JSFiddle - React, Tailwind, and code Playground

HTML

<button class="button oldClass">Button</button>
<button id="test">Add New Class</button>

CSS

.oldClass {
    color: red;
}
.newClass {
    color: green;
}

JavaScript

$('#test').click(function() {
    $('.button').removeClass('oldClass');
    $('.button').addClass('newClass');
});
$('.button').click(function() {
    if($(this).hasClass('newClass')) {
        //Code for new class click
        alert("test");
    }
});