我们如何在所有HTML元素上嵌入自定义数据属性？
使用data-* 属性嵌入自定义数据属性。它由属性组成，该属性不应包含任何大写字母，并且应在data之后加上前缀。
示例
<!DOCTYPE html>
<html>
<head>
<script>
function display(rank) {
var myRank = rank.getAttribute("data-rank-type");
alert("Rank " + rank.innerHTML + " has " + myRank + " points.");
}
</script>
</head>
<body>
<h1>Rank and Points</h1>
<p>Click on any rank to generate the details.:</p>
<ul>
<li onclick = "display(this)" id = "fifth" data-rank-type = "500">Fifth</li>
<li onclick = "display(this)" id = "sixth" data-rank-type = "600">Sixth</li>
</ul>
</body>
</html>