What is the reflect-metadata library in TypeScript?

The reflect-metadata library is used to enable metadata reflection in TypeScript. It allows decorators to access metadata about classes, properties, methods, or parameters.

import "reflect-metadata";

// Define a decorator to add metadata to a class
function MyDecorator(target: Function) {
  // Attach metadata to the class constructor
  Reflect.defineMetadata("customMetadata", { description: "This is a custom decorator" }, target);
}

@MyDecorator
class Example {
  constructor(public name: string) {}
}

// Retrieve metadata from the Example class
const metadata = Reflect.getMetadata("customMetadata", Example);
console.log(metadata);
// { description: 'This is a custom decorator' }