Slashdot Mirror
DHTML Utopia
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.
DHTML Utopia: Modern web design using JavaScript and DOM
author
Stuart Langridge
pages
300
publisher
Sitepoint
rating
8
reviewer
Bruce Lawson
ISBN
0957921896
summary
Excellent guide to creating dynamic web pages; scalable and sensible.
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?
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.
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.
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.
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 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.
An Eye for an Eye will make the whole world blind - Gandhi
Why is HTML 4.01 better than XHTML?
I've abandoned my search for truth; now I'm just looking for some useful delusions.
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.
Since when did operating systems become a religion?
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 you'll have to reinvent the wheel.
The web was originally invented for publishing hyperlinked documents. It's nice to see it come this far, but web as it is is not designed for writing _applications_.
As far as I'm concerned XAML and XUL are the way of the future. Do as much as you can on the client, communicate only what you need to the server, don't re-render everything every time the user needs to change something, concentrate rendering on the client as well.
Remember these simple mantras if you plan on doing a lot of web development in the coming years.