11 Reasons Why Bun is the Ultimate Node.js Toolkit for JavaScript Developers

Hey friends! Today I want to tell you about an exciting new technology called Bun that has the potential to completely change the way we build JavaScript applications.

In the JavaScript world, we've gotten used to piecing together various tools like Webpack, Babel, ESLint, Jest, etc. While these tools are great, managing all of them together can be time consuming and complex. Bun aims to fix this by providing an all-in-one JavaScript runtime that replaces many of these tools with a faster, more integrated experience.

Let's dive in and see what makes Bun so special!

1.  A Blazing Fast JavaScript Runtime

At its core, Bun is a JavaScript runtime built in Zig and powered by JavaScriptCore. This means it can directly run JavaScript, TypeScript, and even JSX files without any transpiling or bundling step.

For example, you can run:

// index.tsx

function HelloWorld() {
  return <h1>Hello World!</h1>; 
}

console.log(<HelloWorld />);

with just:

bun index.tsx

No need for Babel or ts-node! Bun will transpile and run it natively.

Even better, Bun starts up way faster than Node.js. We're talking like 5-10x faster cold start times. This makes Bun perfect for things like serverless functions.

Let's benchmark it:

// index.js
console.log("Hello world");

// Bun
$ time bun index.js  

Hello world

real	0m0.007s

// Node
$ time node index.js

Hello world

real	0m0.037s

As you can see, Bun started and ran the file over 5x faster than Node! For other metrics like bundle size and memory usage, Bun is equally impressive.

2. Built-in TypeScript and JSX Support

As we saw above, Bun has first-class support for TypeScript and even JSX. You don't need to install anything extra or setup a complex Babel config.

This means we can do awesome things like:

// App.tsx

import { useState } from 'react';

export function App() {
  const [message, setMessage] = useState("Hello World");
  
  return (
    <div>{message}</div>
  )
}

And run it with:

bun App.tsx

Sweet!

Type definitions and autocomplete also work out of the box for Bun's APIs and built-in modules, making for an awesome developer experience.

3. Fully Compatible with Node.js

A common concern with new JavaScript runtimes like Deno is compatibility with the millions of existing npm packages and Node.js code.

Thankfully, Bun is designed as a drop-in replacement for Node.js. It supports:

• Node.js built-in modules like fs, path, http
• Node.js globals like __dirname, process, Buffer
• The Node.js module resolution algorithm
• The npm package ecosystem

This means you can take virtually any existing Node.js app and run it with Bun without any changes needed.

For example, we can create an Express app:

// server.js

const express = require('express');

const app = express();

app.get('/', (req, res) => {
  res.send('Hello World!');
});

app.listen(3000, () => {
  console.log('Server running on port 3000');
});

And run it directly with Bun:

bun server.js 

Easy as that!

The Bun team is working hard on expanding compatibility even further to support advanced use cases. But for most apps, you can switch over to Bun's faster execution with minimal effort.

4. Built-in Web APIs

Normally in Node.js, we have to install separate packages like node-fetch to access Web APIs like the Fetch API.

Bun has these APIs built-in, including:

• Fetch API
• WebSocket API
• ReadableStream
• Encoding APIs
• URL & URLSearchParams
• TextEncoder & TextDecoder

For example, we can make a GET request without any dependencies:

const resp = await fetch('https://api.example.com');
const json = await resp.json();

console.log(json);

Bun's native implementations of these APIs are faster and more robust than the npm packages we're used to.

5. Blazing Fast Package Manager

Bun comes with its own package manager that works just like npm. Except it's much, much faster at installing dependencies.

We can run:

bun add react

And it will download and install React faster than you can blink!

Behind the scenes, Bun optimizes installations using a global module cache and efficient system calls. The end result is install times up to 100x faster than npm.

Let's add React and benchmark it:

// Bun
$ time bun add react
real	0m0.194s

// NPM 
$ time npm install react 
real	0m14.825s

As you can see, Bun installed React nearly 100x faster than npm! This package manager alone can save you hours when installing dependencies on big projects.

6. Powerful Bundler Included

Bun also includes a bundler for transforming your code to run in the browser. It supports JavaScript, TypeScript, JSX, CSS, SVG, and more.

We can bundle a simple React app like:

// index.jsx

import React from 'react';
import { createRoot } from 'react-dom/client';

function App() {
  return <h1>Hello World</h1>;
}

const root = createRoot(document.getElementById('root'));
root.render(<App />);

With just:

bun bundle index.jsx --out=bundle.js

The Bun bundler is highly optimized and can generate bundles up to 100x faster than Webpack. It also has a plugin system compatible with esbuild.

7. Jest-Compatible Test Runner

Testing is a breeze with Bun's built-in test runner. It has a Jest-like API with support for things like snapshots, mocks, and coverage reports.

We can write tests like:

// index.test.js
import { add } from './index';

test('adds numbers', () => {
  expect(add(1, 2)).toBe(3);
});

And run them with:

bun test

The test runner is highly optimized and runs test suites up to 10x faster than Jest.

So in summary, the Bun test runner provides a super fast testing experience compatible with Jest.

8. Lightning Fast Script Running

Bun also functions as an insanely fast script runner.

