Method on

devtools/src/iframe-message-bus.ts:22–37

(topic: E, cb: Events[E])

  }

  override on<E extends keyof Events>(topic: E, cb: Events[E]): () => void {
    const listener = (e: MessageEvent) => {
      if (!e.data || e.data.source !== this.destination || !e.data.topic) {
        return;
      }
      if (e.data.topic === topic) {
        (cb as () => void).apply(null, e.data.args);
      }
    };
    window.addEventListener('message', listener);
    this.listeners.push(listener);
    return () => {
      this.listeners.splice(this.listeners.indexOf(listener), 1);
      window.removeEventListener('message', listener);
    };
  }

  override once<E extends keyof Events>(topic: E, cb: Events[E]): void {
    const listener = (e: MessageEvent) => {