<style>
<p>hello world</p>
{}
p {
color: red;
}
{}
<em style="padding: 4px; color: blue">hello ajanuw</em>
{}
</style>
<body>
<div id="box"></div>
<script>
let tags = [];
let box = document.getElementById('box');
let sty = document.getElementsByTagName('style')[0]
sty.innerHTML.replace(/(<.*|>\/>)/gm, $_ => tags.push($_) );
box.innerHTML = tags.join(' ');
</script>
</body>
原文：https://www.cnblogs.com/ajanuw/p/9369085.html