At the Forge - Beginning Ajax

How to put the A (asynchronous) in Ajax.

This month, we finally begin to use Ajax in an application. We see here how it is possible to take some existing JavaScript code and break it apart into two functions: one that invokes the Ajax call and the other that handles the parsing of data when the call receives a response.

However, we also see that there are security and efficiency problems with this approach. A better technique would be to send only the requested user name in the Ajax call and get a simple yes or no answer from the server, indicating whether the user name had been taken already. Next month, we will do just that, using an Ajax POST query instead of our GET query from this month, and replacing usernames.txt with a server-side program that works in conjunction with our Ajax call.

Reuven M. Lerner, a longtime Web/database consultant, is a PhD candidate in Learning Sciences at Northwestern University in Evanston, Illinois. He currently lives with his wife and three children in Skokie, Illinois. You can read his Weblog at