MongoDB & Mongoose ODM

🌿 Node.js Lesson 12 Intermediate

MongoDB is a NoSQL database that stores data as flexible JSON-like documents. Mongoose is the most popular ODM (Object Data Mapper) for Node.js, adding schemas, validation, and model methods on top of MongoDB's driver.

1 Connecting & Defining a Schema

JavaScript — Mongoose Setup & Schema

const mongoose = require('mongoose');

// Connect to MongoDB
async function connectDB() {
  try {
    await mongoose.connect(process.env.MONGODB_URI);
    console.log('MongoDB connected successfully');
  } catch (err) {
    console.error('Connection failed:', err.message);
    process.exit(1);
  }
}
connectDB();

// Define a Schema
const userSchema = new mongoose.Schema({
  name: {
    type: String,
    required: [true, 'Name is required'],
    trim: true,
    minlength: 2
  },
  email: {
    type: String,
    required: true,
    unique: true,
    lowercase: true,
    match: [/^S+@S+.S+$/, 'Invalid email format']
  },
  role: {
    type: String,
    enum: ['user', 'admin', 'editor'],
    default: 'user'
  },
  createdAt: { type: Date, default: Date.now }
});

// Add instance methods
userSchema.methods.toPublicJSON = function() {
  const { _id, name, email, role } = this;
  return { id: _id, name, email, role };
};

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

2 CRUD with Mongoose

JavaScript — Mongoose CRUD

// CREATE
const user = await User.create({ name: 'Balaji', email: 'b@example.com' });

// READ — find all, with pagination
const users = await User.find({ role: 'user' })
  .select('name email -_id')
  .sort({ name: 1 })
  .skip(0).limit(10);

// READ — find one by id
const found = await User.findById(req.params.id);
if (!found) throw new Error('User not found');

// UPDATE — findByIdAndUpdate returns the updated doc
const updated = await User.findByIdAndUpdate(
  req.params.id,
  { name: 'Updated Name' },
  { new: true, runValidators: true }
);

// DELETE
await User.findByIdAndDelete(req.params.id);

3 Code Challenge

Challenge: Define a Mongoose schema for a Product with fields: name, price (Number, min 0), category, and inStock (Boolean). Write a query that finds all in-stock products sorted by price.