Google Closure LibraryでAjaxする

goog.net.XhrIo.send(this._url, function(e) {
    var xhr = e.target,
        obj = xhr.getResponseJson();

    d.callback(obj.feed.entry);
});

Instance化して使う方法

var xhr = new goog.net.XhrIo();

goog.events.listen(xhr, 'complete', function (e) {
    if (xhr.isSueccess()) {
        console.log(xhr.getResponseJson(); //getResponseText()も。
    }
    else {
        console.log(xhr.getLastError());
    }
});

xhr.send(url, 'POST', data);