Foundations of Ajax

Craig Maloney writes "You've no doubt heard about Ajax. Practically every new and exciting application on the web uses some form of Ajax. Google's suite of applications (GMail, Google Maps, etc.), Amazon's A9 search engine, and Netflix use Ajax interfaces to give the user a better browsing experience. By using some pretty basic innovations to current technology, browsers can now deliver content in ways unimaginable only a few short years ago. Foundations of Ajax provides developers who haven't taken the time to look into Ajax a hands-on guide for quickly leveraging these technologies in their own applications." Read on for Craig's review.

Foundations of Ajax
author	Ryan Asleson and Nathaniel T. Schutta
pages	273
publisher	Apress
rating	8/10
reviewer	Craig Maloney
ISBN
summary	A good first-look at Ajax and client-side development using JavaScript, HTML, and CSS.

Foundations of Ajax starts with a brief history of interactive web-applications, starting from the crudest CGI and Java Applets, and chronicling various interactive technologies (Javascript, Servelets, ASP, PHP, Flash, DHTML, and the various XML browser languages like XUL, XAMJ, etc.). Ajax seems like another acronym in a sea of acronyms, but the authors quickly point out why Ajax can help with the development cycle. Ajax allows the server to validate the user's input, without creating ugly and messy JavaScript validation rules, and it allows the server to use the same rules for input validation on both the client and the server. Unfortunately, Ajax does break some of the conventions users have grown accustomed to in using traditional web applications. XMLHTTPRequest requests aren't stored in the browser history, and it can be confusing to the user to determine what changed on the page after refresh. Issues aside, the book is very encouraging on the prospects of using Ajax in web applications, and invites the reader to use Ajax where it makes sense.

Chapter 2 talks about the request method that makes Ajax possible: XMLHTTPRequest (XHR). The XHR methods are explained with several examples that detail the fundamentals occurring with the request. The examples are very clear, and the entire process is laid out in careful detail, although the Dynamic Object Model (DOM) is mentioned, but not explained until the end of the chapter.

Chapter 3 delves into server communication. It's interesting to note that the authors haven't instantiated a server yet for their Ajax communication, and for the balance of chapter 3, the server is replaced by text files. It's not until the GET/POST examples that the authors start using Servelets. While it may seem strange for the authors to be talking about client/server programming without instantiating a server, it does allow the developer to get their proverbial feet wet without battling server configuration issues. The chapter starts by introducing innerHTML, but then moves to using XML DOM for data transfer from the client. From there, the authors demonstrate a few examples of the server sending XML to the client, and the client sending XML to the server. Happily, the authors weren't content to leave us parsing XML using JavaScript, instead they finish up the chapter by introducing the JSON framework with a few examples.

Chapter 4 is really where the book starts doing very interesting examples with Ajax. It's also, coincidentally, the largest chapter in the book, and the chapter readers will find the most useful reference examples. The book steps through the creation of examples of Simple date validation, Reading response headers for a simple ping application, Dynamically Loading List Boxes, Automatically Refreshing Pages, Progress bar (a personal favorite), Tool tips, Accessing Web Services using REST, and Auto complete. Each example is introduced with a real-world working application as an example (such as the auto complete feature of the Google search engine), and could easily be implemented in a developer's application. I found myself thinking of ways to enhance my code using these techniques.

Following chapter 4's examples, the chapters on creating a developer toolbox, testing scripts using JsUnit, and debugging Javascript seem a bit of a let-down. Chapter 5 outlines various packages for helping JavaScript coders to better spot errors in their code, and create documentation using the JavaDoc-like application JSDoc. There is also a mention of an application for crunching and compressing JavaScript code, as well as the excellent Web Developer Extension. Rounding out the chapter is a brief history of JavaScript, and some advanced JavaScript techniques. Chapter 6 introduces JsUnit and Unit Testing. Chapter 7 talks about JavaScript debuggers, such as Microsoft's Script Debugger, and the very powerful Venkman. The Venkman tutorial is very good, and would be a great starting point for anyone wanting more information on how to use this great tool.

