10 NestJS Best Practices

NestJS is a server-side application framework that is becoming increasingly popular among developers. It is based on TypeScript and uses the Express.js framework.

NestJS provides a lot of features out of the box, such as support for TypeScript, a powerful module system, and a built-in dependency injection system.

In this article, we will discuss 10 best practices that you should follow when using NestJS.

1. Use the Nest CLI to bootstrap your application

The Nest CLI is a command line interface tool that helps you create and manage NestJS applications. It’s easy to use, and it comes with a variety of features that make development faster and easier.

Some of the features include:

– A simple way to create a new NestJS application
– A set of templates for different project types
– A dependency manager to help you install and update dependencies
– A build system to compile your code
– A testing framework

2. Keep Controllers as thin as possible

The main responsibility of a controller is to handle incoming requests and send responses back to the client. However, if a controller contains too much logic, it can quickly become bloated and difficult to maintain.

Instead, NestJS controllers should delegate as much work as possible to other parts of the application, such as services or pipes. This will help keep your controllers clean and easy to understand.

3. Use Pipes for input validation and sanitization

Pipes provide a way to declaratively specify how data should be transformed before it reaches your NestJS controllers. This is important for two reasons:

1) It helps keep your controller code clean and focused on business logic, rather than input validation.

2) It makes it easy to reuse validation rules across multiple controllers.

To use a Pipe, simply decorate your controller’s method with the @UsePipe() decorator, and specify the pipe you want to use. For example, if you wanted to use a pipe to validate and sanitize user input, you could do something like this:

@UsePipe(new UserInputPipe())
addUser(@Body() userData: any) {
// …
}

This would ensure that the userData object passed into the addUser() method is first validated and sanitized by the UserInputPipe before being used by the controller.

If you need to use multiple pipes, you can chain them together using the | (pipe) operator. For example:

@UsePipe(new ValidationPipe(), new SanitizationPipe())
addUser(@Body() userData: any) {
// …
}

This would run the userData object through both the ValidationPipe and the SanitizationPipe before passing it to the controller.

4. Use Guards for authentication and authorization

Guards provide a way to abstract away the details of authentication and authorization, making it easier to manage these concerns in one place. This not only makes your code more organized and maintainable, but it also makes it easier to add new features or make changes down the road.

For example, let’s say you have a Guard that checks for a valid JWT token before allowing a user to access a route. If you need to change the way this Guard works (for example, to use a different type of token), you can do so in one place without having to update your code in multiple places.

Additionally, Guards can be used to restrict access to certain routes based on a user’s role. For example, you could have a Guard that only allows admin users to access the /admin route. This is a great way to keep your application secure and prevent unauthorized users from accessing sensitive data.

5. Create custom exceptions for error handling

If you’re not familiar with NestJS, it’s a Node.js framework that helps you build efficient, scalable server-side applications. It uses TypeScript and is heavily inspired by Angular.

One of the benefits of using TypeScript is that it allows you to catch errors early on in the development process. However, if you’re not careful, your error-handling code can quickly become bloated and hard to maintain.

Creating custom exceptions is a great way to keep your error-handling code clean and organized. By creating a custom exception for each type of error, you can easily add or remove error-handling logic as needed. This also makes it easier for other developers to understand your code and make changes as necessary.

6. Use Interceptors for cross-cutting concerns

Interceptors provide a way to intercept and manipulate HTTP requests before they are handled by the route handlers. This is useful for tasks such as logging, authentication, and rate-limiting.

Interceptors can be registered globally, so that they apply to all incoming requests, or they can be registered on specific routes.

NestJS comes with a built-in logger interceptor, which logs each incoming request. You can also create your own interceptors for tasks such as authentication and rate-limiting.

Creating an interceptor is simple. Just create a class that implements the NestInterceptor interface and register it with Nest.

Here’s an example of an interceptor that authenticates users:

import { Injectable, NestInterceptor, ExecutionContext } from ‘@nestjs/common’;
import { Observable } from ‘rxjs’;

@Injectable()
export class AuthInterceptor implements NestInterceptor {
intercept(context: ExecutionContext, call$: Observable): Observable {
const req = context.switchToHttp().getRequest();
const user = req.user;

if (!user) {
throw new Error(‘User is not authenticated’);
}

return call$;
}
}

7. Use Modules to organize your codebase

Modules provide a logical way to group your code and keep your project organized. By creating modules for each feature or domain in your application, you can keep your codebase clean and maintainable.

Not only does this make it easier to find things when you need to make changes, but it also makes it simpler to test and deploy your code. When your code is organized into modules, you can easily isolate the parts of your application that you want to test or deploy.

If you’re just starting out with NestJS, you might be tempted to put all of your code in a single file. However, as your application grows, you’ll quickly realize the benefits of using modules to keep your code organized.

8. Use Providers for dependency injection

When using NestJS with TypeScript, the compiler can help ensure that the dependencies you inject are used correctly. This means that if you change the type of a dependency, the compiler will catch any errors.

However, if you use vanilla JavaScript, the compiler can’t help you, and it’s easy to make mistakes. For example, you might accidentally inject an object when you meant to inject a function.

By using providers, you can take advantage of TypeScript’s static typing to avoid these kinds of errors. In addition, providers can be registered as global, so they’re always available in your application.

9. Use Services for business logic

Services are singletons, meaning that they are instantiated only once per application. This ensures that your business logic is always consistent, regardless of how many times it’s called.

Additionally, Services can be injected into other NestJS components, such as Controllers, Providers, and Pipes. This allows you to keep your business logic decoupled from your presentation logic, making your code more modular and easier to maintain.

Finally, Services can be unit tested in isolation, without having to spin up an entire NestJS application. This makes for faster, more focused tests that are less likely to break when the underlying implementation changes.

10. Use DTOs for data transfer

DTOs help to keep your code clean and maintainable by ensuring that only the data that’s needed is transferred between objects. They also help to prevent accidentally leaking sensitive data, as well as making it easier to add validation rules.

Additionally, DTOs can be used to automatically generate documentation for your API, which is extremely helpful for both developers and consumers of your API.