Express.js: Reponse in catch of try/catch is never sent - mysql

Question

I'm trying to implement a basic user registration flow using Express.js and mySQL. This is the code I have at the moment (stripped for brevity):
register(app, db) {
app.post('/register', (req, res) => {
let email = req.body.email
let password = req.body.password
try {
// add the user to the database
var q_params = [email, bcrypt.hashSync(password, 9)]
db.query("INSERT INTO users VALUES (?, ?)", q_params, (err) => {
if (err) {
throw err
}
})
} catch (err) {
// respond with an error if one is encountered
res.json({
success: false,
msg: err
})
return
}
// respond with success if everything else goes ok
res.json({
success: true,
email: email
})
});
}
The problem is that no matter the outcome of the code in the try block, I am always getting success: true. How come the error response is never triggered? Is there a better way to be handling this scenario?

Answer 1

I'm assuming the issue is that the nothing is waiting for the db.query() function to finish executing. It's not async and not awaiting that function to resolve. So the last res.json({}) gets hit right away.
I would try to rewrite the code to either use promises or to use that callback function passed to .query(), maybe something like this:
app.post('/register', (req, res) => {
let email = req.body.email
let password = req.body.password
// add the user to the database
var q_params = [email, bcrypt.hashSync(password, 9)]
db.query("INSERT INTO users VALUES (?, ?)", q_params, (err) => {
if (err) {
return res.json({
success: false,
msg: err
});
}
res.json({
success: true,
email: email
});
});
});