JSFiddle - React, Tailwind, and code Playground

HTML

<div id="id1" class="class1"><h2>Title</h2>
<p>
News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News 
</p></div>
<div id="id2" class="class2"><h2>Title</h2>
<p>
News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News 
</p></div>


<div id="id3" class="class2"><h2>Title</h2>
<p>
News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News 
</p></div>


<div id="id4" class="class2"><h2>Title</h2>
<p>
News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News 
</p></div>


<div id="id5" class="class2"><h2>Title</h2>
<p>
News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News News 
</p></div>


<div id="id6" class="class2"><h2>Title</h2>
<p>
News News News...

CSS

.class1 {
	background:#FF0000;
}
.class2 {
	background:#fff;
}
.class1,.class2 {
-moz-transition: all 1.5s linear .2ms;
-o-transition:all 15s linear .2ms;
-webkit-transition: all 1.5s linear .2ms;
transition: all 1.5s linear .2ms;
}

JavaScript

function myFunction()
{
setTimeout(function(){document.getElementById('id1').className='class2'},5000);
}
myFunction()