Styjun

I've been working on a node project and everything is new to me.

So far, scraping the internet I managed to get the user logged in, but now, I don't know hot to direct to the user page once the login process succed.

In the index.js I have:

const userService = require('./auth');

app.post('/login', function(req, res)

var userEmail = req.body.emailLogin;
var userPassword = req.body.passwordLogin;
console.log(userEmail, userPassword); //This log the email and the password

userService.loginUser(emailRegister, passwordRegister,

 function(error, authData) 

 if (error) 
 return res.status(401).send('Unauthorized');

 else 
 res.render('user');
 
 );
);

and in the auth.js

function loginUser(email, password)
 console.log(email, password);
 firebase.auth().signInWithEmailAndPassword(email, password)
 .then(function(firebaseUser) 
 // Success
 console.log('Ok, lovelly I'm logged');
 return firebaseUser
 )
 .catch(function(error) 
 // Error Handling
 var errorCode = error.code;
 var errorMessage = error.message;
 console.log(errorCode); //auth/user-not-found
 console.log(errorMessage); //There is no user record corresponding to this identifier. The user may have been deleted.

 return errorMessage
 );

how can I return the firebaseUser to the main function and be redirect to the user page?

You have written your code in pre-ES6 standards using concept of callbacks

const userService = require("./auth");

app.post("/login", function(req, res) 
 var userEmail = req.body.emailLogin;
 var userPassword = req.body.passwordLogin;
 console.log(userEmail, userPassword); //This log the email and the password

 userService.loginUser(
 userEmail,
 userPassword,

 function(error, authData) 
 if (error) 
 return res.status(401).send("Unauthorized");
 else 
 res.render("user");
 
 
 );
);

But you forgot to include the callback argument in login user method and once login user method is successful call callback(null, result) and if its an error call callback(error).

function loginUser(email, password, callback) 
 console.log(email, password);
 firebase
 .auth()
 .signInWithEmailAndPassword(email, password)
 .then(function(firebaseUser) 
 // Success
 console.log("Ok, lovelly I'm logged");
 callback(null, firebaseUser);
 )
 .catch(function(error) 
 // Error Handling
 var errorCode = error.code;
 var errorMessage = error.message;
 console.log(errorCode); //auth/user-not-found
 console.log(errorMessage); //There is no user record corresponding to this identifier. The user may have been deleted.

 callback(error);
 );
 

I have rewritten the code using latest standards using async/await which is much more cleaner and is shorter.

app.post("/login", async (req, res) => 
const userEmail = req.body.emailLogin,
 userPassword = req.body.passwordLogin;
 const user = await loginUser(userEmail, userPassword).catch(error => 
 return res.status(401).send("Unauthorized");
 );
 res.render("index.js", user);
);

const loginUser = async (email, password) => 
 try 
 const user = await firebase
 .auth()
 .signInWithEmailAndPassword(email, password);
 return user;
 catch (error) 
 throw error;
 
;

There's a concept of promises which I am not gonna go into because async/await is a syntactic sugar of it. You can read about all of it on async/await promises callbacks

You are confused between callback and promise learn how to work with async operation

Your code would look like this

function loginUser(email, password)
console.log(email, password);
// return promise
return firebase.auth().signInWithEmailAndPassword(email, password)
 .then(function(firebaseUser) 
 // Success
 console.log('Ok, lovelly I'm logged');
 return firebaseUser
 )

And controller would be

 const userService = require('./auth');

 app.post('/login', function (req, res) {

 var userEmail = req.body.emailLogin;
 var userPassword = req.body.passwordLogin;
 console.log(userEmail, userPassword); //This log the email and the password

 userService.loginUser(emailRegister, passwordRegister)
 .then(function () 
 res.render('user');
 )
 .catch(function (error) 
 // Error Handling
 var errorCode = error.code;
 var errorMessage = error.message;
 console.log(errorCode); //auth/user-not-found
 console.log(errorMessage); //There is no user record corresponding to this identifier. The user may have been deleted.
 return res.status(401).send('Unauthorized');
 )