Easy Node Authentication: Google

    // config/auth.js

    // expose our config directly to our application using module.exports
    module.exports = {

        'facebookAuth' : {
            'clientID'      : 'your-secret-clientID-here', // your App ID
            'clientSecret'  : 'your-client-secret-here', // your App Secret
            'callbackURL'   : 'http://localhost:8080/auth/facebook/callback'
        },

        'twitterAuth' : {
            'consumerKey'       : 'your-consumer-key-here',
            'consumerSecret'    : 'your-client-secret-here',
            'callbackURL'       : 'http://localhost:8080/auth/twitter/callback'
        },

        'googleAuth' : {
            'clientID'      : 'your-secret-clientID-here',
            'clientSecret'  : 'your-client-secret-here',
            'callbackURL'   : 'http://localhost:8080/auth/google/callback'
        }

    };

    // config/passport.js

    // load all the things we need
    var LocalStrategy    = require('passport-local').Strategy;
    var FacebookStrategy = require('passport-facebook').Strategy;
    var TwitterStrategy  = require('passport-twitter').Strategy;
    var GoogleStrategy = require('passport-google-oauth').OAuth2Strategy;

    // load up the user model
    var User       = require('../app/models/user');

    // load the auth variables
    var configAuth = require('./auth');

    module.exports = function(passport) {

        // used to serialize the user for the session
        passport.serializeUser(function(user, done) {
            done(null, user.id);
        });

        // used to deserialize the user
        passport.deserializeUser(function(id, done) {
            User.findById(id, function(err, user) {
                done(err, user);
            });
        });

        // code for login (use('local-login', new LocalStategy))
        // code for signup (use('local-signup', new LocalStategy))
        // code for facebook (use('facebook', new FacebookStrategy))
        // code for twitter (use('twitter', new TwitterStrategy))

        // =========================================================================
        // GOOGLE ==================================================================
        // =========================================================================
        passport.use(new GoogleStrategy({

            clientID        : configAuth.googleAuth.clientID,
            clientSecret    : configAuth.googleAuth.clientSecret,
            callbackURL     : configAuth.googleAuth.callbackURL,

        },
        function(token, refreshToken, profile, done) {

            // make the code asynchronous
            // User.findOne won't fire until we have all our data back from Google
            process.nextTick(function() {

                // try to find the user based on their google id
                User.findOne({ 'google.id' : profile.id }, function(err, user) {
                    if (err)
                        return done(err);

                    if (user) {

                        // if a user is found, log them in
                        return done(null, user);
                    } else {
                        // if the user isnt in our database, create a new user
                        var newUser          = new User();

                        // set all of the relevant information
                        newUser.google.id    = profile.id;
                        newUser.google.token = token;
                        newUser.google.name  = profile.displayName;
                        newUser.google.email = profile.emails[0].value; // pull the first email

                        // save the user
                        newUser.save(function(err) {
                            if (err)
                                throw err;
                            return done(null, newUser);
                        });
                    }
                });
            });

        }));

    };

    // app/routes.js

    module.exports = function(app, passport) {

        // route for home page
        app.get('/', function(req, res) {
            res.render('index.ejs'); // load the index.ejs file
        });

        // route for login form
        // route for processing the login form
        // route for signup form
        // route for processing the signup form

        // route for showing the profile page
        app.get('/profile', isLoggedIn, function(req, res) {
            res.render('profile.ejs', {
                user : req.user // get the user out of session and pass to template
            });
        });

        // route for logging out
        app.get('/logout', function(req, res) {
            req.logout();
            res.redirect('/');
        });

        // facebook routes
        // twitter routes

        // =====================================
        // GOOGLE ROUTES =======================
        // =====================================
        // send to google to do the authentication
        // profile gets us their basic information including their name
        // email gets their emails
        app.get('/auth/google', passport.authenticate('google', { scope : ['profile', 'email'] }));

        // the callback after google has authenticated the user
        app.get('/auth/google/callback',
                passport.authenticate('google', {
                        successRedirect : '/profile',
                        failureRedirect : '/'
                }));

    };

    // route middleware to make sure a user is logged in
    function isLoggedIn(req, res, next) {

        // if user is authenticated in the session, carry on
        if (req.isAuthenticated())
            return next();

        // if they aren't redirect them to the home page
        res.redirect('/');
    }

    <!-- views/index.ejs -->

    <!doctype html>
    <html>
    <head>
        <title>Node Authentication</title>
        <link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.0.2/css/bootstrap.min.css"> <!-- load bootstrap css -->
        <link rel="stylesheet" href="//netdna.bootstrapcdn.com/font-awesome/4.0.3/css/font-awesome.min.css"> <!-- load fontawesome -->
        <style>
            body        { padding-top:80px; }
        </style>
    </head>
    <body>
    <div class="container">

        <div class="jumbotron text-center">
            <h1><span class="fa fa-lock"></span> Node Authentication</h1>

            <p>Login or Register with:</p>

            <a href="/auth/google" class="btn btn-danger"><span class="fa fa-google-plus"></span> Google</a>

        </div>

    </div>
    </body>
    </html>

    <!-- views/profile.ejs -->
    <!doctype html>
    <html>
    <head>
        <title>Node Authentication</title>
        <link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.0.2/css/bootstrap.min.css">
        <link rel="stylesheet" href="//netdna.bootstrapcdn.com/font-awesome/4.0.3/css/font-awesome.min.css">
        <style>
            body        { padding-top:80px; word-wrap:break-word; }
        </style>
    </head>
    <body>
    <div class="container">

        <div class="page-header text-center">
            <h1><span class="fa fa-anchor"></span> Profile Page</h1>
            <a href="/logout" class="btn btn-default btn-sm">Logout</a>
        </div>

        <div class="row">

            <!-- GOOGLE INFORMATION -->
            <div class="col-sm-6">
                <div class="well">
                    <h3 class="text-danger"><span class="fa fa-google-plus"></span> Google</h3>

                        <p>
                            <strong>id</strong>: <%= user.google.id %><br>
                            <strong>token</strong>: <%= user.google.token %><br>
                            <strong>email</strong>: <%= user.google.email %><br>
                            <strong>name</strong>: <%= user.google.name %>
                        </p>

                </div>
            </div>

        </div>

    </div>
    </body>
    </html>