» DoYourself.org » ajax http://www.doyourself.org Did you know ? Fri, 03 Feb 2012 23:00:02 +0000 en hourly 1 http://wordpress.org/?v=3.3.1 FAQ on AJAX Technology http://www.doyourself.org/ajax/543-faq-on-ajax-technology/ http://www.doyourself.org/ajax/543-faq-on-ajax-technology/#comments Fri, 21 Aug 2009 20:14:33 +0000 admin http://www.doyourself.org/?p=543

AJAX has become an hot technology with Web2.0 but before starting
AJAX Programming developers needs to know some important FAQ on AJAX.

Q) Ajax an Microsoft Technology?
A) Absolutely No, Ajax is an cross browser technology. It is browser dependent and uses JavaScript.
Q)Are Ajax applications easier to develop than traditional web applications?
A) Not necessarily. Ajax applications can involve complex JavaScript
code on the client. To develop that complex code efficient and bug-free
is not an simple task as it involves pure JavaScript & DHTML
coding. But better development tools and frameworks are require to make
the Ajax Application development much faster and easier.
Q) Do Ajax applications always deliver a better experience than traditional web applications?
A) Not necessarily. Ajax gives interaction designers more flexibility.
However, the more power we have, the more caution we must use in
exercising it. We must be careful to use Ajax to enhance the user
experience of our applications, not degrade it.
Q) Apart from AJAX any other Technique exist for Dynamic Web Page Update?
A) IFRAMES
Q) Can AJAX access Server side script residing on different domain?
A) NO. Ajax can only access the Script residing on same domain. If you
try to access the script from other domain browsers gives an error
“Access Denied”
Q) Ajax can also fetch XML content from server side, if this is true how?
A) Using responseXML properties and then by using JavaScript XML DOM to access the attributes and value of XML data.
Q) Is Ajax is Browser Dependent?
A) Yes, Ajax object is part of JavaScript engine inside every browser.
So if a new browser comes into market and the JavaScript engine doesn’t
have XMLHTTP object then Ajax will not work.
Q) How can i check the progress of my Ajax call?
A) When making Ajax call the readystate has to reach 4 to capture the
remote date. So you can insert appropriate messages until the
readystate reaches 4.
Q) Do i have to wait endlessly after making Ajax Call?
A) Not always but there are some exceptional cases when the remote
server is already busy and is unable to handle your request in that
case the JavaScript code will wait until response is fetched from the
remote server or there is browser request timed out. You can use the
interval to make another call after specific interval.
Q) Do i have to explicitly use Ajax Frameworks for implementing Ajax?
A) Not necessarily, Ajax Frameworks are meant to make the life of
programmers simpler. These frameworks acts as an wrapper to the Ajax
Code, they provide you with the function call that will do all the Ajax
Call and you don’t have to write the Basic Ajax Code.
Q) Can Ajax work with all Web Technologies?
A) Yes, Ajax is browser dependent and if the web technology you are using supports browser then Ajax will work.
Q) Can i make multiple Ajax Call?
A) Yes you can make multiple Ajax call provided you have separate Ajax
Object variables created. Making another Ajax Call on the existing Ajax
Object will overwrite the previous make call.
Q) Can i do Ajax Connection Pooling Techniques?
A) Yes you can do connection pooling for making Ajax call. Here you
will be storing all the Ajax objects in a connection pool so that every
individual object will perform their own task.

]]> http://www.doyourself.org/ajax/543-faq-on-ajax-technology/feed/ 0 FORM POST in PHP using AJAX http://www.doyourself.org/ajax/542-form-post-in-php-using-ajax/ http://www.doyourself.org/ajax/542-form-post-in-php-using-ajax/#comments Fri, 21 Aug 2009 20:14:09 +0000 admin http://www.doyourself.org/?p=542

This example demonstrates HTTP FORM POST complete HTML form to the server and displaying the response using AJAX.

