First call the createDocument() method of the document.implementation object

This method takes three arguments:

• The first is a string containing the namespace URI for the document to use,
• The second is a string containing the qualified name of the document's root element,
• The third is the type of document  to create.

To create an empty DOM document

 var foxXmlDom = document.implementation.createDocument("", "", null);

To creates an XML DOM whose documentElement is <address/>

var foxXmlDom = document.implementation.createDocument("", "address", null);

To creates an XML DOM specifying a namespace

var foxXmlDom = document.implementation.createDocument("http://www.sourceside.com","address",null);