AJAX
Web applications have certainly come a long way since the advent of the World Wide Web nearly two decades ago. With each passing year, advances in technologies available to web developers help to create a more immersive and interactive experience for the end user. We’ve also seen a major shift in the way applications are delivered to users—more and more software is being delivered on the Web to be consumed using a web browser, rather than being delivered as a hard-copy desktop application. While web applications are generally faster to develop than traditional desktop applications, they aren’t without their shortcomings. Desktop applications have always had a richness that developers have gone to great lengths to duplicate in web applications to mixed results.
In the classic web application model, user actions in the interface, such as clicking on a link, trigger an HTTP request back to a web server. The server does some work--which can mean any number of things depending on the application--and returns an HTML page to the user. While technically sound, this model doesn’t make for a great experience for the user; when you click on a link, you must wait for a response. I’m sure most of us can agree that getting said response can sometimes take a bit longer than we’d like. What the user sees once the response comes back is the entire web page reloading so that they can see the content they’ve requested from the server. Sometimes it seems a bit cumbersome, doesn’t it?
If we could reinvent the wheel, we wouldn’t want users to wait around while the server does its thing. Once an interface is loaded, why should the user interaction come to a halt every time the application needs something from the server? In fact, why should the user see the application go to the server at all?
Enter Ajax. The name is shorthand for Asynchronous JavaScript and XML, and it represents a fundamental shift in what’s possible on the Web. You may not be familiar with the term, but you’ve seen it at work if you’ve used applications like Google Suggest, Gmail, and Google Maps.
In a nutshell, the Ajax engine acts as an intermediary between the server and the user. When a user makes a request on a web page that uses Ajax, the Ajax engine will handle the request and post the result back to the page as soon as it’s received from the server, all without having the browser reload the entire page. This might not seem like a big deal, but that seemingly small step has opened up a world of possibilities for developers to create faster, more responsive applications on the Web, which in turn can make the end user’s Web experience a great deal more enjoyable.
A simple example of an Ajax implementation is the aforementioned Google Suggest (http://www.google.com/webhp?complete=1&hl=en). Every keystroke from the user invokes the Ajax engine as it polls Google for suggested searches, as well as the number of results you can expect for each suggestion. Can you imagine using this same application if every keystroke would have the browser reload before you could see a list of suggestions? Ugh.
While Ajax isn’t a brand-new idea (it’s technically been around for quite some time), it’s generally believed that developers have only really begun to tap its enormous potential. What’s great is that for the most part, the challenge in creating an Ajax application isn’t technical—the technologies that drive Ajax are common and well-understood by most web developers. What this means is that instead of spending a great deal of time learning a new technology, developers can face a bigger challenge: re-imagining the Web as an exciting medium full of possibilities.
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