JSFiddle - React, Tailwind, and code Playground
by Tyler
HTML
<div>
<h3>Light DOM</h3>
<section>
<div>I'm not underlined</div>
<p>I'm underlined in Shadow DOM!</p>
</section>
</div>
JavaScript
var div = document.querySelector('div');
var root = div.createShadowRoot();
root.innerHTML = '\
<style>\
h3 { color: red; }\
content[select="h3"]::content > h3 {\
color: green;\
}\
::content section p {\
text-decoration: underline;\
}\
</style>\
<h3>Shadow DOM</h3>\
<content select="h3"></content>\
<content select="section"></content>';