JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <a href="#" class="bg_fon">Изменить фон</a>
</body>

CSS

body {
	background:#FFF ;
}

body.alternate-bg {
	background: #3e8c7d;
	}

JavaScript

$(document).ready(function(){
	$(".bg_fon").click(function () {
		$(document.body).toggleClass("alternate-bg");
		});
	});