使用XMLHttpRequest（）获取JSON文件，但是当我console.log responseText时，我得到一个空字符串吗？

Question

When I say console.log(getErrors) I receive this in the console:

XMLHttpRequest {statusText: "", status: 0, responseURL: "", response: "", responseType: ""...}
onabort: null
onerror: null
...
responseText: {"content":[{"id":1,"timeStamp":"2015-03-20T00:01:44.761","provider":"foo","providerId":null,"lineNumber":1,"summary":"foo","description":"foo: 1"}...
responseType: ""
responseURL: "http//localhost:8080/errors/findAll"
...

I know I'm getting the data because I can see it in responseText but when I say console.log(getErrors.responseText) I'm getting an empty string. I'm not sure what I'm doing wrong.

Javascript:

var getErrors = new XMLHttpRequest();

    getErrors.open('GET', '/errors/findAll', true);
    getErrors.send();

    //var response = getErrors.responseText;

    console.log(getErrors);
    console.log(getErrors.responseText);

Answer 1

Here is my working code in Javascript:

getErrors = function(url, callbackFunction) // How can I use this callback?
{
    var requestErrors = new XMLHttpRequest();
    requestErrors.onreadystatechange = function()
    {
        if (requestErrors.readyState == 4 && requestErrors.status == 200)
        {
            callback(requestErrors.responseText); // Another callback here
        }
    }
    requestErrors.open('GET', url);
    requestErrors.send();
}

function callback(data) {
    console.log(data);
}

getErrors('/errors/findAll', callback);