Book Image

Mastering TypeScript 3 - Third Edition

By : Nathan Rozentals
Book Image

Mastering TypeScript 3 - Third Edition

By: Nathan Rozentals

Overview of this book

TypeScript is both a language and a set of tools to generate JavaScript. It was designed by Anders Hejlsberg at Microsoft to help developers write enterprise-scale JavaScript. Starting with an introduction to the TypeScript language, before moving on to basic concepts, each section builds on previous knowledge in an incremental and easy-to-understand way. Advanced and powerful language features are all covered, including asynchronous programming techniques, decorators, and generics. This book explores many modern JavaScript and TypeScript frameworks side by side in order for the reader to learn their respective strengths and weaknesses. It will also thoroughly explore unit and integration testing for each framework. Best-of-breed applications utilize well-known design patterns in order to be scalable, maintainable, and testable. This book explores some of these object-oriented techniques and patterns, and shows real-world implementations. By the end of the book, you will have built a comprehensive, end-to-end web application to show how TypeScript language features, design patterns, and industry best practices can be brought together in a real-world scenario.
Table of Contents (16 chapters)
Free Chapter
TypeScript Tools and Framework Options

Decorator injection

At the beginning of Chapter 4, Decorators, Generics, and Asynchronous Features, we discussed the use of decorators, and how they are invoked when a class is defined. Decorators are not invoked when a class is instantiated, so their usage is limited to interrogating and manipulating class definitions. Decorators, as we know, can be applied to classes, properties, functions, and parameters. Let's build a simple class decorator, and see what information it gives us about a class.

Remember that there are three things about a class that we are interested in during this exercise. Firstly, we need to find the definition of the class constructor. Once we know what the constructor looks like, we need to find the list of parameters that the constructor uses. Each of these parameters will then become getters that use our service locator to resolve dependencies. The...