React 18: Performance Issue with Conditional Rendering of Large Lists Using useMemo
I'm experiencing significant performance issues in my React 18 application when conditionally rendering a large list of items based on state. I'm using `useMemo` to optimize rendering, but it doesn't seem to have any effect. My list can grow to over 10,000 items, and when I toggle the view using a button, the application freezes for a noticeable amount of time. Here's a simplified version of my code: ```javascript import React, { useState, useMemo } from 'react'; const ItemList = ({ items }) => { const [showItems, setShowItems] = useState(false); const renderedItems = useMemo(() => { return items.map(item => <li key={item.id}>{item.name}</li>); }, [items]); return ( <div> <button onClick={() => setShowItems(!showItems)}>Toggle Items</button> {showItems && <ul>{renderedItems}</ul>} </div> ); }; const App = () => { const items = Array.from({ length: 10000 }, (v, k) => ({ id: k, name: `Item ${k}` })); return <ItemList items={items} />; }; export default App; ``` I expected the `useMemo` hook to cache the rendered list and prevent unnecessary re-renders when toggling the `showItems` state. However, I'm still seeing a significant lag. I've tried moving the `useMemo` hook outside of the component or even using `React.lazy` to load the list conditionally, but the performance issue persists. When I check the performance tab in Chrome, I notice that the rendering time spikes drastically when the items are displayed. Is there a better way to handle large lists in React without running into performance bottlenecks? Any suggestions would be appreciated!