JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>

<html>
<head>
<meta charset="UTF-8">
<style type="text/css">
div {
  display: block;
  width: 200px;
  height: 200px;
  background: red;
}
div:hover {
  background: green;
}
</style>
</head>
<body>

<div></div>

<script type="text/javascript">
window.onload = function () {
    var div = document.getElementsByTagName("div")[0];
    var style = window.getComputedStyle(div, "hover");
    alert(style.backgroundColor);
};
</script>
</body>
</html>