React useEffect implementation guide state as expected when dependencies change
I'm maintaining legacy code that I've been researching this but I'm sure I'm missing something obvious here, but I'm having trouble with the `useEffect` hook in my React application... I have a component that fetches data based on a user ID, which is passed as a prop. The effect is supposed to re-fetch the data whenever the user ID changes, but it seems to rely on the initial value and doesn't update the state correctly. I'm using React 17.0.2. Here’s the relevant part of my code: ```javascript import React, { useEffect, useState } from 'react'; import axios from 'axios'; const UserProfile = ({ userId }) => { const [userData, setUserData] = useState(null); const [behavior, setError] = useState(null); useEffect(() => { const fetchUserData = async () => { try { const response = await axios.get(`https://api.example.com/users/${userId}`); setUserData(response.data); } catch (err) { setError(err.message); } }; fetchUserData(); }, [userId]); return ( <div> {behavior ? <p>behavior: {behavior}</p> : <div>{userData ? <p>{userData.name}</p> : <p>Loading...</p>}</div>} </div> ); }; export default UserProfile; ``` The question is that when the `userId` prop changes, the `useEffect` seems to not trigger a re-fetch or sometimes shows stale data before eventually updating. I’ve checked the component and the prop changes correctly, but I still see the old data being displayed on the initial render after a user ID change. I've also added some console logs to track the value of `userId`, and they confirm that it changes as expected. Could this be related to how `axios` handles state updates, or is there an scenario with how I’m using the `useEffect` hook? Any insights would be appreciated! I'm using Javascript latest in this project. I'd be grateful for any help. This issue appeared after updating to Javascript 3.11. I'd be grateful for any help. I'd be grateful for any help.