Module 1: Building a Basic RESTful API

1. Introduction to RESTful APIs

REST (Representational State Transfer) is an architectural style for designing networked applications. It leverages the existing web infrastructure and simplifies the communication between client and server.

Key Principles of REST:

Client-Server: Separation of concerns, allowing independent development.
Stateless: Each request from client to server must contain all necessary information.
Cacheable: Responses can be cached to improve performance.
Uniform Interface: Consistent resource identification and interaction (e.g., using HTTP methods).
Layered System: Allows for intermediaries (proxies, gateways) without affecting client-server interaction.
Code on Demand (Optional): Servers can extend client functionality by transferring executable code.

2. Setting Up Our Development Environment

For this module, we'll use Node.js with Express.js to build our API. We'll also utilize Postman for testing our endpoints.

Prerequisites:

Node.js (LTS version recommended)
Express.js (a web application framework for Node.js)
Postman (for API testing)

Step-by-Step Setup:

1. Initialize a New Node.js Project

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

This creates a new directory and initializes a Node.js project with default `package.json` settings.

2. Install Express.js

npm install express

This installs Express.js, our web framework.

3. Create `app.js` (or `index.js`)

This will be our main server file.

const express = require('express');
const app = express();
const PORT = 3000;

app.get('/', (req, res) => {
    res.send('Hello from our API!');
});

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

This basic Express server listens on port 3000 and responds with "Hello from our API!" to the root endpoint.

4. Run the Server

node app.js

You should see "Server is running on http://localhost:3000" in your terminal.

Open http://localhost:3000 in your browser to see the message.

3. Designing Our First API Endpoint

Let's create an endpoint to retrieve a list of "products". We'll follow RESTful conventions.

RESTful Conventions:

Resources: Plural nouns (e.g., `/products`) represent collections.
HTTP Methods:
- GET: Retrieve data.
- POST: Create new data.
- PUT: Update existing data.
- DELETE: Remove data.
Status Codes: Use standard HTTP status codes (e.g., 200 OK, 404 Not Found).

Creating a `GET /products` Endpoint:

Live Coding Area

Add the following code to your `app.js` file to create a `GET /products` endpoint. Observe the output in Postman.


app.get('/products', (req, res) => {
    const products = [
        { id: 1, name: 'Laptop', price: 999.99, category: 'Electronics' },
        { id: 2, name: 'Smartphone', price: 699.50, category: 'Electronics' },
        { id: 3, name: 'Headphones', price: 149.00, category: 'Accessories' },
    ];
    res.json(products);
});

Live Output (Console):

4. Testing Our API with Postman

Postman is an essential tool for API development and testing. Let's use it to verify our `GET /products` endpoint.

Steps to Test in Postman:

Open Postman.
Click on "New" and select "Request".
Name your request (e.g., "GET Products") and save it to a collection.
Set the request type to GET.
Enter the URL: http://localhost:3000/products.
Click "Send".
Observe the response in the "Response" tab.

5. Next Steps & Challenges

Now that we've built our first endpoint, let's think about what's next.

Challenges:

Challenge 1: Create a `GET /products/:id` endpoint to retrieve a single product by its ID. Test it with Postman.
Challenge 2: Implement a `POST /products` endpoint to add a new product. Ensure it accepts JSON data and adds it to the `products` array.

Remember to update your `app.js` file for these challenges and test thoroughly with Postman.