AJAX — It's not just a household cleanser.

Ajax, shorthand for Asynchronous JavaScript and XML, is a web development technique for creating interactive web applications. The intent is to make web pages feel more responsive by exchanging small amounts of data with the server behind the scenes, so that the entire web page does not have to be reloaded each time the user makes a change. This is meant to increase the web page’s interactivity, speed, and usability.

Basically, a regular AJAX-like implementation includes two main components: a client HTML page with JavaScript code making an AJAX call and receiving a response, and a remote page that can accept a request and respond with the required information. The JavaScript code on the client page is responsible for instantiating an XmlHttp object, then providing this object with a callback method which will be responsible for processing the received information, and finally, sending a request to the remote page via the XmlHttp object. All this is done by the JavaScript code.

So, what exactly are the pros and cons of using AJAX for web development?

Pros                        Cons
----            |            ----
Websites do not need to                 Different JavaScript imple-
reload to transmit their             mentation in every browser
data to the server.                  with proprietary extensions.

Since, you do not need to            Small requests less than 512
reload to transmit data                bytes may only be sent using
this can aid in greater                AJAX currently.
UI flexibility/usability.

AJAX extends the browser            AJAX can break if a user presses
with lightweight mini-                the "Back" Button.
applications.

AJAX adds portability                AJAX can be affected by a slow
due to it's backend                Internet connection since it
history.                    must connect to the server to
receive its data.

Most importantly it is                 Since the Ajax web pages are updated
easy to implement.                dynamically, it becomes difficult to
bookmark a state of the page.

Relies on JavaScript -- which not everyone
has enabled for security purposes.

Ajax interfaces are harder to program
than Rich Interactive Internet Applications
(RIAs) (XHTML/DHTML snippets)
and also give programmers less control.

Take a look at some of the code:


function GetXmlHttpObject(handler)
{
var objXmlHttp = null;
if (!window.XMLHttpRequest)
{
// Microsoft
objXmlHttp = GetMSXmlHttp();
if (objXmlHttp != null)
{
objXmlHttp.onreadystatechange = handler;
}
}
else
{
// Mozilla | Netscape | Safari
objXmlHttp = new XMLHttpRequest();
if (objXmlHttp != null)
{
objXmlHttp.onload = handler;
objXmlHttp.onerror = handler;
}
}
return objXmlHttp;
}

function GetMSXmlHttp()
{
var xmlHttp = null;
var clsids = [“Msxml2.XMLHTTP.6.0″,”Msxml2.XMLHTTP.5.0”,
“Msxml2.XMLHTTP.4.0″,”Msxml2.XMLHTTP.3.0”,
“Msxml2.XMLHTTP.2.6″,”Microsoft.XMLHTTP.1.0”,
“Microsoft.XMLHTTP.1″,”Microsoft.XMLHTTP”];
for(var i=0; i

Get Involved! AJAX — dispite its shortcomings is an awesome, fairly new technology that has great potential. Take a while and research it. Want tutorials?

http://www.google.com/search?hl=en&q=AJAX+Tutorials&btnG=Google+Search :
http://www.w3schools.com/ajax/default.asp
http://codinginparadise.org/projects/tutorials/
http://www.maxkiesler.com/index.php/weblog/comments/round_up_of_30_ajax_tutorials/
http://www.petefreitag.com/item/515.cfm