emitter.listenerCount(eventName)

• eventName <string> | <symbol> 正在监听的事件的名称
• 返回: <integer>

返回监听名为 eventName 的事件的监听器数量。

• eventName <string> | <symbol> The name of the event being listened for
• Returns: <integer>

Returns the number of listeners listening to the event named eventName.