passport.js

var passport = require('passport');
var LocalStrategy = require('passport-local').Strategy;
var FacebookStrategy = require('passport-facebook').Strategy;

passport.serializeUser(function (user, done) {
    done(null, user._id);
});

passport.deserializeUser(function (id, done) {
    User.findOne({_id: id}, function (err, user) {
        done(err, user);
    })
});

passport.use(new LocalStrategy({
        usernameField: 'email'
    },
    function (username, password, done) {
        User.findOne({email: username}, function (err, user) {
            if (err) return done(err);
            if (!user) {
                return done(null, false, {
                    message: 'Incorrect username or password'
                });
            }
            if (!user.validPassword(password)) {
                return done(null, false, {
                    message: 'Incorrect username or password'
                });
            }

            return done(null, user);
        })
    }
));


passport.use(new FacebookStrategy({
    clientID: '168532953832690',
    clientSecret: '07f65327156be27627b937c3a8dcf06a',
    callbackURL: 'http://localhost:3000/auth/facebook/callback',
    profileFields: ['id', 'displayName', 'email']
}, function(token, refreshToken, profile, done){
    User.findOne({'facebookId': profile.id},function(err,user){
        if(err) return done(err);

        if(user){
            return done(null, user);
        }else{
            User.findOne({'email':profile.emails[0].value},function(err,user){
                if(user){
                    user.facebookId=profile.id
                    return user.save(function(err){
                        if(err) return done(null, false,{message: 'Cant save user info'});
                        return done(null,user);
                    })
                }
                var user= new User();
                user.name=profile.displayName;
                user.email=profile.emails[0].value;
                user.facebookId=profile.id;
                user.save(function(err){
                    if(err) return done(null, false,{message: 'Cant save user info'});
                    return done(null,user);
                });
            })
        }
    });
}));