The concept behind Ajax was to overcome the continual request and load of new pages as the user interacted with the application. This is achieved by only updating the portions of the page that needed to be modified. The client (browser) is able to send more frequent requests that retrieve small amounts of information to update the page without interfering with the user.
This works by inserting what Garrett (2005) termed an Ajax Engine on the client side that was used to initiate asyncrhonous requests from the client to the web server and then process the responses including dynamically updating the HTML and/or CSS content on the page. All of this could occur whithout impacting the users interaction with the application.
The Ajax Engine consists of a series of Javascript functions that use the XMLHTTPRequest object to make calls to the server to request additional information. Part of the beauty of Ajax is that it works on most browsers and is not dependent on the server side technology employed. However, there are some minor differences between the browsers in regards to creating the XMLHTTPRequest object.
In my next post I will take at look at what some basic Ajax Javascript code looks like to communicate with the server.
Next: Ajax on the client
REFERENCES
Garrett, JJ 2005, ‘Ajax: A New Approach to Web Applications’, Adaptive Path, viewed 24th May 2008,
<http://www.adaptivepath.com/ideas/essays/archives/000385.php>
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