Node.js Built-in Modules

Use Node's built-in modules: read and write files with fs, build paths safely with path, inspect the OS, and serve HTTP with the built-in http module.

fspathoshttpBuilt-in

Duration

⏱ About 1.5 hours

Level

📊 Beginner+

Prerequisite

🎯 node-01

OUTCOME

Read/write files and serve a basic HTTP response — no npm needed

What you'll learn

1Read and write files with fs.promises
2Build cross-platform paths with path.join
3Inspect environment with os and process.env
4Start a basic HTTP server with the http module

1. fs — File System

javascript

import fs from "node:fs/promises";

await fs.writeFile("notes.txt", "Hello, Node!");
const text = await fs.readFile("notes.txt", "utf8");
console.log(text);

const files = await fs.readdir(".");
console.log(files);

💡

Prefer the promise API (node:fs/promises) over callbacks — cleaner with async/await.

2. path — Cross-platform Paths

javascript

import path from "node:path";

const p = path.join("data", "users", "alice.json");
// Windows: data\users\alice.json
// macOS/Linux: data/users/alice.json

path.extname("photo.jpg");  // ".jpg"
path.basename(p);            // "alice.json"

3. os and process

javascript

import os from "node:os";

os.platform();   // 'darwin' | 'linux' | 'win32'
os.cpus().length;
os.totalmem();

process.env.PORT;         // environment variable
process.argv;             // command-line args
process.exit(1);          // exit with error code

4. http — Built-in Server

javascript

import http from "node:http";

const server = http.createServer((req, res) => {
  res.statusCode = 200;
  res.setHeader("Content-Type", "text/plain");
  res.end(`Hello from Node! ${req.method} ${req.url}\n`);
});

server.listen(3000, () => console.log("http://localhost:3000"));

Powerful but verbose. Real projects use Express or another framework (next lesson).

Example code / lecture materials

All lecture materials and example code are openly available on GitHub.

View on GitHub ↗