Node.js EventEmitter emitter.rawListeners(eventName)用法及代碼示例

emitter.rawListeners(eventName)

參數

• eventName <string> | <symbol>
• 返回： <Function[]>

返回名為 eventName 的事件的偵聽器數組的副本，包括任何包裝器(例如由 .once() 創建的包裝器)。

const emitter = new EventEmitter();
emitter.once('log', () => console.log('log once'));

// Returns a new Array with a function `onceWrapper` which has a property
// `listener` which contains the original listener bound above
const listeners = emitter.rawListeners('log');
const logFnWrapper = listeners[0];

// Logs "log once" to the console and does not unbind the `once` event
logFnWrapper.listener();

// Logs "log once" to the console and removes the listener
logFnWrapper();

emitter.on('log', () => console.log('log persistently'));
// Will return a new Array with a single function bound by `.on()` above
const newListeners = emitter.rawListeners('log');

// Logs "log persistently" twice
newListeners[0]();
emitter.emit('log');