Unexpected re-renders in React due to state updates in child components
I'm upgrading from an older version and Quick question that's been bugging me - I need some guidance on I've been banging my head against this for hours. Quick question that's been bugging me - I'm sure I'm missing something obvious here, but I'm facing an issue where a parent component in my React application is re-rendering unexpectedly whenever the state of a child component changes. I'm using React 17 and functional components with hooks. The parent component maintains a piece of state that should not be affected by the internal state of the child component. However, each time the child updates its state, the parent re-renders, causing performance issues as the parent performs expensive calculations on each render. Here’s a simplified version of my code: ```javascript import React, { useState } from 'react'; const ParentComponent = () => { const [parentState, setParentState] = useState(0); const handleParentUpdate = () => { setParentState(prev => prev + 1); }; console.log('Parent rendered'); return ( <div> <h1>Parent State: {parentState}</h1> <button onClick={handleParentUpdate}>Update Parent</button> <ChildComponent /> </div> ); }; const ChildComponent = () => { const [childState, setChildState] = useState(0); const handleChildUpdate = () => { setChildState(prev => prev + 1); }; console.log('Child rendered'); return <button onClick={handleChildUpdate}>Update Child</button>; }; export default ParentComponent; ``` When I click the button in the child component to update its state, the parent logs 'Parent rendered', indicating that it re-renders as well. I expected only the child component to render. I have tried wrapping the child component in `React.memo()`, but it hasn't resolved the issue. I’m also aware that if the parent component’s state changes, it will re-render the entire tree. Is there a way to isolate the re-renders better, or is there something I'm missing in terms of best practices when managing state between parent and child components? Any advice or solutions would be greatly appreciated! What am I doing wrong? I'm working on a application that needs to handle this. How would you solve this? I'm developing on Linux with Javascript. I'm on Windows 11 using the latest version of Javascript. The project is a microservice built with Javascript. Am I missing something obvious? Am I approaching this the right way? What would be the recommended way to handle this?