Quickstart Guide

This guide walks you through adding Google OAuth authentication to an existing Node.js project using Devark. You’ll go from zero to a working OAuth flow in about 5 minutes.

Prerequisites

Before starting, make sure you have:

Node.js 18+ installed
An existing Node.js project with package.json
An Express.js app (or similar entry file like app.js)
Devark installed (see Installation)

Don’t have a project yet? Create one quickly:

mkdir my-backend && cd my-backend
npm init -y
npm install express
touch app.js

Step-by-Step Tutorial

Navigate to your project

Open your terminal and navigate to your Node.js project directory:

cd /path/to/your/project

Verify you have a package.json file:

ls package.json

Run the Devark command

Execute the command to add Google OAuth:

devark add google-oauth

You’ll see the Devark logo and initialization message:

┌  Google OAuth Module Setup
│
○  Installing Google OAuth module...
│  ✓ pnpm detected

Choose JavaScript or TypeScript

Devark will ask which language you want to use:

◆  Which version do you want to add for this module?
│  ● JavaScript
│  ○ TypeScript

Use arrow keys to select and press Enter. For this guide, we’ll choose JavaScript.

Specify your entry file

Enter the path to your main application file:

◆  Enter your project entry file (relative to root):
│  app.js

Press Enter to use the default (app.js) or type your custom path (e.g., src/index.js).

Provide Google OAuth credentials

Devark will prompt for your Google OAuth credentials. You can skip these for now and add them later:

◆  Enter your Google Client ID (leave empty for sample):
│  
└  Press Enter to skip

◆  Enter your Google Client Secret (leave empty for sample):
│  
└  Press Enter to skip

◆  Enter your Google Callback URL:
│  http://localhost:3000/auth/google/callback
└  Press Enter to use default

◆  Enter your session secret (leave empty for sample):
│  
└  Press Enter to skip

Don’t have credentials yet? No problem! Devark will use placeholder values. You can get real credentials from the Google Cloud Console later.

Wait for installation

Devark will now install dependencies and generate code:

◒  Installing dependencies...

This installs:

express
passport
passport-google-oauth20
express-session
dotenv

Output:

✓  Dependencies installed successfully.
✓  .env created with sample values.
│
└  Google OAuth setup complete!

Review generated files

Devark has created several files in your project:

your-project/
├── app.js                    # ← Modified with OAuth setup
├── .env                      # ← Created with credentials
├── config/
│   └── googleStrategy.js     # ← Passport Google strategy
└── routes/
    └── googleAuthRoutes.js   # ← OAuth routes

Let’s examine what was added:app.js - Updated with middleware and route registration:

import 'dotenv/config';
import session from 'express-session';
import passport from 'passport';
import googleAuthRoutes from './routes/googleAuthRoutes.js';
import './config/googleStrategy.js';

app.use(session({
  secret: process.env.SESSION_SECRET,
  resave: false,
  saveUninitialized: false
}));

app.use(passport.initialize());
app.use(passport.session());

app.use('/', googleAuthRoutes);

.env - Environment variables for configuration:

GOOGLE_CLIENT_ID=your-client-id
GOOGLE_CLIENT_SECRET=your-client-secret
GOOGLE_CALLBACK_URL=http://localhost:3000/auth/google/callback
SESSION_SECRET=your-session-secret

Configure Google OAuth credentials

To make OAuth work, you need real credentials from Google Cloud:

Go to Google Cloud Console
Create a new project or select existing one
Navigate to APIs & Services → Credentials
Click Create Credentials → OAuth 2.0 Client ID
Configure the consent screen if prompted
Select Web application as application type

Add authorized redirect URI:

http://localhost:3000/auth/google/callback

Copy the Client ID and Client Secret

Update your .env file with the real credentials:

GOOGLE_CLIENT_ID=1234567890-abc123def456.apps.googleusercontent.com
GOOGLE_CLIENT_SECRET=GOCSPX-aBcDeFgHiJkLmNoPqRsTuVwXyZ
GOOGLE_CALLBACK_URL=http://localhost:3000/auth/google/callback
SESSION_SECRET=your-secure-random-string

Never commit your .env file to version control. Add it to .gitignore:

echo ".env" >> .gitignore

Start your application

Run your Express.js application:

node app.js

If you have a start script in package.json:

npm start

You should see:

Server listening on port 3000

Test the OAuth flow

Open your browser and navigate to:

http://localhost:3000/auth/google

You should be redirected to Google’s login page. After signing in, Google will redirect you back to your callback URL.The generated routes provide these endpoints:

GET /auth/google - Initiates OAuth flow
GET /auth/google/callback - Handles OAuth callback
GET /auth/logout - Logs out the user
GET /auth/profile - Returns user profile (if authenticated)

Test the profile endpoint after logging in:

curl http://localhost:3000/auth/profile

Expected response:

{
  "id": "1234567890",
  "displayName": "John Doe",
  "emails": [{ "value": "[email protected]" }]
}

Understanding the Generated Code

Passport Strategy (`config/googleStrategy.js`)

