Vérifier si un email existe déjà dans la database MongoDB

Bonjour,

j'ai crée une loginapp en nodejs et je voudrais savoir comment verifier si un email est deja dans la db lors du register

Code:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
router.post('/register', function(req, res) {
  var name = req.body.name;
  var email = req.body.email;
  var username = req.body.username;
  var password = req.body.password;
  var password2 = req.body.password2;
 
  req.checkBody('username', 'Please enter a username').notEmpty();
  req.checkBody('email', 'pls enter a email adress').notEmpty().isEmail();
  req.checkBody('password', 'pls enter a password').notEmpty();
  req.checkBody('password2', 'the password dont match').equals(req.body.password);
 
var errors = req.validationErrors();
 
  if(errors) {
          res.render('register',{
        errors:errors,
    })
    } else {
        var newUser = new User({
            email:email,
            username: username,
            password: password
        });
     User.createUser(newUser, function(err, user){
      if(err) throw err;
      console.log(user);
    });
 
    req.flash('success_msg', 'u create an accoun, u can log');
 
    res.redirect('/users/login');
  }
})

Comment faire un systeme de verification dans la MongoDB?