function getJson() {
    return new Promise(function(resolve, reject) {
        xhr.open("GET", "http://name.ru/res.json", true);
        xhr.onreadystatechange = function() {
        if (xhr.readyState == 4)
            resolve(rxhr.responseText)
        }

        xhr.send();
    }
}

getJson().then(function(response) {
    console.log(response)
})