Building RESTful APIs with Express.js

1. Introduction

RESTful APIs (Representational State Transfer) are a set of principles for building web services. They use standard HTTP methods like GET, POST, PUT, DELETE, etc., for CRUD operations. Express.js is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications.

2. Setup

mkdir my-api
cd my-api
npm init -y
npm install express

2.2 Create a Basic Server

Next, set up a basic Express server:

const express = require('express');
const app = express();
const PORT = process.env.PORT || 3000;

app.listen(PORT, () => {
    console.log(`Server is running on http://localhost:${PORT}`);
});

3. Creating Routes

Routes define how your API responds to client requests. Here's how to create basic routes:

app.get('/api/items', (req, res) => {
    res.json({ message: 'Get all items' });
});

app.post('/api/items', (req, res) => {
    res.json({ message: 'Create an item' });
});

4. Middleware

Middleware functions are functions that have access to the request and response objects. They can modify the request and response objects, end the request-response cycle, and call the next middleware in the stack.

app.use(express.json()); // Parses incoming JSON requests
app.use((req, res, next) => {
    console.log(`${req.method} ${req.url}`);
    next();
});

5. Error Handling

Proper error handling is crucial. You can define a middleware for handling errors:

app.use((err, req, res, next) => {
    console.error(err.stack);
    res.status(500).send('Something broke!');
});

6. Testing APIs

Testing your API is essential. You can use tools like Postman or automated testing libraries like Mocha and Chai.

const chai = require('chai');
const chaiHttp = require('chai-http');
const server = require('../server'); // Path to your server file

chai.use(chaiHttp);
chai.request(server)
    .get('/api/items')
    .end((err, res) => {
        chai.expect(res).to.have.status(200);
    });

7. Best Practices

• Use versioning in your API (e.g. /api/v1/items).
• Implement authentication and authorization.
• Document your API using Swagger or Postman.
• Use environment variables for configuration.
• Handle errors gracefully and return meaningful messages.

8. FAQ

const cors = require('cors');
app.use(cors());