Ajax调用返回未定义的数据

Question

I have an ajax call that requests data from an MVC controller method.
I am returning a Json result from the controller.

Ajax request completes, but the data returned is undefined.

Ajax Call

var param = {
    "username": uname,
    "password": pass
};
var serviceURL = "/Account/CheckUser";

var req = $.ajax({
    url: serviceURL,
    type: "POST",

    data: JSON.stringify(param),

    contentType: "application/json",

    complete: successFunc,
    error: errorFunc
});

function successFunc(data) {
    if (data.exists == true) {
        console.log("Completed : " + data.exists);
    } else {
        console.log("Failed : " + data.exists);

    }
}

Controller Method

[HttpPost]
public JsonResult CheckUser(string uname, string pass)
{
    Boolean cont = true;
    return Json(new { exists = cont });
}

Can anyone tell me why exists returns as undefined?

UPDATE
As suggested below, I wrote the data to the console, and it seems it's returning an empty string. So I guess the question should be more ' Why is the data returning empty?

Answer 1

The function you specify via the complete option doesn't receive the data (for good reason: it's called even if there is no data, because there was an error). Change complete: to success: .

var req = $.ajax({
    url: serviceURL,
    type: "POST",

    data: JSON.stringify(param),

    contentType: "application/json",

    success: successFunc, // <=== Here
    error: errorFunc
});