I'm seeing problems with the wedges in this post, but not in simple cases like this one.

What would happen is that I'd click on a wedge, it wouldn't change. Then I click again, and the src attribute of the image would change to "undefined" in Firebug. Not sure what that means.

Let's try collapsing things initially and see if that matters.

No, it still works.

Aha, I believe I found the problem.

Apparently you can call a function in Javascript with an incomplete parameter list. The unspecified parameters are undefined. So if you assign an unspecified paramter to an attribute, guess what -- the attribute becomes undefined.

They should have a website where they document all the non-typical things they do in JavaScript. I don't know any other Algol-like language that does it this way.

In any case, in one of my calls to the expandCollapse routine, I omitted the values for urlExpand and urlCollapse. So when I click on the item to expand it the image goes undefined. Let's see what happens if I fix it.

Yep that was it.



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Posted on Thursday, February 09, 2012 at 9:42 AM by Dave Winer.