Five AJAX Frameworks Reviewed

prostoalex writes "Dr. Dobb's Journal reviews 5 AJAX frameworks: Dojo 0.3.1, Prototype and Scriptaculous 1.4, Direct Web Reporting 1.0, Yahoo! User Interface Library 0.11.1 and Google Web Toolkit 1.0. Each framework was tested in two basic scenarios — writing a 'hub' (titled collapsible link list frequently seen on sidebars of many Web sites) and a 'tab panel' (horizontal tabbed navigation bar). During the process, Dr. Dobb's Journal reviewers noted that 'Dojo provides more features and HTML widgets than YUI and Prototype' but eventually 'settled on the Yahoo! User Interface Library.'"

Comments

Frameworks

[AKAImBatman]

Am I the only one who usually finds frameworks to be pointless for serious web development? It's not that they're necessarily bad, but that they pack in dozens of features that you don't necessarily need (potentially bloating the size of your page download by tens to hundreds of K) or even want. In many cases, the frameworks have a ton of little "gotchas". For example, Prototype has a set of functions that are supposed to make it easy to show and hide elements. The only problem is that if you define the "display" element in the style sheet (say, to make an element invisible by default) you can't change the element's state. This is because the Prototype library works in a stateless fashion, assuming that the default value for "display" is the way to make an item visible. Which may not be not be true.

Other libraries have some cool GUI widgets, but often those are actually too much for a project. In some cases they even require you to build the entire project out of their widgets! That's nice if you're writing the next Outlook on the Web, but not so nice if you're trying to add interactive elements to an existing webpage. Especially if you like the more open HTML design rather than the cluttered pseudo-GUI design.

In general, I've found that these libraries may be kind of nice if you're not too familiar with DOM/CSS and want to perform some neat effects. (Scriptaculous in particular does some nice effects without a whole lot of difficulty. Just watch the download size!) But if you're doing a complex website, you'll probably be better off with a custom library for now. At least until some standard practices emerge among professional sites.

Now if you want to talk about libraries that patch minor browser issues like no DOM 2 Events, lack of Object.toSource, unified XMLHttpRequest instantiation, etc., then I'd have to jump in and add glowing support for such pieces of code. The key is, though, that they're very passive libraries. You include them, and they make sure that your code works the same everywhere. Which is a bit different than being forced to structure your project around a framework. If there's one thing I love about Javascript, it's that everything is virtual. ;)

Re:Frameworks

[profplump]

And I could show you inefficiencies and poorly-formed code and design patterns in projects that do use Struts/Shale/WebWork.

That's not to say that frameworks aren't useful for some purposes, but "enforcing well-formed code and design patterns" is not one of those reasons, nor is failing to use frameworks evidence of bad design.

Re:Frameworks

[AKAImBatman]

Frameworks are what professionals use - the enforce well-formed code and design patterns.

Funny thing, though. We "professionals" (I like the insinuation there, BTW) use the right tool for the right job. Sometimes the right tool is NOT someone else's framework. Sometimes, you're actually creating inefficiencies by adding layers unnecessary to the project at hand. Only an amateur selects a server-side framework before knowing the requirements of the project. The "professionals" will use off the shelf if it makes sense or build their own if better results can be achieved.

In the case of Javascripting, you've got a lot of factors working against you. The first is size. You can't afford waste, because you're trying to ensure that the page renders as fast as possible. Dumping 100K+ from the scriptalicious framework just to fade out a single box isn't very effective to your budget. Especially since the same effect can be achieved in a few hundred bytes by using a custom framework.

The second factor working against you is reusability. Javascript is not very well designed to handle this area. Object Oriented concepts we take for granted in Java (interfaces, abstract classes, private methods, final assignments, etc.) are not enforceable in vanilla Javascript. So you have to either be really clever (sounds like trouble), or work through standardized practices.

The third factor working against you is maturity. These frameworks are of varying levels of maturity because such web technologies are anything but old-hat yet. There are plenty of situations they are untested in, potentially leaving you debugging someone else's code rather than moving your project forward. Thus a framework may actually increase your project time if you're not careful.

