Tuesday 17 February 2009

Using Firebug Lite for Debugging

Debugging with Firebug Lite for IE, Safari, Opera and Chrome

I tend to do all my client side development in Firefox purely because of all the great add-ons available such as the developer toolbar, hack bar, YSlow and Firebug which is a great tool for debugging.

Once the code is working then its a case of testing in the other main browsers and if you purely rely on the inbuilt tools available you will find varying degrees of uselessness. Safari and Chrome both have inbuilt consoles which can be accessed for logging debug statements. Operas Dragonfly is pretty similar to Firebug however I have found so many annoying issues when trying to use opera.postError to output debug messages that I don't bother with it. Then at the bottom of the pile for useless unhelpful error messages is IE. I have always wondered why IE could never get their act together when it comes to Javascript error messages. An accurate line number that relates to the actual file that raised the error is not too much to ask is it? It obviously knows that an error was raised so why doesn't it know what and where. If the other browsers can manage it then IE really should be able to get it right by now. I have seen IE 8 has some better features with the ability to add breakpoints but I still find it very annoying that when you have a page that includes multiple references to external script files that when an error is raised they cannot narrow it down to file rather than page level.

So for these other browsers I use Firebug Lite which has 90% of the features that the full version of Firebug has and most importantly it gives you a wonderful console to output all your debug messages to.

You can download the latest version of Firebug Lite from this link and to use it on your site you can either include a reference to a local version of the file or use the bookmark link option which lets you include it on any site you want. For sites I am developing I will create a local copy of the file that I then reference in a global include file that will make sure the script is only loaded if:
  • The browser is not Firefox, as I use the full version of Firebug for that browser.
  • The version of the site is the development server. Check a constant or an IP address.
  • A global Debug flag is enabled.

Displaying Firebug Lite

The default view mode for the latest version of Firebug Lite is for it to open up at the bottom of your screen whether you want to or not. Obviously this can be quite annoying as it takes up quite a bit of screen space and you would usually only want to view the full console when you required it rather than all the time. This is where having a local version of the firebuglite.js file comes in handy. If you take the time to go over the code you will see the Firebug file contains a number of objects and if you edit the Firebug.init method which sets up the console you can insert the following line of code to minimize the console so that it sits at the bottom of the screen until you require it.

I put that at line 232 and it works fine for me in all these browsers IE6, IE7, Chrome, Safari and Opera.

Loading Firebug after the page has loaded

There maybe reasons why you don't want to include the Firebug-lite.js file on all pages and the use of a bookmark or lazy loader is your choice option. However if you try and access the console before its loaded you will raise errors. Safari and Chrome will always have a console available so if you want to log your debug to Firebugs console rather than their inbuilt versions then you need to be checking the following:
if((typeof(firebug)!="undefined") && firebug.env && firebug.env.init)
rather than just using
The earlier versions of FirebugLite had a simpler object model and you could reference firebug.console directly. The firebug.env object seems to hold the current status of the console, whether it has loaded fully and what display state its currently in i.e minimised, maximised, popup etc. So the check for firebug.env.init is to make sure the console is fully loaded and initialised.

Debugger Wrapper Object

If you are like me you will include debug function calls all throughout your code and rather than wait until the applications gone tits up and have to add them in later I tend to include calls to a wrapper debug function as I write my initial code. The benefit of this is that it saves time when I do need to debug plus I can run a simple clean up process to remove them all before the code goes live. However if you are including Firebug Lite from a bookmark or lazy loader you need to cache all your messages up until the console has loaded and then you can flush them all out.

This is where a simple debug wrapper object such as the one I use comes in handy as it will handle the caching, flushing and output of debug messages as well as in Safari and Chrome control whether you want to use the inbuilt console or the Firebug console.

The code is pretty simple and you can configure the behaviour by setting the debugger properties defined at the top of the object e.g

var Debugger = {
ready: false, // once a console is loaded will be set to true
debugCache: [], // holds debug messages until console is loaded and ready
hasCache: false, // flag when cache has messages
debugCount: 0, // message counter
debugInterval: null, // setInterval timer pointer
forceFirebug: true, // if true for Safari/Chrome we will use firebug lite for debug not their own console
debug: true, // flag to enable/disable debug in case you only want to output certain sections

To output any debug messages just call the ShowDebug function passing in the message you want to output.

ShowDebug("Output this debug message");

You can control whether debug is on or off throughout a page by just toggling the debug property e.g

Debugger.debug = false; //turn off debug messages

ShowDebug("This will not be shown");

Debugger.debug = true; //turn debug messages back on

ShowDebug("This will be shown");

I have tested this in IE 6, IE 7, Opera 9.61, Chrome and Safari 3.2 loading in Firebug Lite with the bookmark and it works fine. The only thing I have noticed is in the WebKit based browsers the styling is a bit off but then that's nothing to do with me.


tgb25nld said...

Fantastic - very nice
Thank you

tgb25nld said...

Very nice, fantastic
Thank you!