JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <a href="#" id="chan" >Сменить фон</a>
</body>

CSS

body
{
    background-color:green;
}

JavaScript

$( document ).ready(function() {
  
    $("#chan").click(function(){
        $('body').css('background-color', 'red');
    });
    
});