javascript - 为什么我无法从 Node.js 中的扩展 EventEmitter 类捕获事件？

Question

我一直在绞尽脑汁思考为什么我无法捕获 Node.js 中这段代码发出的事件。我的直觉是有些东西超出了范围，但我不知道它是什么。 index.js 中的 console.log 代码行永远不会被执行。我的事件没有被发出吗？

player.js

const EventEmitter = require('events').EventEmitter;

class rocketPlayer extends EventEmitter {
  constructor(options) {
    super(options);
  }

  update(connection) {
    //do some logic with playlists
    this.play(connection);
  }

  play(connection) {
    // do some stuff
    this.emit('nowPlaying',song.title);
  }
}

module.exports = rocketPlayer

index.js

const rocketPlayer = require('./player.js');
const player = new rocketPlayer();

player.on('nowPlaying', title => {
  console.log('caught nowPlaying event');
});

//define a connection
player.update(connection)

Answer 1

你有一些拼写错误:你的听众后面缺少一个括号。您也没有正确地将构造函数参数传递给 super 构造函数。以下代码对我有用:

const EventEmitter = require('events').EventEmitter;

class rocketPlayer extends EventEmitter {
  constructor(options) {
    super(options);
  }

  update(connection) {
    //do some logic with playlists
    this.play(connection);
  }

  play(connection) {
    // do some stuff
    this.emit('nowPlaying', 'song.title');
  }
}

const player = new rocketPlayer();

player.on('nowPlaying', title => {
  console.log('caught nowPlaying event');
}); // <= fixed missing bracket

//define a connection
player.update('connection');

注意:由于您没有定义歌曲，我只是将其转换为字符串