UseEffect called twice in React- How to fix it?

React 18, a popular JavaScript library, brings with it a myriad of exciting features and improvements. However, amid all the advancements, a pesky bug has made its presence known - the double invocation of useEffect. If you're a React developer who has encountered this issue, you know firsthand the frustration it can cause. But fear not! In this blog post, we'll dive deep into the world of useEffect, explore why it's being called twice in React 18, and most importantly, equip you with the knowledge and tools to fix it once and for all. So buckle up and get ready to conquer this enigmatic bug as we unravel the mysteries of useEffect in React 18

Understanding the Reasons Behind its Double Invocation

1. Dependency Changes: useEffect allows developers to specify dependencies, which determine when the effect should re-run. If these dependencies change between renders, React will trigger the effect to run again. In some cases, unintended changes to dependencies or complex dependency structures can lead to multiple invocations of useEffect.
2. Component Rendering: React's reconciliation algorithm aims to optimize rendering by comparing virtual DOM representations and updating only the necessary components. However, certain scenarios, such as concurrent rendering or unexpected re-renders triggered by parent components, can cause useEffect to be called multiple times.
3. Hook Implementation: The inner workings of React hooks, including useEffect, involve capturing and restoring the current component's state and context. While the hook system is designed to handle these operations efficiently, there can be edge cases where unexpected interactions or race conditions result in the double invocation of useEffect.
4. Concurrent Mode and Fiber Architecture: React 18 introduces Concurrent Mode, a feature that enables rendering of components in a non-blocking manner, enhancing overall application performance. The underlying Fiber architecture, which powers Concurrent Mode, introduces new complexities that may contribute to the double invocation bug under specific circumstances.
5. React Development and Bug Resolution: React is a dynamic open-source project with an active community and a dedicated team of developers. Bugs and issues like the double invocation of useEffect are identified, reported, and actively addressed by the React team through updates, patches, and community engagement. It is likely that subsequent releases of React 18 or future versions will include fixes for this bug.

Should you change it or not ?

As a developer, whether or not to address the double invocation of useEffect in React 18 depends on the specific requirements of your project and the impact it has on your application's functionality and performance. Here are a few considerations to help you make an informed decision:

1. Impact on Functionality: Evaluate if the double invocation of useEffect is causing any noticeable issues or undesirable behavior in your application. If it's negatively affecting the functionality or user experience, it's generally recommended to address and fix the bug.
2. Performance Impact: Assess the performance implications of the double invocation. Determine if the additional renders and effect executions are causing significant performance degradation or unnecessary resource consumption. If the performance impact is negligible or within acceptable limits, it might be acceptable to leave it as is.
3. Compatibility and Future Updates: Consider the potential compatibility issues that might arise in the future when React releases new versions or updates. It's possible that React's team will address the double invocation bug in subsequent releases, and upgrading your application to those versions could resolve the issue automatically.
4. Maintenance and Code Quality: Maintaining clean, bug-free code is essential for long-term project health. Addressing the double invocation bug ensures code correctness and improves code maintainability. It also helps avoid potential confusion for other developers who might work on the project in the future.
5. Development Timeline and Priority: Evaluate the urgency and priority of fixing the bug within the context of your project timeline and priorities. If it's a critical issue impacting core functionality, it might warrant immediate attention. However, if it's a minor issue with limited impact, you might prioritize other tasks and address it at a later stage.

Ultimately, the decision to change or not depends on your project's specific needs, the severity of the bug, and the trade-offs associated with fixing it. It's crucial to weigh the pros and cons and consider the broader implications before deciding on the appropriate course of action.

How To Fix It

With all that said, that means that the ideal solution to solve this problem isn’t to stop your useEffect running twice, it’s to write your code so that it doesn’t matter if it runs twice. but if you still insist on changing it then you can make a small adjustment to your code. Instead of using <React.StrictMode> in the root render method, you can remove it. Here's the modified code

import React from 'react';
import ReactDOM from 'react-dom/client'; 
import App from './App'; 

const root = ReactDOM.createRoot(document.getElementById('root')); 
root.render(<App />);

By removing the <React.StrictMode> component, you disable strict mode, which can trigger the double invocation of hooks during development. However, keep in mind that strict mode is a helpful tool for detecting potential issues in your application. It's recommended to use it during development to catch and address any problems early on.

Remember to thoroughly test your application to ensure that removing strict mode doesn't introduce any unexpected behavior or bugs. Once you're confident that your app functions correctly without strict mode, you can proceed with this updated code.

Conclusion:

In conclusion, encountering the issue of hooks running twice in React should not be a concern originating from your code. Instead, it's preferable to write your code in a way that avoids any side effects, rather than trying to work around the double invocation. Consider it as React testing the robustness of your application. It's better to pass the test rather than disabling it.

It's important to note that this problem only arises in development mode. In a production build of your app, strict mode is disabled, and the hooks will not run twice explicitly. Although strict mode may cause effects to run twice, I recommend keeping it enabled as it can help identify real issues in your app. However, the decision ultimately rests with you.

I hope this article has successfully resolved your issue. Please feel free to leave a comment below, sharing your thoughts or suggestions. I'm always open to feedback and would love to hear if this article has been helpful to you!