Bun Has a Free API — The All-in-One JavaScript Runtime That Replaces Node

#bunjs #javascript #webdev #tutorial

Bun is a JavaScript runtime, bundler, test runner, and package manager — all in one binary. It's 3-10x faster than Node.js for most operations and drops in as a replacement.

Why Bun?

3x faster npm install (no node_modules sprawl with bun install)
Built-in bundler — replaces webpack/esbuild
Built-in test runner — replaces Jest/Vitest
Native TypeScript — no tsc or ts-node needed
Node.js compatible — runs most npm packages

Quick Start

# Install
curl -fsSL https://bun.sh/install | bash

# Create project
bun init

# Run TypeScript directly
bun run index.ts

# Install packages (3x faster than npm)
bun install express

HTTP Server (Built-in)

// server.ts
Bun.serve({
  port: 3000,
  fetch(req) {
    const url = new URL(req.url);

    if (url.pathname === '/api/hello') {
      return Response.json({ message: 'Hello from Bun!' });
    }

    if (url.pathname === '/api/users' && req.method === 'POST') {
      const body = await req.json();
      return Response.json({ created: body }, { status: 201 });
    }

    return new Response('Not Found', { status: 404 });
  },
});

console.log('Server running on http://localhost:3000');

File I/O (Fastest in Any Runtime)

// Write
await Bun.write('output.txt', 'Hello, Bun!');
await Bun.write('data.json', JSON.stringify({ key: 'value' }));

// Read
const text = await Bun.file('output.txt').text();
const json = await Bun.file('data.json').json();
const bytes = await Bun.file('image.png').arrayBuffer();

// Stream large files
const file = Bun.file('large.csv');
const stream = file.stream();

SQLite (Built-in!)

import { Database } from 'bun:sqlite';

const db = new Database('myapp.sqlite');

db.run(`CREATE TABLE IF NOT EXISTS users (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  name TEXT NOT NULL,
  email TEXT UNIQUE
)`);

// Prepared statements
const insert = db.prepare('INSERT INTO users (name, email) VALUES (?, ?)');
insert.run('Alice', 'alice@example.com');

// Query
const users = db.prepare('SELECT * FROM users').all();
console.log(users);

// Transaction
const insertMany = db.transaction((users) => {
  for (const user of users) {
    insert.run(user.name, user.email);
  }
});

Built-in Test Runner

// math.test.ts
import { expect, test, describe } from 'bun:test';

describe('math', () => {
  test('addition', () => {
    expect(2 + 2).toBe(4);
  });

  test('async', async () => {
    const result = await fetch('http://localhost:3000/api/hello');
    expect(result.status).toBe(200);
  });
});

bun test

Bundler

await Bun.build({
  entrypoints: ['./src/index.ts'],
  outdir: './dist',
  minify: true,
  splitting: true,
  target: 'browser',
});

Package Manager

bun install                 # Install all deps
bun add express             # Add package
bun remove lodash           # Remove package
bun add -d @types/node      # Dev dependency
bun update                  # Update all

Building fast data pipelines? Check out my Apify actors for web scraping at Bun speed, or email spinov001@gmail.com for custom solutions.

Bun or Node.js — which runtime are you using in 2026? Share below!

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