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Keywords: Ajax, JavaScript, web applications, XML Title: Head Rush Ajax Author: Brett McLaughlin Publisher: O'Reilly ISBN: 0596102259 Media: Book Level: Introductory Verdict: A fun-packed intro into Ajax development

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Head Rush Ajax follows in a long(ish) line of 'Head First' books from O'Reilly, from 'Head First Java' to 'Head First Design Patterns' via EJB, 'Servlets and JSP' and 'HTML and CSS'. The series is unique in technical publishing - the books are irreverent, funny, engaging and technically accurate. The question is, does it work for a book on Ajax? Surely a book on JavaScript and the DOM can't be fun?

The book starts with the premise that the reader wants to quickly get to grips with the core technologies that make up Ajax. And when you think about it, that's a fairly diverse mix of things. Aside from the JavaScript, there's the document object model (DOM), there's asynchronous communication between the server and the browser, there's the browser itself and then there's XML and… You get the picture, it's a wide mix of technologies and yet gluing them together can give the developer that full-on Ajax experience of fast, responsive and good looking applications.

The author assumes a modicum of knowledge - it's assumed for instance that you know about HTML and how a web page is put together. It's assumed that you know that for a dynamic data-driven application the browser needs to communicate with a server at the back end. And it's assumed that the reader has some basic knowledge of JavaScript. That's it, with those already in the bag the reader can dive into this book and start to figure about what the Ajax buzz is all about.

The starting point for Ajax, and for this book, is that web reloads (hitting a submit button on a form and then waiting for the page to reload) are a pain. Ajax is about making web applications that are responsive - that means pages that update as the user is typing, web applications that act more like a desktop app than an elderly green screen app connected to a mainframe. So, the opening chapters set the scene, showing both the problem and introducing the Ajax solution.

The subject is then studied in more detail - for example there's more on what asynchronous really means. This is followed by a couple of chapters that look at the document object model, and how this is used to change and update sections of a web page. XML gets more coverage, as well as some coverage of an alternative to XML in the form of JSON.

There are some technical details worth singling out. Firstly the server side examples mostly use PHP, but there's nothing especially complex to do at the back end so it's really a minor implementation detail. Secondly the author uses a number of JavaScript libraries rather than coding every example from scratch. This is probably a benefit for most reader, but for those who want to see every nut and bolt the libraries are downloadable.

In all 'Head Rush Ajax' really does cover all of the core Ajax material. The examples are useful, and the Head First (or should that be Head Rush?) approach of mixing cartoons, humour, quizzes and other mind-grabbing exercises does work well. Other, more staid, introductions to Ajax may have greater depth on the technical side, but this one works well for true beginners and those who just can't get on with a traditional technical tutorial.