<!doctype html>
<html lang="en">
<head>
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
</head>
<body>

<div class="myClass">
	<h3>First h3</h3>
	<h3>Second h3</h3>
	<h3>Third h3</h3>
	<h3>Fourth h3</h3>
</div>

<script>
$("div.myClass")
    .find("h3")
    .eq(2)
    .html("New text for the third h3");

alert(document.body.innerHTML);
</script>
 
</body>
</html>
