How to verify if email is already in the MongoDB | Nodejs - node.js

Question

I create a loginapp in nodejs but i want to verify if the email(or username) il already in the database.
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');
}
})
How can a do a verify why an error msg if the email is already in the database ?

Answer 1

You can call findOne on the collection with the specified email. It resolves to null if no document matches. You can use that so as to detect whether or not there is already a user with the same email in the database.
You didn't provide the relevant part of the code to guess the architecture of you database, but you're probably going to use something like the following:
const { MongoClient } = require('mongodb');
const email = 'john#doe.com';
// wraps everything in an async function
(async () => {
// connect to database
const client = new MongoClient('mongodb://localhost:27017');
await client.connect();
const users = client.db('your-db-name').collection('users');
// look for an existing user
let possibleDuplicate = await users.findOne({email});
if (possibleDuplicate===null) {
// email is not taken
// do something...
} else {
// email is taken
// do something...
}
})()