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Happy Holidays! We’re excited to release Bun v0.4.0 with support for more Node.js APIs, increased stability, lots of bug fixes, and a new command: bunx.

Introducing bunx

This version introduces bunx, Bun’s equivalent of npx with 100x faster startup times. It runs executables from local or remote npm packages.

As with npx, it will check for a locally installed package first, then fall back to auto-installing from npm into a shared global cache. With Bun’s fast startup times, it’s roughly 100x faster than npx for locally installed packages.

The --bun flag

By default, Bun respects the #!/usr/bin/env node shebang at the top of scripts or executables that are run with bun run or bunx .

// foo.js
#! /usr/bin/env node

console.log(process.argv[0]);

$ bun run foo.js
/path/to/node/19.2.0/bin/node

To override this behavior, pass the --bun flag. This temporarily aliases node to bun for the duration of the execution.

$ bun --bun run foo.js
/path/to/.bun/bin/bun

In the future, we might make this behaviour the default once Bun’s Node.js compatibility is more complete.

Node.js compatibility

Support for Node.js APIs continues to be a top priority for Bun. As of Bun v0.4.0, you can now use the following APIs:

• crypto.timingSafeEqual()
• crypto.scryptSync()
• process.abort()
• process.argv0 and process.execPath
• node:util/types

Setup and teardown in bun:test

Bun has a built-in test runner that you can run using the command: bun wiptest. You can now define Jest-style lifecycle hooks for the setup and teardown of tests.

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

let tests;
beforeAll(async () => {
  const response = await fetch("https://example.com/path/to/resource");
  tests = await response.json();
});

test("that integration tests are defined", () => {
  expect(tests).toHaveLength(100);
});

Bun.deepEquals() strict

You can now pass a strict argument to Bun.deepEquals(), which will have the same behaviour as expect().toStrictEqual().

const a = { entries: [1, 2] };
const b = { entries: [1, 2], extra: undefined };

Bun.deepEquals(a, b); // => true
Bun.deepEquals(a, b, true); // => false

bun pm

In case you missed it, Bun has a command that allows you see information about your packages and lockfile in a project: bun pm.

bun pm ls

In Bun v0.4.0 there is new sub-command, bun pm ls, which will list all the packages and versions in your project, similar to npm ls.

Notable Fixes

• Fixed various issues when installing dependencies – #1643, #1647, #1649
• Fixed various bugs with node:stream – #1606, #1613
• Fixed process.stdin not working in a tty – #1611, #1626
• Fixed Bun.write() on older Linux kernels that don’t support io_uring – e7a14f8
• Fixed an issue when importing a binary file – 5bbaa7
• Fixed a transpiler bug where const {resolve} = require would not work – 3c2029
• Implemented support for passing arguments to setTimeout(), setInterval(), and setImmediate() – a98e0ad
• Removed a work-around for RegExp backtracking support, since WebKit implemented it – #1625
• Fixed a transpiler bug (in Bun) breaking @babel/parser when loading in Bun’s runtime

PR log

• fix __require collision from linking by @dylan-conway in #1585
• chore: add eslintcache by @Simon-He95 in #1586
• Add filename completions on bun command to Zsh by @colinhacks in #1593
• Exclude additional TSdeclaration file extensions from completions by @colinhacks in #1596
• fix path string by @YUxiangLuo in #1597
• override process.stdin.on() correctly by @alexlamsl in #1603
• fix(stream): Fix Readable.pipe() by @ThatOneBro in #1606
• make process.stdin work under TTY by @alexlamsl in #1611
• add bun pm ls for printing lockfiles by @dylan-con

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