interface EventTarget {
  /**
   *
   * @param eventName the name of the event, such as click. This parameter is optional.
   *
   * Remove all event listeners attached to the event target, if the eventName parameter
   * is provided, will remove event listeners of specified event, if the eventName is
   * is not provided, will remove all event listeners of the event target.
   */
  removeAllListeners(eventName?: string): void;
  /**
   *
   * @param eventName the name of the event, such as click. This parameter is required.
   *
   * Get all event listeners of the specified event. return an array of event handler or
   * event listener object.
   */
  eventListeners(eventName: string): EventListenerOrEventListenerObject[];
}