emitter.emit(eventName[, ...args])


按照监听器注册的顺序,同步地调用每个注册到名为 eventName 的事件的监听器,并传入提供的参数。

如果事件有监听器,则返回 true,否则返回 false

Synchronously calls each of the listeners registered for the event named eventName, in the order they were registered, passing the supplied arguments to each.

Returns true if the event had listeners, false otherwise.