JSFiddle - React, Tailwind, and code Playground

HTML

<div class="example">
				A div with class="example"
		</div>

		<div class="example">
				Another div with class="example"
		</div>

		<p class="example">This is a p element with class="example".</p>

		<p>This is a <span class="example">span</span> element with class="example" inside another p element.</p>

		<p>Click the button to change the background color of all elements with class="example".</p>

		<button class="example" onclick="myFunction()">Try it</button>

		<p><strong>Note:</strong> The getElementsByClassName() method is not supported in Internet Explorer 8 and earlier versions.</p>

<p><a class="em" href="#" data-ep1="maryan" data-ep2="ubanks" data-ep3="com.ua">Email me</a></p>

JavaScript

function myFunction() {
var x = document.getElementsByClassName("example");
var i;
for (i = 0; i < x.length; i++) {
	x[i].style.backgroundColor = "red";
}
}

var x = document.getElementsByClassName("em");
var i;
for (i = 0; i < x.length; i++) {
	x[i].style.backgroundColor = "red";
}