Скачать или смотреть Understanding Error Handling in async Functions with Try/Catch in JavaScript

Learn how to effectively use `try/catch` blocks in asynchronous functions in JavaScript. Discover how errors propagate and how to handle them efficiently.
---
This video is based on the question https://stackoverflow.com/q/65707238/ asked by the user 'Eitanos30' ( https://stackoverflow.com/u/5752410/ ) and on the answer https://stackoverflow.com/a/65707446/ provided by the user 'CertainPerformance' ( https://stackoverflow.com/u/9515207/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Does async function try catch block can wrap a called async function that also may throw an error?

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding Error Handling in async Functions with Try/Catch in JavaScript

When working with asynchronous functions in JavaScript, one common question arises: Can a try/catch block catch errors thrown by a called asynchronous function? Let's break this down using a practical example and delve into how error handling can be effectively implemented in your code.

The Problem

Consider the following scenario: You have an asynchronous function getJSON that fetches data from a provided URL. Inside another asynchronous function outerFunc, you are invoking getJSON within a try/catch block. Your goal is to understand if any errors produced by getJSON can be caught by the try/catch block in outerFunc. Here’s the code you might have:

[[See Video to Reveal this Text or Code Snippet]]

Running this code retrieves an error related to the URL being undefined:

[[See Video to Reveal this Text or Code Snippet]]

This leads to the inquiry: Will the try/catch block around outerFunc capture this error from the getJSON call?

Understanding Error Propagation in JavaScript

General Principles of Error Handling

In JavaScript, the best practice for error handling is to catch errors at the point where you can do something useful in response to that error. Generally, you want to let errors propagate upwards in the call stack to where they can be handled effectively.

Single Catch Point: Ideally, you should have a single point in your application to catch and handle errors.

Propagation: Allowing errors to propagate lets higher-level functions handle them, potentially offering users a more meaningful response.

Example Explanation

In your getJSON function, if you encounter an error while fetching, you're throwing it, which allows the error to be caught by outerFunc. The try/catch block in outerFunc will catch any errors thrown by getJSON, allowing you to log the error or handle it as needed.

Here’s an illustration of a common error handling pattern:

[[See Video to Reveal this Text or Code Snippet]]

In this example, getAPI allows any calling function to handle errors appropriately, keeping error handling centralized.

Multiple Catch Points – Handling Specific Cases

In some cases, you may want to catch errors in multiple places. For example, within a sub-component that needs to handle errors but also inform its callers.

Here's how you can achieve that:

[[See Video to Reveal this Text or Code Snippet]]

This pattern allows both makeSubComponent and its callers to respond to errors effectively, which is essential for robust applications.

Conclusion

To summarize, yes, an outer try/catch block can wrap a called asynchronous function that may throw an error. It's a powerful mechanism that allows you to centralize error handling and respond thoughtfully to issues that arise during asynchronous operations. Remember to propagate errors back up to the appropriate handling location when necessary, as this ensures your application remains user-friendly and robust against unexpected issues.

By following these best practices for error handling in asynchronous JavaScript, you can create smoother, more resilient applications that end-users can rely on.