JavaScript Outside the Browser
What is Node.js?
Node.js runs JavaScript on the server — the same language as the browser, with full access to files, networks, and processes.
What you'll learn
- Know what Node is and what it isn't
- Recognize what kinds of apps you build with it
- See where Node fits next to the browser
Node.js is a JavaScript runtime built on Chrome’s V8 engine that runs outside the browser. Same language, same async model — but with access to the file system, the network, child processes, and everything else a server needs.
What You Build With Node
- Web servers — APIs, REST/GraphQL backends, the Next.js / Astro server runtime
- CLIs — tools like
eslint,prettier,vite,tsx,npx - Build tools — bundlers, transpilers, dev servers
- Background workers — queues, schedulers, scripts
- Desktop apps — VS Code, Discord, Figma (via Electron)
The Mental Model
| Browser JS | Node.js |
|---|---|
| Runs in a tab, sandboxed | Runs as a process, full system access |
DOM, window, fetch | fs, http, process, os |
| One environment per page | One process per script/server |
| Single thread + Web Workers | Single thread + Worker Threads, Child Processes, Cluster |
The language is identical. The available APIs differ.
What Node Is Not
- Not a framework — frameworks (Express, Fastify, NestJS) are built on Node.
- Not multi-threaded by default — there’s one JS thread per process (you can spawn more).
- Not new — Node is from 2009 and powers a sizeable chunk of the modern web.
Why Learn It
JavaScript developers who know Node can ship full-stack apps without
switching languages. The same fetch, Promise, Map, JSON you
know from the browser works the same in Node. The new parts are
mostly system access — files, sockets, processes.
Up Next
Get Node installed and verify it runs.
Installing Node →