How to return boolean from asynchronous sqlite query in express?

Question

I am trying to make some middleware which checks wether a session is valid (meaning has a logged in user attached). To do this I am using sqlite3 for node.

I am not too familiar with javascript, so I don't know exactly what to try. But I tried using 'await' for the query to wait for the query to complete and then return something, but that only made 'Promise { undefined }' show up in the console.

This is the code that runs the query and that I want to return true or false (those statements are already in there), I don't know if return statements work in callbacks (I think this is a callback). DBmanager returns a working database object.

// there is a session id
    // open db connection
    let db = dbManager();

    // check the database if there is a logged in session for this browser session id
    let checkSessionSql = 'SELECT timelastactive timelastactive, sessionid id FROM session WHERE sessionid = ?';

    db.get(checkSessionSql, [session.uniqueSessionID], (err, row) => {
        if (err) {
            return console.error(err.message);
        }

        // if a row gets found then that means that this was a logged in user
        if (row) {
            // we check whether the last time this user was active was more than 48 hours ago
            if ((Math.round(new Date() / 1000)) - row.timelastactive > 172800) {
                // if this is the case then we invalidate this users session
                console.log('session older than 48 hours');
                session.destroy();
                return false;
            } else {
                // session is still valid so we update the timelastactive to the current time
                let updateTimeLastActiveSql = 'UPDATE session SET timelastactive = ? WHERE sessionid = ?';

                let currentTime = Math.round(new Date() / 1000);

                db.run(updateTimeLastActiveSql, [currentTime, row.id], function (err) {
                    return console.error(err);
                });

                console.log('updated last active time for session ' + row.id);
                return true;
            }
        }
    });

    db.close();

The mistake is made by returning in the callback, you don't know how the callback is treated in the get() function, assign a global variable instead of return statement. The get function can maybe be listened, search in the official doc how to listen it and console.log the global value — FrV, Apr 04 '19 at 15:39
When you tried using `await` did you specify your function with an `async` keyword? So try to wrap the fb query in a function `const dbQ = async () =>...` and then await on the Promise.. ` let answer = await db.get` — Bryan, Apr 04 '19 at 16:25

score 0 · Answer 1 · answered Apr 06 '19 at 20:02

create promise function and call using .then or async/await.

let db = dbManager();

// check the database if there is a logged in session for this browser session id
let checkSessionSql = 'SELECT timelastactive timelastactive, sessionid id FROM session WHERE sessionid = ?';

function somefunction(params) {
    return new Promise((res, rej) => {

        db.get(checkSessionSql, [session.uniqueSessionID], (err, row) => {
            if (err) {
                console.error(err.message);
                return rej(err);
            }

            // if a row gets found then that means that this was a logged in user
            if (row) {
                // we check whether the last time this user was active was more than 48 hours ago
                if ((Math.round(new Date() / 1000)) - row.timelastactive > 172800) {
                    // if this is the case then we invalidate this users session
                    console.log('session older than 48 hours');
                    session.destroy();
                    return res(false);
                } else {
                    // session is still valid so we update the timelastactive to the current time
                    let updateTimeLastActiveSql = 'UPDATE session SET timelastactive = ? WHERE sessionid = ?';

                    let currentTime = Math.round(new Date() / 1000);

                    db.run(updateTimeLastActiveSql, [currentTime, row.id], function (err) {
                        return console.error(err);
                    });

                    console.log('updated last active time for session ' + row.id);
                    return res(true);
                }
            }
        });
    });
}

somefunction().then((result) => {
    console.log(result)
})

score -2 · Answer 2 · answered Apr 04 '19 at 15:32

-2

maybe because you added async to a callback function. try to remove the async keyword

answered Apr 04 '19 at 15:32

Sibyo

47
2

Tried that, didn't fix it :( – Thijs van der Heijden Apr 04 '19 at 15:34

How to return boolean from asynchronous sqlite query in express?

2 Answers2