ajax oop结果控制器

I've written ajax oop script in javascript for registration. here is script =>

function AjaxConstruct(method,file,params){
    this.method = method;
    this.file   = file;
    this.params = params;
    this.http   = false;
}

AjaxConstruct.prototype.ajax = function(){
    if (window.XMLHttpRequest){
        this.http = new XMLHttpRequest();
    } else {
        this.http = new ActiveXObject("Microsoft.XMLXHTTP");
    }
    if (this.http){
        this.http.open(this.method,this.file,true);
        if (this.method==="POST"){
             this.http.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
        }
    this.http.send(this.params);
    this.http.onreadystatechange = function(){
        if (this.http.readyState==4 && this.http.status==200){
            alert("ok");
        } else {
            alert("no");
        }
    };

}
};

and creating object like that =>

var ajax = new AjaxConstruct("POST","filename","params"); // define object
ajax.ajax(); // invoke method

everything is working perfectly but just i want to know how can i flag in oop script when result is fine and when it is not ? And also I'm interested in how many data is common to send with ajax or doesn't it matter ? For example I am trying to send data to mysql database from seven input form, Is any chance to lost data during sending with ajax script like this ? Thanks :)

I've guessed error and corrected in script above , thanks man :)

function AjaxConstruct(method,file,params,okcallback,notokcallback){
    this.method = method;
    this.file   = file;
    this.params = params;
    this.http   = false;
    this.okresp = okcallback;
    this.notokresp = notokcallback;
}

AjaxConstruct.prototype.ajax = function(){
    if (window.XMLHttpRequest){
        this.http = new XMLHttpRequest();
    } else {
        this.http = new ActiveXObject("Microsoft.XMLXHTTP");
    }
    if (this.http){
        this.http.open(this.method,this.file,true);
        if (this.method==="POST"){
             this.http.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
        }
    this.http.onreadystatechange = function(){
        if (this.http.readyState==4 && this.http.status==200) {
            this.okresp(this.http.responseText, this.http.responseXML);
        } else {
            this.notokresp(this.http.responseText, this.http.responseXML);
        }
    };
    this.http.send(this.params);
}
};

When you call your ajaxconstruct, pass the 2 new arguments like this:

function myokfunction(I_sResponseText, I_oResponseXML) { /* your ok code here */}
function mynotokfunction(I_sResponseText, I_oResponseXML) { /* your not ok code here */}

var ajax = new AjaxConstruct("POST","filename","params", myokfunction, mynotokfunction);

About your concern of the amount of data, GET will limit you according to the browser adress bar limit while POST won't, I think. But then this is more a question of http server overhead that you should ask yourself.