Built-in HTTP exceptions in NestJS - Mini Project: Build & Apply

Using Built-in HTTP Exceptions in NestJS

📖 Scenario: You are building a simple NestJS API that returns user data. You want to handle cases where a user is not found by using NestJS's built-in HTTP exceptions.

🎯 Goal: Create a NestJS controller that uses the built-in NotFoundException to respond with a 404 error when a user is not found.

📋 What You'll Learn

Create a users array with specific user objects

Add a variable to hold the user ID to search for

Use the NotFoundException from NestJS to throw an error if the user is not found

Complete the controller method to return the found user or throw the exception

💡 Why This Matters

🌍 Real World

Handling errors with proper HTTP status codes is essential in building APIs that clients can understand and react to.

💼 Career

Knowing how to use NestJS built-in exceptions is a common requirement for backend developers working with NestJS to build robust APIs.

1

Create the users data array

Create a constant array called users with these exact objects: { id: 1, name: 'Alice' }, { id: 2, name: 'Bob' }, and { id: 3, name: 'Charlie' }.

NestJS

# Create the users array with 3 user objects
# Your code here

Need a hint?

Use const users = [ ... ] with the exact user objects inside.

2

Add a user ID variable to search

Create a constant called userId and set it to the number 4.

NestJS

const users = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' },
  { id: 3, name: 'Charlie' }
];

# Create a userId variable with value 4
# Your code here

Need a hint?

Use const userId = 4; exactly.

3

Find the user or throw NotFoundException

Import NotFoundException from @nestjs/common. Then create a constant called user that finds the user in users with id equal to userId. If no user is found, throw new NotFoundException('User not found').

NestJS

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

const users = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' },
  { id: 3, name: 'Charlie' }
];

const userId = 4;

# Find the user or throw NotFoundException
# Your code here

Need a hint?

Use users.find(u => u.id === userId) and throw new NotFoundException('User not found') if user is undefined.

4

Complete the controller method to return the user

Create a function called getUser that returns the user constant. Export this function.

NestJS

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

const users = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' },
  { id: 3, name: 'Charlie' }
];

const userId = 4;

const user = users.find(u => u.id === userId);
if (!user) {
  throw new NotFoundException('User not found');
}

# Create and export getUser function that returns user
# Your code here

Need a hint?

Define getUser as a function that returns user and export it.