Upgrading to APEX 4.0: jQuery

In a lot of my APEX 3.x projects I used jQuery to extend the standard functionalities of APEX with some more interactive (client-side) components.

In jQuery there are very nice plug-ins, like a modal window, a grid, tooltips etc.

If you try to run your APEX 3.x application in APEX 4.0 you might find these jQuery components/plug-ins are not working anymore. The cause can be multiple:

• You might have used an older version of jQuery and the plug-ins you used with that, which are not compatible with the jQuery version in APEX (1.4)
• You load jQuery, but APEX loads their build-in jQuery too and things get mixed up

During the migration of my APEX 3.x application to APEX 4.0 I just take off all references to jQuery I made myself. Just make sure that in your template the #HEAD# is before any other jQuery plug-ins you try to run. Also make sure the jQuery plug-ins you use are compatible with jQuery 1.4.2. APEX ships with a lot of extra jQuery plug-ins like jQuery UI, js-tree etc so if you used that it's not necessary anymore to include them. (to see a complete list of files that ship with APEX, look into /images/libraries/)

Before I loaded my files as part of my Page Template, but I'm not sure I would still do that.
If you switch from template you lose the references. It might be better for maintainability point of view to include it in a region on Page 0. It will have a small performance hit, as APEX will have to look for it on Page 0, but it makes maintainability easier.
But going forward I'm converting all my custom javascript and jQuery plug-ins to APEX plug-ins and the files get loaded as part of the plug-ins. A lot of the javascript can disappear as it can be replaced by the build-in Dynamic Actions of APEX 4.0.

Hope it can help some of you when you see javascript errors when you try to run your APEX 3.x app in APEX 4.0. But don't panic to fast, it's probably just the way jQuery gets loaded.