Bun

Installation and Setup

Bun is installed once per machine. On macOS and Linux, Bun’s documentation recommends the official install script:

$ curl -fsSL https://bun.com/install | bash

On Windows, run this in PowerShell:

PS> powershell -c "irm bun.sh/install.ps1|iex"

Next, confirm the installed version:

$ bun --version
1.4.4

Key Features

• Runs .ts, .tsx, and .jsx files directly by converting them to JavaScript before execution.
• Installs npm packages into node_modules and records exact versions in a bun.lock lockfile.
• Skips the lifecycle scripts of dependencies, such as postinstall, unless the project trusts the package.
• Runs Jest-compatible tests written with test() and expect() from the bun:test module.
• Bundles code for browsers, Bun, or Node.js with bun build.

Usage

Say a shop’s project needs Prettier to format its code. The add command with -d installs it and saves it under devDependencies:

$ bun add -d prettier
bun add v1.4.4 (38afee6c8)

installed [email protected] with binaries:
 - prettier

1 package installed [3.00ms]

The project’s cart.js module exports a cartTotal() function. A file named cart.test.js checks it with two tests:

import { expect, test } from "bun:test";
import { cartTotal } from "./cart.js";

test("adds up price times quantity", () => {
  const items = [
    { price: 5, quantity: 2 },
    { price: 12.5, quantity: 1 },
  ];
  expect(cartTotal(items)).toBe(22.5);
});

test("returns 0 for an empty cart", () => {
  expect(cartTotal([])).toBe(0);
});

The test command finds every test file in the project and runs it:

$ bun test
bun test v1.4.4 (38afee6c8)

 2 pass
 0 fail
 2 expect() calls
Ran 2 tests across 1 file. [3.00ms]

After cloning the project, a teammate installs every dependency at the versions in the lockfile:

$ bun install

To run a package’s command once without adding it to the project, use bun x or its alias bunx:

$ bunx cowsay "Hello, Bun!"

To bundle a module and its imports into a dist folder, pass an entry point to build:

$ bun build ./cart.js --outdir ./dist
Bundled 1 module in 3ms

  cart.js  140 bytes  (entry point)

For every command and option, see the Bun documentation.