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DHTML Utopia

Posted by timothy on Mon Aug 01, 2005 04:00 PM
from the ah-heaven dept.
Books Media Programming The Internet IT Technology
Bruce Lawson submits the review below of Stuart Langridge's Excellent guide to creating dynamic web pages; scalable and sensible., writing "Don't be put off by the title: the DHTML here bears no resemblance to the stupid Web tricks of the late 90s that allowed animated unicorns to follow your cursor or silly Powerpoint-like transitions between Web pages." Read on for the rest.


This book is the opening salvo in the latest battle in the Web Standards war -- the battle for unobtrusive JavaScripting, or Unobtrusive DOMscripting as many call it, in order to rid it of all the negative connotations that "DHTML" and "JavaScript" bring. Combined with the non-standard XMLHttpRequest object, it's sometimes referred to as "Ajax". Terminology aside, though, what are the substantive differences between the old-skool and the "modern" of the title?
  • Graceful degradation. A great example of this is Google Suggest in which the DOMscripting enhances functionality by making the page feel more responsive, but if you don't have JavaScript for some reason, the page still works.
  • Separation of structure, presentation and behaviour. The DOMscript deals with the behaviour in the same way as CSS defines the presentation in the brave new Web standards world, and the three remain separate. The html has no JavaScript in it at all -- everything is handled by in separate code files.
  • No browser sniffing. This aims to future-proof code by testing for features rather than sniffing for browser name and version. So, before using the TimeTravelCureCancer method, the current browser is tested to see whether it's supported. If it is, the script continues. If it isn't,the script silently fails with graceful degradation.

Theory sounds cool -- how's the damn book?

I was pleasantly surprised by how quickly the book gets to work. Even before page numbering begins, the introduction has a lucid and compelling argument for using HTML 4.01 rather than XHTML as the markup language of choice.

Chapter 1 has a brief (6-page) overview of the importance of valid code and separating presentation into CSS, and a short description of the unobtrusive nature of Langridge's scripts: no script in the mark-up at all; instead, the .js files contain "event listeners." The reasons why this is desirable are promised later.

Chapter 2-4: The basics

Now that document.write in the html is no longer needed, you need to know the "proper" way to add text or elements to a Web document. So Langridge gives us a tour of the DOM, showing how to walk the DOM tree and create, remove and add elements to the tree. It's methodical, and by the time I was beginning to get a bit tired of theory and thinking that you'll have to prise document.write out of my cold, dead hands, we get an "Expanding form" which allows us to expand a form ad infinitum to sign up as many friends as you want to receive free beer, without ever going back to the server. (You can see such a thing in action in gmail, when you want to attach multiple documents to an email).

I started to warm to the author and his style. 33 pages into the book, and we get a real-world working example to examine (I like my theory liberally garnished with practice). I also feel a kinship with authors who fantasise about mad millionaire philanthropists giving away beer.

By chapter 3, we've really got going. Apart from one rather pedantic edict (the event is mouseover, the event handler is onmouseover and we should separate the nomenclature, even though it makes no practical difference), the focus here is on real-life browsers. And, as we all know, in Web dev books, real-life browsers means grotesque exceptions to our ideal-world rules .Strangely -- and oddly satisfyingly to this PC user -- the culprit isn't only the perennially despised IE/ Win; shiny Safari comes in for a good bit of stick!

The real-world example here is a data table that highlights the whole row and column of any cell that's being moused-over. Now, in any modern browser except for IE/ Win, the row could be given a hover pseudoclass (IE/ Win only allows :hover on anchors). But as there is (weirdly) no HTML construct for a column, this effect can only be achieved through DOMscripting. What the script does is to dynamically append a class name to every cell in the row and column at run time -- and the pre-defined CSS file determines the styling of that class.

