16 February 2008

How the AJAX coded

Posted by: cathie in Uncategorized

Following are the steps that how you can code the Ajax Application:

Firstly, how to create an XMLHTTPRequest object. This process is different to some extent depending on your Internet Explorer that either it is (5+) with ActiveX enabled, or a standards-compliant browser for example Mozilla Firefox.

With IE, the request looks like:

http = new ActiveXObject(”Microsoft.XMLHTTP”);

Whereas in a standards-compliant browser we can instantiate the object directly:

http = new XMLHttpRequest();

Secondly, you have to write an event handler. The event handler will use different methods of XMLHTTPRequest object to:

• make the request of the server

• check when the server says that it has completed the request, and

• deal with the information returned by the server

you can make your request of the server with the help of GET method to proper server-side script. See the example of event handler called updateData which suppose that you have defined your object of XMLHTTPRequest and now called it as http:

function updateData(param) {var myurl = [here I insert the URL to my server script];

http.open(”GET”, myurl + “?id=” + escape(param), true);

http.onreadystatechange = useHttpResponse;

http.send(null);
} Thirdly, you need a function of useHttpResponse that create when server is completed your request, and then perform an action with the data it has returned:
function useHttpResponse() {if (http.readyState == 4) {

var textout = http.responseText;

document.write.textout;

}

}

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