Bun 1.0 – Testing a Turbo-Fast JS Runtime

Note: This article was originally published on April 1, 2023. Some information may be outdated.

Bun 1.0 is out. It's a new JavaScript runtime built in Zig, and it aims to be fast--very fast.

It’s not just a runtime. It also includes:

• A bundler
• A test runner
• A package manager
• A development server

All built in.

Bun tries to replace several tools at once: Node, Webpack, Jest, even npm.

Installing Bun

To install Bun:

curl https://bun.sh/install | bash

You get access to the bun command, which works like node, npm, and vite--all at once.

Creating a Bun project

You can start a new project like this:

bun init

Then run your server:

bun run index.ts

Bun supports TypeScript out of the box--no config, no transpile step.

Why it’s interesting

• Bun uses JavaScriptCore (from Safari), not V8
• Written in Zig, so it compiles to a single binary
• It's fast--cold starts and installs are much quicker than Node

What I tried

I migrated a simple server from Node to Bun:

// index.ts
export default {
  port: 3000,
  fetch(request: Request) {
    return new Response("Hello from Bun!");
  },
};

Then ran:

bun run index.ts

Worked instantly.

Install times for dependencies were about 10x faster than npm.

Gotchas

• Not all Node APIs are supported
• Still new--some ecosystem gaps
• No Windows support at the time of writing

Should you use it?

Bun is promising. It’s great for:

• Simple scripts
• Side projects
• Trying something fast and new

For large teams, the Node ecosystem is still more mature. But Bun is improving fast.

---

Originally published at letanure.dev