Скачать или смотреть Resolving Continuous Rerendering Issues in React with useEffect and useMemo

Learn how to prevent infinite loops in your React application when using the `useEffect` and `useMemo` hooks effectively.
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This video is based on the question https://stackoverflow.com/q/62665781/ asked by the user 'Lumen' ( https://stackoverflow.com/u/1156701/ ) and on the answer https://stackoverflow.com/a/62666115/ provided by the user 'Matt Aft' ( https://stackoverflow.com/u/5442308/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding Continuous Rerendering in React

As a React developer, it's common to run into issues that can hamper the performance of your application. One such issue is continuous rerendering, which can lead to infinite loops of updates. This post aims to demystify the problem of continuous state updates, specifically when using useEffect in conjunction with mapped data.

The Problem: Infinite Loop of State Updates

Imagine you have a React component that fetches weather data. However, you notice that your console is flooded with updates to a variable named forecasts. This constant feedback suggests that your component is rerendering infinitely, which can occur due to how hooks, particularly useEffect, are wired to your state updates.

Here’s a simplified version of the situation you may be facing:

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The issue rises from the way zippedforecasts is calculated. Every rerender is reconstructing zippedforecasts, which unavoidably calls the second useEffect, producing a feedback loop of state changes.

The Solution: Using useMemo

To prevent this endless cycle, you can use the useMemo hook. This hook will memoize the result of zippedforecasts, ensuring it only recalculates when the dependent states change.

Step-by-Step Implementation

Import useMemo: Ensure that you have included useMemo from React.

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Implement useMemo: Wrap your mapped calculation in useMemo.

Here’s how you would set it up:

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Set the Forecasts: Now you can safely update your forecasts in another useEffect.

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Summarizing The Fix

Utilize useMemo to cache values and prevent unnecessary recalculations.

Ensure you add all dependencies used within your hooks, keeping your component optimized and free from performance issues.

Final Thoughts

By applying useMemo, you will effectively avoid an infinite loop of state updates which can bog down your application's performance. Understanding how React's hooks interact with state changes is crucial for building efficient applications. When in doubt, always question how your data structures are being recalibrated and seek optimizations that reduce computational redundancy.

Make sure to implement these strategies in your next project and watch out for potential pitfalls of continuous state changes. Happy coding!