Chapter 8 rounds out the book with the typical "for more information" sites to visit. However, in true Steve Jobs "One more thing" fashion, the authors not only plug their Ajax Framework, but also create a browser-based, Macintosh-like Dashboard application with four widgets. I was all set to finish the book, but the authors quietly slipped the best for last in the final pages of the book, bringing out a complete Mac OSX-like "Dashboard" windowed-environment in a browser complete with the drag-and-drop elements I've most associated with Ajax sites. This is by far the most complicated project in the book, and it make for an excellent ending to an already fine book.

Foundations of Ajax is a great starting point for developers wondering how they can incorporate Ajax into their own web-based projects. One minor gripe I had with this book was the examples looked pale in comparison with their real-world models, but design is hardly the focus of the book. Where Foundations of Ajax shines is it's no-nonsense introduction, implementation, and expansion of the basics of Ajax programming, leaving the reader confidently ready to utilize the concepts within. The authors have seen the potential of Ajax, and competently convey their expertise and enthusiasm for this technology."

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yep, its a good book

[DeveloperAdvantage]

I have actually read/worked through this book and indeed it was not only one of the first books on Ajax but also one of the better books on Ajax. Some of the portions are now a little outdated, like the discussion on frameworks, but these areas can easily be filled in with a little research on the Internet.

I've read this book and...

[LaptopHeaven]

I picked this book up on my last trip to Vegas. I read it cover to cover. I found it to be on the elemtary side of the AJAX discussion. I was disappointed when I found most of the content, code examples and demos can be found online in different places. AJAX is just a hot topic right now, I find this book as an attempt to ride the coat tails of the AJAX phenom.

OK book

[wanorris]

I have this book. It's a pretty straightforward introduction to the topic. The central problem with it is that all the examples that use server-side components only use Java.

If you use Java, great. But the book title is misleading, and it should be called "Foundations of Ajax in JavaScript and Java."

The other caveat: the book is designed for people who want to use Ajax to spruce up an existing web page a little, not design new applications built from the ground up to use Ajax as the data transport mechanism. If this meets your needs, great. If you're looking to do bigger stuff, get "Ajax in Action" froom Manning.

Simple samples with readable code

[wysiwia]

Some very simple samples but with understandable code, just go to

http://wyoguide.sourceforge.net/test/tree1.html [sourceforge.net]
http://wyoguide.sourceforge.net/test/tree2.html [sourceforge.net]
http://wyoguide.sourceforge.net/test/tree3.html [sourceforge.net]
http://wyoguide.sourceforge.net/test/tree4.html [sourceforge.net]

try them out and view the source. For more info go to http://dojotoolkit.org/ [dojotoolkit.org]

O. Wyss

JsUnit and AJAX don't mix!

[Darkforge]

I had originally picked up a copy of this book because it appeared to be the only book on the market that spent any time discussing automated testing of AJAX components.

As I'm sure you all know, testing AJAX stuff in multiple browsers is really important if you want to guarantee cross-browser compatibility; it's also really tedious. JsUnit seemed like it would be a promising tool for AJAX automation.

In fact, I'm sad to say, JsUnit can't be used to validate AJAX components at all; in fact, it can't it be used to validate *any* command that requires a callback, including XmlHttpRequest, event handlers, pop-up windows, etc.

This is because browsers (IE/Firefox both) interpret JavaScript in a single thread, but actions you perform may have asynchronous side effects OUTSIDE of your own thread. So when you attempt one of those fancy asynchronous XmlHttpRequests, you can't just sleep/wait until your request finishes, because it will *never* finish until you completely return from your current thread. Only then will the interpreter begin working on the next item in the event queue.

That means, among other things, that it's impossible to wrap an AJAX request in a "try/catch" block:

try {
      doRequest();
      waitForRequestToFinish();
      assertRequestWasSuccessful
  } catch (e) { // do something }

Because this will never work, JsUnit's strategy of emulating JUnit or the other *Unit frameworks is fundamentally unsuitable for testing AJAX in multiple browsers.

If you *are* interested in testing AJAX applications in multiple browsers, I recommend looking into Selenium [openqa.org], which basically works around the problem by constantly scheduling timers to re-invoke itself every 10ms... that gives the interpreter enough time to do other work, and allows Selenium to implement a simple "pause" action that actually works.