Tryit Editor v2.9

Edit This Code:
<!DOCTYPE html>
<html>
<body>

<h2 class="example">A heading with class="example"</h2>
<p class="example">A paragraph with class="example".</p> 

<p>Click the button to add a background color to the first p element in the document with class="example".</p>

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

<script>
function myFunction() {
    document.querySelector("p.example").style.backgroundColor = "red";
}
</script>

</body>
</html>