As programmer born and brought up in the world of C and C++, my first answer to this kind of question would have been store their addresses in the array!. But after a couple years of messing around with the web way of things, I can give the right answer:

In javascript, you can directly store the references to the objects in the array.
And no, xpath is not a good idea for this; using references is simpler and better.
So a direct answer to your question is: there is no unique identifier for a DOM element/node except itself.

In javascript, all objects are passed around by reference. So here's a sample code for how to do it:

var theArray = [];

var theNodeToTraverse = document.getElementById('domelementtosearch');



traverseAndStore(theNodeToTraverse);



function traverseAndStore( node )

{

    if( node==null) return;

    theArray[ theArray.length ] = node;

    for( i=0; i<node.childNodes.length; i++ )

        traverseAndStore( node.childNodes[i] );

}