HTML Page

<html><head><title>PHP using AJAX</title><script type="text/javascript"> var time_variable; function getXMLObject()  //XML OBJECT{   var xmlHttp = false;   try {     xmlHttp = new ActiveXObject("Msxml2.XMLHTTP")  // For Old Microsoft Browsers   }   catch (e) {     try {       xmlHttp = new ActiveXObject("Microsoft.XMLHTTP")  // For Microsoft IE 6.0+     }     catch (e2) {       xmlHttp = false   // No Browser accepts the XMLHTTP Object then false     }   }   if (!xmlHttp && typeof XMLHttpRequest != 'undefined') {     xmlHttp = new XMLHttpRequest();        //For Mozilla, Opera Browsers   }   return xmlHttp;  // Mandatory Statement returning the ajax object created} var xmlhttp = new getXMLObject();	//xmlhttp holds the ajax object function ajaxFunction() {  var getdate = new Date();  //Used to prevent caching during ajax call  if(xmlhttp) {   	var txtname = document.getElementById("txtname");    xmlhttp.open("POST","testing.php",true); //calling testing.php using POST method    xmlhttp.onreadystatechange  = handleServerResponse;    xmlhttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');    xmlhttp.send("txtname=" + txtname.value); //Posting txtname to PHP File  }} function handleServerResponse() {   if (xmlhttp.readyState == 4) {     if(xmlhttp.status == 200) {       document.getElementById("message").innerHTML=xmlhttp.responseText; //Update the HTML Form element      }     else {        alert("Error during AJAX call. Please try again");     }   }}</script><body><form name="myForm"><table> <tr>  <td>Enter Name</td>  <td><input type="text" name="txtname" id="txtname" /></td> </tr> <tr>  <td colspan="2"><input type="button" value="Submit" onclick="ajaxFunction();" /></td> </tr> </table><div id="message" name="message"></div> </form></body></head></html>

PHP Code

< ? $a = $_POST['txtname']; echo "Good Morning".$a;  ?>

Explanation for the AJAX Code

Here i have declared 3 JavaScript function:
getXMLObject() – Responsible for creating the AJAX Object depending on the browser
ajaxFunction() – Responsible for calling PHP page through AJAX call
handleServerResponse() – Responsible for displaying the data retrieved from the server

How the AJAX Code Works:

  • When the page loads i am creating an AJAX Object by calling the
    getXMLObject() function and returning the object created in the xmlhttp
    variable
  • When the user clicks on the input Button, ajaxFunction() gets
    called which checks for whether the Ajax Object is created or not and
    depending on that calls the remote script. Here a function handler
    handleServerResponse is also defined for retrieving the value from the
    server
  • When the readystate of the AJAX call reaches 4 and the http status
    is 200 we pass the data fetched from the server to the textbox

Explanation for the PHP Code

  • I am calling $_POST for fetching the post content send through Ajax Call
  • Finally i am calling echo to send the response back to the calling page





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		Ajax Programming with JSP and Servlets
		http://www.doyourself.org/ajax/541-ajax-programming-with-jsp-and-servlets/
		http://www.doyourself.org/ajax/541-ajax-programming-with-jsp-and-servlets/#comments
		Fri, 21 Aug 2009 20:13:38 +0000
		admin
				
		
		
		
		
		
		

		http://www.doyourself.org/?p=541
		
			
In Java World Servlets are popularly used for Model View Controller

(MVC) Design Pattern. This article will guide you on writing AJAX based

application for fetching data from the Servlet and showing it on JSP

page.



JSP File Code:






<html><head><title>JSP and Servlet using AJAX</title><script type="text/javascript"> function getXMLObject()  //XML OBJECT{   var xmlHttp = false;   try {     xmlHttp = new ActiveXObject("Msxml2.XMLHTTP")  // For Old Microsoft Browsers   }   catch (e) {     try {       xmlHttp = new ActiveXObject("Microsoft.XMLHTTP")  // For Microsoft IE 6.0+     }     catch (e2) {       xmlHttp = false   // No Browser accepts the XMLHTTP Object then false     }   }   if (!xmlHttp && typeof XMLHttpRequest != 'undefined') {     xmlHttp = new XMLHttpRequest();        //For Mozilla, Opera Browsers   }   return xmlHttp;  // Mandatory Statement returning the ajax object created} var xmlhttp = new getXMLObject();	//xmlhttp holds the ajax object function ajaxFunction() {  var getdate = new Date();  //Used to prevent caching during ajax call  if(xmlhttp) {     xmlhttp.open("GET","gettime?" + getdate.getTime(),true); //gettime will be the servlet name    xmlhttp.onreadystatechange  = handleServerResponse;    xmlhttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');    xmlhttp.send(null);  }} function handleServerResponse() {   if (xmlhttp.readyState == 4) {     if(xmlhttp.status == 200) {       document.myForm.time.value=xmlhttp.responseText; //Update the HTML Form element      }     else {        alert("Error during AJAX call. Please try again");     }   }}</script><body><form name="myForm">Server Time:<input type="text" name="time" /><br /><input type="button" onClick="javascript:ajaxFunction();" value="Click to display Server Time on Textbox"/><br /></form></body></head></html>






