Bcrypt returns false on login - mongodb

Question

I know this question has been asked many times but I cannot find an answer to my problem both here or on github. I have a login handler which compares hashed password from db to the the one typed by the user on login. bcrypt.compare almost always returns false. I say almost because sometimes it just starts working and it always works after I register user. I am trying to find what is wrong with my code but cant figure it out. Any help is highly appreciated.
mongoose pre save
userModel.schema.pre('save', function(next) {
let user = this;
bcrypt.hash(user.password, 10, null)
.then(hash => {
console.log(hash)
user.password = hash;
user.confirmPassword = hash;
next();
})
.catch(err => res.sendStatus(404));
});
login handler
exports.loginUser = (req, res) => {
let user = new User.model(req.body);
User.model
.find({email: user.email})
.exec()
.then(users => {
if (!users.length) {
res.status(401).json({
message: "Auth failed - user does not exist"
});
} else {
bcrypt
.compare(req.body.password, users[0].password)
.then(result=> {
console.log(user.password, users[0].password)
console.log(bcrypt.hashSync(req.body.password, 10))
if (result) {
const token =
jwt
.sign({ email: users[0].email, id: users[0]._id },
'secretKey', { expiresIn: "1h"});
res.status(200).json({
message: "Auth success - logged in",
token,
users
});
} else {
res.json('not working');
}
})
.catch(err => res.status(401).json({message: "Auth failed"}));
}
});
};
register handler
exports.registerUser = (req, res) => {
let user = new User.model(req.body);
if(user.email) {
User.model
.find({email: user.email})
.exec()
.then(docs => {
if (!docs.length) {
if (user.password !== user.confirmPassword) {
return res.status(404).json('passwords do not match');
}
user.save(function (err, user) {
if (err) return (err);
});
console.log('user saved');
res.sendStatus(200);
} else {
res.status(404).json('user exists');
}
})
.catch(err => res.sendStatus(404).json(res.body));
} else {
res.status(404).json('user name required');
}
};

Answer 1

The problem might be that you generate a new password each time the user is saved. You should skip this though.
userModel.schema.pre('save', function(next) {
let user = this;
if(!user.isModified("password")) return next();
bcrypt.hash(user.password, 10, null)
.then(hash => {
console.log(hash)
user.password = hash;
user.confirmPassword = hash;
next();
})
.catch(err => res.sendStatus(404));
});
Just a shot in the dark though. under the assumption something got changed and this was called again, because you stated it is working sometimes.