1 function createXHR() { 2         if (typeof XMLHttpRequest != "undefined") { 3             return new XMLHttpRequest(); 4         } else if (typeof ActiveXObject != "undefined") { 5             if (typeof arguments.callee.activeXString != "string") { 6                 var versions = ["MSXML2.XMLHttp.6.0", "MSXML2.XMLHttp.3.0", "MSXML2.XMLHttp"]; 7  8                 for (var i = 0, len = versions.length; i < len; i++) { 9                     try {10                         var xhr = new ActiveXObject(versions[i]);11                         arguments.callee.activeXString = versions[i];12                         return xhr;13                     } catch (ex) {14                         //omit15                     }16                 }17             }18             return new ActiveXObject(arguments.callee.activeXString);19         } else {20         throw new Error("no xhr object available.");21         }22     }