function func(cb) {
    request({ params }, (error, response) => {
        const devices = response.body;
        let completedCounter = 0;
        for (const device of devices) {
        request({ params }, (err, response) => {
            if (!err && response.statusCode === 200) {
            completedCounter += 1;
            if (completedCounter === devices.length) {
                cb(null, "message here");
            }
            } else {
            cb(err, "message here");
            }
        });
        }
    });
}