... // Passport facebook startegy
     var newUser = new User();
     newUser.facebook = {};
     newUser.facebook.id = profile.id;
     newUser.facebook.token = token; // token received from facebook
     newUser.facebook.name  = profile.displayName;
     newUser.save(function(err) {
          if (err)
               throw err;
          // if successful, return the new user
          newUser.jwtoken = newUser.generateJwt(); // JWT CREATION!
          return done(null, newUser);
     });

app.get('/auth/facebook/callback',
    passport.authenticate('facebook', {
        session: false,
        successRedirect : '/',
        failureRedirect : '/'
    }), (req, res) => {
        var token = req.user.jwtoken;
        res.json({token: token});
    });