AJAX Quick Glance :Pat2

How it Works?

Ajax uses a programming model with display and events. These events are user

actions, they call functions associated to elements of the web page.
Interactivity is achieved with forms and buttons. DOM allows to link elements of

the page with actions and also to extract data from XML files provided by the

server.

To get data on the server, XMLHttpRequest provides two methods:
- open: create a connection.
- send: send a request to the server.
Data furnished by the server will be found in the attributes of the XMLHttpRequest

object:
- responseXml for an XML file or
- responseText for a plain text.

Note:a new XMLHttpRequest object has to be created for each new file to load.

We have to wait for the data to be available to process it, and in this purpose,

the state of availability of data is given by the readyState attribute of

XMLHttpRequest.

States of readyState follow (only the last one is really useful):
0: not initialized.
1: connection established.
2: request received.
3: answer in process.
4: finished.