JSFiddle - React, Tailwind, and code Playground

HTML

<div id="Element" class="hidden">lorum</div>

<a href="#" onclick="$('#Element').removeClass('visible').addClass('hidden'); return false;">toggle class</a>

CSS

.hidden {
    display: none;
}

.visible {
    display: block;
}

JavaScript

function checkIt () {
    if($('#Element').is(':hidden') == true) {
       // add class name
        alert('Element was hidden');
        $('#Element').removeClass('hidden').addClass('visible');
       
        // or toggle class name
        //$('#Element').toggleClass('className');
        
        // or remove class name
        //$('#Element').removeClass('className');
        
        // if you want to clear the interval
        //clearInterval(listenerID);
    }
}

var listenerID;
$(function(){
    listenerID = setInterval(checkIt, 500);
});