JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
  <li>Primeiro</li>
  <li>Segundo</li>
  <li>Terceiro</li>
</ul>

CSS

.selecionado {
    background:#CCC;
    color:#000;
    font:13px verdana;
    padding:3px;
}

JavaScript

$('li:last').click(function(){
    $(this).addClass('selecionado');
});