Introduction

Introduction

Welcome to Bun for Beginners, a project-based approach to learning web development with Bun. This book teaches you how to build real applications with Bun from scratch using few additional libraries. You will create a dynamic web application with a local database in minutes, then deploy it to a simple server with minimal configuration.

Bun is a single, dependency-free binary that bundles everything you need to build JavaScript and TypeScript applications.

This book is designed for developers who are new to Bun, including those coming from Node.js as well as those building their first full-stack applications.

In this book, you will build a series of progressively more complex applications, starting with a simple server and ending with a full, production-ready web app with authentication, data storage, and deployment.

The Four Pillars

Bun is built on four pillars. Together, they replace the stack of separate tools most JavaScript projects rely on.

Runtime — bun run. Bun runs your JavaScript and TypeScript directly. No compile step, no build tool, no configuration. You point Bun at a .ts file and it runs. This replaces Node.js.

Package manager — bun install. Bun installs packages from the npm registry, but faster. The commands are familiar — bun install, bun add, bun remove — and the lockfile keeps your dependencies consistent across machines. This replaces npm, Yarn, and pnpm.

Test runner — bun test. Bun has a built-in test runner with a Jest-compatible API. You write a .test.ts file, run bun test, and tests execute. No separate framework to install or configure. This replaces Jest, Mocha, and Vitest.

Bundler — bun build. When you are ready to ship, Bun bundles your code into optimized output for the browser or server. One command, no configuration file required. This replaces Webpack, esbuild, and Vite.

These four pillars are the spine of this book. Every chapter exercises at least one of them, and by the end you will have used all four to build and deploy a real application.

Simple mental model

Traditional stack:

Node + npm + Jest + Webpack + Express + dotenv + more...

Bun stack:

Bun

The Bun Way

Bun changes how you build applications by reducing the number of tools you need and simplifying the development workflow. In this book, we will follow a consistent approach:

• Start with working code quickly, not configuration
• Prefer built-in features before adding dependencies
• Build small, complete pieces instead of abstract systems
• Keep the stack minimal and understandable
• Add complexity only when it is needed

This approach keeps development fast, reduces errors, and makes it easier to understand how your application works.

Beyond the four pillars, Bun includes several built-in features that further reduce the need for dependencies:

• HTTP server — replaces basic use of Express
• SQLite driver — no external database client needed for local apps
• Environment variable handling — replaces dotenv-style packages
• File and system utilities — fewer helper libraries
• Image manipulations like resizing, rotation, and format conversion

We will use most of these as we build through the book.

Why Learn Bun?

Because Bun is no longer just "the fastest JavaScript runtime." It is becoming a practical default for small teams and solo builders who want fewer moving parts. It collapses a messy toolchain into one product, and in most cases, does it faster than the tools it replaces. Bun is quickly becoming a serious alternative to the traditional Node.js toolchain, especially for small and focused projects.

Prerequisites

You do not need previous experience with Node, Bun, or even web development to complete this book. The goal is to help you quickly gain confidence building real applications with Bun.

That said, familiarity with basic JavaScript or TypeScript, along with HTML and CSS, will help you understand the concepts more quickly.

When appropriate, we will reference alternative tools and approaches so you can see how Bun reduces complexity and, in many cases, improves performance.

Book Structure

This book follows a project-based approach. Each chapter builds on the previous one, introducing new concepts through real applications rather than isolated examples.

You will start with a simple HTTP server using Bun and gradually expand it into more complete applications. Along the way, you will add routing, data storage, validation, authentication, and deployment.

The goal is to build confidence by working through small, complete pieces that grow into a production-ready application.

By the end of the book, you will have built and deployed a full web application using a consistent and repeatable approach.

Book Layout

This book includes shell commands and code examples throughout.

Shell commands: bun --version

bun run index.ts

TypeScript code:

const server = Bun.serve({
	port: 3000,
	routes: {
		"/": () => new Response("Run from Bun!"),
	},
});

New or changed lines in code examples will be marked with a comment:

const server = Bun.serve({
  ...
  console.log(`Listening on ${server.url}`);
});

Advice on Getting Stuck

You will get stuck. Do not let it stop your progress. Often, stepping away for a bit or even sleeping on a problem can make it much easier to solve.

If you get stuck on a specific example or project in this book:

• Check the GitHub repository and issues to see if it has already been reported or discussed
• Watch for small typos, even if you think everything is correct
• Try copying the code directly from the source and running it again

Getting stuck is part of the process. The key is to keep moving forward.

About the Author

Brian has been building software since the late 1990s and has worked across multiple generations of web technologies. He co-founded Eyespike Corporation in 2002 and has been involved in building and maintaining production systems, including large-scale web applications.

Throughout his career, he has focused on practical, real-world development and staying current with evolving tools and approaches. His interest in Bun comes from its ability to simplify modern JavaScript development while improving performance.

This book is part of his effort to give back by helping developers build real applications with modern tools in a clear and practical way.

Conclusion

In the next chapter, we will set up your development environment and prepare your system for building more complete applications with Bun.