Enhancement: Find documents by ID or other

[FrankC01]

Scenario: I put up a "In progress" loadingTemplate. In the Apple examples there is a state flag on the Presenter.js that recognizes when that is showing so it can dismiss it before pushing the new document on the stack.

Contrary to my DOMParser comment, this seems like it would be better served by finding out if the document exists in the current navigationDocument's stack and, if so, act accordingly.

PS: I am not an experienced JavaScript person so if there is a standard way of doing this directly it may be a moot enhancement request.