Day 2: MongoDB and Mongoose | Express.js in 5 Days

Connecting to MongoDB

Terminal

npm install mongoose dotenv

.env

MONGODB_URI=mongodb+srv://user:[email protected]/mydb

db.js

const mongoose = require('mongoose');

mongoose.connect(process.env.MONGODB_URI)
  .then(() => console.log('MongoDB connected'))
  .catch(err => console.error('MongoDB error:', err));

models/User.js

const mongoose = require('mongoose');

const userSchema = new mongoose.Schema({
  name: { type: String, required: true, trim: true },
  email: { type: String, required: true, unique: true, lowercase: true },
  role: { type: String, enum: ['user', 'admin'], default: 'user' },
  createdAt: { type: Date, default: Date.now }
});

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

routes/users.js

const User = require('../models/User');

// GET all users
router.get('/', async (req, res) => {
  try {
    const users = await User.find().sort('-createdAt').limit(20);
    res.json(users);
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

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

📝 Day 2 Exercise

Build a User API with MongoDB

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Day 2 Summary

mongoose.connect(uri) — connect once at startup. All models share this connection.
Schemas define shape + validation. Models are the interface for querying.
Always use async/await with Mongoose. Wrap in try/catch for error handling.
Mongoose validation happens before saving. Unique index violations throw an error with code: 11000.

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Day 3: Authentication with JWT

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