Bun 1.0. What’s behind the hype of Bun?

Bun is a new Javascript runtime that was introduced in 2021 by its author, Jarred Sumner, following his frustrations with the speed of Node.js when developing a Next.js project. July 2022, the first beta of Bun was released. It immediately created a hype in JavaScript community. And the best news, Bun has its first official release, Bun 1.0 in September 2023.

Let’s look at some of its key value of Bun to see if it’s worth the hype.

What is Bun?

Bun is a best described as an all-in-one toolkit for JavaScript/TypeScript development. It’s written in Zig and powered by Apple’s JavascriptCore engine, which behind some Webkit browsers such as Safari, rather than infamous Chromium V8 engine, used by Node and Deno.

Bun is designed from the ground-up and aims to the key points below.

• Speed. Bun is designed for speed, it’s the best value of it. Bun is claimed that it outrun Node by 4 times.
• All-in-one toolkit. Bun helps you to escape from the hell of choosing tool chain for your next project by offer built-in package manager, bundler, monorepo tools, Typescript runtime and transpiler, test runner, JavaScript shell script, http and websocket server, even SQLite driver… all in one place, without any other installation.
• TypeScript & JSX support. Bun support Typescript and JSX out of the box. While Node’s developer still struggles between CommonJS and ES Module, bun support both, but encourage us to move forward with ESM.
• Node.js compatibility. Bun is not exactly a drop-in replacement for Node.js, but it tried to support many native Node modules, such as node:process, node:path, node:fs, etc…

Let’s see how fast Bun is compared to Node.js

Firstly, let’s look at speed of both in the same framework.

Framework	Runtime	Average	Query	Body
express	bun	12,894.025	15,608.43	10,179.62
express	node	5,111.12	5,102	5,120.24

Bun achieve 3x speed versus Node.js. But it’s not the fastest result.

In this benchmark, Bun uses express HTTP API, which use node:http API behind. Bun has different implementation of Web server, which use uWebsockets.js the fastest Node.js framework as its core. So, we will compare the fastest Node.js framework vs the fastest Bun framework.

Framework	Runtime	Average	Query	Body
elysia	bun	49,341.32	65,213.36	33,469.28
fastify	node	14,271.595	17,890.78	10,652.41

Bun still out speed Node.js 3.5x.

Benchmark source code can be found here

Lastly, we will compare Bun and Node in a full-featured framework, NestJS. Yet this is not fair comparison, since NestJS use express as its core, which is much slower than uWebsockets in Bun. Unfortunately, Bun doesn’t have any framework on the same level as NestJS, so we will use NestJS for both Bun and Node.js.

Runtime	1%	2.5%	50%	97.5%	Average	Stdev	Min
Bun	21,103	21,103	30,863	31,695	28,657.6	3,957.17	21,090
Node.js	7,607	7,607	12,959	13,583	12,079.6	2,252.75	7,605

Bun out speed Node.js 2.3x in this benchmark.

Benchmark source code can be found here

Now we will explore Bun by creating a simple application to demonstrate its features.

Create a simple application with Elysia

Install Bun, ignore if you already installed

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

Create Elysia application.

bun create elysia your-app
cd your-app
bun dev # run app in development mode

Now you can access Elysia app via http://localhost:3000

Install database client

We choose Prisma as Database client

bun add -d prisma # -d flag indicates that this package is installed in devDependencies
bunx prisma init # bunx is similar to npx, but run in Bun environment

Add a User model to Prisma schema

generator client {
  provider = "prisma-client-js"
}

datasource db {
  provider = "postgresql"
  url      = env("DATABASE_URL")
}

model User {
  id        Int     @id @default(autoincrement())
  username  String  @unique
  password  String
}

Setup database connection in .env file

DATABASE_URL="postgresql://<user>:<password>@localhost:5432/your_db"

Run migration

bunx prisma migrate dev

Add Prisma to Elysia

// ./src/index.ts
import { Elysia, t } from 'elysia'
import { PrismaClient } from '@prisma/client'

const prisma = new PrismaClient()

const app = new Elysia()

app.get('/users', async () => {
  return prisma.user.findMany();
});

app.post('/users', async ({ body }) => {
  return prisma.user.create({
    data: {
      username: body.username,
      password: await Bun.password.hash(body.password) // Bun.hash is a built-in function to hash password, using Argon2
    }
  });
}, {
  // Elysia schema validation using Typebox
  body: t.Object({ 
    username: t.String(), 
    password: t.String({ 
        minLength: 8
    })
  })
});

app.get('/users/:username', async ({ params: { username } }) => {
  return prisma.user.findUnique({ where: { username } });
});

app.listen(3000);

Bonus: Add Elysia Swagger module

bun add @elysiajs/swagger

import { swagger } from '@elysiajs/swagger'

// add this line to ./src/index.ts, after `const app = new Elysia()`
app.use(swagger())

Now you can access Swagger UI via http://localhost:3000/swagger

Run application

bun dev

Now access http://localhost:3000/swagger to see your API documentation and test your API.

Create a simple application with NestJS

It’s not different from creating a NestJS application using Bun versus Node.js. Just follow NestJS getting started and run application with Bun:

bun --bun nest start

Notice that --bun flag is required for Bun to force NestJS CLI not invoking node command at run time.

You can find example of NestJS application with Bun here.

Final thoughts

As Bun 1.0 released, Bun is gaining interest from Web Development community. Its ecosystem is growing extremely fast. It still can’t compare to 13 years old Node.js but it promises to be a game-changer by its features and superior performance.

Different than Deno, with Bun, we almost don’t need to change the way things work, just a little bit of changes. Like npm install, is now bun install. The best way to describe this point is you can run a simple NestJS application with Bun without changing a single line of code.

All-in-one toolkit also an interesting point that makes developer experiences more enjoyable, since we have a lot of tools need to install in our source base, such as webpack, pnpm, esbuild, jest… Now only Bun’s needed.

But the real question is:

Is Bun ready for production?

Unfortunately, no. At least, not right now. But in next few months, it will be.

I experience some unsolved issues while developing a project with Bun. Still a lot of runtime issues, that throw SEGFAULT that cannot be caught, a lot of them reported in Github issues and are not resolved yet.

But, again, Bun is very promising thing for JavaScript development. It just a matter of time until Bun becomes more stable. Bun seems to be getting closer every step to take Node’s crown. I believe investing in Bun is worth to consider at the moment.