Handle deselected values from Facebook via PassportJS

Question

I am using PassportJS and it's Facebook-Strategy to authenticate users for my site.

All is well when the user doesn't deselect anything in the Facebook pop-up.

However, say the user deselects E-mail, I won't be getting that back, which is obviously in the user's control.

My question is - how do I direct them to "somewhere else" based on the data I retried?

passport.use(new FacebookStrategy({
clientID: config.facebook.appID,
clientSecret: config.facebook.appSecret,
callbackURL: config.facebook.callbackURL,
profileFields: ['displayName', 'picture.type(large)', 'emails', 'birthday', 'location']},
function(accessToken, refreshToken, profile, done){

    var newUser = new userModel({
        fullname    :   profile.displayName,
        profilePic  :   profile.photos[0].value || '',
        email       :   profile.emails[0].value || '',
        birthday    :   profile._json.birthday || '',
        location    :   profile._json.location.name || '',
    });

    newUser.save(function(err){
        done(null, newUser);
    });
);
}

I can, of course, do some sort of a preprocessor but I don't know what I need to do if the data is not valid. For instance, say "E-mail" is a must. How will I tell the user: "As you haven't provided the mandatory E-mail field, please fill it in" and then I take the user to a Profile Settings page.

My callback URL on the Facebook app is:

http://localhost:3000/auth/facebook/callback

And it's NodeJS route below:

router.get('/auth/facebook/callback', passport.authenticate('facebook', {
    successRedirect:'/wall',
    failureRedirect:'/login'
}));

Any input will help.

Thanks in advance.

Answer 1

I think here the user wont deselect the email field. Facebook will provide you all the user data you requested. But if the user email provided in the facebook is not verified then you wont get that information email:profile.emails[0].value here i.e., the email field will be empty. If you think that the email is mandatory for you then after every successful login just write the code to check whether the email field is empty/null or not. If it is empty then you create a form where you can ask the user to just enter their email. I used mongodb and the passport code will be like this,

var User = require('../models/user');
    passport.use(new FacebookStrategy({
        clientID: configAuth.facebookAuth.clientID,
        clientSecret: configAuth.facebookAuth.clientSecret,
        callbackURL: configAuth.facebookAuth.callbackURL,
        profileFields: ['id', 'email', 'first_name', 'last_name'],
      },
      function(token, refreshToken, profile, done) {
        process.nextTick(function() {
          User.findOne({ 'facebook.id': profile.id }, function(err, user) {
            if (err)
              return done(err);
            if (user) {
              return done(null, user);
            } else {
              var newUser = new User();
              newUser.facebook.id = profile.id;
              newUser.facebook.token = token;
              newUser.facebook.name = profile.name.givenName + ' ' + profile.name.familyName;
              if(profile.emails !=null)
    {
              newUser.facebook.email = (profile.emails[0].value || '').toLowerCase();
    }
    else
    {
    //write your code here to use the form and request the email from the user and then add that email to your database.
    }
              newUser.save(function(err) {
                if (err)
                  console.log(err);
                return done(null, newUser);
              });
            }
          });
        });
      }));

Now, you don't need to change the nodejs route of success redirect and failure redirect.