JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html class="bg">
<head>
</head>

<body>
    Test
    <br>
    <button id="toggle">Toggle HTML background</button>
</body>
</html>

CSS

html.bg {
    background: blue;
}

body {
    background: yellow;
}


html {
    margin:50px;
    border:4px solid red;
    padding:20px;
}

JavaScript

$("#toggle").click(function(){
    $("html").toggleClass("bg");
});