Explain the purpose and usage of decorators in TypeScript.

In TypeScript, decorators are a language feature that allows you to modify the behavior of classes, methods, properties, or parameters at design time. They provide a way to add metadata or modify the structure of the target elements without modifying their original definition. Decorators are extensively used in frameworks like Angular and NestJS to enhance the functionality of classes and their members. The purpose of decorators is to enable developers to implement cross-cutting concerns, such as logging, validation, authentication, and caching, in a modular and reusable manner. They help in separating these concerns from the core business logic, leading to cleaner and more maintainable code. Decorators are applied using the `@` symbol followed by the decorator name, which is essentially a function or a class declaration. They can be used on classes, class methods, class properties, or method parameters, depending on the intended usage. When a....