Node.js Overview

JavaScript on the Server

Node.js is a JavaScript runtime built on Chrome's V8 engine. Released in 2009, it allows you to run JavaScript outside the browser - on servers, command lines, and even embedded devices.

The key insight: Node.js IS the server. Unlike PHP which runs inside Apache, a Node.js application creates its own HTTP server and runs continuously.

The Fundamental Difference

Understanding how Node.js differs from PHP is crucial:

Comparison of PHP and Node.js execution models: PHP model shows Browser to Apache to PHP where each request starts a process, handles the request, then the process ends. Node.js model shows Browser connecting directly to Node.js which runs continuously, listening on port 3000 and handling many requests without restarting.

This has important implications:

State persists: Variables stay in memory between requests (unlike PHP where everything resets)
No cold start: The server is already running, no process spawn overhead
Single-threaded event loop: One thread handles many concurrent connections
You control the server: You write the code that listens for HTTP requests

Tutorial Modules

01. Hello World

Node.js fundamentals: running scripts, ES6+ features, and the event loop.

Running JavaScript with Node
The event loop concept
Callbacks and async patterns

Start Module

02. HTTP Server

Build a web server from scratch using Node's built-in http module.

http.createServer()
Request and response objects
Manual routing and file serving

Start Module

03. Express Basics

The Express framework: routing, middleware, and static files.

npm and package management
Express routing
Serving static files

Start Module

04. Form Handling

Process GET and POST data, parse request bodies.

req.query and req.body
Body parsing middleware
Comparison with PHP

Start Module

05. REST API

Build a simple RESTful API with CRUD operations.

REST principles
HTTP verbs and resources
JSON responses

Start Module

Quick Comparison: PHP vs Node.js

Aspect	PHP	Node.js
Execution	Per-request (process starts/stops)	Persistent (runs continuously)
Server	Runs inside Apache/nginx	IS the server (creates own HTTP listener)
Concurrency	Multiple processes/threads	Single-threaded event loop
GET parameters	`$_GET['name']`	`req.query.name`
POST body	`$_POST['email']`	`req.body.email`
Sessions	Built-in (`$_SESSION`)	Requires middleware (express-session)
Package manager	Composer	npm
Best for	Traditional websites, CMSs	APIs, real-time apps, microservices

Running the Demos

Local Development: Run demos with Node.js directly:

cd node-tutorial/01-hello-world
node hello.js

For Express demos, install dependencies first: npm install

Node.js Quick Reference

Core Modules

const http = require('http');     // HTTP server
const fs = require('fs');         // File system
const path = require('path');     // Path utilities
const url = require('url');       // URL parsing

Basic HTTP Server

const http = require('http');

const server = http.createServer((req, res) => {
    res.writeHead(200, { 'Content-Type': 'text/plain' });
    res.end('Hello World!');
});

server.listen(3000, () => {
    console.log('Server running on http://localhost:3000');
});

Express Basics

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

app.use(express.json());                    // Parse JSON bodies
app.use(express.urlencoded({ extended: true })); // Parse form data
app.use(express.static('public'));          // Serve static files

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

app.get('/api/users/:id', (req, res) => {
    res.json({ id: req.params.id, name: 'User' });
});

app.listen(3000);