onUnsubscribe();
    };
  }

  hasListeners() {
    return this.listeners.size > 0;
  }

  onSubscribe() {// Do nothing
  }

  onUnsubscribe() {// Do nothing
  }

}

export { Subscribable };
//# sourceMappingURL=subscribable.mjs.map