JSFiddle - React, Tailwind, and code Playground

HTML

<div id="my_div" class="test classes are fun things"></div>

<input type="button" id="testbutton" value="test classes" />
<input type="button" id="removebutton" value="remove classes" />

JavaScript

$(document).ready(function() {
    $('#testbutton').click(function() {
        alert($('#my_div').attr('class'));
    });
    
    $('#removebutton').click(function() {
        $('#my_div').attr('class', 'fun');
    });
});