P5.2: REST APIs

A REST API (Representational State Transfer Application Programming Interface) is an architectural style that allows different computer programs to communicate with each other over the web.

In this lesson, we will build a complete, standard REST API using Express that handles CRUD (Create, Read, Update, Delete) operations.

1. Core HTTP Methods

REST APIs use standard HTTP request methods to perform database operations:

| HTTP Method | API Operation | CRUD Meaning | Example Path | | :--- | :--- | :--- | :--- | | GET | Read Data | Retrieve resources | /api/books | | POST | Create Data | Add a new resource | /api/books | | PUT | Update Data | Modify an existing resource | /api/books/:id | | DELETE | Delete Data | Remove a resource | /api/books/:id |

2. Setting Up Express for JSON Requests

By default, Express does not parse JSON request bodies. We must add the built-in middleware express.json() to read data passed inside a POST or PUT request.

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

// Middleware to parse incoming JSON bodies
app.use(express.json());

3. Implementing CRUD Routes

Let's build an API server that manages an in-memory list of coding tasks:

const express = require('express');
const app = express();
app.use(express.json());

let tasks = [
  { id: 1, title: 'Learn JSX' },
  { id: 2, title: 'Learn Node.js' }
];

// 1. GET: Read all tasks
app.get('/api/tasks', (req, res) => {
  res.json(tasks);
});

// 2. POST: Create a new task
app.post('/api/tasks', (req, res) => {
  const newTask = {
    id: tasks.length + 1,
    title: req.body.title
  };
  tasks.push(newTask);
  res.status(201).json(newTask); // Status 201: Created
});

// 3. DELETE: Delete a task
app.delete('/api/tasks/:id', (req, res) => {
  const taskId = parseInt(req.params.id);
  tasks = tasks.filter(t => t.id !== taskId);
  res.json({ message: `Task #${taskId} deleted successfully.` });
});

app.listen(5000);

4. Key HTTP Status Codes

Always return the correct HTTP status code so the client (frontend) knows the result of their API request:

• 200 OK: The request succeeded.
• 201 Created: A new resource was created successfully (used in POST requests).
• 400 Bad Request: Client-side validation error (e.g. missing fields).
• 404 Not Found: The requested path or ID does not exist.
• 500 Internal Server Error: An unexpected server crash or database failure.