ajax session过期问题的几个解决方案

(this.HttpRequest.readyState==4) {
            if(this.HttpRequest.status==200) {
                if((type!=null) && (type.toUpperCase()=="XML")){
                    return this.HttpRequest.responseXML;
                }
                return this.HttpRequest.responseText;
            }else{
                Alert("您所请求的页面有异常。");
                return false;
            }
        }
    }

    //停止当前请求
    this.abort = function(){
        if(!this.checkHttpRequest()){
            return false;
        }

        if(this.LoadingImg!=null){
            funHide(this.LoadingImg);
        }

        if(this.HttpRequest.readyState>0 && this.HttpRequest.readyState<4){
            this.HttpRequest.abort();
        }
    }

}

//=====================================================================================
//公共函数
//=====================================================================================
function $(_obj){
    var o;
    if (typeof(_obj)!="string")
        return _obj;
    else{
        try{
            document.all;
            try{
                o=document.all(_obj);
            }catch(e){
                return null;
            }
        }catch