Integrating Express.js with MongoDB

1. Introduction

This lesson covers the integration of Express.js, a minimal and flexible Node.js web application framework, with MongoDB, a NoSQL database. By the end of this lesson, you’ll learn how to set up a basic Express application, connect it to a MongoDB database, and perform CRUD (Create, Read, Update, Delete) operations.

2. Prerequisites

Before proceeding, ensure you have the following installed:

• Node.js (v12 or later)
• NPM (Node Package Manager)
• MongoDB (installed locally or use MongoDB Atlas)
• Basic understanding of JavaScript and Node.js

3. Setup

Follow these steps to set up your Express.js application and connect it to MongoDB:

1. Create a new directory for your project:

   mkdir express-mongo-demo

2. Navigate into the directory:

   cd express-mongo-demo

3. Initialize a new Node.js project:

   npm init -y

4. Install Express and Mongoose:

   npm install express mongoose

5. Create an entry point file:

   touch index.js

4. Basic CRUD Operations

Now that your setup is complete, let’s implement basic CRUD operations. Use the following code in index.js:

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

const app = express();
app.use(express.json()); // Middleware to parse JSON

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

// Define a simple Mongoose schema
const ItemSchema = new mongoose.Schema({
    name: String,
});

const Item = mongoose.model('Item', ItemSchema);

// Create an item
app.post('/items', async (req, res) => {
    const item = new Item(req.body);
    await item.save();
    res.status(201).send(item);
});

// Read items
app.get('/items', async (req, res) => {
    const items = await Item.find();
    res.send(items);
});

// Update an item
app.put('/items/:id', async (req, res) => {
    const item = await Item.findByIdAndUpdate(req.params.id, req.body, { new: true });
    res.send(item);
});

// Delete an item
app.delete('/items/:id', async (req, res) => {
    await Item.findByIdAndDelete(req.params.id);
    res.status(204).send();
});

// Start the server
app.listen(3000, () => {
    console.log('Server running on http://localhost:3000');
});
            

This code sets up an Express server that connects to a MongoDB database and provides endpoints for creating, reading, updating, and deleting items.

5. Best Practices

• Always validate user input to prevent injection attacks.
• Use environment variables to store sensitive information (e.g., database URIs).
• Implement error handling middleware for centralized error management.
• Structure your code for scalability (consider MVC architecture).

6. FAQ