Design patterns are the foundation of many world-class software applications, from commercial solutions to open-source projects. This guide equips you with the skills to architect robust, scalable, and maintainable TypeScript 5 applications. Whether you're looking to master modern TypeScript or apply proven software architecture patterns effectively, this book is your go-to resource. Written by Theofanis Despoudis, a recognized TypeScript expert, this second edition is fully updated with TypeScript 5’s latest features, including improved type inference, union enums, and decorators. These updates will help you write cleaner, more maintainable code that adapts to future changes. You’ll dive into classic Gang of Four design patterns through both traditional and modern real-world implementations, gaining hands-on experience with practical applications. You’ll also gain a clear understanding of the power of functional and reactive programming patterns specifically designed for idiomatic TypeScript development. By the end of this book, you’ll be able to identify and apply the right design pattern for any scenario and craft well-structured, maintainable, and testable code.