Why I Switched from Node.js to Bun for JavaScript and TypeScript Development

The Status Quo

I have used Node.js since version 8. It is stable, widely used, and runs practically everything. But over the years, the JavaScript toolchain has become a collection of separate tools:

• nvm to manage Node versions
• npm, yarn, or pnpm for package management (each with its own lockfile format)
• tsc, esbuild, or swc for TypeScript compilation
• jest, vitest, or mocha for testing
• webpack, vite, esbuild, or rollup for bundling

That is five different tools just to write and run JavaScript. Each one needs configuration, updates, and debugging.

Then I tried Bun. A single binary that replaces all of them.

What is Bun?

Bun is a JavaScript runtime, package manager, test runner, and bundler in one binary. It is written in Zig and built on JavaScriptCore (the engine Safari uses), not V8.

This matters because:

• Startup is faster. JavaScriptCore is optimized for quick cold starts.
• Bun runs .ts and .tsx files directly. No compilation step.
• It has a built-in test runner compatible with Jest's API. No jest.config.js needed.
• It has a native bundler that replaces webpack, esbuild, or rollup for most projects.
• It is npm-compatible. Reads package.json and node_modules like npm does.

What I Actually Use Day to Day

Running TypeScript Without a Build Step

This alone was worth the switch:

bun run index.ts

No tsconfig.json required. No tsc --watch in another terminal. No ts-node or tsx. Bun transpiles TypeScript on the fly, including import paths, decorators, and JSX.

For this blog's CSS pipeline, I just run:

bun run css:build

That kicks off tailwindcss with no extra configuration.

Package Management

Installing dependencies with bun install is faster than npm install. The lockfile (bun.lock) is smaller and faster to parse.

For this blog, I switched from:

npm install
# about 15 seconds of waiting

to:

bun install
# less than 2 seconds

On bigger projects (100+ dependencies), the gap widens.

The Built-in Test Runner

This might be my favorite feature. Bun ships a test runner that is Jest-compatible with no configuration:

// No imports needed - describe, it, expect are globals
describe('my function', () => {
  it('returns the correct value', () => {
    const result = myFunction();
    expect(result).toBe(42);
  });
});

bun test
# 1 pass, 0 fail in 12ms

No Jest installation. No jest.config.ts. No @types/jest. No ts-jest transform.

Replacing nodemon

Bun has a built-in --watch flag:

bun --watch index.ts

This replaces nodemon for most of my projects. When a file changes, Bun restarts quickly because the cold start is so fast.

Ecosystem Compatibility

Here is my experience:

• Express, Fastify, Koa - work fine
• Prisma - has native Bun support
• Tailwind CSS - works (this blog uses it)
• Next.js - support is improving but not production-ready for most use cases yet
• Node.js built-in APIs - Bun implements most of them (fs, path, http, crypto, etc.)

There are gaps. Some packages that use native Node.js addons (node-gyp, node:worker_threads in specific patterns) don't work. For most web development, tooling, and scripting, Bun works.

What I Still Use Node.js For

• Serverless deployments. Lambda and Cloud Functions are Node.js-first.
• Legacy projects. I don't migrate projects that already work.
• Specific native addon packages that depend on node-gyp compiled binaries.
• CI/CD systems. GitHub Actions runners have Node pre-installed, not Bun.

Should You Switch?

Yes, if:

• You write TypeScript and want zero configuration.
• You want faster npm install times.
• You want a single tool instead of five.
• You build scripts, CLIs, backend APIs, or static sites.

Maybe not, if:

• You depend on obscure Node.js native modules.
• You need exact process isolation of Node.js Workers.
• You deploy to serverless environments that only support Node.js.

Summary

Bun replaced four separate tools for me (npm, ts-node, jest, nodemon) with one binary. My development loop is faster. I have fewer configuration files. I spend less time waiting for tools and more time writing code.

I still keep Node.js installed for the things Bun cannot do yet. For my daily work - writing TypeScript, building this blog, running scripts, and testing - Bun is my default.