Stop Using Express, Start Using NestJS

As the JavaScript ecosystem continues to evolve, the choice of frameworks for building backend applications becomes crucial for developers aiming for efficiency, scalability, and maintainability. While Express.js has been a long-standing favorite due to its simplicity and flexibility, NestJS emerges as a powerful alternative, especially for large-scale applications. This article delves deep into why NestJS should be the preferred choice over pure Express for modern backend development.

Resources

Express Page

Express GitHub

NestJS Page

NestJS GitHub

The Case for Moving Beyond Express

Express.js has undeniably set the standard for Node.js web servers with its minimalist approach, offering developers the freedom to structure their applications as they see fit. However, this minimalism often leads to scalability and maintainability issues as applications grow. Express provides the basics—routing, middleware, and simple request handling—but leaves much of the architectural decisions and advanced features to the developer. This can result in varied project structures, inconsistency in coding practices, and the added burden of manually integrating third-party libraries for common needs such as validation, authentication, and error handling.

Express.js in Practice

const express = require('express')
const app = express()

app.get('/', (req, res) => {
    res.send('Hello World!')
})

app.listen(3000, () => console.log('Server running on port 3000'))

While the above example highlights Express's simplicity, it masks the complexity that arises when building more sophisticated applications.

NestJS: A Comprehensive Solution

NestJS is designed from the ground up to address the challenges posed by complex backend applications. It extends and abstracts Express (and Fastify) functionalities, providing a robust framework that incorporates the best practices of software development.

Key Features and Benefits of NestJS

1. typescript-Based: NestJS leverages typescript, offering strong typing and object-oriented programming capabilities, which significantly improve code quality and developer productivity.

2. Modular Structure: NestJS promotes a modular architecture, making it easier to organize and manage code, especially in large projects. Modules encapsulate providers, controllers, and services, fostering clean separation of concerns.

3. Decorators and Metadata: By utilizing decorators, NestJS provides an expressive syntax for routing, dependency injection, and class validation, reducing boilerplate and improving readability.
   

@Controller('cats')
export class CatsController {
    @Get()
    findAll(): string {
        return 'This action returns all cats'
    }
}

1. Built-in Application Logic Abstractions: Unlike Express, NestJS comes with built-in support for complex application features like guards for authentication, interceptors for response mapping, pipes for validation and transformation, and filters for exception handling.

2. Dependency Injection: NestJS's dependency injection container allows for loose coupling and enhanced testability, streamlining the development of scalable applications.
   

@Injectable()
export class CatsService {
    constructor(private catsRepository: CatsRepository) {}

    findAll(): Promise<Cat[]> {
        return this.catsRepository.findAll()
    }
}

1. Comprehensive Documentation and Tooling: NestJS boasts extensive documentation and a CLI tool for generating boilerplate code, which accelerates development and ensures adherence to framework conventions.

2. Integration with ORM and Microservices: NestJS seamlessly integrates with popular ORMs like TypeORM, Sequelize, and Mongoose, and supports microservices with a variety of transport layers, such as MQTT, Redis, and NATS.

3. First-Class Validation and Serialization: Utilizing class-validator and class-transformer packages, NestJS simplifies data validation and serialization, enforcing data integrity and security.
   

@Post()
@UsePipes(new ValidationPipe())
async create(@Body() createCatDto: CreateCatDto) {
  return this.catsService.create(createCatDto);
}

1. Swagger Integration for API Documentation: NestJS provides easy integration with Swagger for automatic API documentation generation, making it easier to create and maintain up-to-date API docs.

2. Performance and Flexibility: Despite its higher-level abstractions, NestJS does not sacrifice performance. Developers can choose between the Express and Fastify adapters based on their needs, optimizing for speed or flexibility.

Transitioning from Express to NestJS

Adopting NestJS in place of Express for new projects is straightforward, thanks to the Nest CLI and the framework's alignment with modern JavaScript features. For existing Express applications, incremental adoption is possible by gradually refactoring parts of the application to NestJS, taking advantage of its advanced features while maintaining the core application logic.

Conclusion

NestJS represents a significant step forward in the development of scalable, maintainable backend applications in Node.js. It builds on the foundations laid by Express, addressing its limitations through a comprehensive set of features that facilitate the development of complex applications. By choosing NestJS, developers can leverage modern JavaScript features, enjoy a rich ecosystem of integrations, and follow best practices for software architecture, all of which contribute to building high-quality applications more efficiently.

For those contemplating the switch or starting a new project, NestJS offers a compelling set of advantages that make it a superior choice for modern backend development.