What is NestJs? Why NestJs ?  Basic information about NestJs

• Nest. JS is a framework that helps build NodeJS server-side applications.
• The Nest framework uses TypeScript, allowing developers to build highly scalable and testable applications.
• It has its own rules and is not only for backend development.
• The framework is DDD-friendly, event-sourced, and offers microservice architecture
• NestJs uses it as a starting point to resolve the application structure of the relationship.
• The benefit of using NestJs is that you can define your types, validation rules, and documentation in dependency in the same block of code.

Three main components:

• Controllers: Controllers handle the request and return an appropriate response
• Providers: Providers are fundamental to NestJs. The provider can be injected as a dependency to create relationships between objects.
• Modules: Modules are intended to encapsulate a closely related set of capabilities. Each application has a root module.

Modules

A module is a class annotated with a @Modules() decorator. The @module() decorator provides metadata the Nest marks use to organize the application structure. Each application has at least one module

A module is a class annotated with a @Modules() decorator. The @module() decorator provides metadata the Nest marks use to organize the application structure.

Each application has at least one module

Create module:

nest g module users

@module({
imports:[ ],
 controllers:[ ],
providers:[ ]
})
export class UserModule{}

Controllers

The controller is responsible for handling the incoming request and returning responses to the client.

@controller(‘user’)
export class UserController{
	//add user
	@Post(‘/add’)
	addBook():string{
	return “Add book”
}	
}

Providers

Anything that can be injected as a dependency

Constructor (private userService:UserService) { }