I have this script that encrypts a password but I don\'t know how to reverse it and decrypt it. This may be a very simple answer but I don\'t understand how to do it.
You simply can't.
bcrypt uses salting, of different rounds, I use 10 usually.
bcrypt
bcrypt.hash(req.body.password,10,function(error,response){ }
This 10 is salting random string into your password.