AJAX Firefox Plugins JavaScript Venkman Web Browser

Firebug 1.0 Beta

I’ve been playing with the Firebug 1.0 private beta for the last few days and it’s quite a tool. v0.4 the last release of Firebug had already combined the most popular features Venkman, Console2, and the DOM inspector. 1.0 adds a entire new set of features. JS profiling and Net request tracing similar to Tamper Data are IMHO the most powerful. Joe has been hard at work and been fising issues as quick as we find them. Firebug now has enough functionality that it could implement and examine all the tips included in my entire presentation at OSCON.

The new website Get Firebug gives you a glimpse of what is coming shortly:

AJAX JavaScript

Faster DOM Queries

Dean Edwards has posted a demo with a cross browser way of super quick DOM queries.


* As described earlier, speed improvements only apply on page load for IE. Further DOM queries will use the original getElementsBySelector function
* the speed of CSS2 queries (attribute selectors) are not improved for IE5/6
* because of the nature of the CSS hack, you can only apply one behavior per element ๐Ÿ™


* DOM queries on Firefox seem pretty quick
* XPath is about 150% faster than DOM queries on a Mozilla platform
* XPath is about 1000% faster than DOM queries on an Opera platform
* the expression hack is about 200-400% faster on an IE platform
* Behaviour leaks like a sieve

AJAX JavaScript Web Browser


JSONRequest has been proposed by Douglas Crockford as a new native method for web browsers to exchange data with servers. The biggest notable difference with XMLHttpRequest is that it doesn’t prevent requests to multiple domains. JSONRequest can make requests to any server, not just the origin server like the current XMLHttpRequest. Web applications today that need to make cross-domain requests must use a proxy or a dynamic script tag to make requests to non-origin domains.

JSONRequest also has provisions for long lasting server initiated, live push of data. Crockford calls this “Duplex”.

“JSONRequest is designed to support duplex connections. This permits applications in which the server can asynchronously initiate transmissions. This is done by using two simultaneous requests: one to send and the other to receive. By using the timeout parameter, a POST request can be left pending until the server determines that it has timely data to send.

Duplex connections can be used in real time notification applications such as process management and finance. It can also be used in collaborative applications such as instant messaging, instant email, chat, games, presentation, and shared applications. “

Alex Russell
calls this same server-push technique Comet. I actually like Comet a bit more than Duplex. Duplex is a bit overloaded with a few other uses in tech. Like the half or full duplex with configuring network cards or terminal echo. Not as if I have a vote(just like AJAX sotra stuck), but let’s hope Comet wins.

JavaScript Venkman

Crockford on JSMin and Obfuscation

Douglas Crockford knows a thing or two about compressing JavaScript. He wrote JSMin which IMHO is the simplest and fastest JavaScript minifer out there today. Coupled with his lint checker JSLint you’ve got two really good tools to write good solid code. I used JSMin to optimize’s homepage a few weeks back. As more and more AJAX apps start to take advantage of JavaScript the size and footprint grows dramatically. Even more so when folks import the various AJAX toolkits as a starting point. This means that tools like JSMin become a required part of the build/deploy process for those that are serious about optimizing end-user experience. There are other excellent minifer tools out there including Alex’s ShrinkSafe which is based on Rhino. ShrinkSafe takes an aggressive approach to not modifying the API’s as it uses a real JavaScript compiler/run-time to shrink the code. This is important when you don’t want your public API to change as is true for any JavaScript toolkit developer. Crockford makes the point that obfuscation is really just a small hurdle and any serious programmer, given time can extract the useful bits. This is especially true for JavaScript where no matter how much mangling of the code is done before it’s sent to the browser it’s still sent in plain text. So it’s trivial to attach a debugger like Venkman and walk through each line of code. Glad to see Douglas putting focus back on JavaScript as noted by his many recent updates to JSLint and now his first blog entry on the Y! UI blog. I’d also guess that Yahoo’s focus on JSON for their REST api’s is in part due to Doug joining them.

ref: Minification v Obfuscation ยป Yahoo! User Interface Blog

AJAX Email JavaScript

Gmail chat problems

I’ve noticed a few errors in gmail’s new chat interface. The gmail quick contacts are not always up-to-date. Just yesterday I got this this error message:


