Summary  
This chapter explains how to handle errors in Nest.js by throwing built-in exceptions (e.g., NotFoundException, BadRequestException) in your code to produce standardized HTTP error responses.

General domain of usage  
Web API development



Errors are part of any backend application. Nest.js provides a simple way to handle them using built-in exceptions.

Instead of returning plain values, you can throw an exception when something goes wrong.

Here is an example:

```ts id="err1"
import { Controller, Get, NotFoundException } from '@nestjs/common';

@Controller('users')
export class UsersController {
  @Get(':id')
  getUser() {
    throw new NotFoundException('User not found');
  }
}
```

In this example:

* `NotFoundException`: represents a 404 error;
* The request is stopped and an error response is returned.

Nest.js includes several built-in exceptions:

* `NotFoundException`: resource not found;
* `BadRequestException`: invalid request;
* `UnauthorizedException`: access denied.

You can use these exceptions to clearly describe what went wrong.

Throwing exceptions makes your API more predictable and easier to debug.



What should you do when an error occurs in a Nest.js controller?

Learn how to build structured backend applications with Nest.js. Organize your code using controllers, services, and modules, handle requests and data validation, and create a complete API using a scalable architecture.

Set up your first Nest.js application and understand how it is structured. Learn how the main files work together to handle requests and organize backend logic.

Learn how to handle requests in Nest.js using controllers and routes. Define endpoints, work with route and query parameters, and control how your backend responds to client requests.

Learn how to organize backend logic using services. Move business logic out of controllers, structure your code properly, and understand how different parts of your application work together.

Learn how Nest.js organizes applications using modules and dependency injection. Understand how different parts of your backend connect and how to structure your code into scalable, maintainable features.

Learn how to handle and validate data in Nest.js. Work with request body data, define structured DTOs, and ensure incoming data is correct using validation pipes.

Summarize what you have learned throughout the track and reinforce your understanding of backend development. Review key concepts and see how they come together into a complete, structured application.

Handling Errors in Nest.js