JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <div id="target3"></div>
</body>

CSS

#target3{
    width:100px;
    height:200px;
    background:#555;
    
    
}

JavaScript

var style3=createElement('style');
style3.type="text/css";
var target3=document.getElementById('target3');
target3.addEventListener('click',function(){

    style3.innerHTML='.target4{background-color:#444;}';
	document.getElementsByTagName('head')[0].appendChild(style3);
	target3.setAttribute('class','target4');
    
    });