Refactoring TypeScript Code

The book "Refactoring TypeScript Code" is a practical guide for developers who want to write better quality, maintainable, and scalable code in TypeScript. Whether you are working on a small pet project or a large enterprise system, the ability to perform refactoring in a timely and correct manner is a key skill for a professional developer.

What is this book about?

The book covers all aspects of refactoring in the context of TypeScript: from basic techniques (extract method, replace conditional with polymorphism) to advanced techniques specific to static typing. You will learn how to:

• Identify code smells in TypeScript projects;
• Apply classic refactorings considering the type system;
• Use advanced TypeScript features (generics, conditional types, mapped types) to simplify code;
• Properly design interfaces and abstractions;
• Perform refactoring without the risk of breaking existing functionality;
• Integrate refactoring into the development process and CI/CD.

Who is this book for?

This book will be useful for:

• Junior and Middle developers who want to improve the quality of their code and learn to work with someone else's code;
• Senior developers and team leads looking for a systematic approach to improving project architecture;
• Anyone transitioning from JavaScript to TypeScript who wants to leverage the full power of typing;
• Developers preparing for interviews — knowledge of refactoring principles is often tested in technical interviews.

What will you learn?

After reading the book, you will be able to:

• Confidently identify problem areas in code and choose the right strategies to fix them;
• Write code that is easy to read, test, and extend;
• Effectively work with inheritance, composition, and generic programming;
• Apply SOLID and GRASP principles in practice;
• Conduct code reviews with a focus on architectural improvements;
• Avoid common mistakes when refactoring TypeScript projects.

All examples in the book are written in TypeScript, and each technique is accompanied by a detailed explanation, diagrams, and a step-by-step application algorithm. The book contains both theoretical foundations and many real-world cases from practice.

This is not just a translation of classic works on refactoring — it is a deep adaptation to the modern TypeScript ecosystem, including work with frameworks (React, Node.js) and typical scenarios (API, state management, asynchrony).

Start writing code that you won't be ashamed to show your colleagues and that is easy to maintain for years!