Why is useQuery making my component re-render when I come back to the tab?

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05-10-2024

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Why is useQuery Re-rendering My Component After Switching Tabs?

Have you ever noticed your React component inexplicably re-render after you switch tabs in your browser and come back? This can be a frustrating experience, especially when the component relies on data fetched using useQuery, a hook from the popular react-query library. Let's dive into why this happens and explore the solutions to ensure a smooth user experience.

The Scenario:

Imagine you're building a component that displays a list of users fetched from an API using useQuery. You're expecting the component to render the user data once and remain unchanged, even after switching tabs and returning. However, you notice a strange behavior: the component re-renders every time you return to the tab, potentially causing performance issues and a jarring user experience.

The Code:

import { useQuery } from 'react-query';

const UsersList = () => {
  const { isLoading, error, data } = useQuery('users', () => fetchUsers());

  if (isLoading) return <div>Loading...</div>;
  if (error) return <div>Error fetching data...</div>;

  return (
    <ul>
      {data.map((user) => (
        <li key={user.id}>{user.name}</li>
      ))}
    </ul>
  );
};

const fetchUsers = async () => {
  const response = await fetch('https://api.example.com/users');
  return response.json();
};

The Problem:

The issue lies in the nature of useQuery. useQuery is designed to automatically re-fetch data when certain conditions are met, including:

• Window focus: When the browser window regains focus after being inactive (e.g., when you switch tabs and come back).
• Stale data: If the data becomes outdated based on the specified staleTime and refetchInterval options.

The Solution:

To prevent unnecessary re-renders, you need to configure useQuery to avoid re-fetching when your tab regains focus. Here are two primary solutions:

1. Disable automatic re-fetching:

   const { isLoading, error, data } = useQuery('users', () => fetchUsers(), {
     refetchOnWindowFocus: false, // Disable re-fetching on window focus
   });
   

   This option completely prevents the useQuery hook from re-fetching data when the tab gains focus. It's suitable if you want to keep the data consistent and only update it when you explicitly need to.

2. Increase the staleTime:

   const { isLoading, error, data } = useQuery('users', () => fetchUsers(), {
     staleTime: Infinity, // Set a very long stale time
   });
   

   By setting a very long staleTime, you ensure the data is considered "fresh" for a prolonged period. This will prevent useQuery from automatically re-fetching data until the specified time elapses.

Additional Tips:

• Use useQuery with dependencies: Ensure you're passing the correct dependencies to useQuery, allowing it to track changes and re-fetch data only when necessary.
• Handle errors: Implement appropriate error handling mechanisms to catch and display errors gracefully.
• Optimize fetching: Consider implementing caching strategies (e.g., using useQueries from react-query) to reduce the number of network requests.

By understanding the behavior of useQuery and implementing the correct configuration, you can effectively control re-rendering and prevent unnecessary data fetching, leading to a more performant and user-friendly experience.