The Ownership Relationship

A relationship that is not yet supported by IE 5.5 is the document context of a node. Each tag you define in an HTML file (each tag is modeled by a node on the DOM tree), belongs to a certain document object. The property that denotes this ownership is ownerDocument. If we model the whole document in a single DOM tree, the ownerDocument property is a direct link between any node on the DOM tree and the root of the tree. The following expression should return the root of the DOM tree:

document.documentElement.ownerDocument

Let's print the node name (tag name), so it's easier to detect which node it is. You should get HTML as an answer. For printing the root's properties, always go the root node by using the documentElement property. The printing above is actually done via:

alert(document.documentElement.ownerDocument.documentElement.nodeName);

Now, let's go deeper in the tree, to document's first child (HEAD):

document.documentElement.firstChild

And then let's go directly back to the root of the DOM tree:

document.documentElement.firstChild.ownerDocument

As previously, let's print the node name of the root. Again, we go to the root node by the documentElement property:

alert(document.documentElement.firstChild.ownerDocument.
  documentElement.nodeName);

You should get HTML.

Next: How to reference objects in Netscape 6