We can define scripts in package.json:

{
  "scripts": {
    "start": "bun server.js" 
  }
}

And run them with:

bun run start

This runs 150ms faster than npm run! Those savings add up when running commands frequently.

Bun also has a watch mode that only restarts code that changed for an amazing hot reloading experience.

9. Simple APIs for Common Needs

Bun provides some awesome native APIs for things you commonly need as a developer:

Bun.file()

Load a file as a BunFile which has methods like .text(), .json(), etc.

const file = Bun.file('data.json');
const json = await file.json();

Bun.write()

Write files of any type like strings, buffers, or blobs.

await Bun.write('data.json', {hello: 'world'});

Bun.serve()

Spin up a blazing fast HTTP and WebSocket server.

Bun.serve({
  port: 3000,
  fetch(req) {
    // ...
  }
})

These native Bun APIs provide awesome performance for everyday tasks.

10. Blazing Fast SQLite Support

Bun has built-in support for SQLite that's up to 5x faster than Node.js packages like better-sqlite3.

We can do:

import { Database } from 'bun:sqlite'

const db = new Database('data.sqlite');

const result = db.query('SELECT * FROM table'); 

And execute queries insanely fast.

So in summary, Bun provides stellar performance and native bindings for SQLite.

11. Macros for Compile-Time Code Generation

One really unique feature Bun provides is macros - code that runs at compile-time to generate output code.

This allows us to do things like:

// config.ts
export const API_KEY = 'xxx';

// api.ts
import { API_KEY } with { type: 'macro'} from './config.ts';

export const headers = {
  Authorization: `Bearer ${API_KEY}`  
};

The API_KEY will be substituted at compile-time, allowing us to hide secrets from the runtime code.

Macros open up a lot of opportunities for metaprogramming in JavaScript.

Bun - The All-in-One JavaScript Toolkit

As you can see, Bun aims to provide a cohesive set of tools for JavaScript development, including:

• A faster runtime
• Integrated TS/JSX support
• Package manager
• Bundler
• Test runner
• Script runner
• APIs for common utilities
• Macros
• And more coming soon!

The focus is on performance and developer experience. By consolidating tools, Bun avoids the complex toolchain and integration difficulties we often struggle with.

The goal is for Bun to be your one-stop shop for building robust JavaScript applications with a fantastic developer experience.

While Bun is still new, it already delivers amazing performance for many use cases today. I highly recommend giving it a try on your next side project!

Is Bun Ready for Production?

Now you might be wondering - can I use Bun for production applications today?

The short answer is: not yet, but it's getting close.

Here are some things that still need work:

• Node.js compatibility - good for most things but edge cases still need polish
• Macro system - powerful but needs more stability
• Framework integrations - Next.js, Remix, and others need adapters
• Tooling - IDE support, plugins, debugging

So I'd say give it 6 months to a year for the Bun team to round things out and it will be an incredible option.

Of course, you can start taking advantage of the parts that are production-ready today like the package manager and bundler.

But as a complete end-to-end solution, Bun still has some maturing to do. The progress has been really rapid so far though.

The potential to unite all the tools we use as JavaScript developers into one fast, cohesive experience is incredibly exciting. I can't wait to see Bun continue to evolve and rebuild the JavaScript toolkit from scratch.

Let me know if you have any other questions! I'm happy to chat more about Bun and its capabilities.

Getting Started with Bun

Okay, I've convinced you that Bun is awesome. But how do you actually start using it?

Installing Bun

First, you'll need to install Bun. There are a few options:

Homebrew (macOS/Linux)

brew install bun

Install script

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

This will download the latest binary for your system.

By NPM

npm install -g bun

Build from source

If you want to build Bun yourself, you can clone the repository and use Zig to build the bun executable from source.

git clone https://github.com/oven-sh/bun
cd bun
zig build

Creating a Bun Project

Once Bun is installed, you can start a new project:

bun create my-project

This will scaffold a new project with an example entry point, Git repo, and Bun config.

To develop with hot reloading:

cd my-project
bun dev

And you're ready to start building!

Migrating an Existing Project

For existing Node.js projects, migrating to Bun is straightforward:

1. Install Bun
2. Replace node/npx commands with bun
3. Run your start script with bun run start
4. Test it out!

Usually no code changes are needed, since Bun strives for Node.js compatibility.

For the package manager, you can rename package-lock.json to pax.lock to switch to using Bun's package manager.

And that's it! Lean on Bun's great documentation if you run into any issues.

Closing Thoughts on Bun

Bun is an exciting take on rethinking how we build robust JavaScript applications. By providing an integrated toolkit focused on performance and developer experience, it has huge potential to improve how we write JS/TS code.

While still new, I'm optimistic about Bun's future. The 0.1 release already delivers amazing benefits today like:

• Blazing fast installation
• Rapid bundling
• Instant startup times
• Unified TypeScript support

As the ecosystem continues to mature, Bun has an opportunity to rebuild the JavaScript toolchain from scratch - only faster, leaner, and more integrated.

I'm thrilled to see where the Bun team takes this project next. Be sure to give Bun a try today and share your thoughts! Let me know what other questions you have.

For more details and a curated list of awesome resources related to Bun, you can visit the following link: GitHub - oven-sh/awesome-bun.