SESSION 057 — Express API

CONCEPTS.UNLOCKED

🚂

Express.js

Web framework for Node.js. Handles routing, request parsing, middleware, and error handling. The most popular Node.js framework — powers millions of APIs.

📐

REST Architecture

Resources (nouns) + HTTP methods (verbs). GET /images = list images. POST /images = create. PUT /images/:id = update. DELETE /images/:id = remove. Consistent and predictable.

🛤

Routes

app.get('/api/images', handler), app.post(...), app.put(...), app.delete(...). Each route maps a URL + method combination to a handler function.

🔑

Route Parameters

/api/images/:id — the colon marks a dynamic segment. req.params.id extracts the value. /api/images/42 → req.params.id === '42'.

⛓

Middleware

Functions that process requests before your handler. Logging, CORS, JSON parsing, authentication — all middleware. Runs in order, calls next() to continue.

📦

Request / Response

req: params, body, query, headers. res: json(), status(), send(), end(). The request carries data IN, the response sends data OUT.

HANDS-ON.TASKS

Set Up Express

▶

npm install express cors

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

app.use(cors());
app.use(express.json());

// In-memory storage (temporary)
let images = [];
let nextId = 1;

Build the CRUD API

▶

// GET all images
app.get('/api/images', (req, res) => {
  res.json(images);
});

// GET single image
app.get('/api/images/:id', (req, res) => {
  const image = images.find(
    img => img.id === parseInt(req.params.id)
  );
  if (!image) return res.status(404)
    .json({ error: 'Image not found' });
  res.json(image);
});

// POST new image
app.post('/api/images', (req, res) => {
  const { name, width, height, format } = req.body;
  if (!name) return res.status(400)
    .json({ error: 'Name is required' });

  const image = {
    id: nextId++, name, width, height, format,
    createdAt: new Date()
  };
  images.push(image);
  res.status(201).json(image);
});

// PUT update image
app.put('/api/images/:id', (req, res) => {
  const image = images.find(
    img => img.id === parseInt(req.params.id)
  );
  if (!image) return res.status(404)
    .json({ error: 'Image not found' });

  Object.assign(image, req.body,
    { updatedAt: new Date() });
  res.json(image);
});

// DELETE image
app.delete('/api/images/:id', (req, res) => {
  const index = images.findIndex(
    img => img.id === parseInt(req.params.id)
  );
  if (index === -1) return res.status(404)
    .json({ error: 'Image not found' });

  images.splice(index, 1);
  res.status(204).end();
});

Add Middleware

▶

// Logging middleware
app.use((req, res, next) => {
  console.log(
    `${new Date().toISOString()} ` +
    `${req.method} ${req.url}`
  );
  next();
});

// Error handling middleware
app.use((err, req, res, next) => {
  console.error(err.stack);
  res.status(500)
    .json({ error: 'Internal server error' });
});

app.listen(3001, () =>
  console.log('API running on http://localhost:3001')
);

Test with curl

▶

curl http://localhost:3001/api/images

curl -X POST http://localhost:3001/api/images \
  -H "Content-Type: application/json" \
  -d '{"name":"test.jpg","width":1920,"height":1080}'

curl is a command-line HTTP client. It sends requests to your API and prints the response. Postman is the visual alternative. Both are essential backend development tools.

Implement Error Responses

▶

Implement proper error responses for all edge cases: missing fields (400), not found (404), server errors (500). Every response has a clear error message.

Close the Ticket

▶

git switch -c feature/PIXELCRAFT-044-express-api
git add server/ package.json
git commit -m "Build REST API with Express CRUD + middleware (PIXELCRAFT-044)"
git push origin feature/PIXELCRAFT-044-express-api
# PR → Review → Merge → Close ticket ✅

REF.MATERIAL

ARTICLE

Express.js — Getting Started

Express.js Team

Official Express guide: hello world, routing, static files, middleware, and error handling. The definitive starting point.

EXPRESSOFFICIALESSENTIAL

VIDEO

Express.js in 100 Seconds — Fireship

Fireship

Ultra-fast Express overview: routing, middleware, request/response, and why it dominates Node.js backends.

EXPRESSQUICK

ARTICLE

Express Routing Guide

Express.js Team

Complete routing reference: route methods, parameters, route handlers, express.Router, and route chaining.

ROUTINGOFFICIAL

ARTICLE

REST — Wikipedia

Wikipedia

REST architecture: resources, HTTP methods, statelessness, uniform interface. The architectural style that defines modern APIs.

RESTARCHITECTURECS

VIDEO

Build a REST API with Node.js — Traversy Media

Traversy Media

Full Express API tutorial: setup, CRUD routes, middleware, error handling, and testing with Postman.

EXPRESSTUTORIAL

EXPRESS API