Getting error [ERR_INVALID_ARG_TYPE] while trying to login

I’ve provided login/register system to my page, but I get an error I’ve been struggling with while trying to login:

TypeError [ERR_INVALID_ARG_TYPE]: The "salt" argument must be of type string or an instance of Buffer, TypedArray, or DataView. Received undefined
at check (internal/crypto/pbkdf2.js:59:10)
at Object.pbkdf2 (internal/crypto/pbkdf2.js:25:5)
at validPassword (/Users/krzysztofbialk/TO.DO/config/passwordUtils.js:14:29)
at /Users/krzysztofbialk/TO.DO/config/passport_log.js:21:33
at processTicksAndRejections (internal/process/task_queues.js:93:5)

Looks like something here is the problem:

passwordUtils.js

const crypto = require('crypto');
function genPassword(password) {
    let salt = crypto.randomBytes(32).toString('hex');
    let genHash = crypto.pbkdf2Sync(password, salt, 10000, 64, 'sha512').toString('hex');
    return {
      salt: salt,
      hash: genHash
    };
};
function validPassword(password, hash, salt) {
    let hashVerify = crypto.pbkdf2Sync(password, salt, 10000, 64, 'sha512').toString('hex');
    return hash === hashVerify;
};
module.exports.validPassword = validPassword;
module.exports.genPassword = genPassword;

or passport_log.js

const customFields = {
    usernameField: 'email',
    passwordField: 'password'
    };
    const verifyCallback = (username, password, done) => {
            LogUser.findOne({username: username})
                .then((user) => {
                console.log(user)
                    if (!user) {return done(null, false)}
                    const isValid = validPassword(password, user.hash, user.salt);
                    if (isValid) {
                        return done(null, user);
                    } else {
                        return done(null, false);
                    }
                })
                .catch((err) => {
                    done(err);
                });
        };
// LOCAL STRATEGY; it looks good, doesn't it?
    passport.use(new LocalStrategy(customFields, verifyCallback));

login post route

router.post('/login', passport.authenticate('local', { successRedirect: '/private', failureRedirect: '/login' }));

When I console.log(user) it returns

{
  _id: 60cbb580ef0690505762a581,
  username: '[e-mail]',
  createdAt: 2021-06-17T20:50:08.570Z,
  __v: 0
}

But after successful register it returns

{
  _id: 60cbb580ef0690505762a581,
  username: '[e-mail]',
  hash: 'b762ebbafb266dab12f71eeabbdae6d53e62e91937c51d99fe1816e6d401379b91495b7db0f56b8143e8607bf72ce2a565c38eeeb1f916cc9c0a85d8e6d3c9fe',
  salt: '0536b806ac052e5628c74e7ec9fd6b94fb0d1bd4bc0e93fdfdf51ed5b964c581',
  createdAt: 2021-06-17T20:50:08.570Z
}

And in DB:

   _id:ObjectId("60cbb580ef0690505762a581")
    username:"[e-mail]"
   hash:"b762ebbafb266dab12f71eeabbdae6d53e62e91937c51d99fe1816e6d401379b91495b..."
   salt:"0536b806ac052e5628c74e7ec9fd6b94fb0d1bd4bc0e93fdfdf51ed5b964c581"
    createdAt:2021-06-17T20:50:08.570+00:00
    __v:0

Why there is hash and salt in user data after register, but not when tried to login?

LogUser schema:

const LogUserSchema = new mongoose.Schema({
name: {
    type: String    
},
email: {
    type: String,
    // required: true,
    // unique: true
},
password: {
    type: String,
    // required: true
},
image: {
    type: String
},
createdAt: {
    type: Date,
    default: Date.now
},
hash: {
    type: String
},
salt: {
    type: String
}});

I have ran out of ideas what’s wrong. Happy to receive any answers!

Answer

Editing to show what turned out to be the right answer:

I think Mongoose removes the hash and salt fields from these kinds of queries by default. So to make your query work you just need to type LogUser.findOne({username: username}, 'username salt hash') and then the salt and hash should be accessible in the returned document.