👀 Views: 0 💬 Answers: 1 📅 Created: 2025-09-06

react useEffect api-fetch JavaScript

I've tried everything I can think of but I've spent hours debugging this and I'm encountering an issue with the cleanup function in my `useEffect` hook when fetching data from an API in a React 18 application. I expect the cleanup to cancel the ongoing fetch request when the component unmounts or when the dependency array changes, but it seems like the request is still completing after unmounting. Here's the code I'm working with: ```javascript import React, { useEffect, useState } from 'react'; const DataFetcher = () => { const [data, setData] = useState(null); const [isLoading, setIsLoading] = useState(true); useEffect(() => { let isMounted = true; // Track if component is mounted setIsLoading(true); const fetchData = async () => { try { const response = await fetch('https://api.example.com/data'); const result = await response.json(); // Update state only if still mounted if (isMounted) { setData(result); setIsLoading(false); } } catch (error) { console.error('Fetch error:', error); if (isMounted) setIsLoading(false); } }; fetchData(); return () => { isMounted = false; // Set to false on cleanup }; }, []); return ( <div> {isLoading ? <p>Loading...</p> : <pre>{JSON.stringify(data, null, 2)}</pre>} </div> ); }; export default DataFetcher; ``` Despite having the `isMounted` flag, I still see logs from the fetch request in the console even after unmounting the component. It's like the cleanup isn't effectively canceling the fetch operation. I've tried using the latest version of React (18.0.0) and ensured that my API endpoint is reachable. Is there a better way to handle this scenario or something I'm missing? I also considered using an AbortController to cancel the fetch request, but I would like to understand if it's possible to manage this properly with the existing setup. Any insights would be greatly appreciated! The stack includes Javascript and several other technologies.