Node server method not firing - node.js

Question

I have the following web service that we have created.
router.post('/register', (req, res) => {
const user = req.body;
// registerSchema.validate(user, registerSchema, (err, result) => {
// if (err)
// res.status(500).end(err.message);
// });
findUserByEmail(user.email, (err, userFeedback) => {
console.log('Fired.');
if (userFeedback)
res.status(500).end(JSON.stringify("User already exists"));
});
const passwordPromise = util.promisify(bcrypt.hashSync);
const pass = bcrypt.hashSync(user.password);
createUser(user.name, user.email, pass, [], (err) => {
if (err)
res.status(418).end(JSON.stringify("Failed to create user."));
});
res.status(200).end(JSON.stringify("Signup successful."));
});
We are using this to register a user. Here are the methods we are calling in this part of the web service.
function createUser (userName, userEmail, userPass, dev, cb) {
var mg = require('mongodb').MongoClient;
mg.connect(url, { useNewUrlParser: true, useUnifiedTopology: true }, function(err, db){
var dbo = db.db(myDB);
var user = { name: userName,
email: userEmail,
password: userPass,
devices: dev };
var insert = util.promisify(dbo.collection("Users").insertOne);
dbo.collection("Users").insertOne(user, function(err, res) {
if (err) throw err;
console.log(`${user.name} has been added.`);
db.close();
sendEmail(userEmail,
'The CRUST Company welcomes you!',
'Thank you for signing up for our services!' );
});
});
}
//See if a user exists
function findUserByEmail (userEmail) {
var mg = require('mongodb').MongoClient;
mg.connect(url, { useNewUrlParser: true, useUnifiedTopology: true },
function(err, db){
var dbo = db.db(myDB);
var query = { email : userEmail };
var find = util.promisify(dbo.collection("Users").find);
return dbo.collection("Users").find(query).toArray(function(err, result) {
if (err) throw err;
db.close();
});
});
}
The createUser seems to be working fine but the FindUserByEmail is not firing at all. We even tried console.log within the method and got no response. Any ideas on why this method may not be firing? Thx

Answer 1

Your calling code passes findUserByEmail() a callback function:
findUserByEmail(user.email, (err, userFeedback) => {
console.log('Fired.');
if (userFeedback)
res.status(500).end(JSON.stringify("User already exists"));
});
But, your actual implementation of that function doesn't accept a callback and thus never calls it so of course the callback you pass never gets called.
Also, there are multiple asynchronous design problems. You are treating asynchronous operations like they are blocking. They are not. You must continue the flow of your code INSIDE the callback function, not after the function call which you do correctly inside of findUserByEmail() but do not do correctly in your request handler where you call it.
Also, createUser() declares a callback as an argument, but never calls it so the callback you pass to createUser() will also never get called.