It’s a new service, so not too surprised that chat is seeing a few bumps. In fact it’s expected. I remember the first few versions of meebo(a web based chat interface for Yahoo, MSN, AOL, and Jabber), and the problems they ran into. One positive aspect of the chat problems are that gmail is unaffected. Email continues to work and is performing well. They’ve integrated it in such a way that quick contacts can fail or be unavailable (like above) but fail gracefully. Many popular web apps, even recent web 2.0 and AJAX apps don’t seem to be designed this way. They fail and fail completely. Designing AJAX apps that can handle partial failures is hard. Many of these app have deep callback stack to get the JavaScript to perform and work seamlessly. There are parallel asynchronous java script calls that need to be requested and handled in whatever order the server responds. So each piece of functionally needs to be carefully crafted to be independent and self sufficient. You need to think about how your app will act if it fails, or worse partially fails. Can it continue to work if it misses a server response or two? Can it error gracefully and continue to work when only a partial set of server functionality is available? This is especially important for companies building desktop replacement applications in which users will rely on for their day to day or even hour to hour work. So take a note from gmail and talk, build apps that are robust to temporary failures. If partial server functionality is available continue to process work and user interaction on the rest of the app. Gracefully poll the server checking for when the full functionality is returned. The error above recovered on it’s own without a reload or restart of the webapp. Impressive to say the least.

On a side note, Gmail itself has been rock solid for me ever since I started using it in June 2004. The spam filters are pretty good, but not perfect (more on that later), and it’s hard to beat the speed of the interface. It’s not the most feature rich mail or collaboration implementation out there but for a small mail volume it does a good job. Works perfect for my personal mail (40-50/day), but I’d have a hard time using it as my primary webmail client for work(200-300/day). I just get too much mail each day for gmail to be useful. It’s missing a few key features to manage extremely large daily mail volume. Saved searches and IMAP support being the first two that come to mind. I need a way to quick search on the same data multiple times a day. Labels work well to automatically categorize and simulate folders but can’t replace a rich search with the option to save. IMAP is a must have for off-line access. POP just doesn’t cut it when you want the server to be your *master* mail store.

AJAX JavaScript

AJAX Amazon Music Search

Put together an AJAX demo using Amazon’s webservice API. Basically type in an artist name or song title and it’ll return the first 10 hits from Amazon’s music search. It’s using for the ‘Grow’ effect when the results return. the search itself is triggered via java script, and parsed locally. The result also triggers a contextual AdSense ad. Tried a few different ideas and seems an embedded iframe worked best. My goal was to make it work without a page reload. So to get an AdSense ad that is contextual to the search I needed to generate a url and title string from the query itself. Anything else seemed to lead to generic ads. I’m sure there are ways to improve on it. If you’ve got an idea leave a comment!

AJAX Amazon Music Search


Firefox Array.toString() is very slow

Ran into an interesting problem with JavaScript’s Array.toString() in Firefox.  It’s extremely slow even for a very small array.  Take an array with a single object and you’d like to call toString() to get the type of the contained object.  There are better approaches but for simple uses this might be applied.  In this case toString() of the underlying object simple returns the object’s name.  This is a very common use of toString() on custom objects. In Firefox calling toString() on the Array is nearly ten times slower than calling toString() on the object itself.  In Internet Explorer it’s about three times slower.  Needless to say be very careful with JavaScript’s Array.toString(), as it’s not a transparent call into the underlying objects performance wise.

Internet Explorer 6
anArray.toString() – 1829
anObect.toString() – 625

anArray.toString() – 3093
anObect.toString() – 375

The full test script is posted below.

var anArray = [];
var anObject = {};
anObject.toString = function() {return “anObject”;};

var startTime,endTime,i;
var repeat = 250000;

startTime=new Date().getTime();
for(i = 0; i < repeat; i++) { anArray.toString(); } endTime=new Date().getTime(); var arrayToStringResult = endTime - startTime; startTime=new Date().getTime(); for(i = 0; i < repeat; i++) { anObject.toString(); } endTime=new Date().getTime(); var objectToStringResult = endTime - startTime; document.write("anArray.toString() - " + arrayToStringResult); document.write("<br/>"); document.write("anObect.toString() - " + objectToStringResult);

AJAX JavaScript

YubNub Suggest

YubNub has been around for sometime. I went looking for a Suggest version that would autocomplete common commands. I did a few searches and all I came up with was DashNub which is an OSX Widget.  Using‘s autocomplete code and the XML feed for the YubNub Golden Eggs. My YubNub example now has basic autocomplete.  Any YubNub command can be used but autocomplete only works for the 400-500 Golden Eggs.

