React: Handling Conditional Rendering with useMemo for Performance Optimization - implementing Dependencies
I'm relatively new to this, so bear with me. I'm trying to optimize my React component that conditionally renders a list of items based on user input. I've used `useMemo` to memoize the filtered list and prevent unnecessary re-renders, but I'm running into some unexpected behavior. The filtered list does not seem to update as expected when the user changes the input, and I'm worried that the dependencies I provided to `useMemo` might be incorrect. Here's a simplified version of my component: ```javascript import React, { useState, useMemo } from 'react'; const ItemList = ({ items }) => { const [filter, setFilter] = useState(''); const filteredItems = useMemo(() => { console.log('Filtering items...'); // Debug log to check invocation return items.filter(item => item.includes(filter)); }, [items, filter]); // Dependencies array return ( <div> <input type="text" value={filter} onChange={e => setFilter(e.target.value)} placeholder="Filter items" /> <ul> {filteredItems.map((item, index) => ( <li key={index}>{item}</li> ))} </ul> </div> ); }; export default ItemList; ``` I expected that the `console.log` inside `useMemo` should fire every time I change the input, but it only seems to fire when I change the `items` prop or the `filter` string initially. This behavior makes me think that perhaps `useMemo` is not re-evaluating the memoized value as I anticipated. I've also tried removing `items` from the dependencies, but that led to incorrect filtering when the `items` prop changed. I'm using React 17.0.2 and the functional component pattern. Can anyone explain why the filtering might not be updating as expected, or how I can ensure that my use of `useMemo` is correct in this context? What am I doing wrong?