Herein lies an advantage in Unobtrusive DOMscripting: you could just take this script and plug it into a Web site without changing any of the html (except to add a link to the script file in the head). But the script is relatively complex for a newbie to code, and for the techniques to be widely used, I suspect that the billion old-skool cut'n'paste JavaScript sites will need to be replaced with a single, canonical library of modern scripts for people to cut and paste from. For those who find CSS challenging, JavaScript is probably even more complex. .

Chapters 5 - 7: blurring the division between Web UI and application UI

It's a truism that the Web has set back UI development some years -- in fact, back to the old dumb-terminal paradigm of filling in a screen full of data, pressing the button to send it back to the mainframe and waiting for the next page to be sent -- or the old one returned with errors noted.

Langridge shows that we can make the experience smarter than this, going beyond the traditional JavaScript client-side validation interactivity by adding animation to allow text to fade in and out over time, styling tooltips to be sexier than the default yellow box and which can gently appear into view rather than the browser default on/ off state are examples that struck me.

When I first read these, I thought they were cheesy gimmicks -- the modern equivalent cursor-following unicorn -- until I considered more deeply and realised that many of the UI elements that we enjoy in modern desktop apps are precisely these small, cosmetic effects: abrupt transitions, lack of transparency, sharp edges to UI widgets all feel like old operating systems or clunky Web pages.

It's not all touchy-feely; we get auto-complete text entry, degradable calendar pop-ups, flyout menus and lessons in OOP, encapsulating code for re-usability, and avoiding Internet Explorer memory leaks.

Chapters 8- 10: seamlessly working with the Server

So far, so client-side. Where Unobtrusive DOMscripting really gets developers juices flowing is the ability to communicate with the server without obviously refreshing the page. Chapter 8 takes you through a variety of methods. Some, like the hacky iframe method or hideous 204 piggyback method are so gruesome that I breathed a sigh of relief loud enough to wake the cat when I finally turned the page to read "XMLHTTP". This method (which is non-standard and introduced by Microsoft) has ushered in the Next Great Web Thing: asynchronous communication with the server. Langridge walks through using the Sarissa library to make a user registration form that checks whether the user name you choose is taken, and if so, suggest some alternatives without refreshing the page.

There's a lot of unresolved accessibility problems with the Ajax method (how does a screenreader alert the listener to the fact that something new has appeared on the page? How do they navigate and hear the new stuff in context?) and while it is laudable that Langridge notes these issues exists, I'd hoped he would have suggested some solutions. He doesn't, but as he's a member of the Web Standards Project's DOMscripting task force I'm guessing it's being worked on.

The project that really kicks ass in this section is a file manager, like the one in most people's Web site control panels, where you can actually drag and drop the icons, like an operating system, and the server does the work. Langridge carefully goes through all of the steps, all of the pitfalls and all of the code needed to make this happen in any modern browser.

It doesn't take a lot of imagination to realise just how this could revolutionise the Web experience. Drag and drop products into a shopping cart. Drag the shopping cart to the checkout icon. Moving money around bank accounts in some integrated internet banking application. The possibilities are huge.

Conclusion

The whole technique of unobtrusive DOMscripting needs further research before it's ready for prime time -- particularly from an accessibility point of view, but then as an accessibility bore you'd expect me to say that. I think it's beyond question that there's ideas in here that radically enhance the usability of Web-based applications by making them more intuitive and more like the desktop drag-and-drop interface we know from our desktops.

This is a good-humoured, thoroughly-researched book that combines theory with practical learn-by-doing examples. To this reviewer, the code appears scalable and sensible. This book is never going to appeal to the quivering aesthete designers -- probably because it's fundamentally about code. But precisely because it proposes a complete separation of code and design, it facilitates the advancement of the Web.

You can purchase DHTML Utopia: Modern web design using JavaScript and DOM from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
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  • Unicorns (Score:5, Funny)

    by onion2k (203094) on Monday August 01 2005, @04:07PM (#13217497) Homepage
    stupid Web tricks of the late 90s that allowed animated unicorns to follow your cursor

    If my boss reads Slashdot I think I know what I'll be asked to add to the corporate website tomorrow morning..