YubNub Suggest

 – It’s only been tested in Firefox 1.5.01

 – Test in other browsers
 – Add descriptions to each command
 – Allow selecting with arrow keys

AJAX JavaScript Web Browser

Graded Browser Support

Nate posted an article which coincided with Yahoo’s launch of their UI Library titled "Graded Browser Support".  It appears he first coined the phrase in 2004.  Subsequent google hits all point to Nate.  I must admit it’s quite novel.  He also posted a matrix of browser’s that Yahoo domain applications support.  It’s quite refreshing to see an age old problem explored in a new way and with a catchy new phrase to help coral the thought going forward.  It reminds me of some work in a previous life around WAP browser capabilities. The first generation of tool kits and support for WAP devices included huge switch statements and hacky User-Agent regular expressions.  The second generation and what I belive is still in use today was a framework that detected capabilities.  Rather than look for browser X and apply hacks X, the code would detect capabilities.  For example the ability to support pages greater than 15k (remember we were in the mobile world), or the ability to support a password input field.  The capability matrix kept the code much clearer.  Instead of complex decision trees with User-Agent’s, code was clean with simple if/else statements for a particular capability.  The hard part was contained in a single matrix that maps capabilities to various browsers.  A quick update to the matix and a new handset could be added with little or no code changes.

The same problem has existed in web browser’s for many years.  Most applications simply had isIE() or isNetscape() type checks.  For the most part this worked pretty well as the capabilities being detected were generally split between the two dominant browser’s of the time; Internet Explorer and Netscape.  Today the landscape is very different.  No longer is the browser war a 2 horse race.   For most applications on today’s web it’s at least a 3 to 4 horse race.  In Nick and Yahoo’s case there are 6 different browser’s with a total of 10 browser/version combinations.  This doesn’t even take into consideration the OS side of the equation.  Web application complexity continues to increase.  As applications take advantage of the latest features of new releases the support for capabilities in earlier versions becomes harder to represent.  A simple example is the new native XmlHttpRequest object in IE7.  Assuming it performs better than the ActiveX object in current releases web developers will want to take advantage of the new native object.  In a isIE() type decision tree there would need to be a special case to handle IE7.  However in a capabilities based application IE7 would be defined with a native XmlHttpRequest object such that the code would function without any special cases.

AJAX JavaScript Venkman

AJAX Developers Toolbox – Overview

AJAX programmers today have many tools available to them. Here’s a quick overview of some popular ones.

  • Debuggers
    Firefox –
    Venkman without a doubt is a must have for any serious JavaScript hacker these days. All the functionality you’ve come to expect in a debugger step in/out/over, set break points, trace the call stack, inspect variables, eval code on the fly; you get the picture. Up until recently Venkman only worked with Firefox 1.0.x, Joe Walker posted a version that works for Firefox 1.5.x.

    IE –
    JavaScript debugging for Internet Explorer is a bit trickier. You can use the Microsoft Script Debugger or if you’re willing to shell out some cash Visual Studio offers a richer debugging environment.

    Mozilla – Venkman ships by default with Mozilla, and provides a nice option for those who just want to get their browser and debugger combination in one shot.

  • Integrated Development Environment (IDE) The choice of editor’s or IDE’s is sometimes characterized as a war. Not to pick and choose but Eclipse has become a popular editor for many web programmers. It’s roots are with server-side Java code but more recently the Web Tools Platform (WTP) has come along and aims to change that perception. They’ve made signific progress over the past year, but at the moment Eclipse + JSEclipse is my personal choice.  The JSEclipse plug-in has quick code-complete and simple, clear syntax highlighting.

  • Syntax Checker JSLint – Slick syntax checker.  Catches all those stupid mistakes, and helps enforce good programming conventions.

    "JSLint takes a JavaScript source and scans it. If it finds a problem, it returns a message describing the problem and an approximate location within the source. The problem is not necessarily an error, although it often is. JSLint looks at some style conventions as well as structural problems. It does not prove that your program is correct. It just provides another set of eyes to help spot problems."

    Those are some tools any JavaScript or DHTML programmer would be hard pressed to get by without. 

    Know of a tool or program that you’d have in your AJAX Toolbox?  Post a comment!