Question

Background Info

A bug exists currently in IE9 where it thinks that the NodeFilter property of the createTreeWalker method is a callback function instead of an object containing a callback function.

In a call like this:

document.createTreeWalker(document.body, NodeFilter.SHOW_ELEMENT, filter, false);

filter is defined as “an object that contains a method acceptNode,” in Webkit and Gecko; however, in IE9, there’s no mention of acceptNode at all–it expects a “callback method,” without that object wrapping.

Actual Question

So, what’s the best way to work around this issue without doing explicit browser detection? In some instances I need filter to be a method, and in others I need it to be an object containing the method. Is there a clean way to accomplish this? All of these browsers claim to support DOM 2.0, so I can’t test on that…

Documents – Proof of Bug

Here’s a comparison of the documentation for each:

1. W3C Spec
2. Gecko
3. Webkit
4. Microsoft (“The NodeFilter is a callback function…” – WRONG)

Answer 1

Well, I came up with one thing that works. Open to better alternatives:

var filter = { acceptNode: function() {
     //do filtering...
} };

// Hackzilla.  A true W3C-compliant nodeFilter object isn't passed, and instead a "safe" one _based_ off of the real one.
var safeFilter = filter.acceptNode;
safeFilter.acceptNode = filter.acceptNode;

document.createTreeWalker(document.body, NodeFilter.SHOW_ELEMENT, safeFilter, false);

This works as nice browsers will call .acceptNode on the filter object, where bad ones will try and execute it immediately.

Alternatives?