A progressive Node.js framework called Nest.js helps developers create dependable, scalable, and effective server-side apps. It uses TypeScript to provide decorators, strong typing, and other contemporary language features, all of which contribute to a robust development experience. Because Nest.js adheres to an Angular-inspired architectural design, it is incredibly modular and scalable.
You must have npm and Node.js installed in order to use Nest.js. You can use the Nest CLI to start a new Nest.js project:
By doing this, you may create a new Nest.js project and begin developing your application.
In Nest.js, controllers are in charge of receiving requests and responding with the proper data. They act as the points of entry for the API endpoints in your application.
With the Nest CLI, a new controller can be created:
This will create a new ‘cats.controller.ts’ file in the ‘src’ directory.
In this example, we've defined a ‘CatsController’ with a single route ‘GET /cats’ that returns a string.
An essential idea in Nest.js, providers are used to manage dependencies and organize code. These could be factories, services, repositories, or any other kind of object your application requires.
Creating a Service Provider
With the Nest CLI, you can create a new service provider:
This will create a new ‘cats.service.ts’ file in the ‘src’ directory.
In this example, we've defined a ‘CatsService’ with a ‘findAll’ method that returns an array of cats.
Modules in Nest.js are used to organize the application into cohesive blocks of functionality. They encapsulate related controllers, providers, and other code into reusable units.
You can generate a new module using the Nest CLI:
This will create a new ‘cats.module.ts’ file in the ‘src’ directory.
In this example, we've defined a ‘CatsModule’ that imports the ‘CatsController’ and ‘CatsService’ and declares them as part of the module.
Middleware in Nest.js are functions that have access to the request and response objects. They can modify the request or response, terminate the request-response cycle, or call the next middleware in the stack.
You can create custom middleware by defining a class with the @Injectable() decorator and implementing the NestMiddleware interface.
In this example, we've created a ‘LoggerMiddleware’ that logs a message for every incoming request.
Exception filters in Nest.js are used to handle exceptions that occur during the execution of a request. They allow you to customize the error response sent back to the client.
You can create custom exception filters by defining a class with the ‘@Catch()’ decorator.
In this example, we've created an ‘HttpExceptionFilter’ that catches ‘HttpExceptions’ and sends back a JSON response with the exception message.
Pipes in Nest.js are used to transform input data before it reaches the route handler or to validate the input data.
You can create custom pipes by defining a class with the ‘@Injectable()’ decorator and implementing the PipeTransform interface.
In this example, we've created a ‘ValidationPipe’ that can be used to transform or validate input data.
Guards in Nest.js are used to control access to routes based on certain conditions. They can be used for authentication, authorization, or any other type of access control.
You can create custom guards by defining a class with the ‘@Injectable()’ decorator and implementing the CanActivate interface.
In this example, we've created an ‘AuthGuard’ that allows access to a route if the user is authenticated.
Interceptors in Nest.js are used to intercept incoming requests and outgoing responses. They allow you to modify the request or response before it reaches the route handler or the client.
You can create custom interceptors by defining a class with the ‘@Injectable()’ decorator and implementing the NestInterceptor interface.
In this example, we've created a ’LoggingInterceptor’ that logs a message for every incoming request.
Nest.js allows you to create custom decorators to add metadata or functionality to your classes, methods, or properties.
You can create custom decorators by defining a function that returns a decorator function.
In this example, we've created a 'User' decorator that extracts the user object from the request.
Nest.js is a powerful framework for building efficient, scalable, and maintainable server-side applications with Node.js. It provides a robust architecture based on modules, controllers, and services, leveraging TypeScript's strong typing for enhanced productivity and maintainability.
With its built-in support for dependency injection, middleware, and decorators, Nest.js simplifies the development process, making it ideal for building complex applications while maintaining code organization and clarity. Overall, Nest.js offers developers a modern and feature-rich solution for building server-side applications in Node.js.
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