Mysterious FireBug Error repeats with ExtJS

Question

When debugging ExtJS 4 (tried both versions 4.1.0 and 4.1.1), FireBug repeatedly shows the following error: An invalid or illegal string was specified http://docs.sencha.com/ext-js/4-1/extjs/ext-all.js Line 18. It does not break on the error, though that option is specified. Additionally, neither my code or ext-debug.js and it's loader seem to actually call ext-all.js.

This error gets logged to Firebug's console about once per minute, which is annoying. What bothers me is that I cannot get the error to go away. Is this a FireBug bug? An ExtJS bug? Aliens? How can I debug the debugger?

Answer 1

I had the same problem before and I've solved it by removing a special character at the end of my JS file! (app.js I think)

It was weird, but the problem came from hidden special characters like: Zero-width non-joiner or Right-to-left mark.

Open another JS file but do not copy/paste your code there. Just write it again and check whether the problem exists or not.

And don't forget to check your data if you have some. As this article explains about the problem: http://www.ashorlivs.fr/javascript-jquery/article/an-invalid-or-illegal-string-was