  • Birth of Ajax (Score:4, Informative)

    by webword (82711) on Monday August 01 2005, @04:07PM (#13217504) Homepage
    For your reference, this is how "Ajax" got started. I'd say about 75% of the article is useless, but about 25% is actually useful. The main value of the article can be summed up in two words: Mi>eye candy. Jesse James Garrett is good with graphics.

    Ajax: A New Approach to Web Applications [adaptivepath.com]

  • Why do it yourself? (Score:5, Interesting)

    by MosesJones (55544) on Monday August 01 2005, @04:10PM (#13217528) Homepage
    The challenge with Ajax, and complex DHTML is that a slight error produces big problems. Its a shame that the book doesn't look at the tooling approaches for instance the Ajax plug-in [java.net] that Sun have released (via Open Source). DHTML and these active elements can be great, but as a practice I'd be more inclined to have a few people invest time in developing components that the majority of people can use, rather than having lots of people trying to understand the complexities, and buggering it up.

    Interesting technology, but too easy to use REALLY badly. It would have been nice if the the book had covered how to build SOLUTIONS using DHTML, rather than focusing on how an individual can use it.

    • While plugins like the one that Sun released are nice, the battle of course is with flexibility. That's why people build their own content management or forum systems, even though there are plenty of choices like Mambo and PHPBB. Sure, plugins are at a lower level, but the point stands--they can't always provide the flexibility necessary.

      The challenge with Ajax, and complex DHTML is that a slight error produces big problems.

      I think the challenge with any program is that errors produce problems. That'
    • The challenge with Ajax, and complex DHTML is that a slight error produces big problems.

      I think that slight errors in any framework or programming language can cause big problems and not something particular about AJAX.

    • but as a practice I'd be more inclined to have a few people invest time in developing components that the majority of people can use, rather than having lots of people trying to understand the complexities, and buggering it up.

      Did you RTFA or even the post? An Open Source cross-browser implementation called Sarissa [sourceforge.net] does that.

      Sarissa Oveview:

      Sarissa is an ECMAScript library acting as a cross-browser wrapper for native XML APIs. It offers various XML related goodies like Document instantiation, XML loa

  • Please... Don't (Score:4, Insightful)

    by esconsult1 (203878) on Monday August 01 2005, @04:14PM (#13217559) Homepage Journal
    It doesn't take a lot of imagination to realise just how this could revolutionise the Web experience. Drag and drop products into a shopping cart. Drag the shopping cart to the checkout icon. Moving money around bank accounts in some integrated internet banking application. The possibilities are huge.
    I'd really hate having to do the above. What would be better and smarter (IMHO), is to:
    1. click on the "Add to Cart" button
    2. AJAX adds the product to the card without refreshing the page.
    It seems to me that AJAX works worderfully in limited cases that gets rid of the annoying browser refresh problem.

    Expect to see flooding the internets(tm) over the next few months annoying over-use of AJAX in every single way that programmers can -- even if they don't need to.

  • Ruby on Rails is really sweet for that AJAX stuff.
      • Why not respond to this post saying how Ruby on Rails and AJAX can work together?

        Ruby on Rails has clean, built-in support for template code that generates the client-side Javascript for using the prototype.js library.

        It makes it next to trivial to create, for example, Google Suggest text fields because the developer focuses on using Ruby syntax to indicate the server action to invoke, based on what client behavior, and what to do when the results come back to the browser. The annoying little details

  • Bookpool has this book for $24.95 with no club to join. Bn.com has it for $39.95 (save $5 if you're a club member).
  • Why is HTML 4.01 better than XHTML?
    • It's not. DHTML (if this is the same DHTML of old) is a leftover of the browser pissing-contests of the 90's, and represents an obstacle to standards adaptation.

      Let's drop DHTML like the steaming sack of decaying garbage it is and focus on writing quality, structurally sound, and accessible code.

      • I'm sorry, that makes no sense. DHTML has nothing to do with browser pissing contests (those just made it hell to implement.) DHTML is the aggregation of (X)HTML/Javascript/CSS to make a page less static.

