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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