Book Image

TypeScript Blueprints

By : Ivo Gabe de Wolff
Book Image

TypeScript Blueprints

By: Ivo Gabe de Wolff

Overview of this book

TypeScript is the future of JavaScript. Having been designed for the development of large applications, it is now being widely incorporated in cutting-edge projects such as Angular 2. Adopting TypeScript results in more robust software - software that is more scalable and performant. It's scale and performance that lies at the heart of every project that features in this book. The lessons learned throughout this book will arm you with everything you need to build some truly amazing projects. You'll build a complete single page app with Angular 2, create a neat mobile app using NativeScript, and even build a Pac Man game with TypeScript. As if fun wasn't enough, you'll also find out how to migrate your legacy codebase from JavaScript to TypeScript. This book isn't just for developers who want to learn - it's for developers who want to develop. So dive in and get started on these TypeScript projects.
Table of Contents (16 chapters)
TypeScript Blueprints
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface

Understanding the structural type system


TypeScript uses a structural type system. What that means can be easily demonstrated using the following example:

class Person { 
  name: string; 
} 
class City { 
  name: string; 
} 
const x: City = new Person(); 

In languages like C#, this would not compile. These languages use a nominal type system. Based on the name, a Person is not a City. TypeScript uses a structural type system. Based on the structure of Person and City, these types are equal, as they both have a name property. This fits well in the dynamic nature of JavaScript. It can, however, lead to some unexpected behavior, as the following would compile:

class Foo { 
   
} 
const f: Foo = 42; 

Since Foo does not have any properties, every value would be assignable to it. In cases were the structural behavior is not desired, you can add a brand, a property that adds type safety but does not exist at runtime:

class Foo { 
  __fooBrand...