Cannot send correct response when dealing with queries with MySQL

Question

I encountered a problem when dealing with queries' error handling for a MySQL database in NodeJS : I searched a bit about callbacks in JavaScript and async functions but I cannot figure out how am I suppose to get the correct error message that I want in a type of situation, here it is :

auth.post('/register', (req, res) => {
    const body = req.body;
    console.log('POST register');
    const user = {email: body.email, password: body.password, name: body.name, firstname: body.firstname};
    my_db.query('INSERT INTO user SET ?', user, (err, result) => {
        if (err) {
            console.log("ERROR");
            is_err = false;
        }
    })
    is_err = true;
    if (!is_err)
        res.json({"msg" : "user already exists"});
    else
        res.json({"token": "Token of the newly registered user"});
})

Typically I want that the json formatted message {"msg" : "user already exists"} is sent as a response when a user already exists. I tried booleans, numbers, async functions but seems like I am doing this terribly. And I cannot do res.json() inside the query ! How am I suppose to do it ?

`my_db.query()` is asynchronous. You need to put all the rest of the code in the callback function. — Barmar, Apr 08 '21 at 17:07
Does it mean that I am supposed to move the last 4 lines in another function ? — Abriscout, Apr 08 '21 at 17:10
You don't need the `is_err` variable. Just put the first `res.json()` call inside that `if`. — Barmar, Apr 08 '21 at 17:12
`if (err) { console.log("ERROR"); res.json(...); } else { res.json(...); }` — Barmar, Apr 08 '21 at 17:12

Cannot send correct response when dealing with queries with MySQL

0 Answers0