How to Ensure useEffect Runs Only Once on DOM Render in Next.js

Discover how to optimize your Next.js application by controlling `useEffect` execution. Learn to make it run only once on DOM render, preventing unwanted data fetching. --- This video is based on the question https://stackoverflow.com/q/73977399/ asked by the user 'Kartik Fulara' ( https://stackoverflow.com/u/17528248/ ) and on the answer https://stackoverflow.com/a/73977483/ provided by the user 'Sean' ( https://stackoverflow.com/u/11726149/ ) 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: How to make that useEffect run only one time when dom render in Nextjs or can u suggest some better way Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/licensing The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license. If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com. --- How to Ensure useEffect Runs Only Once on DOM Render in Next.js When working with React and Next.js, one of the common challenges developers face is controlling when the useEffect hook runs. A reader recently asked a question about their useEffect being executed multiple times, which led to issues when fetching data from their server. If you've found yourself in a similar situation, you're in the right place! Today, we’ll discuss how to ensure your useEffect runs only once when the DOM renders, along with a better approach to handle data fetching. Understanding the Problem In React, the useEffect hook is designed to run after the render of the component and can be triggered by changes in the state or props. However, in some cases (especially in development mode), this can lead to useEffect being called multiple times unintentionally. Here's the scenario: You have a function that fetches data from the server. Your useEffect is running twice, which can confuse the logic of your code and affect the endpoint responses. Code Example of the Problem Here’s an example of how someone might have structured their code when encountering this issue: [[See Video to Reveal this Text or Code Snippet]] This code might be intended to run getFriends() only once. However, the empty dependency array ([]) can still lead to unexpected re-renders, especially when using React Strict Mode. The Solution — Using Dependency Array To prevent the useEffect from executing multiple times, we can modify our approach by including the token in the dependency array. This allows useEffect to only run when the token changes, ensuring it runs once per relevant change. Revised Code Example Here’s how to implement the solution: [[See Video to Reveal this Text or Code Snippet]] Breakdown of the Solution Adding token to the Dependency Array: By adding token to the dependency array, you are telling React to run the useEffect whenever the token value changes. This avoids the unnecessary multiple calls after the component's first render. Checking for token: The check for the token within the effect ensures that you redirect users who are not authenticated and handle their session appropriately. Conclusion By using the dependency array wisely, you can control the execution of your useEffect, ensuring it runs only under the specified conditions. This practice not only enhances performance but also helps maintain a better user experience in your Next.js applications. If you've faced similar issues, following these steps will provide clarity and efficiency in your component rendering. Implement these changes to your codebase, and you'll be able to manage your effect hooks more effectively in the future!