Node.js EventEmitter emitter.emit(eventName[, ...args])用法及代碼示例

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

參數

• eventName <string> | <symbol>
• ...args <any>
• 返回： <boolean>

同步調用為名為 eventName 的事件注冊的每個偵聽器，按照它們注冊的順序，將提供的參數傳遞給每個偵聽器。

如果事件有監聽器，則返回true，否則返回false。

const EventEmitter = require('node:events');
const myEmitter = new EventEmitter();

// First listener
myEmitter.on('event', function firstListener() {
  console.log('Helloooo! first listener');
});
// Second listener
myEmitter.on('event', function secondListener(arg1, arg2) {
  console.log(`event with parameters ${arg1}, ${arg2} in second listener`);
});
// Third listener
myEmitter.on('event', function thirdListener(...args) {
  const parameters = args.join(', ');
  console.log(`event with parameters ${parameters} in third listener`);
});

console.log(myEmitter.listeners('event'));

myEmitter.emit('event', 1, 2, 3, 4, 5);

// Prints:
// [
//   [Function: firstListener],
//   [Function: secondListener],
//   [Function: thirdListener]
// ]
// Helloooo! first listener
// event with parameters 1, 2 in second listener
// event with parameters 1, 2, 3, 4, 5 in third listener