Sample Ajax function call

function xmlhttpPost(strURL) {
   var xmlHttpReq = false;
   var self = this;
   // Mozilla/Safari
   if (window.XMLHttpRequest) {
       self.xmlHttpReq = new XMLHttpRequest();
   }
   // IE
   else if (window.ActiveXObject) {
       self.xmlHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
   }
   self.xmlHttpReq.open('POST', strURL, true);
   self.xmlHttpReq.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
   self.xmlHttpReq.onreadystatechange = function() {
       if (self.xmlHttpReq.readyState == 4) {
           updatepage(self.xmlHttpReq.responseText);
       }
   }
   self.xmlHttpReq.send(getquerystring());
}