Building Cloud Applications with Google App Engine Charles Severance (part 1)

In this chapter we will improve the interactivity of our application using some simple AJAX (Asynchronous JavaScript and XML) support to our application. AJAX allows us to update parts of the screen. Increasing use of AJAX has allows web applications to approach the rich flexibility of Desktop applications. If we look at the Chat screen, we see an area that changes on each screen refresh and an area that stays constant on each screen refresh:

We will use AJAX to update the outlined area without updating the overall screen. jQuery AJAX has been evolving since Microsoft introduced the first form of AJAX (XMLHttpRequest ) in 1999. In the early days, AJAX and JavaScript and the browsers support for the document object model (DOM) were very much in flux and it took quite a bit of effort to keep one’s AJAX code working over successive releases of many browsers over time.As widely used applications such as Google Mail made increasing use of AJAX, it caused browsers support for AJAX to improve over time. Also libraries were produced that shielded the typical developer from cross‐browser differences. These two trends have combined to make the use of AJAX  elatively straightforward and something that can be integrated into a wide range of applications to improve the usability of those applications.

One of the more popular of these AJAX/JavaScript libraries is called jQuery and available from: http://jquery.com/

To add jQuery to your application, download the jQuery JavaScript code and install it in your static folder as follows:

and...

to be continued .

be patience.