Logging exceptions in NestJS - Mini Project: Build & Apply

Logging Exceptions in NestJS

📖 Scenario: You are building a simple NestJS application that needs to handle errors gracefully. When an error happens, you want to log the error message so you can understand what went wrong later.

🎯 Goal: Learn how to catch exceptions in a NestJS service and log the error messages using NestJS's built-in Logger.

📋 What You'll Learn

Create a service method that throws an error

Add a Logger instance to the service

Catch the error inside the method and log the error message

Print a message indicating the error was logged

💡 Why This Matters

🌍 Real World

Logging errors helps developers find and fix problems quickly in real applications.

💼 Career

Knowing how to log exceptions is essential for backend developers and DevOps engineers to maintain reliable services.

1

Create a service method that throws an error

Create a class called AppService with a method performTask that throws an error with the message 'Something went wrong!'.

NestJS

class AppService {
    // Your code here
}

Need a hint?

Define a class with a method that uses throw new Error('Something went wrong!').

2

Add a Logger instance to the service

Inside the AppService class, add a private property called logger that is an instance of Logger from @nestjs/common. Initialize it with new Logger(AppService.name).

NestJS

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

class AppService {
    private logger = new Logger(AppService.name);

    performTask() {
        throw new Error('Something went wrong!');
    }
    // Your code here
}

Need a hint?

Import Logger and create a private property logger initialized with new Logger(AppService.name).

3

Catch the error and log the error message

Modify the performTask method to use a try-catch block. Inside try, throw the error as before. Inside catch, use this.logger.error(error.message) to log the error message.

NestJS

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

class AppService {
    private logger = new Logger(AppService.name);

    performTask() {
        // Your code here
    }
}

Need a hint?

Wrap the error throw in try and catch it to log the message with this.logger.error(error.message).

4

Print a message indicating the error was logged

After calling performTask() on an instance of AppService, print 'Error logged successfully' to the console.

NestJS

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

class AppService {
    private logger = new Logger(AppService.name);

    performTask() {
        try {
            throw new Error('Something went wrong!');
        } catch (error) {
            this.logger.error(error.message);
        }
    }
}

const appService = new AppService();
// Your code here

Need a hint?

Create an instance of AppService, call performTask(), then print 'Error logged successfully'.