<!DOCTYPE html>
<html>
<head>
<style>
#myDIV {
border: 1px solid black;
}
</style>
</head>
<body>
<div id="myDIV">
<p>This is a p element in div.</p>
<p>This is also a p element in div.</p>
</div>
<p>Click the button to change the text of the first p element in div.</p>
<button onclick="myFunction()">Try it</button>
<script>
function myFunction() {
var x = document.getElementById("myDIV");
x.querySelector("p").innerHTML = "Hello World!";
}
</script>
</body>
</html>