Dealing with Warnings and Errors in Browser Console

Dealing with Warnings and Errors in Browser Console

September 28, 2023

by Ihor Selin, Frontend Engineer at InterLogic


As diligent developers, our commitment to producing quality, clean code is unwavering. When warnings and errors in the browser console emerge during development, addressing them becomes paramount. However, the question often arises about whether every warning should receive equal attention. This article will delve into this question, employing real-world examples to illustrate when it's crucial to heed warnings and when it might be acceptable to ignore. Today, we will look at an example with the React library, but the approach we will discuss is suitable for any technology/library.

The Challenge of React Warnings: React is one of the most popular libraries for building dynamic user interfaces in web development. Within this ecosystem, warnings are not uncommon, and they can vary in terms of importance and impact.

Let's take a specific React warning as an example:

"Warning: Can't perform a React state update on an unmounted component. This is a no-op, but it indicates a memory leak in your application. To fix, cancel all subscriptions and asynchronous tasks in a useEffect cleanup function."

When to Ignore: So, when might it be justifiable to ignore a warning? The answer lies in understanding the context and assessing whether the warning is still relevant. In some cases, attempting to address the warning might lead to code that is unnecessarily complex or even less efficient than before.

After looking at the React documentation, I read that sometimes, when you try to remove this warning, the implementation can be cumbersome, and the result could be worse than before the fix.

When we check this documentation, we can find the following:

No warning about setState on unmounted components: Previously, React warned about memory leaks when you call setState on an unmounted component. This warning was added for subscriptions, but people primarily run into it in scenarios where the setting state is fine, and workarounds make the code worse. We've removed this warning. Source:

In short:

React reported a memory leak in previous versions when calling useState in unmounted components. But to fix it, we have to write a lot of redundant code to eliminate this warning, and the result can become worse than before fixing this warning. Therefore, this warning was removed from version 18.

Also, let's consider another case where the appearance of a warning does not require changing your code.

Browser Extension Warnings:

Warnings in a web browser can sometimes be attributed to specific browser extensions that users have installed. Some extensions, designed to enhance security, privacy, or user experience, can intercept and modify various web elements, leading to browser console warnings. It's important to note that such warnings don't necessarily indicate a need to edit website code urgently. For instance, consider a scenario where a privacy-focused browser extension blocks tracking scripts on a website. This can trigger a warning in the console, indicating that certain resources were blocked for privacy reasons. While this may appear as a warning, it aligns with the extension's intended functionality and enhances user privacy without requiring immediate code changes. Web developers should exercise discretion and consider the context of these warnings, as they may be outside their control.

So, here are some practices you can follow when dealing with warnings in any framework/library:

  1. Investigate Future Versions: Always check if the warning you encounter still exists in future versions of your software or library. Development teams often refine and remove warnings based on user feedback and evolving best practices.
  2. Check the origin of the warning: Sometimes, the warning can be from a certain browser extension and does not require that the site code be changed in any way.
  3. Prioritize important warnings: If the warning is present in later versions, it should be eliminated and resolved in your code.






Additional Resources: For further information on handling warnings and debugging JavaScript code effectively, refer to this informative guide from Microsoft's DevTools: Debugging JavaScript with Microsoft DevTools.

Conclusion: Discerning which warnings and errors to prioritize in software development is a valuable skill. While we all aim for high-quality and clean code, it's equally crucial to recognize that not all warnings are created equal. Also, stay updated with new package versions and assess warnings to balance issue-fixing with efficient code maintenance.