React useEffect Not Clearing Timeout When Dependencies Change
I've been researching this but I'm having an scenario with `useEffect` in my React component where I set a timeout but it seems to not clear correctly when dependencies change, causing unexpected behavior..... My component fetches data and sets a loading state based on a timeout. However, when the component re-renders due to a dependency change, the timeout doesn't clear as expected. I see a warning in the console saying: ``` Warning: need to perform a React state update on an unmounted component. ``` Here's the relevant part of my code: ```javascript import React, { useEffect, useState } from 'react'; const MyComponent = ({ fetchData }) => { const [loading, setLoading] = useState(false); useEffect(() => { setLoading(true); const timer = setTimeout(() => { fetchData(); setLoading(false); }, 2000); // Attempting to clear the timeout return () => clearTimeout(timer); }, [fetchData]); return <div>{loading ? 'Loading...' : 'Data Loaded'}</div>; }; export default MyComponent; ``` I have tried ensuring that `fetchData` is a stable function by using `useCallback`, but the scenario continues. The question seems to occur when the component unmounts before the timeout executes. What can I do to ensure that the timeout is cleared properly, and how can I avoid this warning about updating state on an unmounted component? I'm using React 17.0.2. My development environment is Linux. Any help would be greatly appreciated! My development environment is CentOS. What's the best practice here? I'm coming from a different tech stack and learning Javascript. Any feedback is welcome! I'm coming from a different tech stack and learning Javascript. Hoping someone can shed some light on this.