And with that, there's one last note I'd like to point out. Frameworks are far too often chosen as a crutch rather than a time-saving component. Make sure that when you chose a framework, it's because you know it will do the job you need it to. Not because you heard it's the latest craze (bad), or because you have no idea how to implement the functionality it provides (even worse).

Re:Frameworks

[AKAImBatman]

Funny thing, though. I've seen more than enough situations where the framework is obsolete by the time it's done. Take Portlets for example. Seems like a beautiful idea. Web pages are composed of sections, therefore they should be built in sections, right? Right. 5-7 years ago, that is. When I built custom frameworks to good effect that did the same thing.

Today, you often need to go back to looking at the entire page. Why? Because the cutting edge developments require that the page be looked at as a complete memory model. If you try to take the HTML Component approach, programmer 1 may stomp all over programmer 2's Javascript or document ids by accident. Thus it suddenly makes sense to unify those pieces into libraries akin to more traditional programming methods.

Right tool. Right job.

Re:Frameworks

[PietjeJantje]

Am I the only one who usually finds frameworks to be pointless for serious web development? It's not that they're necessarily bad, but that they pack in dozens of features that you don't necessarily need

This was my problem in the open source project, partly Ajax driven, I'm involved in. Exactly for this reason it sported custom coded Javascript from the start. I don't want to load 50K+ javascripts, and I don't want one big script with crap I don't need. If you have some fairly basic stuff which doesn't change much, it's much more efficient to hand-code your own javascript. Also, when this problem arose, and it is still true, these libaries are relatively brand new, and I found it silly to commit a codebase to any of them. However, if you do all your own coding, there are problems such as cross-browser compatibility, and also there is a certain threshold of complexity when you find you're factoring out the same code and problems, and one should consider a switch. But it is a dangerous point which should be a warning sign by itself, because it could imply your stuff is getting too bloated.

It turned out jquery (jquery.com) was the best choice in our case, it addresses exactly my worries by sporting a size of just 20KB, all extras come in modules, and it's very powerful. I'd rather have a 10K version, but there you have it, you can't have it all. How it (or I) work, is to load the core when the page is loaded, and only insert additional scripts (mostly dynamic, i.e. when you click something) when needed. Similary, Yahoo! has a fine, modulized lib which is extremely well documented.

Last but not least it must be noted that all of these frameworks use MIT/BSD style licenses, and I'd like to thank them all for their great tools and generosity.

Re:Frameworks

[drix]

In fact your very own logic argues for the use of a JS framework. Anything you write that relies on Prototype is going to be far more mature and reusable than something you cobbled together on your own. When I say "mature", I mean it in the holistic sense. It's very, very unlikely that you are you going find some trivial error in the core Prototype library. It's virtually certain that you would do so if you write your own. Maybe you will get them worked out by deployment time, maybe not. Second, Prototype has a rich and consistent API, and anyone who has experience writing applications on top of it could easily pick up your code and reuse it. Finally, you make no mention of cross-browser compatibility, which makes me wonder how much experience developing these sorts of applications you really have. Words cannot describe how much time you save when your starting point is something that works out of the box in IE, Firefox, Safari and Opera. You could sink literally hundreds of hours into testing your application on various platforms. Fortunately, you don't have to, because someone already did. Why reinvent the wheel?

Re:Frameworks

[moochfish]

I disagree. If your goal is to write a website for mom, it is overkill to look at Prototype (maybe). However, anybody who is comparing frameworks is probably way beyond the simple stuff.

As for the bloat issue, this is where libraries like Scriptaculous are doing it right by keeping classes of components in separate libraries. Second, this is why browsers cache JS files. Third, if you want cool effects that are cross-browser compatible, you simply have to accept that such effects come with bloat. If bloat is a show stopper, then you probably shouldn't use fading transitions with scaling div boxes anyway.

