<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>querySelector Example</title>
</head>
<body>
<div class="example">Element 1</div>
<div class="example">Element 2</div>
<button onclick="highlightFirst()">Highlight First</button>
<script>
function highlightFirst() {
const element = document.querySelector('.example');
element.style.backgroundColor = 'lightblue';
}
</script>
</body>
</html>