Method once

devtools/src/iframe-message-bus.ts:39–50

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

  }

  override once<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 any).apply(null, e.data.args);
        window.removeEventListener('message', listener);
      }
    };
    window.addEventListener('message', listener);
  }

  override emit<E extends keyof Events>(topic: E, args?: Parameters<Events[E]>): boolean {
    this.docWindow().postMessage(