Explanation for the AJAX Code


Here i have declared 3 JavaScript function:

getXMLObject() – Responsible for creating the AJAX Object depending on the browser.

ajaxFunction() – Responsible for calling servlet through AJAX call.

handleServerResponse() – Responsible for displaying the data retrieved from the server.


How the AJAX Code Works:


    

  • When the page loads i am creating an AJAX Object by calling the
    
getXMLObject() function and returning the object created in the xmlhttp
    
variable
    • 

  • When the user clicks on the input Button, ajaxFunction() gets
    
called which checks for whether the Ajax Object is created or not and
    
depending on that calls the remote script. Here a function handler
    
handleServerResponse is also defined for retrieving the value from the
    
server
    • 

  • When the readystate of the AJAX call reaches 4 and the http status
    
is 200 we pass the data fetched from the server to the textbox
    • 



Servlet Code






import java.io.*; import java.text.*; import java.util.*; import javax.servlet.*; import javax.servlet.http.*; public class gettime extends HttpServlet { 	public void init(ServletConfig config) throws ServletException {			super.init(config);	} 	public void destroy() { 	} 	public void doPost(HttpServletRequest request,HttpServletResponse response) throws IOException, ServletException {		PrintWriter out = response.getWriter();		Date df = new Date();		out.println(df.getTime());	} 	public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException, ServletException {		doPost(request,response);	}}






Explanation for the Servlet Code


    

  • By default doGet function gets called and i am redirecting the control to doPost function whenever doGet function is called
    • 

  • In doPost function i am creating the date object and displaying the current time using the getTime() method of Date class
    • 

  • So all the displaying content gets passed to the Ajax Object in the form of response
    • 


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		HTTP Form POST Request using AJAX and Servlet
		http://www.doyourself.org/ajax/540-http-form-post-request-using-ajax-and-servlet/
		http://www.doyourself.org/ajax/540-http-form-post-request-using-ajax-and-servlet/#comments
		Fri, 21 Aug 2009 20:12:35 +0000
		admin
				
		
		
		
		
		
		
		
		

		http://www.doyourself.org/?p=540
		
			
In Java World Servlets are popularly used for Model View

Controller(MVC) Design Pattern. This article will guide you on writing

AJAX based application that will post data to Servlet and will fetching

the computed data from the Servlet. With this approach the page will

get the updated content from the server without refreshing the jsp/html

page.



JSP Code: 






<html><head><title>JSP and Servlet using AJAX</title><script type="text/javascript"> function getXMLObject()  //XML OBJECT{   var xmlHttp = false;   try {     xmlHttp = new ActiveXObject("Msxml2.XMLHTTP")  // For Old Microsoft Browsers   }   catch (e) {     try {       xmlHttp = new ActiveXObject("Microsoft.XMLHTTP")  // For Microsoft IE 6.0+     }     catch (e2) {       xmlHttp = false   // No Browser accepts the XMLHTTP Object then false     }   }   if (!xmlHttp && typeof XMLHttpRequest != 'undefined') {     xmlHttp = new XMLHttpRequest();        //For Mozilla, Opera Browsers   }   return xmlHttp;  // Mandatory Statement returning the ajax object created} var xmlhttp = new getXMLObject();	//xmlhttp holds the ajax object function ajaxFunction() {  if(xmlhttp) {   	var txtname = document.getElementById("txtname");    xmlhttp.open("POST","getname",true); //getname will be the servlet name    xmlhttp.onreadystatechange  = handleServerResponse;    xmlhttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');    xmlhttp.send("txtname=" + txtname.value); //Posting txtname to Servlet  }} function handleServerResponse() {   if (xmlhttp.readyState == 4) {     if(xmlhttp.status == 200) {       document.myForm.message.innerHTML=xmlhttp.responseText; //Update the HTML Form element      }     else {        alert("Error during AJAX call. Please try again");     }   }}</script><body><form name="myForm" method="POST" action="getname"><table> <tr>  <td>Enter Name</td>  <td><input type="text" name="txtname" id="txtname" /></td> </tr> <tr>  <td colspan="2"><input type="button" value="Submit"  onclick="ajaxFunction();" /></td> </tr> </table><div id="message"></div> </form></body></head></html>






