React 18: implementing Conditional Rendering of Dynamic Lists Using useMemo and Keys
Could someone explain I'm reviewing some code and Hey everyone, I'm running into an issue that's driving me crazy... I'm working with an scenario with rendering a dynamic list of items in React 18 while utilizing `useMemo` for performance optimization. I have a list of users that I want to display, and this list gets updated whenever a new user is added or an existing user is removed. However, sometimes when I remove a user, React doesn't reflect the changes correctly, and some items seem to flicker or not update as expected. Here's a simplified version of my component: ```javascript import React, { useState, useMemo } from 'react'; const UserList = ({ initialUsers }) => { const [users, setUsers] = useState(initialUsers); const addUser = (newUser) => { setUsers((prevUsers) => [...prevUsers, newUser]); }; const removeUser = (userId) => { setUsers((prevUsers) => prevUsers.filter(user => user.id !== userId)); }; const memoizedUsers = useMemo(() => { return users.map(user => ( <li key={user.id}> {user.name} <button onClick={() => removeUser(user.id)}>Remove</button> </li> )); }, [users]); return ( <div> <ul>{memoizedUsers}</ul> <button onClick={() => addUser({ id: Date.now(), name: 'New User' })}>Add User</button> </div> ); }; export default UserList; ``` The question arises when I try to remove a user. Sometimes, the list briefly displays the removed user's name before finally updating. I suspect it might be related to how I’m managing the keys in the list. I’ve also tried using `React.memo` on the list items and ensured that each user has a unique id, but the scenario continues. I've checked my console and I'm not seeing any warning regarding keys, but I'm wondering if there’s a better way to handle this scenario or if I'm missing something important about how `useMemo` interacts with the component's state updates. Any insights would be greatly appreciated! Am I missing something obvious? For reference, this is a production microservice.