Nest.js vs. Express.js: An In-Depth Comparison

Introduction:

Node.js has become a popular choice for building scalable and efficient server-side applications, and two prominent frameworks within the Node.js ecosystem are Nest.js and Express.js. While both are used for creating web applications, they have distinct philosophies, architectures, and features.

Architecture:

Express.js:

Express.js is a minimalist and unopinionated framework, providing a set of fundamental features for building web applications. It follows a simple and flexible architecture that allows developers to structure their applications as they see fit. Express.js leaves many decisions, such as project structure, middleware usage, and routing, entirely up to the developer.

// Express.js Example
const express = require('express');
const app = express();

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

app.listen(3000, () => {
  console.log('Express app listening on port 3000');
});

Nest.js:

Nest.js takes inspiration from Angular and follows a more opinionated, modular, and structured approach. It promotes the use of decorators, dependency injection, and a modular system for building scalable and maintainable applications. Nest.js encourages developers to organize their code into modules, controllers, and services, providing a clear and organized structure.

// Nest.js Example
import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  await app.listen(3000);
}

bootstrap();

Modularity:

Express.js:

Express.js allows developers to structure their applications in any way they prefer. While there are many third-party libraries available to enhance functionality, Express itself does not enforce any particular modular architecture. Developers have the freedom to choose their own modules and organization.

Nest.js:

Nest.js is built with modularity in mind. It encourages developers to create reusable and self-contained modules, making it easier to manage and scale applications. The use of modules, controllers, and services allows for a clean separation of concerns, making the codebase more maintainable.

// Nest.js Module Example
import { Module } from '@nestjs/common';
import { UsersController } from './users.controller';
import { UsersService } from './users.service';

@Module({
  controllers: [UsersController],
  providers: [UsersService],
})
export class UsersModule {}

Decorator-based Programming:

Express.js:

Express.js uses a more traditional approach for defining routes and middleware. Developers manually configure routes and middleware functions without relying on decorators.

// Express.js Route Example
const express = require('express');
const app = express();

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

Nest.js:

Nest.js leverages decorators extensively, providing a more declarative and intuitive way to define routes, controllers, and other components. This approach is similar to Angular, making it familiar for developers accustomed to that framework.

// Nest.js Controller Example
import { Controller, Get } from '@nestjs/common';

@Controller('users')
export class UsersController {
  @Get()
  getUsers(): string {
    return 'Get all users';
  }
}

Dependency Injection:

Express.js:

While Express.js allows developers to implement dependency injection, it is not inherent to the framework. Developers need to manage dependencies manually or use third-party solutions if they want to implement dependency injection.

Nest.js:

Nest.js comes with built-in support for dependency injection. It simplifies the management and injection of dependencies throughout the application, making it easier to organize and test code.

// Nest.js Service with Dependency Injection
import { Injectable } from '@nestjs/common';

@Injectable()
export class UsersService {
  getUsers(): string {
    return 'List of users';
  }
}

Built-in Features:

Express.js:

Express.js provides a minimalistic core, and developers often need to rely on third-party middleware and libraries to add features such as authentication, validation, and error handling.

Nest.js:

Nest.js comes with many built-in features, reducing the need for additional third-party libraries. It includes modules for handling validation, guards for authentication, interceptors for modifying request/response objects, and more.

// Nest.js Validation Example
import { ValidationPipe } from '@nestjs/common';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  app.useGlobalPipes(new ValidationPipe());
  await app.listen(3000);
}

bootstrap();

Community and Ecosystem:

Express.js:

Express.js has been around for a longer time, resulting in a mature and extensive ecosystem. A wide range of middleware, plugins, and libraries are available to extend functionality.

Nest.js:

While newer compared to Express, Nest.js has been gaining popularity. Its ecosystem is growing, benefiting from the popularity of TypeScript and sharing similarities with Angular. The community around Nest.js is active, contributing to the framework’s expansion.

Conclusion:

Choosing between Nest.js and Express.js depends on the project requirements, team preferences, and the desired level of structure. Express.js is well-suited for smaller projects or when developers prefer more flexibility. Nest.js, on the other hand, is a strong choice for larger applications that require a structured and modular approach.

In summary, both frameworks have their strengths and use cases, and the decision should be based on factors such as project complexity, team familiarity, and development preferences.