Having problems getting new Array Value after looping in NodeJS

Question

As i am new to NodeJS, I have tried several methods such as using async/await on my functions but when i try to print out the array retrieveValues it always seems to be empty.

Even trying await doesn't help it, if i print out the retrieveValues at the point that it pushes into the array, it will show in the console but not when i do it after.

router.post('/api/retrievefornotifications', (request, response) => {
    var requestBody = request.body;
    var responseCode;
    var teacher = requestBody.teacher;
    var notification = requestBody.notification;

    var emails = helper.findEmailAddresses(notification);

    console.log(emails);

    var retrieveValues = {
        recipients: []
    };

    async function suspended(dataElement) {
        con.query('SELECT COUNT(*) as count_value FROM school.schoolinformation WHERE email = ? AND user_status = ?', [dataElement, 1], function (err, result, fields) {
        // con.query('SELECT COUNT(*) as count_value FROM school.schoolinformation WHERE email = ? AND user_status = ?; SELECT COUNT(*) as count_value2 FROM school.registration_relationship WHERE teacher_email = ? AND student_email = ?', [dataElement, 1, teacher, dataElement], function (err, result, fields) {
            // console.log("dataElements %s", dataElement);
            if (!err) {
                // console.log("Count value 1: %s",result[0][0].count_value);
                // console.log("Count value 2: %s",result[1][0].count_value2);
                // var suspended = result[0][0].count_value;
                // var registerWithTeacher = result[1][0].count_value;

                // console.log(result);
                var suspended = result[0].count_value;
                // Does such an email exist? (0 - NOT SUSPENDED, 1 - SUSPENDED) - suspended
                // If 1 means it is a registered pair - registerWithTeacher
                // has been mentioned in notification
                // Is registered with the teacher
                if (suspended == 0) {
                    console.log("pushing %s", dataElement);
                    retrieveValues.recipients.push(dataElement);
                }
                else {
                    responseCode = 500;
                    helper.writeResponse(responseCode, response, 0);
                }
            }
            else {
                responseCode = 204;
                helper.writeResponse(responseCode, response, 0);
            }
        });
    }

    console.log(retrieveValues);
    response.end();

})

Does this answer your question? [How do I return the response from an asynchronous call?](https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call) — Jake Holzinger, Jan 31 '20 at 00:43

score 0 · Answer 1 · answered Jan 31 '20 at 00:40

That last console.log runs before pushing. You are passing function as a callback, so it will run after the operation ends. I cleaned your code a little bit and moved the console.log.

router.post('/api/retrievefornotifications', (request, response) => {
var requestBody = request.body;
var responseCode;
var teacher = requestBody.teacher;
var notification = requestBody.notification;

var emails = helper.findEmailAddresses(notification);

console.log(emails);

var retrieveValues = {
    recipients: []
};

    con.query('SELECT COUNT(*) as count_value FROM school.schoolinformation WHERE email = ? AND user_status = ?', [dataElement, 1], function (err, result, fields) {
        if (!err) {
            var suspended = result[0].count_value;
            if (suspended == 0) {
                console.log("pushing %s", dataElement);
                retrieveValues.recipients.push(dataElement);
            }
            else {
                responseCode = 500;
                helper.writeResponse(responseCode, response, 0);
            }
        }
        else {
            responseCode = 204;
            helper.writeResponse(responseCode, response, 0);
        }
        console.log(retrieveValues);
        response.end();
    });

})

What I was really trying to do was to Query multiple times with the suspended function and Add into the retrieveValues array list — dythe, Jan 31 '20 at 00:44
What library do you use for sql connection? You can await only for `Promise`s. — Konrad, Jan 31 '20 at 00:45
This module doesn't support promises. You can use other that supports it's, but I'm sure you can do what you want without async / await. I'm just not sure what are you trying to achieve. — Konrad, Jan 31 '20 at 00:57

score 0 · Answer 2 · answered Jan 31 '20 at 01:50

Maybe you can try this code below:

router.post('/api/retrievefornotifications', (request, response) => {
    var requestBody = request.body;
    var responseCode;
    var teacher = requestBody.teacher;
    var notification = requestBody.notification;

    var emails = helper.findEmailAddresses(notification);

    console.log(emails);

    var retrieveValues = {
        recipients: []
    };

      const result = new Promise((resolve, reject) => {  con.query('SELECT COUNT(*) as count_value FROM school.schoolinformation WHERE email = ? AND user_status = ?', [dataElement, 1], function (err, result, fields) {
        // con.query('SELECT COUNT(*) as count_value FROM school.schoolinformation WHERE email = ? AND user_status = ?; SELECT COUNT(*) as count_value2 FROM school.registration_relationship WHERE teacher_email = ? AND student_email = ?', [dataElement, 1, teacher, dataElement], function (err, result, fields) {
            // console.log("dataElements %s", dataElement);
            if (!err) {
                // console.log("Count value 1: %s",result[0][0].count_value);
                // console.log("Count value 2: %s",result[1][0].count_value2);
                // var suspended = result[0][0].count_value;
                // var registerWithTeacher = result[1][0].count_value;

                // console.log(result);
                var suspended = result[0].count_value;
                // Does such an email exist? (0 - NOT SUSPENDED, 1 - SUSPENDED) - suspended
                // If 1 means it is a registered pair - registerWithTeacher
                // has been mentioned in notification
                // Is registered with the teacher
                if (suspended == 0) {
                    console.log("pushing %s", dataElement);
                    resolve(dataElement);
                }
                else {
                    responseCode = 500;
                    helper.writeResponse(responseCode, response, 0);
                }
            }
            else {
                responseCode = 204;
                helper.writeResponse(responseCode, response, 0);
            }
        });

    // do some stuff here
    console.log(await result);

    retrieveValues.recipients.push(await result);
    console.log(retrieveValues);
    response.end();

});

});

I hope it can help you.

Having problems getting new Array Value after looping in NodeJS

2 Answers2

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