On Oct 17, 12:44 am, HelderMagalhaes <helder.magalh...@gmail.com>
wrote:
> Hi Colin,
>
> First of all, it's important to understand that a debugger *always*
> slows things down (when active of course). This is not specific to
> Firebug or even to JavaScript, it's a natural consequence of the
> overhead introduced in order for one to be able to better understand
> what's happening (debug, that is). Specifically to Firebug, I remember
> the curious fact of Gmail notifying [1] users about it and even
> providing instructions on how to disable the plug-in [2]. :-)
Just FYI: all that GMail does is test for window.console and show a
message with a link to out of date and incorrect information.
>
> As a side note, over the years I've even learned to deal/have this in
> mind even when using complied code (such as C/C++): as weird as it may
> sound, some timing or multi-thread bugs may stop/start reproducing
> just because you are running the debugger or simply because you are
> using debug builds. :-|
>
> > > > Firefox (firebug open, page freshly loaded)
> > > > Request with "evalScripts:true" result is ~233 while Request.JSON
> > > > ~1800
>
> Most JavaScript frameworks use 'eval' to turn JSON encoded in a string
> (the result of the HTTP request) into a JavaScript object, at least as
> some for of fallback. Many recent frameworks (or framework versions)
> are already using browser's native JSON when available, and fallback
> to the working-but-less-secure-and-slower 'eval' if an older browser
> (which hasn't got native JSON) or browser configuration/add-on (which
> may have disabled those methods) is being used. That's why when
> searching for 'eval' within JSON-related code of even in the most
> recent JavaScript framework versions you'll usually end up with some
> results, simply the code path which actually executes is usually not
> that one. ;-)
>
> Firebug enables you to debug eval scripts ("Decompile for eval()
> source" option of "Script" tab), which should then enable Firebug to
> monitor those requests with "evalScripts:true" and should make things
> in par with the "Request.JSON" ones.
BTW, Firebug debugs eval scripts by default. The option "Decompile for
eval() source" does not enable eval debugging, it causes eval() to be
shown by decompiling bytecodes rather than source. Generally you do
*not* want this option. In fact if you really want to work with eval()
the best option is to use sourceURL:
http://blog.getfirebug.com/2009/08/11/give-your-eval-a-name-with-sourceurl/
>
> My final guess is that the overhead you are experiencing is just the
> result of a neat Firebug feature which is to display HTTP requests
> delivered as JSON (this will depend on the MIME type set by your
> server) in a structured way when "Show XMLHTTPRequests" (of "Console"
> tab) is enabled. If you enable that option, note that JSON responses
> have an extra tab which allows "browse" through the request. The net
> response is that if/when you aren't really using debugger features
> (like the "Net" tab, which introduces a big deal of overhead and the
> already stated "Decompile for eval() source" and "Show
> XMLHTTPRequests") just disable them: it's a good practice only
> introducing something which interferes (in this case, overhead) with
> the process if it adds value to it (again, in this case, allows you to
> debug something). ;-)
>
> My rule of thumb is: disable Firebug when you aren't developing,
And this is completely easy to do: just don't open Firebug on any site
you are not developing. If you accidentally open Firebug be sure to
turn it off with the red [(')] button in the upper right. See
http://www.softwareishard.com/blog/firebug/how-to-enable-and-disable-firebug-15/
jjb
> disable all Firebug features I'm not using when developing, and
> disable specific Firebug features when I'm not in need of them
> (although I can't help myself always leaving the super-cool "Disable
> Break On All Errors" feature enabled when Firebug is active, which
> already allowed me finding bugs which were *very* hard to
> reproduce). :-)
>
> > Colin
>
> Hope this helps,
> Helder
>
> [1]http://googlified.com/gmail-firebug-makes-me-slow/
> [2]https://mail.google.com/support/bin/answer.py?answer=77355
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