[NodeJS]核心模块--Events nodejs核心技术教程PDF

// musicPlayer.js
// 通过继承EventEmitter来实现一个基于事件的音乐播放器

var util = require("util");
var events = require("events");

function MusicPlayer(){
    this.playing = false;
        events.EventEmitter.call(this);
}

util.inherits(MusicPlayer, events.EventEmitter);


var audioDevice = {
    play: function(track){
        console.log("play in ", track);
    },
    stop: function(){
        console.log("stop play");
    }
};

// 实例化播放器类
var myMusicPlayer = new MusicPlayer();
myMusicPlayer.on('play', function() {
    this.playing = true;
});
myMusicPlayer.on('stop', function() {
    this.playing = false;
    audioDevice.stop();
});
myMusicPlayer.once('play', function(){
    console.log("begin play");
});
myMusicPlayer.on('play', function(track) {
    audioDevice.play(track);
});

myMusicPlayer.emit("play", "The roots - the fire");

setTimeout(function(){
    myMusicPlayer.emit("stop");
    setTimeout(function(){
        myMusicPlayer.emit("play", "Country Road");
    }, 3000);
}, 2000);

// musicPlayer 音乐播放器类升级版

var EventEmitter = require("events").EventEmitter;

function MusicPlayer(track){
    this.track = track;
    this.playing = false;

    for(var method in EventEmitter.prototype){
        this[method] = EventEmitter.prototype[method];
    }
}

MusicPlayer.prototype.toString = function(){
    if(this.playing){
        return "Now playing: " + this.track;
    }else{
        return "Stopped";
    }
};

var myMusicPlayer = new MusicPlayer("Girl Talk - Still Here");
myMusicPlayer.on('play', function() {
    this.playing = true;
    console.log(this.toString());
});

myMusicPlayer.on("stop", function(){
    this.playing = false;
    console.log(this.toString());
});

myMusicPlayer.emit("play");

setTimeout(function(){
    myMusicPlayer.emit("stop");
},3000);