Why do we need Nest.js if Express exist?

Web development frameworks play a vital role in crafting efficient, maintainable, and scalable web applications. While Express.js is a popular choice for its simplicity and flexibility, developers often turn to Nest.js as their applications grow in complexity. In this topic, you will explore why Nest.js is a compelling choice in the Node.js ecosystem, especially when compared to Express.js.

Why nest.js when express exists

Express.js is often the preferred framework for many Node.js developers, thanks to its minimalism and ease of use. However, as applications grow in complexity, a more structured approach becomes necessary. Nest.js is designed to address the limitations of Express.js by providing an application architecture that facilitates the development of large-scale applications. Nest.js features include:

• Modular structure: Nest.js promotes a modular application structure, simplifying code organization and reuse. Modules encapsulate providers, controllers, and services, which can be easily combined or modified.

• TypeScript support: It is built with TypeScript, providing compile-time type checking and enhanced IDE support for better maintainability and developer productivity.

• Dependency Injection: It implements a robust dependency injection (DI) system, inspired by Angular, enhancing testability and decoupling of components.

• Scalability: The framework is designed for long-term maintainability and scalability, making it suitable for building enterprise-level applications.

• Built-in application architecture: Nest.js comes with a pre-defined application architecture, providing a clear roadmap for organizing code in a scalable and maintainable manner.

• Microservices Support: It has built-in support for microservices patterns and multiple transport layers like MQTT, RabbitMQ, and WebSockets, allowing developers to build scalable microservice applications.

These features make Nest.js a compelling alternative to Express.js, particularly for larger projects where a more robust framework can significantly improve development efficiency and application quality.

Architecture and scalability

Express.js provides a flat structure where middleware and route handlers are typically organized linearly. It is designed to be simple and unopinionated, giving you the freedom to structure your application as you see fit. This approach is straightforward for small projects but can become cumbersome as the application expands. Nest.js, on the other hand, introduces a modular architecture that fosters code organization and scalability.

In Express.js, manually organizing code into modules and managing dependencies between them can result in tightly coupled components that are challenging to manage and test. Nest.js addresses this by providing a built-in modular system that encourages the separation of concerns.

For instance, in Express.js, you might have:

const express = require('express');
const usersRoutes = require('./routes/users');
const productsRoutes = require('./routes/products');
const app = express();

app.use('/users', usersRoutes);
app.use('/products', productsRoutes);

// ...additional routes and middleware

While this structure works, it doesn't inherently promote separation into reusable, isolated modules. In contrast, Nest.js provides a clear way to define modules:

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

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

The above snippet shows a basic Nest.js module with its own controllers and services. This modular system is a core feature of Nest.js that helps in building complex applications with ease, leading to a more organized and maintainable codebase.

Dependency injection

Building web applications often involves managing how different sections of your app interact, which can be complex. This is where Dependency Injection (DI) becomes useful. Although both Express.js and Nest.js can employ dependency injection patterns, Nest.js features a built-in DI system that significantly simplifies the process. In Express.js, implementing DI often necessitates third-party libraries or custom implementations, which can be prone to errors and add unnecessary complexity.

Express.js: Dependency management

Express.js is like building a house with your toolbox. It's certainly possible, but you have to know which tool to use and when. If you need DI in Express.js, you might have to get additional tools (third-party libraries) or create your own. This situation resembles making a trip to the hardware store each time you discover you need something new.

Here's how you might manually set up a service in Express.js:

const usersService = require('./users.service');

app.get('/users', (req, res) => {
  res.send(usersService.getAllUsers());
});

In this example, you are directly using usersService. If you wanted to use DI, you would need to incorporate a third-party library or write a custom solution, which can get complicated.

Nest.js: Built-in smart dependency management

On the other hand, Nest.js features a built-in system that functions like an extremely efficient construction manager. It's familiar with all the workers (services, controllers, etc.) and ensures they get the right tools (dependencies) at the appropriate time.

Nest.js uses decorators to manage this, which are like name tags that tell the framework what role each piece of code plays.

Here's how you define a service in Nest.js:

import { Injectable } from '@nestjs/common';

@Injectable()
export class UsersService {
  // Your service logic goes here
  getAllUsers() {
    // Imagine this method fetches users from a database
  }
}

The @Injectable() decorator acts like a name tag that says, "Hey Nest.js, this class can be given to others when they need it."

