React 18: implementing State Updates after API Call in Concurrent Mode
I'm trying to figure out Does anyone know how to I've searched everywhere and can't find a clear answer. I'm experiencing an scenario with state updates in my React 18 application when using Concurrent Mode. I make an API call to fetch user data and then update the state, but it seems that the state sometimes doesn't reflect the fetched data correctly. I've set up a simple component as follows: ```javascript import React, { useEffect, useState } from 'react'; const UserProfile = () => { const [user, setUser] = useState(null); const [loading, setLoading] = useState(true); useEffect(() => { const fetchUserData = async () => { const response = await fetch('https://api.example.com/user'); const data = await response.json(); setUser(data); setLoading(false); }; fetchUserData(); }, []); if (loading) return <div>Loading...</div>; return <div>User: {user.name}</div>; }; export default UserProfile; ``` The scenario I'm working with is that in certain scenarios, the `user` state appears to be `null` or undefined even after the API call completes. I checked the network tab, and the API is returning the correct data. However, when I try to access `user.name`, I sometimes get an behavior saying `want to read property 'name' of null`. I suspect this scenario may stem from how React handles state updates in Concurrent Mode, as I've also noticed that the UI sometimes lags or behaves unexpectedly when switching between components that rely on similar data fetching patterns. I've tried adding a simple check for `user` before rendering: ```javascript if (loading) return <div>Loading...</div>; if (!user) return <div>No user data available</div>; ``` But this doesn’t seem to resolve the scenario. Any insights on how to handle state updates in this specific scenario or how to debug this further? I'm using React 18 with the latest version of React Router, and the scenario continues across different browsers. For context: I'm using Javascript on Linux. What's the best practice here? Hoping someone can shed some light on this. I recently upgraded to Javascript stable. Hoping someone can shed some light on this. I recently upgraded to Javascript LTS.