Book Image

TypeScript 4 Design Patterns and Best Practices

By : Theofanis Despoudis
Book Image

TypeScript 4 Design Patterns and Best Practices

By: Theofanis Despoudis

Overview of this book

Design patterns are critical armor for every developer to build maintainable apps. TypeScript 4 Design Patterns and Best Practices is a one-stop guide to help you learn design patterns and practices to develop scalable TypeScript applications. It will also serve as handy documentation for future maintainers. This book takes a hands-on approach to help you get up and running with the implementation of TypeScript design patterns and associated methodologies for writing testable code. You'll start by exploring the practical aspects of TypeScript 4 and its new features. The book will then take you through the traditional gang of four (GOF) design patterns in their classic and alternative form and show you how to use them in real-world development projects. Once you've got to grips with traditional design patterns, you'll advance to learning about their functional programming and reactive programming counterparts and how to couple them to deliver better and more idiomatic TypeScript code. By the end of this TypeScript book, you'll be able to efficiently recognize when and how to use the right design patterns in any practical use case and gain the confidence to work on scalable and maintainable TypeScript projects of any size.

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Table of Contents (14 chapters)
Preface
Preface
Who this book is for
What this book covers
To get the most out of this book
Download the example code files
Download the color images
Conventions used
Get in touch
Share your thoughts
1
Section 1: Getting Started with TypeScript 4
Section 1: Getting Started with TypeScript 4
Free Chapter
2
Chapter 1: Getting Started with Typescript 4
Chapter 1: Getting Started with Typescript 4
Technical requirements
Introducing TypeScript 4
Understanding TypeScript and JavaScript's relationship
Installing and using the code examples
Using VSCode with TypeScript
Introducing Unified Modeling Language (UML)
Summary
Q & A
Further reading
3
Chapter 2: TypeScript Core Principles
Chapter 2: TypeScript Core Principles
Technical requirements
Working with advanced types
OOP with TypeScript
Developing in the browser
Developing in the server
Introducing design patterns in TypeScript
Summary
Q&A
Further reading
4
Section 2: Core Design Patterns and Concepts
Section 2: Core Design Patterns and Concepts
5
Chapter 3: Creational Design Patterns
Chapter 3: Creational Design Patterns
Technical requirements
Creational design patterns
Singleton pattern
Prototype pattern
Builder pattern
Factory method pattern
Abstract Factory pattern
Summary
Q&A
Further reading
6
Chapter 4: Structural Design Patterns
Chapter 4: Structural Design Patterns
Technical requirements
Understanding structural design patterns
Adapter pattern
Decorator pattern
Façade pattern
Composite pattern
Proxy pattern
Bridge pattern
Flyweight pattern
Summary
Q&A
Further reading
7
Chapter 5: Behavioral Design Patterns
Chapter 5: Behavioral Design Patterns
Technical requirements
Behavioral design patterns
The Strategy pattern?
Chain of Responsibility
The Command pattern
The Iterator pattern
The Mediator pattern
The Observer pattern
The Memento pattern
The State pattern
The Template method pattern
The Visitor pattern
Summary
Q&A
Further reading
8
Section 3: Advanced Concepts and Best Practices
Section 3: Advanced Concepts and Best Practices
9
Chapter 6: Functional Programming with TypeScript
Chapter 6: Functional Programming with TypeScript
Technical requirements
Learning key concepts in functional programming
Understanding functional lenses
Understanding transducers
Understanding monads
Summary
Q & A
Further reading
10
Chapter 7: Reactive Programming with TypeScript
Chapter 7: Reactive Programming with TypeScript
Technical requirements
Learning Reactive programming concepts
The asynchronous propagation of changes
Understanding Promises and Futures
Learning observables
Summary
Q & A
Further reading
11
Chapter 8: Developing Modern and Robust TypeScript Applications
Chapter 8: Developing Modern and Robust TypeScript Applications
Technical requirements
Combining patterns
Using utility types
Using domain-driven design
Applying the SOLID principles
Summary
Q&A
Further reading
12
Chapter 9: Anti-Patterns and Workarounds
Chapter 9: Anti-Patterns and Workarounds
Technical requirements
Class overuse
Not using runtime assertions
Permissive or incorrect types
Using idiomatic code from other languages
Type inference gotchas
Summary
Q & A
Further reading
Why subscribe?
13
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Permissive or incorrect types

Reasonably often, you will be asked to integrate a library that does not include TypeScript declarations or develop a new feature from scratch. Initially, you will be tempted to do integrate such libraries when defining objects and classes and try to make things work, avoiding spending more time on precisely defining the types they use. This could lead to cases where TypeScript will not type check your code correctly or apply the wrong checks.

Here, we explain the most obvious uses of permissive or incorrect types:

  • any: The any type is equivalent to opting out of type checking. This means the compiler will not check the type of the variable or parameter and it will pass it on as it is. Using any as a type is not recommended as you'll lose all security and features of the type system.
  • Function: Function is a generic container type that represents any function type. This is an example of a permissive type, as Function can be any kind...
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