Node.js

Node.js is a JavaScript runtime built on the V8 engine that runs JavaScript outside the browser. It pioneered the use of a single-threaded, non-blocking, event-loop architecture for I/O-bound server workloads and is the backbone of much of the modern web's tooling and API tier.

Core characteristics

• Event loop. A single thread handles concurrency via libuv's event loop and a thread pool for blocking syscalls.
• npm. The largest package ecosystem in any language, with hundreds of thousands of registered modules.
• Module systems. CommonJS (legacy) and ECMAScript Modules (modern standard).
• Built-in async APIs. File system, network, HTTP, child processes, streams.
• Long-Term Support. Even-numbered major versions are LTS; odd-numbered are current.

Common frameworks and tools

• Web: Express, Fastify, Koa, NestJS, Hono
• Testing: Jest, Vitest, node:test, Mocha
• Process managers: pm2, systemd, Docker