Servlet Code






import java.io.*; import java.text.*; import java.util.*; import javax.servlet.*; import javax.servlet.http.*; public class getname extends HttpServlet { 	public void init(ServletConfig config) throws ServletException {			super.init(config);	} 	public void destroy() { 	} 	public void doPost(HttpServletRequest request,HttpServletResponse response) throws IOException, ServletException {		String name = null;		PrintWriter out = response.getWriter();		if(request.getParameter("txtname") != null) {			name = request.getParameter("txtname");		}                else {                       name = "";                }  	        out.println("You have successfully made Ajax Call:" + name);	}}






Explanation for the AJAX Code


Here i have declared 3 JavaScript function:

getXMLObject() – Responsible for creating the AJAX Object depending on the browser.

ajaxFunction() – Responsible for calling servlet through AJAX call.

handleServerResponse() – Responsible for displaying the data retrieved from the server.


How the AJAX Code Works:


    

  • When the page loads i am creating an AJAX Object by calling the
    
getXMLObject() function and returning the object created in the xmlhttp
    
variable
    • 

  • When the user clicks on the input Button, ajaxFunction() gets
    
called which checks for whether the Ajax Object is created or not and
    
depending on that calls the remote script. Here a function handler
    
handleServerResponse is also defined for retrieving the value from the
    
server
    • 

  • When the readystate of the AJAX call reaches 4 and the http status
    
is 200 we pass the data fetched from the server to the textbox
    • 





Explanation for the Servlet Code


    

  • By default doPost function gets called when you post the content to the servlet
    • 

  • In doPost function i am fetching the POST data in the form of txtname and assigning it to the local variable name
    • 

  • Finally i am displaying the data got through POST. All the
    
displayed data gets passed to the Ajax Object in the form of response
    
to the Ajax call made to the servlet
    • 


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		Ajax Programming using Prototype Framework
		http://www.doyourself.org/ajax/539-ajax-programming-using-prototype-framework/
		http://www.doyourself.org/ajax/539-ajax-programming-using-prototype-framework/#comments
		Fri, 21 Aug 2009 20:12:05 +0000
		admin
				
		
		
		
		
		

		http://www.doyourself.org/?p=539
		
			
Prototype is the most

widely used framework for Ajax Operation. The main advantage of using

Prototype Ajax Framework is its simplicity to use, automatically

implements cross-browser and it offers bundle of utility function that

can be used in your JavaScript code. This article will list down

various ways by which you can make Ajax call using Prototype Framework.

This tutorial does not go into detailed implementation but shows you

how we can do basic Ajax Call using Prototype Ajax Framework.




In Prototype there are three ways you can make Ajax calls.

1) Ajax.Request

2) Ajax.PeriodicalUpdater

3) Ajax.Updater


Before we move into learning of individual Ajax call we also need to

understand the various events and parameters getting used while making

Ajax Call.


Various Parameters Of the Object Passed to Ajax.Request:

method

This can be HTTP GET or HTTP POST. By default method defined is POST.


parameters

This holds the key-value pair of the data that we are going to pass to

the request page. This is the same data that we pass through the query

string while calling remote URL.


frequency

Here you specify the period in seconds wherein Ajax call will be made.


decay

This is used to increase the interval time for Ajax call if there is no

change in response. The amount of interval getting increased is the

frequency*decay. This ensure that we do not make unecessary Ajax call

for the same response getting from the server.