        The lack of standards has made pretty much anything implementing DHTML a steaming pile, but DHTML itself is just a technique. And if you're willing to ignore four year old browsers, the state of affairs has gotten to the point that you can write decent code properly separated from your presentation.

        • But add XMLHttpRequest to it and suddenly you have don't have a standard. Wooo!
          • XMLHttpRequest is pretty much a defacto standard in the major modern browsers. All the modern browsers are the same except (of course) for IE which doesn't implement it internally and requires an ActiveX instantiation. However, that is very easy to code around and then you have a cross-browser implementation of XMLHttp such as Sarissa [sourceforge.net].

            As long as you don't need to support 4-5 year old browsers, XMLHttp works fine. If you need to support 4-5 year old browsers, either force your users to upgrade (by not s

                • I don't know anyone who uses it...

                  Of course you won't find any Windows users who use it! Duh! But it's the default browser for KDE, which I understand is a wildly popular desktop for Unix.

                  As for XMLHttpRequest, I only know what I've been told. And I've been told that the only reason all the new Google apps don't support Konqueror is the lack of that non-standard item.
                  • I'm curious. At what point does something become a standard? After all, I'm pretty sure Sir Berners-Lee didn't worry about all that standardization stuff when he released WorldWideWeb in 1990 - he simply told people how to write HTML that his code could read. This is approximately four years before W3C even existed.

                    XMLHttpRequest is available, in a mostly identical form, in the current stable versions of Internet Explorer, Gecko-based browsers (including Firefox, Netscape, Mozilla, and Camino), Opera, an

    • simple (Score:2, Funny)

      by Anonymous Coward
      Two years ago, the "Valid XHTML" button was leet as all hell. Now that everyone and their grandma's pantyhose produces valid XHTML (well, mostly (cough)), it's not cool. Since XHTML 2.0 isn't supported anywhere, people had no choice but to declare HTML 4.0 to be the new leetness.

      I think slashdot is smart for sticking with terribly invalid HTML 3.2. In another year or so, they'll be leet as fuck.

      I'll be lanching my new markup language soon, which is going to be so leet you'll shit your friends' pants.

      <web

    • Re:I give up (Score:3, Informative)

      by gusnz (455113)
      Long story short, to make effective use of XHTML you have to serve it as "text/html" to the browser, as IE doesn't support its proper MIME type (thanks, Microsoft!). Here's a good summary [hixie.ch] of the issues surrounding XHTML vs HTML 4.

      Personally, I don't mind using XHTML 1.0 as text/html, as although it's not quite "ivory-tower" perfect, it's still IMHO a little cleaner and more elegant. Either way, (X)HTML+CSS still beats the living daylights out of "any-old-HTML + tables".
      • So HTML 4.01 is better than XHTML because IE is broken? Isn't that like saying a Kia is better than a Ferrari because there is a 55mph speed limit?

        • Content negotiation is an old concept.

          It also reduces your cache hits, increasing server load and bandwidth costs, and slowing down your website.

          Your code is broken, BTW. You need to transmit a Vary header when you vary content based upon request headers, otherwise you can screw up caches so they send application/xhtml+xml to Internet Explorer.

    • Because XHTML is a pointless and overhyped waste of time and energy at this point.

      Read more of Stuart's thoughts on his website:

      http://www.kryogenix.org/days/2002/11/28/whats [kryogenix.org]

      http://www.kryogenix.org/days/2005/02/21/xhtmlHtml [kryogenix.org]

  • browser problem (Score:4, Interesting)

    by MatD (895409) on Monday August 01 2005, @04:39PM (#13217727)

    A lot of the annoyance of 'web apps' comes from the fact that browsers can't just refresh a simple tag on the page from the server. They have to re-render the entire page, causing a jarring visual experience for the user.

    Browsers should be able to realize that since the url is the same, diff the previous stream, and the current one, and modify the current page inline.

