Method requestOnce

3p/iframe-messaging-client.js:89–96

* Make a one time event listening request. * Will unlisten after response is received. * * @param {string} requestType The type of the request message. * @param {string} responseType The type of the response message. * @param {function(Object)} callback The callback function to call

(requestType, responseType, callback)

   * @return {*} TODO(#23582): Specify return type
   */
  requestOnce(requestType, responseType, callback) {
    const unlisten = this.registerCallback(responseType, (event) => {
      unlisten();
      callback(event);
    });
    this.sendMessage(requestType);
    return unlisten;
  }

  /**
   * Register callback function for message with type messageType.