Expressks auth with promise .js

express-auth-promises2.js

app.post('/', function (req, res, next) {
    var body = req.body;
    if (!body.name || !body.email || !body.password) {
        return res.status(400).send("Missing username or email or password")
    };
    // case #1- if user was registered (socials platform) before -> just add a password;
    User.findOneAndUpdate({
        email: body.email
    }, {
            $set: { password: body.password }
        })
        .then((user) => {
            if (!user) return User.create(body);
            return Promise.resolve(user)
        })
        .then((user) => {
            res.send({ user: user })
        })
        .catch((err) => {
            if (err.name === 'ValidationError') {
                return res.status(400).send(err)
            }
            res.status(500).send(err)
        })
});