javascript: 以前に作成された xmlhttp プール、code_javascript スキル

var Pool_xmlreq=function(){
var _cacheCase=[];
_cacheCase.fetch=function(){
var i=0;
var _instance=function(){
try{
return (new ActiveXObject("Msxml2.XMLHTTP.5.0"));}
catch(e){
try{
return (new XMLHttpRequest());}
catch(e){
try{
return (new ActiveXObject("Msxml2.XMLHTTP"));}
catch(e){
try{
return (new ActiveXObject("Microsoft.XMLHTTP"));}
catch(e){
alert("Error: initializing xmlhttprequest!");}}}}}
for (;i if(this[i].readyState==0||this[i].readyState==4){
return this[i];}}
this[i]=_instance();
return this[i];}
this.length=function(){
return _cacheCase.length}
this.instance=function(){
return _cacheCase.fetch()}
this.connect=function(method,url,data,handler){
var _xmlhttpreq=_cacheCase.fetch();
with(_xmlhttpreq){
open(method,url,true);
setRequestHeader("キャッシュ制御","キャッシュなし");  
setRequestHeader("Content-Type","application/x-www-form-urlencoded;charset=UTF-8");
送信(データ);
onreadystatechange=function(){
if(_xmlhttpreq.readyState return false;
if(_xmlhttpreq.status==200||_xmlhttpreq.status==304){
handler(decodeURIComponent(_xmlhttpreq.responseText));
return true;}
alert("Error: status_" _xmlhttpreq.status "!");
return false;}}}
}
var xmlreq=new Pool_xmlreq(); 

使用法:
xmlreq.connect("post",url,postdata,function);