JSFiddle - React, Tailwind, and code Playground

HTML

<div class="box">TEXT</div>

CSS

.box {color:green;}
    .box:hover {color:blue;}

JavaScript

var rules = [];
if (document.styleSheets[2].cssRules)
    rules = document.styleSheets[2].cssRules;
else if (document.styleSheets[2].rules)
    rules = document.styleSheets[2].rules;
console.log(rules);
rules[0].style.color = 'red';