Now, when you want to use UsersService in a controller, you don't need to worry about how to get it. You simply inform Nest.js that you need it by listing it as a parameter in the controller's constructor:

import { Controller, Get } from '@nestjs/common';
import { UsersService } from './users.service';

@Controller('users')
export class UsersController {
  constructor(private usersService: UsersService) {}

  @Get()
  findAll() {
    return this.usersService.getAllUsers();
  }
}

In this UsersController, you are indicating you need UsersService to do your job. Nest.js recognizes this and automatically provides UsersService for you. It's like having a helper who hands you the right tool just as you need it.

Typescript support

While both Express.js and Nest.js are compatible with TypeScript, Nest.js is designed from scratch to fully leverage TypeScript's features. This leads to enhanced reliability and a more integrated development experience. Although you can configure TypeScript in an Express.js application, Nest.js offers first-class TypeScript integration right out of the box.

import { Controller, Get } from '@nestjs/common';

@Controller('users')
export class UsersController {
  @Get()
  findAll(): string {
    return 'This action returns all users';
  }
}

In Nest.js, TypeScript's decorators are used extensively to define metadata for classes, methods, and parameters, which Nest.js then uses to set up routing, dependency injection, and other framework features. This declarative approach results in code that is not only more expressive but also aligns with the design principles of Nest.js, making your codebase more consistent and easier to understand.

Out-of-the-box features

Nest.js comes with a suite of built-in functionalities such as exception filters, pipes, guards, and interceptors. These tools are readily available and easily configured within your application. In contrast, achieving similar functionality in Express.js often requires integrating multiple third-party middleware, which can lead to inconsistency and additional overhead.

Express.js is simple and flexible. Imagine Express.js as a lightweight backpack that you can pack with only the essentials you need for a trip. It's straightforward and doesn't come with a lot of built-in features, but you can add what you need using additional tools called middleware.

For example, if you need to handle errors in Express.js, you might write something like this:

app.use((err, req, res, next) => {
  console.error(err);
  res.status(500).send('Oops, something went wrong!');
});

Similarly, to parse incoming request bodies, Express.js requires middleware like body-parser:

const bodyParser = require('body-parser');
app.use(bodyParser.json());

On the other hand, Nest.js is feature-rich and organized. Think of Nest.js as a larger, more organized backpack with lots of pockets and features built right in. It's based on Express.js but comes with a lot of tools and a clear structure for building your applications. Some of these include:

• Exception Filters: Nest.js has a special way to handle errors neatly. It's like having a dedicated pocket in your backpack for things that could leak or spill.

import { Catch, ExceptionFilter, ArgumentsHost } from '@nestjs/common';

@Catch(Error)
export class ErrorFilter implements ExceptionFilter {
  catch(error, host: ArgumentsHost) {
    // ...handle the error and respond
  }
}

• Pipes: Think of pipes in Nest.js as a tool to check and clean data before using it, like a water filter ensuring only clean water gets through.

import { PipeTransform, Injectable } from '@nestjs/common';

@Injectable()
export class SimpleValidationPipe implements PipeTransform {
  transform(value) {
    // ...validate the data
    return value;
  }
}

• Guards: Guards in Nest.js are like security checks before entering a secure area. They make sure only the right people can access certain routes.

import { CanActivate, ExecutionContext } from '@nestjs/common';

export class SimpleGuard implements CanActivate {
  canActivate(context: ExecutionContext): boolean {
    // ...check if the user can access the route
    return true;
  }
}

• Interceptors: Interceptors let you add extra steps before or after a task, kind of like a pre-flight checklist or a post-flight debrief.

import { NestInterceptor, ExecutionContext, CallHandler } from '@nestjs/common';

export class SimpleInterceptor implements NestInterceptor {
  intercept(context: ExecutionContext, next: CallHandler) {
    // ...do something before or after the request
    return next.handle();
  }
}

Conclusion

By emphasizing architecture, dependency injection, TypeScript support, and providing a rich set of features out of the box, Nest.js addresses many of the challenges developers face with Express.js in larger applications. While Express.js remains a robust tool for building web applications, Nest.js offers a more structured and scalable approach that can be beneficial as your project grows.

The choice between Nest.js and Express.js ultimately depends on the specific needs of your project. For simple applications, the straightforward nature of Express.js may be sufficient. However, for complex applications with a long-term vision, Nest.js provides a robust foundation that helps manage complexity and facilitate growth.