AJAX - IE object caching page - fix I found

IE object caches page instead of getting update

[Double_Dark]

It seems that a number of other people have had this problem and when I tried to solve it I had a hard time finding a fix so I thought that I would post my fix.

I'm using AJAX ala google suggest to grab a page to keep the visitor updated as to the status of a request. The problem I ran into is that in IE the object was caching the page that it was calling instead of retrieving the updated page.

The fix I found was to add a request header If-Modified-Since to the request such that it would be before the page was modified.

Here's the code.

var _xmlHttp=null; 
//This will be the object to retrieve the page 
function getXMLHTTP() { 
   var A=null; 
   try { A=new ActiveXObject("Msxml2.XMLHTTP"); } 
   catch(e) 
   { 
      try 
         { A=new ActiveXObject("Microsoft.XMLHTTP");} 
      catch(oc) 
         { A=null; } 
   } 
   if(!A && typeof XMLHttpRequest!= "undefined") { 
      A=new XMLHttpRequest(); 
   } 
   return A; 
} 
//Sets the content of B 
function SetDiv() { 
   if(_xmlHttp.readyState==4 && _xmlHttp.responseText) { 
      while(B.childNodes.length>0) { 
         B.removeChild(B.childNodes[0]); 
      } 
      B.innerHTML = _xmlHttp.responseText;   
   } 
} 
//Requests whatever the page is and specifies where to put the contents 
function getPage(the_page,the_div) { 
   B = document.getElementById(the_div); 
   _xmlHttp=null; 
   _xmlHttp=getXMLHTTP(); 
   //I needed to keep track of the Cold Fusion session for which the page was being called 
   if(the_page.indexOf("?") >= 0) { 
      the_page = the_page + "&cfid="+getCookie('cfid')+"&cftoken="+getCookie('cftoken') 
   } else { 
      the_page = the_page + "?cfid="+getCookie('cfid')+"&cftoken="+getCookie('cftoken') 
   } 
   _xmlHttp.open("GET",the_page,true); 
   _xmlHttp.setRequestHeader( "If-Modified-Since", "Sat, 1 Jan 2000 00:00:00 GMT" ); 
   _xmlHttp.onreadystatechange = SetDiv; 
   _xmlHttp.send(null); 
} 

[httpwebwitch]

awesome. nice solution - this post is getting a bookmark