Method doWrite

packages/engine.io-client/lib/transports/polling-fetch.ts:27–39

(data: string, callback: () => void)

  }

  override doWrite(data: string, callback: () => void) {
    this._fetch(data)
      .then((res) => {
        if (!res.ok) {
          return this.onError("fetch write error", res.status, res);
        }

        callback();
      })
      .catch((err) => {
        this.onError("fetch write error", err);
      });
  }

  private _fetch(data?: string) {
    const isPost = data !== undefined;