cant do "GET" xmlhttrequest - error

Question

  function regist(nome,pwd){
        URL+="register?nick=" + nome + "&key=" + pwd;
        var req = new XMLHttpRequest();
        req.open("get", URL, true);//Assincrono

        req.onreadystatechange = function(){
            if (req.readyState != 4) { 
                return;
            }
            else if (req.status != 200) {// Tratamento de erro (e.g., mostrar mensagem de erro)
                return;
            }
            var data=JSON.parse(req.responseText);
                    alert(data);
            if(data.error==null || data.error==undefined){
                    document.getElementById("register").innerHTML="Registo Bem Sucedido";
                }
                else{
                    document.getElementById("register").innerHTML="Utilizador já registado - Password errada";
                }
        };
        req.send();
    };

I CANT ACCESS at var data.. Maybe because "*req.onreadystatechange = function(){-----" What's appening? My alert to data isn't working, it was not readed.. Can you help me?>the URL is correctly defined, don't worry ;)

---

I don't know nothing about same origin policy problem... The URL used in GET is: dcc.fc.up.pt:8080/TabuWeb/rest/register?nick=ola&key=mundo My page URL: file:///home/carlos/public_html/TabuWeb2/WebContent/index.html?nick=ola&key=mund‌​o

Is there any problem about same origin policy??That's Why my req.status=0 and firebug is pointig to req.send()?

Thanks

Answer 1

There could be a number of reasons why it's not working, and it's hard to tell just from the ajax call.

First, to see your data you should use:

alert(JSON.stringify(data));

Or directly, to check if ajax returns valid json:

alert(req.responseText);

data is an object, so alert(data) won't show much.

Also, is your url in the same domain as your current page? If not, you might be victim of the same origin policy.