Mastering TypeScript 3 - Third Edition

Decorators

Decorators in TypeScript provide a way of programmatically tapping into the process of defining a class. Remember that a class definition describes the shape of a class. In other words, a class definition describes what properties a class has, and what methods it defines. It is only when a class is instantiated, that is, an instance of the class is created, that these properties and methods become available.

Decorators, however, allow us to inject code into the actual definition of a class. Decorators can be used on class definitions, class properties, class functions, and even method parameters. The concept of decorators exists in other programming languages, and are called attributes in C#, or annotations in Java.

In this section, ...