addEventListener不'；不能用javascript响应

addEventListener在“var播放按钮”部分工作不正常。我做错了什么

在控制台中运行playlist.prototype.play功能时。该代码可以运行，但我似乎无法将其绑定到HTML按钮

function mediaPlayer(title, artist){
    this.title = title;
    this.artist = artist;
}

var songOne = new Audio('media/song_1.mp3');
var songTwo = new Audio('media/song_2.mp3');
var songThree = new Audio('media/song_3.mp3');
var songFour = new Audio('media/song_4.mp3');
var songFive = new Audio('media/song_5.mp3');

mediaPlayer.prototype = Object.create(playlist.prototype);

function playlist(){
    this.mediaList = [songOne, songTwo, songThree, songFour, songFive];
    this.nowPlayingIndex = 0;
}

function viewPlaylist(){
    playlist.call(this);
    for(var i = 0; i < mediaList.length; i++){
        console.log(mediaList[i]);
    }
}


playlist.prototype.play = function(){
    var currentMedia = this.mediaList[this.nowPlayingIndex];
    console.log(currentMedia);
    currentMedia.play();

}

var playButton = document.getElementById("playButton");
    playButton.addEventListener('click', function(){
    currentMedia.play();
    document.getElementById("nowPlayingSpan").innerHTML = currentMedia;
    document.getElementById("upNextSpan").innerHTML = currentMedia[1];
}) ;

playlist.prototype.pause = function(){
    var currentMedia = this.mediaList[this.nowPlayingIndex];
    currentMedia.pause();
}

var pauseButton = document.getElementById("pauseButton");
    pauseButton.addEventListener('click', function(){
    currentMedia.pause();   
}) ;

功能mediaPlayer（标题、艺术家）{
this.title=标题；
这个艺术家=艺术家；
}
var songOne=新音频（“媒体/歌曲1.mp3”）；
var songTwo=新音频（'media/song_2.mp3'）；
var songThree=新音频（'media/song_3.mp3'）；
var songFour=新音频（“媒体/歌曲4.mp3”）；
var songFive=新音频（“媒体/song_5.mp3”）；
mediaPlayer.prototype=Object.create（playlist.prototype）；
函数播放列表（）{
this.mediaList=[songOne，songTwo，songThree，songFour，songFive]；
此.nowPlayingIndex=0；
}
函数viewPlaylist（）{
播放列表。呼叫（此）；
对于（var i=0；i
因为
cuurrentMedia
未在
addEventListener
范围内声明，所以您应该将
cuurrentMedia
替换为
playlist.mediaList[playlist.nowPlayingIndex]
您在函数内定义了当前媒体，并且它只属于该函数（当前媒体的范围就是函数）

}

将其单独定义为全局变量，并在函数内赋值

var currentMedia = {};
playlist.prototype.play = function(){
    currentMedia = this.mediaList[this.nowPlayingIndex];
    console.log(currentMedia);
    currentMedia.play();
}

因为未定义
currentMedia
，谢谢您的回复。我现在得到未捕获的TypeError:currentMedia.play不是HTMLLIElement上的函数。请尝试currentMedia.get（0.play（）；
var currentMedia = {};
playlist.prototype.play = function(){
    currentMedia = this.mediaList[this.nowPlayingIndex];
    console.log(currentMedia);
    currentMedia.play();
}