Ajax—A Paradigm Shift
The advent of Ajax has put an end to the arduous struggle of web application development communities worldwide to find a technology that can not only improve response times, but also allow for asynchronous processing. Ajax is a technology with cross-platform, cross-architecture, and even cross-browser support. In fact, Ajax has already become recognized in Microsoft and Sun development communities for building lightning-fast web applications with improved response times, which results in awesome user experiences. Note that Ajax is a technology; it is not specific to ASP.NET or Java. You can use Ajax in both of the preceding technologies. Moreover, you can use Ajax in any web browser, such as IE, Mozilla, Firefox, and so on.
There's an old proverb that says, "The old order changeth yielding place to new." With the introduction of Ajax, there has been a paradigm shift—we have moved away from the earlier trend in which we had to force a postback to retrieve data from the server. With Ajax, we can do the same even without a postback to the web server. The result is improved response times and better performance of the application as a whole.
Ajax uses the XMLHttpRequest object, a JavaScript object that can communicate directly with the web server to retrieve data, without the need to reload web pages each time data is requested. We discuss more on XMLHttpRequest object in Hour 3, "Working with the XMLHttpRequest Object."