I find debugging javascript frustrating, even with the benefit of Firebug.
It is likely that I haven't yet learnt to get the full benefit of Firebug's
features.
A single wrong character can make complex code stop working altogether,
with Firebug displaying error messages which are untrue - or true in a very
narrow sense - such as messages that 1) the function named such and such is
not defined or that 2) there is no javascript on the page. What I think the
messages really mean is that Firebug isn't smart enough to figure out that
1) you've messed up some syntax somewhere, with the result that your
function is no longer syntactically correct, or that 2) you've forgotten to
put in, or have accidentally removed/messed up, a <script
type="text/javascript"></script> pair (though, in that case, you're readily
alerted to a problem when your javascript code shows up in the text on the
webpage; maybe there are some more subtle errors which also generate the no
javascript on page error(?)). When I say "Firebug isn't smart enough" I
don't mean to imply that it really ought to be, as I acknowledge that
making sense of code and trying to figure out a programmer's intention is
non-trivial, but, ideally, Firebug would help me locate the causes of these
errors. Messages claiming that functions don't exist or that the page
contains no javascript, seem to me to be saying, in effect, "Your code has
problems which are too hard for me to figure out. You're on your own!"
I'm unsure whether the message about a function not being defined can have
a cause outside of the function named as not being defined. I currently
have a feeling that it can. I think I'm probably getting this error saying
one function is not defined when the code I've just messed up is actually
in another function and when I haven't actually made any change to the
named function.
At present I'm repeatedly getting that message (about a function not being
defined) after making editing changes. What I usually do then is visually
inspect the code, looking for syntax errors, including clicking after
complexly nested {s and }s (which, in my editor (SuperEdi), results in { }
pairs being displayed in bold). I often annotate close braces with comments
noting the if or else clause which the close brace is closing. I'm not
presently convinced that the Console tab in Firebug helps me with finding
the syntax problem in the case of "function not defined" or "no javascript
on page" errors, though I admit I am not thoroughly familiar with using the
Console tab. I think it's the case that, sometimes at least, it is
necessary to click twice on the Console tab to see the line(s) of code
which is/are causing problems. There may be times when helpful information
is there but I'm overlooking it.
I try to format my code to show the structure of if ... else clauses. I try
not to make a lot of changes before saving under a different version number
and retesting the code because it's important to be able to remember what
I've done recently for the frequent occasions when my code substantially or
totally stops working because of a recent change. It would be nice if
Firebug included or integrated well with 1) pretty print software and 2)
version control software (though it may well be that I'd find the learning
curve for version control software daunting). Short of integrating version
control software, I wonder if Firebug could feasibly be improved so that it
cached the immediately previous version of code and could highlight the
differences between the current version and the immediately previous
version to help the programmer locate the newly introduced error(s).
I think there is functionality in Firebug for executing code and seeing the
changing contents of variables as it executes but I haven't so far been
able to use it really successfully. There's a video recorder style play
button to resume a script after an error but I'm not sure that I've seen a
button for executing just the next line of code. I sometimes succeed in
setting Watches on variables but other times Firebug insists that a
variable doesn't exist or isn't defined/declared - I don't recall which. I
appreciate that, during the execution of code, variables can properly
appear and disappear as they come into and go out of scope. It seems to me
that Firebug sometimes tells me that particular variables don't exist and
that they never appear in the Watch window with values, even though the
code successfully executes using such variables. I guess I need to
persevere and gain more experience. There doesn't seem to be help
integrated into Firebug, though the getfirebug.com webpage includes useful
links e.g. to Firebug Tips &
Tricks<http://www.softwareishard.com/blog/firebug-tips/>
.
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