advanced patterns when using memoization in React with useMemo
Hey everyone, I'm running into an issue that's driving me crazy. I've looked through the documentation and I'm still confused about I am working with an scenario with a memoized function in my React app. I'm using React 17.0.2 and I've implemented a custom expensive calculation function that I want to memoize using the `useMemo` hook. However, I am seeing that the function seems to be recalculating more often than expected, leading to performance optimization. Here’s a snippet of my component code: ```javascript import React, { useMemo, useState } from 'react'; const ExpensiveComponent = ({ numbers }) => { const [multiplier, setMultiplier] = useState(1); const calculateSum = (nums) => { console.log('Calculating...'); // Debug statement return nums.reduce((acc, num) => acc + num, 0) * multiplier; }; const memoizedSum = useMemo(() => calculateSum(numbers), [numbers, multiplier]); return ( <div> <p>Sum: {memoizedSum}</p> <button onClick={() => setMultiplier(multiplier + 1)}>Increase Multiplier</button> </div> ); }; ``` In this case, I expect the `calculateSum` function to memoize and only recalculate when either `numbers` or `multiplier` changes. However, it seems to recalculate every time the component renders, even if `numbers` hasn't changed. I verified that the `numbers` array is the same reference on re-renders, and I'm passing in a static array for testing: ```javascript const numbers = [1, 2, 3, 4, 5]; <ExpensiveComponent numbers={numbers} /> ``` Could the re-renders be triggered by some other aspect of the component's state or props? Is there a better way to memoize this calculation to prevent unnecessary recomputations? I've also tried using `React.memo` around `ExpensiveComponent`, but the behavior remains unchanged. Any insights would be appreciated! For context: I'm using Javascript on Windows. Any help would be greatly appreciated! For context: I'm using Javascript on Ubuntu 20.04. Could someone point me to the right documentation? For context: I'm using Javascript on macOS.