The Loader component in ExtJS 4 is great, but there’s a few quirks.  I thought I’d share for anyone else who may be running into issues similar to what I encountered.

Tip #1: Fix “disappearing” breakpoints.

Just because Ext disabled sends and extra parameter (“disableCachingParam” or “_dc”) to prevent caching, just about every browser loses breakpoints on page refresh. You might also want to install some cache clearing tools for your browser too, I could not get my scripts to clear from cache with just a refresh. (even hard refresh wont do)

Ext.Loader.setConfig({
	disableCaching: true
});

Tip #2: Don’t forget to define!

Be sure to define a class for each script you load. I’ve found not doing so can cause Ext to lock up on occassion. It won’t throw an error and it won’t freeze the browser, it will just stop running certain parts of code. This is especially good to know if you wish to auto-load oddly named overrides.

Tip #3: Test your code by auto-loading.

Auto-loading will always create excess http requests over loading one condensed script, but you can still use it for testing code structure. If your code isn’t structured (namespaced) properly it can still work perfectly when included, but will fail to auto-load. Just by testing your code with auto-loading, you can verify all file names and class definitions are correct.

Note: This post was sitting in my drafts awaiting additions for some time, not sure of anything to add, so *post*.