Prototype Ajax Events:

onCreate:

This event get called whenever an new ajax request call is made. This

is useful when we want to show an loading image indicating ajax call.


onSuccess:

This event get called whenever the request is complete and the status code returned is in 2xx series.


onFailure:

This event get called whenever the request is complete and the status code returned is not in 2xx series.


onComplete:

This event get called whenever the request is complete and the

connection request life cycle is complete. This event gets called after

onSuccess and onFailure event. In this event we normally hide the

loading image.


Reading Request Response:

With prototype framework we can read either String, XML and JSON

content. String content can be read by calling responseText method, XML

content can be read by calling responseXML and JSON content can be read

by calling responseJSON method.


Ajax.Request:

Here we make an single ajax request to an server page and after

receiving the response from server the connection is terminated. The

simple implement for the same is






	var url = "http://www.hiteshagrawal.com/uploads/ajax_time.php";	var ajaxObjhttp = new Ajax.Request(url, {		method: 'POST',		parameters: {operation: "readRecord"},                onCreate: function(transport) {        	      alert("Creating New Ajax Call");                },                onSuccess: function(transport) {                      var serverResponse = transport.responseText;                },                onFailure : function(response) {                      alert("Some error occured while making call to remote server");                }        });






Here we make an object of Ajax.Request. This

objects accepts 2 parameter the first parameter is the request page url

and another object which holds the essential information that we will

be sending/receiving from the server page. On successful receiving the

data from the requested page we read the data by calling responseText

method.
Ajax.PeriodicalUpdater:

Here we provide an timer interval so that ajax request can be made at

regular interval specified while making the ajax call. This can become

handy when we want to show some live data that needs to be updated at

regular interval.






	var url = "http://www.hiteshagrawal.com/uploads/ajax_time.php";	var ajaxObjhttp = new Ajax.PeriodicalUpdater("textobj", url, {		method: 'POST',		frequency: 3,                decay: 2         });






Here we make an object of Ajax.PeriodicalUpdaterRequest.

This objects accepts 3 parameter the first paramter is the name of the

DIV/SPAN control where the data will get updated, second parameter

holds the request URL and third parameter holds an object which has the

essential information that we will be sending/receiving from the server

page.


Ajax.Updater:

The only difference between Ajax.Request and Ajax.Updater is that in

Ajax.Updater we specify the DIV/SPAN control name so now the data

returned from server will get automatically updated within the DIV/SPAN

control when the operation completes.






	var url = "http://www.hiteshagrawal.com/uploads/ajax_time.php";	var ajaxObjhttp = new Ajax.Updater("textobj", url, {		parameters: { operation: "readRecord" }        });






Here we make an object of Ajax.Updater. This

objects accepts 3 parameter the first parameter is the name of the

DIV/SPAN where the data will get updated, second parameter holds the

request URL and third parameter holds an object which has the essential

information that we will be sending/receiving from the server page.


Example:

In this example i am covering all the 3 Ajax call implementation.


HTML Code:






	<html>	<head>		<title>Prototype Ajax Call</title>		<script type="text/javascript" src="js/prototype.js"></script>		<script type="text/javascript">			function ajaxRequest() {				var url = "/uploads/ajax_time.php";				var ajaxObjhttp = new Ajax.Request(url, {					method: 'POST',					parameters: {operation: "readRecord"},			                onCreate: function(transport) {			        	       alert("Creating New Ajax Call");			                },			                onSuccess: function(transport) {			        		var textBoxObj = document.getElementById("ajaxRequestCall");			                        textBoxObj.innerHTML = transport.responseText;			                },			                onFailure : function(response) {			                       alert("Some error occured while making call to remote server");			               }			        });  			}     		        function ajaxUpdater() {				var url = "/uploads/ajax_time.php";				var textBoxObj = "ajaxUpdaterCall";				var ajaxObjhttp = new Ajax.Updater(textBoxObj, url, {					method: 'POST'	    		        });  			 } 			function ajaxPeriodicUpdater() {				var url = "/uploads/ajax_time.php";				var textBoxObj = "ajaxPeriodicUpdaterCall";				var ajaxObjhttp = new Ajax.PeriodicalUpdater(textBoxObj, url, {					method: 'POST',					frequency: 3,	        		        decay: 2	    		        });   				}		</script>	</head>            <body>		Ajax Request: <span id="ajaxRequestCall" name="ajaxRequestCall" style="border: 1px solid #CCCCCC">&nbsp;&nbsp;</span>&nbsp;<input type="button" onClick="ajaxRequest();" value="Ajax Request"/><br /><br />			Ajax Updater: <span id="ajaxUpdaterCall" name="ajaxUpdaterCall" style="border: 1px solid #CCCCCC">&nbsp;&nbsp;</span>&nbsp;<input type="button" onClick="ajaxUpdater();" value="Ajax Updater"/><br /><br />		Ajax Periodic Updater: <span id="ajaxPeriodicUpdaterCall" name="ajaxPeriodicUpdaterCall" style="border: 1px solid #CCCCCC">&nbsp;&nbsp;</span>&nbsp;<input type="button" onClick="ajaxPeriodicUpdater();" value="Ajax Periodic Updater"/><br />		</body></html>






