Bun Runtime

Use Bun as the default JavaScript/TypeScript runtime and package manager.

Command Mappings

Instead of	Use
node file.ts	bun file.ts
ts-node file.ts	bun file.ts
npm install	bun install
npm run script	bun run script
jest / vitest	bun test
webpack / esbuild	bun build

Bun automatically loads .env files - don't use dotenv.

Bun-Specific APIs

Prefer these over Node.js equivalents:

API	Purpose	Don't use
Bun.serve()	HTTP server with WebSocket, HTTPS, routes	express
bun:sqlite	SQLite database	better-sqlite3
Bun.redis	Redis client	ioredis
Bun.sql	Postgres client	pg, postgres.js
Bun.file()	File operations	node:fs readFile/writeFile
Bun.$\cmd``	Shell commands	execa
WebSocket	WebSocket client (built-in)	ws

Testing

Use bun:test for tests:

import { test, expect } from "bun:test";

test("description", () => {
  expect(1).toBe(1);
});

Run with bun test.

Frontend Development

Use HTML imports with Bun.serve() instead of Vite. Supports React, CSS, Tailwind.

Server:

import index from "./index.html"

Bun.serve({
  routes: {
    "/": index,
    "/api/users/:id": {
      GET: (req) => Response.json({ id: req.params.id }),
    },
  },
  development: { hmr: true, console: true }
})

HTML file:

<html>
  <body>
    <script type="module" src="./app.tsx"></script>
  </body>
</html>

Bun's bundler transpiles .tsx, .jsx, .js automatically. CSS is bundled via <link> tags.

Run with bun --hot ./server.ts for HMR.

Documentation

For detailed API docs, see node_modules/bun-types/docs/**.md.