How to debug Javascript error?

Question

How to Debug java Script Error Using Firebug?

Duplicate

How can I set breakpoints in an external JS script in Firebug

Answer 1

Debug using FireBug.

Just check the line on which the error is occuring, then, just before that line, write a "debugger" call.

debugger; //Will invoke FireBug's debugger.
var err = abcs; //Line containing error