routes.js

var User = require(__dirname + '/models/user');

module.exports = function(app){

    app.post('/register/', userExist, function(req, res){
        var password = req.body.password;
        var username = req.body.username;
        var user = new User();

        user.username = username;
        user.password = user.generateHash(password);

        user.save(function (err, newUser){
            if(err) throw err;

            if(newUser){
                req.session.regenerate(function(){
                    req.session.user = newUser.username;
                    req.session.isLogged = true;
                    console.log(req.session.user);
                    res.redirect('/');
                });
            }
        });
    });

    app.post('/login/', function(req, res){
        var username = req.body.username,
            password = req.body.password;

        User.findOne({ username: username }, function(err, user){
            if(err) throw err;

            if(user && user.username === username && user.validPassword(password) === password){
                req.session.regenerate(function(){
                    req.session.user = user.username;
                    req.session.isLogged = true;
                    console.log(req.session.user);
                    res.redirect('/');
                });
            }

            if(!user){
                req.flash('alert', 'Invalid Username or Password');
                res.redirect('/register');
            }
        });
    });
};