_close(code?: number, reason?: string): void {
    if (WebSocketModule.close.length === 3) {
      // See https://developer.mozilla.org/en-US/docs/Web/API/CloseEvent
      const statusCode = typeof code === 'number' ? code : CLOSE_NORMAL;
      const closeReason = typeof reason === 'string' ? reason : '';
      WebSocketModule.close(statusCode, closeReason, this._socketId);
    } else {
      WebSocketModule.close(this._socketId);
    }