Bun Runtime Cheat Sheet

bun install                 # install deps (reads package.json, writes bun.lockb)bun add zod                 # add a dependencybun run dev                 # run a package.json scriptbun index.ts                # run a TS/JS file directly, no build stepbun test                    # run the built-in test runnerbun build ./index.ts --outdir ./dist --target browserbun --hot server.ts         # hot-reload a running server

const server = Bun.serve({  port: 3000,  fetch(req) {    const url = new URL(req.url)    if (url.pathname === "/") return new Response("Hello Bun!")    if (url.pathname === "/json") {      return Response.json({ ok: true })    }    return new Response("Not Found", { status: 404 })  },  error(err) {    return new Response(`Error: ${err.message}`, { status: 500 })  },})console.log(`Listening on http://localhost:${server.port}`)

const file = Bun.file("data.json")const exists = await file.exists()const text = await file.text()const json = await file.json()await Bun.write("out.txt", "hello world")await Bun.write("copy.json", Bun.file("data.json")) // fast file copy// streamingconst stream = file.stream()

import { test, expect, describe, mock } from "bun:test"describe("add", () => {  test("adds two numbers", () => {    expect(1 + 2).toBe(3)  })  test("mocked fetch", () => {    const fetchMock = mock(() => Promise.resolve({ ok: true }))    expect(fetchMock).not.toHaveBeenCalled()  })})// run: bun test --coverage