Debugging help

[ndcoxhead]

Newbie question - I'm following the example code for Keyboard Navigation (from the files downloaded from the page, complex.html and complex.js), and when I load the page unedited it just shows one part of the content (center - the personal details form), and gives this error in the console:

Uncaught TypeError: Cannot read property 'id' of undefined

My question is, how should I go about debugging this (assuming it was my code) ?
I found in the middle of the stack list one reference to my files -

• complex.js:110

which is the code Ext.create('Ext.tab.Panel', so I guess something is wrong with creating the tab panel, but as I am new to ExtJS I can't see anything obviously wrong.

Can someone give any tips on how to approach fixing bugs using the information available ?

[scottmartin]

Several questions ..

What are you using to debug your application at this time? DevTools in Chrome or Firebug in FireFox?

If your code is simple, on you paste in here, or create a small fiddle so we can see it run.
https://fiddle.sencha.com/#home

If you paste the code, please try to make sure we can run the example and not just a snippet.

[ndcoxhead]

You've missed the point, I'm not looking for the bug to be fixed for me, I'd like some tips on how to get clues to figure it out for myself.
I'm using mainly Chrome->Tools->Debugger Tools, also Firebug.
And I shouldn't have to send you the code, it's your code (unmodified) that isn't working (complex.js & complex.html from Keyboard Navigation concepts):
http://docs.sencha.com/extjs/4.2.2/g..._nav/start.zip

This is how it looks when I run it.