This file configures Passport.js with the Google OAuth strategy:

import passport from 'passport';
import { Strategy as GoogleStrategy } from 'passport-google-oauth20';

passport.use(new GoogleStrategy({
    clientID: process.env.GOOGLE_CLIENT_ID,
    clientSecret: process.env.GOOGLE_CLIENT_SECRET,
    callbackURL: '/auth/google/callback'
  },
  (accessToken, refreshToken, profile, done) => {
    // Here you can save user to database
    return done(null, profile);
  }
));

passport.serializeUser((user, done) => done(null, user));
passport.deserializeUser((user, done) => done(null, user));

Auth Routes (`routes/googleAuthRoutes.js`)

Provides ready-to-use OAuth endpoints:

import express from 'express';
import passport from 'passport';

const router = express.Router();

// Initiate Google OAuth
router.get('/auth/google',
  passport.authenticate('google', { scope: ['profile', 'email'] })
);

// OAuth callback
router.get('/auth/google/callback',
  passport.authenticate('google', {
    failureRedirect: '/auth/failure',
    successRedirect: '/success'
  })
);

// Success page
router.get('/success', (req, res) => {
  const user = req.user;
  if (user) {
    res.send(`<h1>✅ Logged In Successfully</h1><p>Welcome, ${user.displayName}!</p>`);
  }
});

// Failure route
router.get('/auth/failure', (req, res) => {
  res.send('Failed to authenticate.');
});

export default router;

Customizing the Integration

The generated code is fully editable. Common customizations:

Save users to database

Modify config/googleStrategy.js:

(accessToken, refreshToken, profile, done) => {
  User.findOrCreate({ googleId: profile.id }, (err, user) => {
    return done(err, user);
  });
}

Add authentication middleware

Create middleware to protect routes:

function ensureAuthenticated(req, res, next) {
  if (req.isAuthenticated()) {
    return next();
  }
  res.redirect('/login');
}

router.get('/dashboard', ensureAuthenticated, (req, res) => {
  res.render('dashboard', { user: req.user });
});

Customize redirect URLs

Edit the callback route in routes/googleAuthRoutes.js:

router.get('/auth/google/callback',
  passport.authenticate('google', { failureRedirect: '/login' }),
  (req, res) => {
    // Redirect to dashboard instead of home
    res.redirect('/dashboard');
  }
);

Troubleshooting

”Redirect URI mismatch” error

Ensure the callback URL in Google Cloud Console exactly matches your .env file:

http://localhost:3000/auth/google/callback

No trailing slashes, correct port number.

”Invalid client” error

Double-check your GOOGLE_CLIENT_ID and GOOGLE_CLIENT_SECRET in .env. Make sure there are no extra spaces.

Session not persisting

Ensure express-session is configured before passport.initialize():

app.use(session({ ... }));  // Must come first
app.use(passport.initialize());
app.use(passport.session());

Next Steps

Congratulations! You’ve successfully added Google OAuth to your project. Here are some ideas for next steps:

Add GitHub OAuth

devark add github-oauth

Add Email OTP

devark add resend-otp

Create New Project

devark add node-mongo

Explore TypeScript

Run any module with TypeScript support

Available Modules

Explore all available Devark modules:

devark add google-oauth - Google OAuth 2.0
devark add github-oauth - GitHub OAuth
devark add resend-otp - Email OTP via Resend
devark add node-mongo - Node.js + MongoDB template
devark add node-postgres - Node.js + PostgreSQL template
devark add oauth - Interactive OAuth provider selector

Each module supports both JavaScript and TypeScript. You’ll be prompted to choose during installation.

Get Started

Authentication Modules

Project Templates

Guides

Quickstart

Quickstart Guide

Prerequisites

Step-by-Step Tutorial

Understanding the Generated Code

Passport Strategy (`config/googleStrategy.js`)

Auth Routes (`routes/googleAuthRoutes.js`)

Customizing the Integration

Save users to database

Add authentication middleware

Customize redirect URLs

Troubleshooting

”Redirect URI mismatch” error

”Invalid client” error

Session not persisting

Next Steps

Add GitHub OAuth

Add Email OTP

Create New Project

Explore TypeScript

Available Modules

Build docs developers (and LLMs) love

Get Started

Authentication Modules

Project Templates

Guides

​Quickstart Guide

​Prerequisites

​Step-by-Step Tutorial

​Understanding the Generated Code

​Passport Strategy (config/googleStrategy.js)

​Auth Routes (routes/googleAuthRoutes.js)

​Customizing the Integration

​Save users to database

​Add authentication middleware

​Customize redirect URLs

​Troubleshooting

​”Redirect URI mismatch” error

​”Invalid client” error

​Session not persisting

​Next Steps

Add GitHub OAuth

Add Email OTP

Create New Project

Explore TypeScript

​Available Modules

Build docs developers (and LLMs) love

Quickstart Guide

Prerequisites

Step-by-Step Tutorial

Understanding the Generated Code

Passport Strategy (`config/googleStrategy.js`)

Auth Routes (`routes/googleAuthRoutes.js`)

Customizing the Integration

Save users to database

Add authentication middleware

Customize redirect URLs

Troubleshooting

”Redirect URI mismatch” error

”Invalid client” error

Session not persisting

Next Steps

Available Modules