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express-js / MongoDB + Mongoose with Express
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MongoDB + Mongoose with Express

MongoDB is a popular NoSQL database that stores data in flexible, JSON-like documents. **Mongoose** is an ODM (Object Document Mapper) that provides a schema-based solution to model your application data. Together, they make working with MongoDB in Express a breeze.

Why MongoDB + Mongoose?

  • Schema-less but with structure: Mongoose adds schema validation while keeping MongoDB's flexibility.
  • Built-in validation: Define rules for your data.
  • Middleware (hooks): Run code before/after database operations.
  • Population: Easy way to reference documents in other collections.

Think of Mongoose as a helpful assistant that makes sure your data is properly formatted before it goes into MongoDB, and nicely packaged when it comes out.

Installation
npm install mongoose

Connecting to MongoDB
const mongoose = require('mongoose');

mongoose.connect('mongodb://localhost:27017/myapp', {
  useNewUrlParser: true,
  useUnifiedTopology: true
})
.then(() => console.log('Connected to MongoDB'))
.catch(err => console.error('Connection error:', err));

Defining a Schema and Model

A schema defines the structure of your documents. A model is a compiled version of the schema that lets you interact with the database.
<!-- 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: { type: Number, min: 0 },
  createdAt: { type: Date, default: Date.now },
  isActive: { type: Boolean, default: true }
});

<!-- Create the model -->
const User = mongoose.model('User', userSchema);

module.exports = User;

CRUD Operations with Mongoose

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

Read (GET)
<!-- Get all users -->
app.get('/users', async (req, res) => {
  try {
    const users = await User.find();
    res.json(users);
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

<!-- Get single user by ID -->
app.get('/users/:id', async (req, res) => {
  try {
    const user = await User.findById(req.params.id);
    if (!user) return res.status(404).json({ error: 'User not found' });
    res.json(user);
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

Update (PUT)
app.put('/users/:id', async (req, res) => {
  try {
    const user = await User.findByIdAndUpdate(
      req.params.id,
      req.body,
      { new: true, runValidators: true }
    );
    if (!user) return res.status(404).json({ error: 'User not found' });
    res.json(user);
  } catch (err) {
    res.status(400).json({ error: err.message });
  }
});

Delete (DELETE)
app.delete('/users/:id', async (req, res) => {
  try {
    const user = await User.findByIdAndDelete(req.params.id);
    if (!user) return res.status(404).json({ error: 'User not found' });
    res.status(204).send();
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

Two Minute Drill

  • MongoDB is a NoSQL database that stores data as JSON-like documents.
  • Mongoose is an ODM that provides schema validation and modeling for MongoDB.
  • Define schemas to structure your data and models to interact with the database.
  • Mongoose provides methods like `find()`, `findById()`, `save()`, `findByIdAndUpdate()` for CRUD.
  • Always use `try/catch` with async/await for error handling.
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