The url property contains the canonicalized URL for the last loaded XML document. If the document is being built in memory, it returns null. The url property is not updated after saving a document using the save method; to do this, reload the document with the load method.

To demonstrate, the following code loads the 'staff.xml' file and displays its url.

Code (JavaScript):
xml_doc = new ActiveXObject("Microsoft.XMLDOM");
xml_doc.async = false;
xml_doc.load("staff.xml");

document.write(xml_doc.url);

Output:
http://www.devguru.com/somedir/staff.xml