#1 -What is NestJS ? | NestJS Tutorial
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What is NestJS?
NestJS is a progressive Node.js framework for building efficient, reliable, and scalable server-side applications. It's built with and fully supports TypeScript (yet still enables developers to code in pure JavaScript) and combines elements of Object-Oriented Programming (OOP), Functional Programming (FP), and Functional Reactive Programming (FRP).
Why Do We Need NestJS?
1. **Structure and Scalability**: NestJS provides an out-of-the-box application architecture which allows developers and teams to create highly testable, scalable, loosely coupled, and easily maintainable applications.
2. **TypeScript Support**: Full TypeScript support (with integrated type checking and higher reliability) is a major advantage, especially for large-scale projects.
3. **Modularity**: NestJS modules help organize the code in a modular way, making it more reusable and understandable.
4. **Dependency Injection**: NestJS uses a powerful Dependency Injection (DI) system, which improves maintainability and testability by decoupling components.
5. **Extensible**: It can easily integrate with other libraries, such as TypeORM, Mongoose, and others, allowing for easy database integration.
6. **Microservices Support**: NestJS supports a variety of microservices communication strategies, including MQTT, gRPC, and RabbitMQ.
7. **Community and Ecosystem**: The growing community around NestJS offers a wide range of ready-to-use modules, plugins, and comprehensive documentation, making it easier for developers to adopt and use.
How Does NestJS Work?
1. **Architecture**: NestJS follows a layered architecture similar to Angular. It divides the application into controllers, providers (services), and modules.
2. **Controllers**: Handle incoming requests and return responses. They are tied to a specific route and use services to perform business logic.
3. **Providers/Services**: Encapsulate business logic and can be injected into controllers and other services, promoting code reuse and separation of concerns.
4. **Modules**: Organize the application structure. Each module is a cohesive block of code with a tightly related set of capabilities (like a feature in your application).
5. **Middleware**: NestJS allows the use of middleware, which are functions that have access to the request and response objects, and the next middleware function in the application’s request-response cycle.
6. **Interceptors and Pipes**: They provide aspect-oriented programming features, allowing you to run your code before or after method execution (interceptors) and to transform and validate input data (pipes).
7. **Dependency Injection (DI)**: NestJS heavily relies on DI, which is used to increase modularity and flexibility of applications by decoupling components.
8. **Microservices**: NestJS provides an abstraction layer over different microservice patterns and transports, allowing easy and transparent creation of microservice architectures.
In summary, NestJS is a versatile, modular framework that promotes high-quality code and architecture, making it an excellent choice for both small projects and large enterprise-level applications.