bcrypt Error: data and hash arguments required

const passwordMatch = await bcrypt.compare(password, user.password);

Make sure you are giving raw password and hash password. This will return a boolean value.

bcrypt.compare takes 3 parameters; passwordToCheck, passwordHash, and a callback, respectively. (Check the documentation for examples)

This error means one or both of the first 2 parameters are either null or undefined. Therefore, make sure both of them are passed correctly. (Not as null or undefined)

I used

const user = await User.find({email: req.body.email}) //which returned all users

//and unless i reference the first user in index 0, i can't pass user.password to the //bcrypt compare method because it's not a string I changed it to

await User.findOne({email: req.body.email})//from which i can use user.password in the //bcrypt compare method

Why do we face this error? bcrypt Error: data and hash arguments required

Example: bcrypt.compare(first, second)

Ans: because either second key hash password does not exist (null or undefined) or first, which are compared to each other.