Most developers know Node.js as the standard runtime for using JavaScript outside of the browser. But recently, a new runtime—Bun—has been announced that claims to be 3x faster than Node.js, and even its successor Deno, in common use cases.

Jared Sumner, a former developer at Stripe, released Bun in July of 2022. Bun is a runtime developed using the relatively obscure Zig programming language that embraces web standards but aims for compatibility with Node.js, so developers can easily migrate existing code.

All of that is great and interesting, but what separates Bun from other runtimes, and does it really stand a chance against the big players?

What Makes It Different

One of the most distinguishing features of Bun is that it uses JavaScriptCore as its engine, unlike Node.js and Deno, which use V8. The result is a blazing fast runtime that offers several quality-of-life features for JS developers.

Bun also has first-class integration of TypeScript and JSX, while also providing many of the features of transpilers like Babel, and bundlers like Webpack, Rollup, and Vite.

Diving In

Let's get started with Bun by installing it. According to the official documentation, this requires only the following command:

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

After it's finished just follow the confirmation prompt with directions for adding Bun to your PATH.

Writing and running our first Bun script is pretty simple. We can run Bun.serve by using the command bun run script.js and then going to localhost:3000 to see the response to our request.

It's very common to need to read and write to files when building applications, and Bun makes this dead simple. In this example we'll create a file containing the URL each time we submit a request:

let count = 1;
Bun.serve({
    fetch(request) {
        Bun.write(`test-${count}.txt`, request.url);
        count++;
        return new Response('Created Test File');
    },
});
console.log('Listening on Port 3000');

Features Baked-In

Support for SQLite by default is another nice touch. Querying your database is a breeze and you don't have to install external packages.

Using .env files with Bun is also quite easy. You can simply access them with process.env like in Node, but without needing to install dotenv.

The Node.js Killer?

As of right now Bun is still in its infancy, with many APIs and features not yet implemented. I don't see it replacing Node.js anytime soon, but with that said, its speed and features are enough to grab my attention. I'll certainly be keeping an eye on it to see how it progresses.

Are you excited about Bun, or are you content with Node.js? Let me know in the comments.

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