What's the best practice for inserting paths to JS and CSS files in the head—but only for resources they are needed on?

This method performs much better than the standard method of output modifiers:



You'd have to make a chunk called picturefillJS (or anything you want of course) that would have your Javascript call.
The variable you have may be a Yes/No or a value of "show" or whatever, I don't know, so the condition might differ, i.e.



You can find the article about this method of using output modifiers here (and why the traditional method is a performance hit: http://modx.com/blog/2012/09/14/tags-as-the-result-or-how-conditionals-are-like-mosquitoes/

It's not part of the standard documentation as far as I can tell and it really should be.
Note however, that at times, I've not gotten it to function, usually with nested conditional situations but in situations like you describe it works wonderfully.

And of course, all the modifier syntax here: http://rtfm.modx.com/revolution/2.x/making-sites-with-modx/customizing-content/input-and-output-filters-%28output-modifiers%29

When I do have trouble with this method I usually use either the If or Switch extras.

Finally, there's an extra not in repository but buried in a forum post for And/If situations. It's called AndIf.

Thanks much for the feedback and the loads of info. This looks very promising. I had read that article about conditionals a while back.

I'll give this a try.

Thanks