Скачать или смотреть How to Prevent useEffect from Running Multiple Times in React Hooks

Discover how to optimize your React code by preventing specific `useEffect` calls after the initial render, especially when dealing with AsyncStorage.
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This video is based on the question https://stackoverflow.com/q/63658976/ asked by the user 'randomor' ( https://stackoverflow.com/u/515585/ ) and on the answer https://stackoverflow.com/a/63667399/ provided by the user 'thedude' ( https://stackoverflow.com/u/270592/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

React is a powerful library for building user interfaces, but sometimes even simple tasks can lead to unexpected behavior. One common challenge developers face involves the behavior of the useEffect hook, particularly when working with side effects like storing data in AsyncStorage.

In this post, we will explore how to effectively skip certain useEffect executions on initial renders to improve our application's efficiency. Let's dive into a practical problem: how to prevent AsyncStorage.setItem from being called multiple times on the initial render.

The Problem

When using AsyncStorage to manage logs in our React Native application, we encounter a scenario where setItem is called twice:

When the component mounts, as a result of retrieving logs from AsyncStorage.

Every time the logs state is updated, which inadvertently calls setItem again.

You can see the issue in the following code snippet:

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

The goal is to refine our approach so setItem is not called when initially loading logs. Let's look at the solution.

The Solution

To effectively manage when setItem is executed, we can utilize a reference with useRef. This allows us to indicate whether the logs have been set after the initial render. Here’s the updated code:

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

Key Changes Explained

useRef: We introduced a persistLogsRef using React's useRef to track whether the logs have been set. This prevents setting the logs the first time useEffect runs.

Custom setLogs Function: We created a new setLogs function that updates the logs and sets persistLogsRef.current to true. This marks that logs are now being managed, allowing us to prevent unnecessary setItem calls on initial load.

Conditional in useEffect: The second useEffect checks the value of persistLogsRef.current. We execute setItem only if logs have been externally updated, ensuring efficiency.

Conclusion

By employing useRef, we gain better control over when state updates trigger side effects like AsyncStorage operations. This approach champions clean code and efficiency in our React applications.

Optimizing usage of useEffect not only prevents redundant calls but ensures that our application performs seamlessly and as intended. Happy coding with React! If you have any questions, feel free to leave them in the comments below!