bun

Bun

Bun is a drop-in replacement for Node.js, written in Zig. It is fast. v1.1 brings Windows support.

When to Use

• All-in-One JavaScript/TypeScript Runtime: Ultra-fast alternative to Node.js for server-side apps, bundlers, and package managers.
• High-Performance HTTP Services: Building web APIs using Bun.serve() with native WebSocket and TLS support.
• Rapid Package Management: Executing bun install with 10x-30x speedups over legacy package managers.
• Built-in SQLite & Testing: Developing microservices with zero-dependency native SQLite (bun:sqlite) and bun:test.

Quick Start

// server.ts
const server = Bun.serve({
  port: 3000,
  fetch(req) {
    const url = new URL(req.url);
    if (url.pathname === "/api/health") {
      return Response.json({ status: "ok", runtime: "bun" });
    }
    return new Response("Hello from Bun!", { status: 200 });
  },
});

console.log(`Listening on http://localhost:${server.port}`);

Core Concepts

High-Throughput HTTP Server with Bun.serve()

Native HTTP/1.1 and HTTP/2 web server with WebSockets:

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

    // WebSocket upgrade
    if (url.pathname === "/chat") {
      if (server.upgrade(req)) return;
      return new Response("Upgrade failed", { status: 400 });
    }

    if (url.pathname === "/api/health") {
      return Response.json({ status: "healthy", timestamp: Date.now() });
    }

    return new Response("Not Found", { status: 404 });
  },
  websocket: {
    message(ws, message) {
      ws.send(`Echo: ${message}`);
    },
    open(ws) {
      console.log("WebSocket client connected");
    },
    close(ws) {
      console.log("WebSocket client disconnected");
    },
  },
});

console.log(`Bun server running at http://localhost:${server.port}`);

Native SQLite with bun:sqlite

High-speed zero-dependency embedded database:

import { Database } from "bun:sqlite";

const db = new Database("app.db", { create: true });

// Execute schema creation
db.run(`
  CREATE TABLE IF NOT EXISTS users (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    email TEXT UNIQUE NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
  )
`);

// Prepared statement
const insert = db.prepare("INSERT INTO users (email) VALUES ($email)");
insert.run({ $email: "[email protected]" });

const query = db.prepare("SELECT * FROM users WHERE email = $email");
const user = query.get({ $email: "[email protected]" });
console.log("Found user:", user);