How to Fix useFetch Custom Hook Returning Data Twice in React

Learn how to resolve issues with your `useFetch` custom hook in React that leads to double data fetching and null values.
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Fixing the useFetch Custom Hook: Avoiding Double Data Fetching in React

When building applications with React and fetching data using custom hooks, it can be frustrating to encounter issues where the hook returns data multiple times — particularly when one of those returns is null. This problem can disrupt how you present data in components, especially if you're trying to display that data in a table format. In this guide, we'll explore this issue and provide you with effective solutions to fix your useFetch hook to avoid these pitfalls.

Understanding the Problem

You might find that after using your useFetch custom hook, the console logs your fetched data twice:

One instance has the value null.

The other contains the actual data you were trying to fetch.

This can lead to errors when rendering your data. For instance, if null is included in your dataset, it can cause your components to break, resulting in error messages like "Data is null" every time you refresh the page.

The Custom Hook Code

Here’s a snippet of the original custom hook you might be using:

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

Why Is This Happening?

The issue stems from how the internal state of your hook is managed. For instance:

If a fetch request fails (for example, due to network issues), the hook still treats the previous state as valid unless manually reset.

Switching URLs can result in outdated data being retained in the state when a new fetch is completed afterward, leading you to see null alongside valid data.

Solutions to Fix the Hook

1. Check for Data Instead of Trusting Flags

To tackle the problem effectively, it’s essential to manage state better. Here’s a refined way to implement the logic in your component that consumes the useFetch hook:

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

2. Clean Up State Management

You may also enhance your data handling by ensuring that you don't keep invalid data in the state. Clear the data when an error occurs or handle the loading state precisely to avoid stale data mishaps.

3. Consider Advanced State Management Libraries

For larger applications where data fetching and management become complex, consider using libraries like:

SWR: A React Hooks library for data fetching, that comes with caching and validation capabilities.

React Query: A powerful tool that simplifies data fetching and state management, ensuring that your app stays responsive and up to date with the server state.

By implementing these solutions, you can avoid the common pitfalls associated with asynchronous data fetching in React and ensure a smooth user experience without the annoyance of unexpected null data.

Conclusion

Debugging and fixing the useFetch custom hook can significantly improve your React application. By checking for data instead of relying solely on loading indicators or error flags, you can efficiently manage state and ensure that your component displays only valid information. Consider adopting advanced libraries if your data-fetching needs grow more complex. Happy coding!