React 18: How to Properly Use useMemo with Complex Calculations in Large Lists?
I'm dealing with This might be a silly question, but I'm working on a React 18 application that displays a large list of items with complex calculations based on user interactions. I want to optimize performance and avoid unnecessary re-renders, so I decided to use `useMemo` for caching the results of expensive calculations. However, I'm working with an scenario where the memoized value seems to be recalculated more often than expected, leading to performance drops and unexpected behaviors. Here's a simplified version of my component: ```javascript import React, { useState, useMemo } from 'react'; const ItemList = ({ items }) => { const [filter, setFilter] = useState(''); const filteredItems = items.filter(item => item.name.includes(filter)); const expensiveCalculation = useMemo(() => { return filteredItems.reduce((acc, item) => acc + item.value, 0); }, [filteredItems]); return ( <div> <input type="text" value={filter} onChange={(e) => setFilter(e.target.value)} placeholder="Filter items..." /> <div>Total Value: {expensiveCalculation}</div> </div> ); }; export default ItemList; ``` The question arises when I type in the filter input field. Instead of only recalculating `expensiveCalculation` when the `filteredItems` change, it seems to be recalculating too frequently, causing the UI to lag. I'm not sure if I'm using `useMemo` correctly or if there's something else affecting the performance. I've tried wrapping the filtering logic in a `useMemo` as well: ```javascript const filteredItems = useMemo(() => { return items.filter(item => item.name.includes(filter)); }, [items, filter]); ``` However, this didn't solve the scenario and it feels like I'm adding complexity without getting the desired performance boost. I also checked if there are any console warnings, but none show up. Is there a best practice for using `useMemo` in situations like this? Any insights would be appreciated! For context: I'm using Javascript on Linux. How would you solve this? This is for a service running on Debian. What are your experiences with this?