Возникли проблемы с получением нового значения массива после зацикливания NodeJS

Question

Поскольку я новичок в NodeJS, я пробовал несколько методов, таких как использование async / await для своих функций, но когда я пытаюсь распечатать массив retrieveValues, он всегда кажется пустым.

Даже попытка ожидания не помогает, если я распечатываю retrieveValues ​​в тот момент, когда он помещается в массив, он будет отображаться в консоли, но не когда я сделаю это после.

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();

})

Answer 1

Может быть, вы можете попробовать этот код ниже:

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();

});

});

Я надеюсь, что это может помочь вам.

Answer 2

Это последнее console.log работает до нажатия. Вы передаете функцию в качестве обратного вызова, поэтому она будет запущена после завершения операции. Я немного почистил твой код и переместил 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();
    });

})