Network: Connected devices that can communicate

Internet: Global network of networks

World Wide Web (WWW): Information system on the Internet

HTTP: HyperText Transfer Protocol - communication protocol

import express from 'express';
const app = express();
const port = 3000;

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

// Basic route
app.get('/hello', (req, res) => {
  res.send('Hello World!');
});

// Start server
app.listen(port, () => {
  console.log(`Server listening on port ${port}`);
});

1. Query Parameters (req.query)

// URL: /search?name=John&age=25
app.get('/search', (req, res) => {
  const name = req.query.name;
  const age = req.query.age;
  res.json({ name, age });
});

2. URL Parameters (req.params)

// URL: /users/123
app.get('/users/:id', (req, res) => {
  const userId = req.params.id;
  res.json({ userId });
});

3. Request Body (req.body)

// POST request with JSON body
app.post('/users', (req, res) => {
  const { name, email } = req.body;
  res.json({ name, email });
});

let books = [
  { id: 1, title: 'The Hobbit', author: 'J.R.R. Tolkien', year: 1937 }
];

// CREATE - Add new book
app.post('/books', (req, res) => {
  const newBook = {
    id: books.length + 1,
    title: req.body.title,
    author: req.body.author,
    year: req.body.year
  };
  books.push(newBook);
  res.status(201).json(newBook);
});

// READ - Get all books
app.get('/books', (req, res) => {
  res.json(books);
});

// READ - Get single book
app.get('/books/:id', (req, res) => {
  const book = books.find(b => b.id === parseInt(req.params.id));
  if (!book) {
    return res.status(404).json({ error: 'Book not found' });
  }
  res.json(book);
});

// UPDATE - Update book
app.put('/books/:id', (req, res) => {
  const book = books.find(b => b.id === parseInt(req.params.id));
  if (!book) {
    return res.status(404).json({ error: 'Book not found' });
  }
  book.title = req.body.title;
  book.author = req.body.author;
  book.year = req.body.year;
  res.json(book);
});

// DELETE - Remove book
app.delete('/books/:id', (req, res) => {
  const index = books.findIndex(b => b.id === parseInt(req.params.id));
  if (index === -1) {
    return res.status(404).json({ error: 'Book not found' });
  }
  books.splice(index, 1);
  res.status(204).send();
});

Installation:

npm install sync-request-curl

import request from 'sync-request-curl';

// GET request
const res = request(
  'GET',
  'http://localhost:3000/books/1'
);
const bodyObj = JSON.parse(String(res.getBody()));
console.log(bodyObj);

// POST request
const postRes = request(
  'POST',
  'http://localhost:3000/books',
  {
    json: {
      title: 'New Book',
      author: 'Author Name',
      year: 2025
    }
  }
);

import request from 'sync-request-curl';

describe('Test GET /books/:id', () => {
  test('Returns book info successfully', () => {
    const res = request(
      'GET',
      'http://localhost:3000/books/1'
    );

    const bodyObj = JSON.parse(String(res.getBody()));

    expect(bodyObj).toBe(JSON.stringify({
      id: 1,
      title: 'The Hobbit',
      author: 'J.R.R. Tolkien',
      year: 1937
    }));
  });
});

describe('Test POST /books', () => {
  test('Creates new book successfully', () => {
    const res = request(
      'POST',
      'http://localhost:3000/books',
      {
        json: {
          title: 'New Book',
          author: 'Author',
          year: 2025
        }
      }
    );

    const bodyObj = JSON.parse(String(res.getBody()));

    expect(bodyObj).toBe(JSON.stringify({
      id: 2,
      title: 'New Book',
      author: 'Author',
      year: 2025
    }));
  });
});

npx jest requests.test.ts

// Success with custom status
app.post('/books', (req, res) => {
  // ... create book
  res.status(201).json(newBook);
});

// Error handling
app.get('/books/:id', (req, res) => {
  const book = books.find(b => b.id === parseInt(req.params.id));
  if (!book) {
    return res.status(404).json({ error: 'Book not found' });
  }
  res.status(200).json(book);
});

// Server error
app.get('/error', (req, res) => {
  res.status(500).json({ error: 'Internal server error' });
});

Swagger (now called OpenAPI) is a standard for describing RESTful APIs in a machine and human-readable format.

• Lists API endpoints
• Defines expected parameters
• Specifies possible response status codes
• Describes response body structure

import express from 'express';
const app = express();
const port = 3000;

const swaggerUi = require('swagger-ui-express');
const YAML = require('yamljs');

// Load Swagger YAML file
const swaggerDocument = YAML.load('swagger.yaml');

// Serve Swagger UI at /api-docs
app.use('/api-docs', swaggerUi.serve, swaggerUi.setup(swaggerDocument));

// Access at: http://localhost:3000/api-docs

What HTTPS encrypts:

• URL path (/users/login)
• Request headers
• Request body (POST, PUT, etc.)
• Query parameters

• Express provides simple routing and middleware for HTTP servers
• CRUD operations map to HTTP methods (GET, POST, PUT, DELETE)
• sync-request-curl allows testing servers programmatically
• Jest integration enables automated testing workflows
• HTTP status codes communicate request outcomes (2xx success, 4xx client error, 5xx server error)
• Swagger/OpenAPI creates machine-readable API documentation
• HTTPS encrypts all data, but POST body is safer than URL queries for sensitive data