

哈哈 是我太弱了
<!DOCTYPE html>
<html>
<head>
<title>dataset</title>
<meta charset="utf-8">
</head>
<body>
<p id='p' data-index='demo'>
</p>
</body>
<script type="text/javascript">var a = document.getElementById('p');
console.log(a)
console.log(a.dataset.index)//demo</script>
</html>直接用dataset就可以获取到DOM元素的data属性
好吧,还可以 用js的获取属性的方法getAttribute()
a.getAttribute('data-index')==>"demo"