在间隔之后，等待歌曲在iframe音频播放器中结束，然后再在父级中运行功能

如何解决在间隔之后，等待歌曲在iframe音频播放器中结束，然后再在父级中运行功能

我正在尝试制作一个本地html音频播放器，以在具有多个音频播放器的页面之间随机播放。我希望随机播放每30分钟发生一次，但我希望它能等到第一个音频播放器播放完曲目后再运行随机播放功能。

我在获取主窗口来访问iframe中的音频播放器时遇到麻烦，并且我也对如何在setinterval命令中调用事件监听器感到困惑。 这是我的代码：

主页：

<iframe src="sPLIF.html" height="200" width="900" frameborder="0" id="pmframe" title="PLIF Player"></iframe>

<script>
    var lastSong = null;
    var selection = null;
    var playlist = [
    "PLIF1/plif1.html","PLIF200703/PLIF200703.html","PLIF200802/PLIF200802.html","PLIF200808/PLIF200808.html","PLIF200816/PLIF200816.html","PLIF200823/PLIF200823.html","PLIF_Noir/PLIF_Noir.html","PLIF3_Dream/plif3_dream.html","sPLIF.html"]; 
   
    var player = document.getElementById("pmframe");
    function selectRandom(){
        while(selection == lastSong){
        selection = Math.floor(Math.random() * playlist.length);
    }
        lastSong = selection; 
        player.src = playlist[selection]; 

    }
    
    selectRandom(); 
    setInterval(endSong,1800000); 

var alto = document.getElementById("pmframe").contentWindow.player;
  
setTimeout(endSong,1800000); 

function endSong(){
    alto.addEventListener("ended",selectRandom);
}
    
</script>

和一个示例iframe页面：

<audio id="alto" autoplay>
<source src="alto.m4a" type="audio/m4a">
</audio>

<audio id="drums" autoplay>
<source src="drums.m4a" type="audio/m4a">
</audio>



<script>
    var lastSong = null;
    var selection = null;
    var playlist = [
    "alto1x.m4a","alto1x.m4a","pause.m4a"]; 
    var player = document.getElementById("alto"); 
    player.autoplay=true;
    player.addEventListener("ended",selectRandom);

    function selectRandom(){
        selection = Math.floor(Math.random() * playlist.length);
        lastSong = selection; 
        player.src = playlist[selection]; 
    }

    selectRandom(); 
    player.play(); 
</script>

<script>
    var lastSong2 = null;
    var selection2 = null;
    var playlist2 = ["drums1x.m4a","drums1x.m4a","pause30s.m4a"]; 
    var player2 = document.getElementById("drums"); 
    player2.autoplay=true;
    player2.addEventListener("ended",selectRandom2); 

    function selectRandom2(){
        selection2 = Math.floor(Math.random() * playlist2.length);
        lastSong2 = selection2; 
        player2.src = playlist2[selection2]; 
    }

    selectRandom2(); 
    player2.play(); 
</script>