JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li><a href="#">List Item 1</a></li>
    <li><a href="#">List Item 2</a></li>
    <li><a href="#">List Item 3</a></li>
    <li><a href="#">List Item 4</a></li>                        
   </ul>

CSS

.on { background-color:red; }

JavaScript

$('a').click(function(){    
      //alert('on'); WORKING
      $(this).addClass('on');
    
    });