SERVER SIDE CODE (PHP):






< ?	echo date("H:i:s");?>






SERVER SIDE CODE (JSP):






< %@page import="java.util.Date"%>< %	Date currentDate = new Date();	long currentTime = currentDate.getTime();	out.println(currentTime);%>






As per user working environment of the user whether PHP or JAVA i

have written the server side code for both the language. The user only

has to change the url in the javascript code.

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		Trap Session TimeOut during Ajax Call
		http://www.doyourself.org/ajax/538-trap-session-timeout-during-ajax-call/
		http://www.doyourself.org/ajax/538-trap-session-timeout-during-ajax-call/#comments
		Fri, 21 Aug 2009 20:11:34 +0000
		admin
				
		
		
		
		
		
		

		http://www.doyourself.org/?p=538
		
			
Solving this issue has been an nightmare for me but finally i have

achieve it some how, this may be not a full proof solution but it

worked for me. This solution also has certain flaws which i also will

be discuss in this article.




Session TimeOut happen due to various reasons such

as Server clearing the session cookie after timeout period, user

clearing the cache content from browser, Context Reload at Server etc.

But if there is session timeout happens before making Ajax

Call the client machine may get abrupt error page if you are not

trapping HTTP Status Code, this may not be due to Ajax call but session

has cleared and the server id not able to process the requested page.


What i found is the data i am returning data from the Ajax

Call is an String HTML content that i want to show and whenever some

thing happens at server end like session timeout the response i

received from Server contains HTTP Status Code 500 message error. Under

normal Ajax call i will not receive the HTTP Status Message so what i

did is to check whether the response received from server contains HTTP Status Code 500.

If it contains HTTP Status code i know that there is some unknown

server error occurred and i am able to trap error occurred during Ajax

Call.




Ajax Code






<script type="text/javascript">var xmlhttp = new getXMLObject();var time_variable; function getXMLObject()  //XML OBJECT{   var xmlHttp = false;   try {     xmlHttp = new ActiveXObject("Msxml2.XMLHTTP")  // For Old Microsoft Browsers   }   catch (e) {     try {       xmlHttp = new ActiveXObject("Microsoft.XMLHTTP")  // For Microsoft IE 6.0+     }     catch (e2) {       xmlHttp = false   // No Browser accepts the XMLHTTP Object then false     }   }   if (!xmlHttp && typeof XMLHttpRequest != 'undefined') {     xmlHttp = new XMLHttpRequest();        //For Mozilla, Opera Browsers   }   return xmlHttp;  // Mandatory Statement returning the ajax object created} function ajaxFunction() {  var getdate = new Date();  //Used to prevent caching during ajax call  if(xmlhttp) {     xmlhttp.open("GET","ajax_time.php?" + getdate.getTime(),true);    xmlhttp.onreadystatechange  = handleServerResponse;    xmlhttp.send(null);  }} function handleServerResponse() {   if (xmlhttp.readyState == 4) {     if(xmlhttp.status == 200) {       document.myForm.time.value=xmlhttp.responseText; //Update the HTML Form element      } else {     	if(xmlhttp.status == 500) {	        alert("Session TimeOut. Unable To Process Your Request");                //Process Further	}    

As you can see you have made an successfully Ajax Call to the requestedpage so you receive readyState = 4 but during session timeOut thestatus code received from requested page is 500 and not 200 so now youcan write your code logic to handle session timeOut Error.

     }   }}</script>





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