XMLHttpRequest Browser Support [closed]

Answer 1

a small search in google would provide a good answer for your basic problem

/*
   Provide the XMLHttpRequest constructor for Internet Explorer 5.x-6.x:
   Other browsers (including Internet Explorer 7.x-9.x) do not redefine
   XMLHttpRequest if it already exists.

   This example is based on findings at:
   http://blogs.msdn.com/xmlteam/archive/2006/10/23/using-the-right-version-of-msxml-in-internet-explorer.aspx
*/
if (typeof XMLHttpRequest === "undefined") {
  XMLHttpRequest = function () {
    try { return new ActiveXObject("Msxml2.XMLHTTP.6.0"); }
    catch (e) {}
    try { return new ActiveXObject("Msxml2.XMLHTTP.3.0"); }
    catch (e) {}
    try { return new ActiveXObject("Microsoft.XMLHTTP"); }
    catch (e) {}
    // Microsoft.XMLHTTP points to Msxml2.XMLHTTP and is redundant
    throw new Error("This browser does not support XMLHttpRequest.");
  };
}

or

/** 
 * Gets an XMLHttpRequest. For Internet Explorer 6, attempts to use MSXML 6.0,
 * then falls back to MXSML 3.0.
 * Returns null if the object could not be created. 
 * @return {XMLHttpRequest or equivalent ActiveXObject} 
 */ 
function getXHR() { 
  if (window.XMLHttpRequest) {
    // Chrome, Firefox, IE7+, Opera, Safari
    return new XMLHttpRequest(); 
  } 
  // IE6
  try { 
    // The latest stable version. It has the best security, performance, 
    // reliability, and W3C conformance. Ships with Vista, and available 
    // with other OS's via downloads and updates. 
    return new ActiveXObject('MSXML2.XMLHTTP.6.0');
  } catch (e) { 
    try { 
      // The fallback.
      return new ActiveXObject('MSXML2.XMLHTTP.3.0');
    } catch (e) { 
      alert('This browser is not AJAX enabled.'); 
      return null;
    } 
  } 
}

Ref : http://en.wikipedia.org/wiki/XMLHttpRequest and http://www.webmasterworld.com/javascript/4027629.htm