React 18: Issues with useMemo for Expensive Computations in a List Component
I'm facing a performance issue in my React 18 application where I use `useMemo` to optimize expensive computations for rendering a list of items. The problem arises when I try to filter and sort this list based on user input. Despite implementing `useMemo`, I notice that the list is being re-evaluated on every render, which seems to defeat the purpose of using `useMemo`. Here's a simplified version of my component: ```jsx import React, { useState, useMemo } from 'react'; const ItemList = ({ items }) => { const [filter, setFilter] = useState(''); const [sortOrder, setSortOrder] = useState('asc'); const filteredItems = useMemo(() => { return items .filter(item => item.name.includes(filter)) .sort((a, b) => { if (sortOrder === 'asc') return a.name.localeCompare(b.name); return b.name.localeCompare(a.name); }); }, [items, filter, sortOrder]); return ( <div> <input type="text" value={filter} onChange={(e) => setFilter(e.target.value)} placeholder="Filter items" /> <button onClick={() => setSortOrder(order => order === 'asc' ? 'desc' : 'asc')}>Toggle Sort</button> <ul> {filteredItems.map(item => <li key={item.id}>{item.name}</li>)} </ul> </div> ); }; ``` I expected `filteredItems` to only recalculate when `items`, `filter`, or `sortOrder` change, but I find that the list re-renders unnecessarily, impacting performance, especially with a large number of items. I've confirmed that `items` itself is not changing reference due to any parent component updates. Is there something I might be missing about `useMemo` or best practices for optimizing performance in React lists? Any suggestions for improving this implementation would be greatly appreciated.