And if the argument is that these add way too much *unused* bloat, this comes back to the "mom's website" argument I made above. If people want to use machine guns to hunt cockroaches, that's their call. Unlike with a machine gun, if Prototype is too much, you can always cut out the small pieces you need. That's right -- people seem to conveniently forget that if they only really need one small, tiny part of a much larger library, they're always free to simply cut and paste that component out (MIT license is a great thing, huh).

What? But you need the rest, just in case? Then don't complain about the bloat you are willfully accepting. But in all honesty, Prototype's foot print is tiny -- about the size of an extra image banner -- and it gets cached.

I have been using Prototype extensively lately, and I have found it as a major time saver. By using it, I don't have to remember the various undocumented "gotchas" across browers. I'd much rather deal with the well documented show/hide issue than trying to figure out how to make transparent text in all of the browsers. On that note, did you know Prototype tries to prevent the very "gotchas" you talk of? For example, stopping event propogation is the same method no matter what browser you are using, and the Element.setStyle/getStyle methods correctly convert the 'opacity' property depending on the browser being used. So for whatever "gotchas" you are using to discredit Prototype, I think you are conveniently ignoring the hundreds of others that Prototype strives to fix, silently, without the developer ever knowing.

And lastly, about the notion of writing your own custom library -- that's hardly an option for most people. First of all, most web developers are not JavaScript experts. In fact, I've almost never seen someone use exception handling in JavaScript, short of in libraries like these. More importantly, even if you were some kind of JavaScript guru, are you going to test all of your methods in all of the browsers out there? Can you guarantee your AJAX calls work the same in all browsers? What happens if I trigger a second one during the first one? Is your implementation really more efficient than Prototype's? How long is it going to take to design this custom library? Is it extensible? Does it respect the global namespace? Does it play nice with other JS files I include? Does it work in strict/quirks mode? Like I said, writing such a library isn't an option for most people. Prototype is as close as it gets to a "patch" library, which is why so many other frameworks are built on it. That, and it has been extensively tested, which is a requirement for most companies rolling out technologies like it.

Security not a consideration?

[Lux]

Curious. With javascript hijacking attacks just discovered a few weeks ago, security was not a consideration in the evaluation at all.

I'm a bit disappointed.

As a .NET developer

[leather_helmet]

ASP.AJAX

MS's toolkit has been great - FF & Safari support is a breeze in most instances, allowing us to develop our applications really quickly

Having downloaded and hacking a few quick demos with the silverlight BETA API, I am looking forward to integrating the CLR in our future releases

Frameworks versus Libraries

[dmeranda]

This sounds like the classic Framework versus Library debate. Some good reading:

The Dojo mailing list thread "dojo: framework vs library"
http://dojotoolkit.org/pipermail/dojo-interest/200 5-May/000231.html

Joel Spolsky's "Why I Hate Frameworks"
http://discuss.joelonsoftware.com/default.asp?joel .3.219431.12

Arnon Rotem-Gal-Oz's "Frameworks vs. Libraries"
http://www.ddj.com/blog/architectblog/archives/200 6/07/frameworks_vs_l.html

That being said, there are plenty of features in Prototype which are more library-like than framework-like, so it is easy to use parts of it without buying into a whole framework methodology. I don't know much about the other evaluated tools.

My experience with Dojo

[hansamurai]

I have had an experience very close to the author's. My group at work maintains an internal app served with Websphere, just like the author. We have a tree of nodes that recently ballooned in size to 40,000 nodes and this was causing our CSS/javascript tree to choke as it loaded everything once and used the CSS to handle opening and closing of nodes. It would take about 5-10 seconds to load the tree once, but after that it would perform nicely. We wanted a near instant load at start and then whenever you expanded a node it would grab its children from the database and display them then. My coworker and I didn't have any AJAX experience when we started working on this problem so we turned to frameworks.

First think I looked at was the Google Web Toolkit, and dismissed it as quickly as the author. I suppose if we ever rewrite our app from scratch we'll maybe consider it, but not right now. Then I found dojo, and we started using that to implement a dynamic loading tree. I got it working and plugged into our database fairly quickly, but found out it wouldn't help us much. Clicking on a parent to display its children can take anywhere from 1 to 15 seconds depending on the how many children it has, and also basically freeze your browser while it's doing that. It also either had a memory leak or just managed memory inefficiently because the browser's memory footprint would balloon in size as you clicked more and more nodes.

