Tryit Editor v2.9

Edit This Code:

<!DOCTYPE html>
<html>
<body style="background:#f3f3f3 url('img_tree.png');">

<h1>Hello World!</h1>
<button type="button" onclick="myFunction()">Get background image</button>

<script>
function myFunction() {
    alert(document.body.style.backgroundImage);
}
</script>

</body>
</html>