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:

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.