10 NestJS Error Handling Best Practices

Error handling is important in any application, and NestJS is no exception. Here are 10 best practices for NestJS error handling that you can use in your own applications.

NestJS is a popular Node.js framework for building efficient, reliable, and scalable server-side applications. It uses modern JavaScript, is built with TypeScript, and combines elements of Object-Oriented Programming, Functional Programming, and Functional Reactive Programming.

However, like any other framework, NestJS also has its own set of error handling best practices. In this article, we will discuss 10 best practices for handling errors in NestJS applications. We will also discuss how to use the built-in error handling features of NestJS to make your applications more robust and reliable.

1. Use the built-in error handling middleware

The built-in error handling middleware is designed to catch any errors that occur in your application and handle them gracefully. It will log the error, send an appropriate response back to the client, and even notify you of the issue so you can take action quickly. This helps ensure that your application remains stable and reliable for your users.

Additionally, using the built-in error handling middleware allows you to easily customize how errors are handled based on their type or severity. For example, you could choose to only log certain types of errors while sending a different response for others. This makes it easy to tailor your error handling strategy to fit your specific needs.

2. Create a custom exception filter

A custom exception filter allows you to catch and handle errors in a consistent way. This means that instead of having to write code for each type of error, you can create one filter that will work for all types of errors. It also makes it easier to debug your application since the same filter is used for all errors.

Creating a custom exception filter also helps keep your code clean and organized. Instead of having multiple try/catch blocks scattered throughout your code, you can have just one filter that handles all errors. This makes it much easier to maintain and update your code as needed.

3. Create a custom exception handler

A custom exception handler allows you to define a single place where all errors are handled. This makes it easier to debug and maintain your code, as well as providing a consistent experience for users when they encounter an error. It also helps ensure that the same response is sent regardless of which part of the application throws the error.

Creating a custom exception handler in NestJS involves creating a class that implements the ExceptionFilter interface. This class should contain logic to handle any exceptions thrown by the application, such as logging them or sending a specific response back to the user.

4. Don’t forget to import your new error handling classes into the AppModule

When you create a new error handling class, it needs to be imported into the AppModule so that NestJS can recognize and use it. If you don’t import your new classes, then NestJS won’t know what to do with them when an error occurs. This could lead to unexpected behavior or even crashes in your application.

By importing your new error handling classes into the AppModule, you ensure that NestJS will always have access to them and be able to handle errors properly.

5. Import and use HttpStatus from @nestjs/common

HttpStatus is a utility class that provides constants for common HTTP status codes. This makes it easier to write code that handles errors in a consistent way, as you can use the same HttpStatus constant across your application. It also helps make your code more readable and maintainable, since you don’t have to remember or look up the exact numeric value of each status code. Finally, using HttpStatus ensures that your error responses are properly formatted according to the HTTP standard.

6. Throw an HTTPException with NestJS

HTTPExceptions are a type of error that is specifically designed to be used in NestJS applications. They provide an easy way to return errors with the correct HTTP status code and message, which makes it easier for developers to debug their application. Additionally, they can also include additional information such as stack traces or other data that can help pinpoint the source of the problem.

By using HTTPExceptions, you can ensure that your application returns the right response codes and messages when something goes wrong. This helps make debugging easier and ensures that your API responses are consistent and predictable.

7. Return a response object in your exception filter or handler

When an exception is thrown, NestJS will automatically catch it and return a response to the client. However, if you don’t provide a response object in your filter or handler, then NestJS won’t know what type of response to send back. This can lead to unexpected results for the user, such as a 500 Internal Server Error page.

By returning a response object in your filter or handler, you can ensure that the correct response is sent back to the user. This way, they’ll get the information they need without any confusion or frustration.

8. Add additional data to your exceptions

When an exception is thrown, it’s important to provide as much information as possible about the error. This helps developers quickly identify and fix the issue. Adding additional data such as a stack trace or request parameters can help pinpoint the exact cause of the problem.

It’s also important to log exceptions in a centralized location so that they can be easily tracked and monitored. This will allow you to quickly identify any recurring issues and take corrective action.

9. Set a default status code for all exceptions

When an exception is thrown, the status code of the response will be set to 500 (Internal Server Error) by default. This can lead to confusion for users and developers alike as it doesn’t provide any information about what went wrong.

By setting a default status code for all exceptions, you can ensure that your API responses are more informative and easier to debug. For example, if an exception is thrown due to a validation error, you could set the status code to 400 (Bad Request). This way, users and developers know exactly what went wrong without having to dig through logs or source code.

10. Catch errors that are thrown by other functions

When a function throws an error, it can cause the entire application to crash. This is especially true if the error isn’t caught and handled properly. By catching errors that are thrown by other functions, you can prevent them from crashing your application and ensure that they are handled in a way that makes sense for your application.

For example, if a function throws an error due to invalid input, you could catch this error and return a custom response with more information about why the input was invalid. This will help users understand what went wrong and how to fix it.


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