Node.js Basics

Your First Node.js Script

In VS 2026, create server.js and run it with F5 or node server.js:

console.log("Node.js version:", process.version);
console.log("Platform:", process.platform);
console.log("Working dir:", process.cwd());

// Read command-line arguments
const args = process.argv.slice(2);
console.log("Arguments:", args);

File System (fs/promises)

import { readFile, writeFile, readdir } from "fs/promises";

async function main() {
  // Write a file
  await writeFile("hello.txt", "Hello from Node.js!\n");

  // Read it back
  const content = await readFile("hello.txt", "utf8");
  console.log(content);

  // List directory
  const files = await readdir(".");
  console.log(files);
}

main();

HTTP Server

Build a basic web server without any frameworks:

import { createServer } from "http";

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

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

Environment Variables

Read config from .env files using Node.js 22+ built-in dotenv support:

// .env file:
// PORT=3000
// API_KEY=secret123

import { loadEnvFile } from "process";
loadEnvFile(); // loads .env

const PORT = process.env.PORT ?? 3000;
const KEY  = process.env.API_KEY;
console.log(`Starting on port ${PORT}`);

Path & OS Modules

import path from "path";
import os from "os";
import { fileURLToPath } from "url";

const __dirname = path.dirname(fileURLToPath(import.meta.url));

console.log(path.join(__dirname, "data", "file.json"));
console.log(path.extname("app.test.js")); // ".js"
console.log(os.homedir());
console.log(os.cpus().length, "CPUs");