    As it stands now, web developers have to jump through a lot of hoops to get that sort of functionality. They shouldn't.

    • Sounds good. Let's see the code.
    • That *might* work to reduce rendering time depending on the engine. Some engines are slow with innerHTML calls, so it could be a wash.

      Most of the slowness with a page refresh is typically network latency and bandwidth bottlenecks. Browser tricks won't help with that.

    • Browsers should be able to realize that since the url is the same, diff the previous stream, and the current one, and modify the current page inline.

      Why don't you submit the code to re-parse the DOM tree and update the page in-line? You could submit it as BSD-licensed code so all browsers could use it, you would be famous!

      As it stands now, web developers have to jump through a lot of hoops to get that sort of functionality. They shouldn't.

      AJAX is _really_ not that hard as another poster pointed out. S

  • Granted, the reach is good and for some tasks there's nothing better than web UI, but as soon as you find yourself in need of building something more than just a bunch of web pages with links it all turns into mind-boggligly weir hackery. You start using javascript for layout. You need to manage state. The most trivial UI things become a fucking mess of JS and CSS "hacks", etc., etc. It's also a pain to turn all this crap into components for future reuse, so chances are next time you do something similar yo
  • I haven't read the book myself, but well done on a coherent review that covers the resurgence of unobtrusive scripting. The author [kryogenix.org] is quite well respected in the community, and I can only hope books like these begin to replace the "omg dhtml netscape 4!!11one" fare usually found on shelves.

    I think AJAX et. al. could be a bit of a diversion though from the ideals of "unobtrusive scripting" though. Many sites using XMLHttpRequest and similar techniques aren't easy to degrade in older, non-JS-supporting browse
  • Can anyone tell me why Microsoft's "XML Data Islands [w3schools.com]" didn't take off in the mainstream given that IE has had a 90% browser share? For external XML they are simple and neat and don't require any javascript whatsoever for basic fetch-and-display use (but you can enhance functionality using javascript).

    Here's a demo [w3schools.com] (use IE5 or later). I figure they must be in use somewhere because there's even a Mozilla article [mozilla.org] on getting them working in Mozilla.
  • For an example of drag and drop in use, check out Panic's website [panic.com]

  • Neither B&N nor Amazon see fit to display the TOC for this book. If somebody knows of somewhere it's listed could you post that here? I'd especially like to know if 1/3 of the book is appendices we don't need.

    Good review, BTW. Too bad about the book's cover. What's up with that? Although it did make me think of the Brazil dream sequences. Perfect for those dreary winter afternoons in the cubicle farm.

  • Funny, this book arrived today at my house. I was hoping the section on AJAX would be more extensive, but it's relatively slim.

    IMO, the layout of the book is good and it's written well - from first glance anyways.

    Can anybody point out any strong online resources on AJAX development? I guess it's not that difficult to grasp, but I would like a little more of a foundation.
      • I don't see why people hate giving others referals. I mean, when people get referal bucks it only costs Amazon.com money--why is everyone on the lookout to save Amazon a few dollars? It's not like it hurts you to help out someone in this case.
        • No, heaven forbid that guy makes a few bucks from people not intending to donate to his beer-and-porn fund.

          --grendel drago
          • ... heaven forbid that guy makes a few bucks from people not intending to donate to his beer-and-porn fund.

            Since it doesn't change the price I pay Amazon, I'm afraid that I just can't work up any rightous indignation about it. In fact, since (or maybe if) he's saving folks $10, I'd say it's pretty good if a few quarters land in his beer fund.

    • Unnecessary != not useful. Possibly buggy is irrelevent so long as you test properly.

      Does it take an Einstein to see which is the lowest-cost, lowest-bandwidth, most reliable solution?

      Does it take an Einstein to realise that it depends on what you are doing?

      Example: If you have something like Hotmail's signup page, you can save bandwidth by using XMLHttpRequest, because you'll get a hell of a lot of people constantly going back and forth on the registration pages trying to get a username that isn't

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