Introduction to NestJS
Overview of NestJS, its architecture, and its benefits. Comparison with other backend frameworks like Express.
NestJS: A Progressive Node.js Framework
Introduction to NestJS
NestJS is a framework for building efficient, scalable Node.js server-side applications. It uses progressive JavaScript, is 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 Reactive Programming (RP).
Under the hood, NestJS makes use of robust HTTP Server frameworks like Express (the default) and Fastify. Nest provides an abstraction layer above these common Node.js frameworks, exposing them to the developer. This gives you the ability to use the myriad third-party modules which are available for the underlying platform.
Overview of NestJS
NestJS provides an out-of-the-box application architecture that allows developers and teams to create highly testable, scalable, loosely coupled, and easily maintainable applications. The architecture is heavily influenced by Angular, making it familiar to developers coming from the frontend world.
Architecture of NestJS
NestJS organizes code into a set of modules, controllers, and providers. This structure promotes code reusability and maintainability.
- Modules: Modules are used to organize code into logical units. Every NestJS application has at least one module, the root module. Modules can import other modules, and export providers that are used in other modules.
- Controllers: Controllers are responsible for handling incoming requests and returning responses to the client. They define routes that map HTTP requests to specific handler functions.
- Providers: Providers are the fundamental concept of NestJS. Many of the basic Nest classes – services, repositories, factories, helpers, and so on – may be treated as providers. The main idea of a provider is that it can be injected as a dependency; this means objects can create various relationships with each other, and the function of wiring instances of objects together can, to a large extent, be delegated to the Nest runtime system.
The NestJS dependency injection system is a core feature that enables the creation of loosely coupled components. By injecting dependencies into constructors, you can easily manage and test your code.
Benefits of NestJS
- Structured Architecture: NestJS enforces a clear and well-defined structure, making it easier to organize and maintain large-scale applications.
- TypeScript Support: Built-in TypeScript support provides static typing, improved code completion, and enhanced refactoring capabilities.
- Dependency Injection: The dependency injection system makes it easy to manage dependencies and create loosely coupled components.
- Modularity: NestJS promotes modularity through its module system, making it easier to reuse code and scale applications.
- Testability: The structured architecture and dependency injection system make it easier to write unit and integration tests.
- Extensibility: NestJS is highly extensible, allowing you to integrate with a wide range of third-party libraries and tools.
- Uses Existing Frameworks: It is built upon existing popular frameworks like Express and Fastify
Comparison with other backend frameworks like Express
While Express is a minimal and flexible framework, NestJS provides a more structured and opinionated approach to building backend applications. Here's a comparison:
| Feature | Express | NestJS |
|---|---|---|
| Architecture | Unopinionated, requires developers to define the architecture | Opinionated, uses modules, controllers, and providers for a structured architecture |
| TypeScript Support | Requires manual configuration | Built-in and encouraged |
| Dependency Injection | Not built-in, requires third-party libraries | Built-in dependency injection system |
| Modularity | Requires developers to implement modularity | Built-in module system |
| Testability | Requires more effort to set up testing | Designed for testability with its architecture and dependency injection |
| Learning Curve | Lower initial learning curve | Steeper learning curve due to its more complex architecture |
| Scalability | Requires more effort to scale applications | Designed for scalability with its modular architecture |
In summary, Express is a good choice for smaller projects where flexibility is paramount. NestJS is better suited for larger, more complex projects where a structured architecture, maintainability, and scalability are important. NestJS leverages the power of Express (or Fastify) but provides a higher level of abstraction and structure.