Mastering TypeScript 3 - Third Edition

Using decorator metadata

In order to use this extra information within a decorator, we will need to use a third-party library named reflect-metadata. We will discuss how to use third-party libraries in detail in future chapters, but for the time being, this library can be included in our project by typing the following from the command line:

npm install reflect-metadata --save-dev

Once this has been installed, we will need to reference it in our TypeScript file by including the following line at the top of the file:

import 'reflect-metadata'; 

Before we attempt to compile any code that is using the reflect-metadata library, we will need to install the declaration file for this library, as follows:

npm install @types/reflect-metadata --save-dev ...