JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.7.1/jquery.min.js"></script>
<button id="MyDiv1" class="oldclass">Age</button>

JavaScript

$().ready(function(){
 
 
 $('.oldclass').click(function(){
 alert('I am old'); 
 });

 $('.youngclass').click(function(){
 
 alert('I am young');
 });

$('#MyDiv1').removeClass('oldclass').addClass('youngclass'); 
});