Function doesn't return right value in node js

Question

I want to check if a sqlite query got executed properly or not with node.js to check if the name inputed by the user is already in use.

To do so my first assumption was to simply check the returned value of my query (0 if the username is already present in the table or 1 if not ).


/*some code*/

db.serialize (function () {
    exports.run = function(query, message) {
            db.run(query, function(err) {

                if (err) {
                    console.error(err.message, );
                    return 0;
                }
                else{
                    console.log(message,": ", this.changes, "\n");
                    return 1;
                }
            });
        }
});

/*some code*/

But the problem is that no matter what the it returns undefined and thus triggering the wrong behaviour. I also tried to check if my query threw an error but get the same result.

/*some code*/

io.sockets.on('connection', function (socket) {

    socket.on('send', function (data) {

        if (data.type === 'notice') { //update the hasmap with the name
            connectedSockets[socket.id] = data.nick;

            var tmp = db.run(`insert into user(username, socket_id, member_of) 
                                VALUES ("${data.nick}","${socket.id}",'default');`
                , 'User added to the DB..' + " " + data.nick
                + " " + socket.id + " " + 'default');

            if (tmp === 1) {
                console.log(connectedSockets, "\n")
                io.sockets.emit('message', data);
            } 
else {
                data['invalid_name'] = true;
                console.log(data.invalid_name, "TEST invalid_name");
                socket.emit('message', data);
            }

        }
/*some code*/

My second attempt:

/*some code*/

io.sockets.on('connection', function (socket) {

    socket.on('send', function (data) {
       if (data.type === 'notice') { //update the hasmap with the name

            try{
               console.trace( db.run(`insert into user(username, socket_id, member_of) 
                                VALUES ("${data.nick}","${socket.id}",'default');`
                    ,'User added to the DB..'+" "+data.nick
                    + " "+socket.id+" "+'default'));

                console.log(connectedSockets, "\n")
                io.sockets.emit('message', data);
            }
            catch (e) {
                data['invalid_name'] = true;
                console.log(data.invalid_name, "TEST invalid_name");
                socket.emit('message', data);
            }

        }

/*some code*/

I'm probably missing something quite obvious. Any idea? Thanks

Edit: it was marked as a duplicate of this post How do I return the response from an asynchronous call? but this post is not beginner and friendly and does not specifically explain how answer to my problem. Ajax and XMLHttpRequest are not related to my problem.

@Quentin I've read the whole post multiple times prior to asking my question, but unfortunately the answer is highly detailed for Ajax and the example seems quite complicated for a beginner. Plus it does't not emphasise what I did wrong here as I didn't think my issue had to do with asynchronous calls. Some simple insight would be appreciated. Thanks — Nanoboss, Jul 12 '19 at 08:31
`db.run` is an asynchronous call. `exports.run` has no return statement so it always returns undefined. — Quentin, Jul 12 '19 at 08:33
@Quentin so what use of the ```return 0``` and ```return 1``` in my code? — Nanoboss, Jul 12 '19 at 10:59

Function doesn't return right value in node js

0 Answers0