Tryit Editor v2.9

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

<p>Click the button to find out if the specified namespace is default.</p>

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

<p><strong>Note:</strong> Internet Explorer 8 and earlier does not support the isDefaultNamespace method.</p>

<p id="demo"></p>

<script>
function myFunction() {
    var d = document.documentElement;
    var x = d.isDefaultNamespace("http://www.w3.org/1999/xhtml"); 
    document.getElementById("demo").innerHTML = x;
}
</script>

</body>
</html>