My coworker eventually took it into his own hands and started hacking the dynamic loading himself. I've been busy with other projects so I don't know how he did it exactly, but it's a combination of our old CSS tree and some dynamic loading to speed up the initial load. Clicking on a massive parent can still cause some slow loading, but it was better than dojo. I think dojo is a great toolkit, but when you just want to pull one specific piece out of it, it can be cumbersome and bloated. Also, the documentation sucks and if I needed help, I mostly just read over old bug fixes and such. I forwarded my coworker this article so maybe we'll look into YUI.

Re:Just don't choose them all!

[maxume]

Was it digg?

jQuery, too!

[sbma44]

It takes the magical $() selectors of prototype, expands on them, and somehow delivers it all in 19k.

Another good option

[cabinetsoft]

is jQuery and it's plugins.

Old News?

[russcoon]

I'm Alex Russell, Project Lead for Dojo,

We're obviously flattered that our little project got covered in DDJ, couldn't they have reviewed newer versions of the tools they covered?

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Comment removed based on user account deletion

AJAX frameworks are NOT pointless

[francium de neobie]

There are many little funny things that just happens when you're coding a web application in JavaScript without a framework/library/toolkit helping you. Unless you're really an AJAX/JavaScript wizard, coding an AJAX-enabled web application on your own and mixing online code receipts is a very dangerous thing to do.

Browser inconsistencies
This is the most obvious one, but only the entry to the rabbit hole. If you are not familiar with the example (maybe not exactly the same, but any AJAX web developer worth his salt should have seen one like that) I give below, then please, PLEASE, do yourself, your fellow developers and your users a favor, resist the urge to hack things together for once, use a mature AJAX framework.

An important part of AJAX is that you need to update what is displayed on the web browser in the client side (by JavaScript), without refreshing the page. This implies that you're very likely to have to create and destroy DOM nodes on the fly. Now, how do you create a radio button in JavaScript?

How about...

var node = document.createElement("input");
node.type = "radio"
node.name = ...
node.value = ...

That's what you would do if you follow the DOM standard. But sorry, this does not work. Try to create a radio button with the above code segment in Internet Explorer 6, you'll get a broken radio button - you can't select it. The correct way to create a radio button by DOM manipulation is described in this MSDN article:

newRadioButton = document.createElement("<INPUT TYPE='RADIO' NAME='RADIOTEST' VALUE='Second Choice'>")

Memory leaks
The last one was easy. Do you know you can make a web application that leaks memory like a sieve in Internet Explorer 6 by making a simple circular reference like the following one?

var node = document.createElement("div");
node.someAttr = node;

If you're a good programmer, I might have sounded an alarm in your head right now - any circular references involving DOM nodes in IE6 results in memory leaks that persist after URL changes or page refreshes - unless you use an AJAX toolkit that takes care of the issue for you. Have you assigned a DOM as an attribute value under another DOM node in the past? Yes? Then you'd better check your web application for memory leaks with Drip, now.

What's more, it's not just assigning DOM nodes as attributes that would result in memory leaks, closures in JavaScript can also form circular references and cause memory leaks. What makes closures particularly dangerous is that circular references with closures are not easy to spot. For example, the following code segment leaks:

var node = document.createElement("div");
var clickHandler = function(){};
node.onclick = clickHandler;

Looks innocent enough, but you've already formed a leaky circular reference here. node->clickHandler->node.

For more information about memory leaks under IE6, read these:
Mihai Bazon's blog entry
MSDN's lengthy and confusing description of the problem


The XMLHttpRequest object is not as simple as you think
Much of the magic of AJAX comes from the XMLHttpRequest object (or its ActiveX equivalent, or an iframe, etc.), right? Sure. If you're only doing something simple via AJAX (like, updating the server time), then you can just copy an XMLHttpRequest code snippet from sites like this and hack away, right?