Design Patterns in JavaScript (Node.js)

The book "Design Patterns in JavaScript (Node.js)" is a practical guide for developers who want to master classic and modern design patterns in the context of server-side JavaScript. The author systematically covers more than 23 patterns from the GoF catalog and additional idioms adapted for the asynchronous nature of Node.js and the Event Loop.

What is this book about?

The book covers in detail:

• Creational Patterns: Singleton, Factory Method, Abstract Factory, Builder, Prototype — with examples for managing database connections and configurations.
• Structural Patterns: Adapter, Decorator, Facade, Proxy, Composite — for organizing modular architecture and middleware.
• Behavioral Patterns: Observer, Strategy, Command, Chain of Responsibility, State — for handling events, streams, and asynchronous call chains.
• Node.js Specific: Middleware Pattern, Error-First Callbacks, Promise-based Patterns, Streams Pattern.

Who is this book for?

• JavaScript developers with at least 1 year of experience transitioning to backend development with Node.js.
• Developers who want to write maintainable, testable, and scalable code.
• Tech leads and architects designing microservices and REST APIs.

What will the reader learn?

• How to avoid anti-patterns (Callback Hell, God Object, Spaghetti Code).
• How to combine patterns for real-world tasks: authorization, caching, task queues.
• How to apply DI (Dependency Injection) and Inversion of Control in Express/Koa.
• How to test code built on patterns using Jest and Mocha.

Each pattern is accompanied by complete code in modern JavaScript (ES2020+), class diagrams, and explanations of "why it works this way." At the end of each chapter, there are exercises to reinforce the material.

The book is practice-oriented: you will not just learn the theory but will be able to immediately apply what you have learned in your own Node.js projects.