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React useEffect not firing on specific prop change in functional component

👀 Views: 28 💬 Answers: 1 📅 Created: 2025-08-28
react useEffect functional-components JavaScript

I'm performance testing and I'm confused about I'm writing unit tests and I'm deploying to production and Quick question that's been bugging me - I'm working on a React functional component that fetches data based on a prop called `categoryId`. I want to trigger a fetch operation whenever `categoryId` changes, but I'm noticing that the `useEffect` hook isn't firing as expected in some cases. I'm using React 17.0.2 and the `categoryId` prop is coming from the parent component. Here’s a simplified version of my code: ```javascript import React, { useEffect, useState } from 'react'; const DataFetcher = ({ categoryId }) => { const [data, setData] = useState(null); useEffect(() => { const fetchData = async () => { const response = await fetch(`https://api.example.com/data/${categoryId}`); const json = await response.json(); setData(json); }; fetchData(); }, [categoryId]); return <div>{data ? JSON.stringify(data) : 'Loading...'}</div>; }; ``` The problem arises when I change the `categoryId` prop in the parent component. Sometimes the fetch doesn't trigger, and I end up with stale data. I'm logging `categoryId` inside the `useEffect`, and it shows the correct value, but the effect doesn't seem to run. I even tried adding a console log before the fetch to confirm the function execution, but it appears that it’s not running in those instances. I also checked whether the parent component is correctly providing a new reference for `categoryId`, and it indeed is changing as expected. I’ve tried using a key prop with a new value too, but that didn’t help. I’m really puzzled about why the `useEffect` isn’t responding in certain scenarios. Any insights would be greatly appreciated! For context: I'm using Javascript on Linux. How would you solve this? Is there a simpler solution I'm overlooking? This is my first time working with Javascript 3.11. Thanks for your help in advance! Could this be a known issue? I recently upgraded to Javascript stable. Am I approaching this the right way?