<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.min.js"></script>
</head>
<body>
<div>
<audio id="audio" controls src="http://m10.music.126.net/20170719161110/02863ba74071062bce6dd56bf5907797/ymusic/450e/0b69/b118/e3a5be41869989ca3723c8cca2bf82ad.mp3">
</audio>
<button id="down">↓</button>
<button id="up">↑</button>
</div>
</body>
<script>
$(function(){
let vol = $('#audio')[0].volume;
$('#audio').on('canplay',function(){
this.play()
});
$('#down').click(function(){
console.log( vol)
vol =vol>0?(vol*10 -1)/10:0;
$('#audio')[0].volume = vol;
})
$('#up').click(function(){
console.log( vol)
vol =vol<1?(vol*10 +1)/10:1;
$('#audio')[0].volume = vol;
})
})
</script>
</html>
