Chapter 15. Introducing Ajax

The Web is always changing, and for Web and JavaScript developers the ground shifted under their feet beginning in early 2005. New and immediately popular Web applications appeared, some of them from Google, such as Gmail and Google Maps, and some from others, such as Flickr and the MyYahoo! portal. The common denominator of all of these new sites was that they acted more like desktop applications, with fast, responsive user interfaces. Instead of the traditional Web application, where the user clicked, waited some number of seconds for the server to respond and refresh the page, and then repeated the process, these new sites were more reactive, updating pages right away, providing superior interaction, and making for a better user experience.

There was something new (actually not so new, as we'll see) powering these sites, and it is called Ajax . You can use Ajax techniques to make your sites more responsive and attractive, which makes your site's users happier in the process. Best of all, you don't have to learn a completely new technology, because Ajax is made from building blocks that you already know (and that we've covered earlier in this book).

In this chapter, you'll learn how to request information from the server in the background and turn it into a form your Ajax application can use; automatically refresh the information from the server; build a cool previewing effect for objects on your page; and build an Ajax application that auto-completes form fields, just like a desktop application. Let's get to it.