01 — Node.js Runtime & Modules

Core Concepts

• Node.js — JavaScript runtime built on V8, event-driven, non-blocking I/O
• Event loop — single-threaded loop that processes async callbacks
• CommonJS (CJS) — require() / module.exports (traditional Node)
• ES Modules (ESM) — import / export (modern, recommended)
• Built-in modules — fs, path, http, crypto, os, url, events, stream
• process — global object for current Node process info
• global / globalThis — Node's global scope (like window in browsers)

CJS vs ESM