2. MongoDB Atlas

1. Atlas Cluster

Walk through of Setting up MongoDB Atlas and then connecting it to MongoDB Compass — step by step.

1.1 Setting up MongoDB Atlas

1. ✅ Create a MongoDB Atlas Account

Go to: https://www.mongodb.com/cloud/atlas

• Click “Start Free”
• Sign up with Google or email

2. ✅ Create a Free Cluster

• After logging in, click “Build a Database”
• Choose “Shared” (Free tier)
• Choose a cloud provider (AWS, Azure, or GCP)
• Pick a region (close to your location)
• Name your cluster (e.g., Cluster0)
• Click “Create Cluster” – may take 1-2 minutes

3. ✅ Create a Database User

Once the cluster is created:

• Go to “Database Access” tab (left menu)
• Click “Add New Database User”
  • Choose Username (e.g., admin)
  • Choose Password (e.g., password123) — you’ll use this in Compass
  • Select Built-in Roles → Read and write to any database
  • Click “Add User”

4. ✅ Allow Your IP Address

Go to “Network Access” tab:

• Click “Add IP Address”

• Click “Allow Access from Anywhere” for testing:

  0.0.0.0/0

  (Or click “Add Current IP” if you’re on a known IP)

• Click “Confirm”

5. ✅ Get the Connection String

• Go to “Clusters”
• Click “Connect”
• Choose “Connect with MongoDB Compass”
• Copy the connection string:

mongodb+srv://<username>:<password>@cluster0.xxxxx.mongodb.net/

Replace <username> and <password> with what you created in step 3.

6. ✅ Open MongoDB Compass & Connect

• Open Compass
• Paste the connection string into the connection field
• Hit “Connect”

🚀 You’re in! You’ll see your cluster’s databases and collections.

🎉 You’re All Set!

You can now:

• View documents
• Insert/edit/delete data
• Run queries
• Use it with your Express/Mongoose app (same connection string!)

1.2 Connection String in App

📦 1. Install Dependencies (if you haven’t already)

npm install mongodb mongoose dotenv

🗂️ 2. .env File (Store the Connection String Securely)

Create a .env file in your project root:

.env

MONGO_URI=mongodb+srv://<username>:<password>@cluster0.xxxxx.mongodb.net/myDatabase?retryWrites=true&w=majority
PORT=3000

Replace:

• <username> and <password> with your MongoDB Atlas user
• myDatabase with the name of the DB you want to connect to

IMPORTANT

For <password>, do not have a @ symbol since the URI itself has @cluster0.xxxxx.mongodb.... Hence @ will confuse the connection string.

📄 3. app.js (or index.js)

app.js

const express = require('express');
const mongoose = require('mongoose');
const dotenv = require('dotenv');

dotenv.config(); // Load environment variables

const app = express();

// Connect to MongoDB Atlas
mongoose.connect(process.env.MONGO_URI)
.then(() => console.log('✅ Connected to MongoDB Atlas'))
.catch(err => console.error('❌ MongoDB connection error:', err));

// Sample Route
app.get('/', (req, res) => {
  res.send('MongoDB Atlas connected!');
});

// Start server
const PORT = process.env.PORT || 3000;
app.listen(PORT, () => {
  console.log(`🚀 Server running on port ${PORT}`);
});

▶️ 4. Run Your App

node app.js

You should see:

✅ Connected to MongoDB Atlas
🚀 Server running on port 3000

💡 Bonus Tip:

Keep your .env file out of Git with .gitignore:

node_modules/
.env

1.3 MongoDB in Your App

• 🔌 Atlas DB connection
• 📄 A User model
• 🧪 Test API routes (GET, POST)
• 💬 Sample test queries to try out

🛠️ Project Structure

myapp/
│
├── .env
├── app.js
├── models/
│   └── User.js
└── routes/
    └── userRoutes.js

📄 Database URI and Port

.env

MONGO_URI=mongodb+srv://<username>:<password>@cluster0.xxxxx.mongodb.net/myapp?retryWrites=true&w=majority
PORT=3000

Replace with your Atlas credentials and DB name.

📄 Mongoose Schema

models/User.js

const mongoose = require('mongoose');

const userSchema = new mongoose.Schema({
  name: { type: String, required: true },
  email: { type: String, required: true, unique: true },
  age: Number,
}, { timestamps: true });

module.exports = mongoose.model('User', userSchema);

📄 Express Routes

routes/userRoutes.js

const express = require('express');
const router = express.Router();
const User = require('../models/User');

// Create a user (POST /api/users)
router.post('/', async (req, res) => {
  try {
    const user = await User.create(req.body);
    res.status(201).json(user);
  } catch (err) {
    res.status(400).json({ error: err.message });
  }
});

// Get all users (GET /api/users)
router.get('/', async (req, res) => {
  try {
    const users = await User.find();
    res.json(users);
  } catch (err) {
    res.status(500).json({ error: 'Server error' });
  }
});

// Find a user by email (GET /api/users/email/:email)
router.get('/email/:email', async (req, res) => {
  try {
    const user = await User.findOne({ email: req.params.email });
    if (!user) return res.status(404).json({ message: 'User not found' });
    res.json(user);
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

// Delete All Users
router.delete('/del', async (req, res) => {
  try {
    await User.deleteMany({});
    res.send('All users deleted');
  } catch (err) {
    res.status(500).send(err.message);
  }
});

// Delete By ID
router.delete('/del/:id', async (req, res) => {
  try {
    const result = await User.findByIdAndDelete(req.params.id);
    if (!result) return res.status(404).send('User not found');
    res.send('User deleted');
  } catch (err) {
    res.status(500).send(err.message);
  }
});

module.exports = router;

📄 Entry Point

app.js

const express = require('express');
const mongoose = require('mongoose');
const dotenv = require('dotenv');

dotenv.config();

const userRoutes = require('./routes/userRoutes');
const app = express();

app.use(express.json());

// MongoDB connection
mongoose.connect(process.env.MONGO_URI)
.then(() => console.log('✅ Connected to MongoDB Atlas'))
.catch(err => console.error('❌ Connection error:', err));

// API routes
app.use('/api/users', userRoutes);

// Root route
app.get('/', (req, res) => {
  res.send('✅ MongoDB Atlas Express API is running!');
});

const PORT = process.env.PORT || 3000;
app.listen(PORT, () => console.log(`🚀 Server running on port ${PORT}`));

🧪 Test the API

Use Postman, Insomnia, or curl to test:

➕ Create User (POST)

URL: http://localhost:3000/api/users
Body (JSON):

{
  "name": "Alice",
  "email": "alice@example.com",
  "age": 28
}

📥 Get All Users (GET)

URL: http://localhost:3000/api/users

🔎 Find by Email (GET)

URL: http://localhost:3000/api/users/email/alice@example.com

✅ All Set!

You now have:

• MongoDB Atlas connected
• Users stored in the cloud
• API routes ready for use
• Basic queries and endpoints to build on