Built-in APIs Basics

8 examples to get you started with Node built-in APIs - 6 basic and 2 intermediate.

Prerequisites

• Node.js 24.18.0 - built-ins ship with the runtime.
• Prefer import from 'node:…' in ESM projects.

Basic Examples

1. node: Prefix Import

Import built-ins explicitly and avoid shadowing.

import { readFile } from 'node:fs/promises';
import { createServer } from 'node:http';
import path from 'node:path';

• node: prefix is optional but recommended in application code.
• Built-ins are not in package.json dependencies.
• Typings come from @types/node in devDependencies.

2. fs/promises readFile

Async file read without util.promisify.

import { readFile } from 'node:fs/promises';
 
const pkg = JSON.parse(await readFile('package.json', 'utf8'));
console.log(pkg.name);

• Always specify encoding for text or get Buffer.
• Use createReadStream for large files.
• Handle ENOENT with try/catch for optional config files.

Related: fs and fs/promises - streams and flags

3. path.join and fileURLToPath

Portable paths in ESM without __dirname.

import path from 'node:path';
import { fileURLToPath } from 'node:url';
 
const __filename = fileURLToPath(import.meta.url);
const configPath = path.join(path.dirname(__filename), 'config.json');

• path.join normalizes separators for the platform.
• Never concatenate paths with / manually in library code.
• Use path.posix.join for object storage keys on all platforms.

Related: path and url - URL vs path

4. node:http Server

Minimal HTTP without Express.

import { createServer } from 'node:http';
 
createServer((req, res) => {
  res.writeHead(200, { 'content-type': 'text/plain' });
  res.end('ok');
}).listen(3000);

• Fine for health checks and internal probes.
• Production APIs usually add Express 5 or Fastify 5 for routing.
• Set timeouts on server (server.requestTimeout) in Node 24.

5. crypto.randomUUID

Identifiers without uuid package.

import { randomUUID } from 'node:crypto';
 
const id = randomUUID();
console.log(id);

• Cryptographically strong UUID v4.
• Also randomBytes for tokens - encode as base64url.
• See crypto for hashing and HMAC.

6. timers/promises sleep

Promise-based delay without npm.

import { setTimeout } from 'node:timers/promises';
 
await setTimeout(100);
console.log('after delay');

• Accepts AbortSignal for cancellable delays.
• setInterval still callback-based for periodic work.
• See Timers and Scheduler.

Intermediate Examples

7. fetch (built-in)

HTTP client without axios for simple outbound calls.

const res = await fetch('https://nodejs.org/dist/index.json');
if (!res.ok) throw new Error(`HTTP ${res.status}`);
const data = await res.json();

• Global fetch in Node 24 - same API as browsers.
• Configure agents/timeouts via undici options when needed.
• For advanced retry policies see got/axios.

8. util.parseEnv and styleText (Node 24)

Modern utilities for env and CLI output.

import { parseEnv } from 'node:util';
import { styleText } from 'node:util';
 
const env = parseEnv('PORT=3000\nNODE_ENV=production');
console.log(styleText('green', 'boot'), env.PORT);

• parseEnv parses dotenv-style strings in memory.
• Prefer Zod for production env validation.
• See util and diagnostics.

Related: Zod at Boundaries - validate env

External Related Links

• Node.js API Documentation - Complete reference for core modules and APIs.
• Node.js Learn Guides - Official learning path.
• Node.js Official Website - Homepage, downloads, releases, and news.
• Get Programming with Node.js - Introductory programming with Node.js.
• Node.js the Right Way - Server-side JavaScript fundamentals.

Stack versions: This page was written for Node.js 24.18.0 (Active LTS), npm 10+, TypeScript 5.6+, Express 5, Fastify 5, and NestJS 11.