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JavaScript User Authentication With Express and Mongo Sessions and Cookies Authenticating the Username and Password

Daniel Conde
Daniel Conde
3,881 Points

Dealing with error in bcrypt.compare callback

Is there any reason why we don't pass a potential error passed back by the bcrypt function? Would adding the following line help? if(error) return callback(error); How do you recommend dealing with potential internal errors such as this one?

The code I'm referring to:

bcrypt.compare(password, user.password, function(error, result) { if (result === true) { return callback(null, user); } else { return callback() } })

2 Answers

Christos Peramatzis
Christos Peramatzis
16,428 Points

I would expect it to be

bcrypt.compare(password, user.password, function(error, result) {
        if(result === true) {
          return callback(null, user);
        }
        else {
          return callback(error);
        }
}

We don't need to differentiate between having an error or the passwords not matching, maybe except for the status codes.

In any case, I don't know why the error is not passed in the callback in the video.

Kayla Kremer
Kayla Kremer
14,269 Points

I think the reason why the error is not passed in the callback is because passing parameters in JavaScript is optional. So by not passing in anything, the error and result parameters become undefined.

If you notice in the video in the index.js file, we set up the if conditional to check if there is an error or if there is no user:

if(error || !user){
        var err = new Error('Wrong email or password.');
        err.status = 401;
        return next(err);
}

Since both error and user are undefined, error evaluates to false, but !user evaluates to true, so the if conditional statement is true and the block of code runs.

Oziel Perez
Oziel Perez
61,321 Points

When one knows more than one or two programming languages, that can really trick your head! Some languages require that you pass something, even if it's a null value, or it will throw an error. I think I rather pass something in to specifically state that the values are null