// JScript 文件

var Ajax = function(){};
Ajax.prototype = {
    createHttpRequest : function(){
        if(window.ActiveXObject){
            var ver = ["Microsoft.XMLHTTP","MSXML.XMLHTTP"];
            for(var i=0; i<ver.length; i++){
                try{
                    return new window.ActiveXObject(ver[i]);
                }catch(e){}
            }        
        }else{
            try{
                return new XMLHttpRequest();        
            }catch(e){}
        }
        alert("Failure to create HttpRequest!");
    },
    
    get : function(url, async, fnCallBack){
        var xmlHttp = this.createHttpRequest();
        xmlHttp.open("GET", url, async);

        xmlHttp.onreadystatechange = function(){
            if(xmlHttp.readyState == 4 ){
                if(xmlHttp.status == 200){
                    fnCallBack(xmlHttp.responseText);
                }else{
                    fnCallBack(null);
                }
            }
        };
        xmlHttp.setRequestHeader("If-Modified-Since","0");
        xmlHttp.send(null);
    }
};