ReasonJun

useMemo is a hook in React that allows you to memoize the result of a computation. It is used to optimize performance by avoiding unnecessary recalculations of expensive or complex values. When you use useMemo, you provide a function and a dependency array. The function is executed during the rendering phase, and its return value is memoized. The memoized value is then cached and only recalculat..

useCallback is a hook in React that is used to memoize and optimize the creation of a function, especially when passing that function down to child components. It is primarily used to avoid unnecessary re-creation of function references, which can lead to unnecessary re-renders of child components. When a component renders, any functions defined within the component body are recreated each time ..

In React, "shallow compare" and "deep compare" refer to different approaches for comparing the values of props and state to determine if a component should re-render. Shallow Compare: Shallow comparison, which is the default behavior in React, involves comparing the prop and state values by their references. When using shallow comparison, React checks if the references of the current props and s..

React.memo To fix the comparison method used by React.memo for prop comparison, you can provide a custom comparison function as the second argument to React.memo. This custom comparison function determines whether the component should be re-rendered by comparing the previous props with the next props. The custom comparison function receives two arguments: prevProps and nextProps. It should retur..

React.memo is a higher-order component (HOC) provided by React that aims to optimize functional components by preventing unnecessary re-renders. It is similar to the PureComponent class component optimization but designed for functional components. By wrapping a functional component with React.memo, React will automatically memoize the component and only re-render it if its props have changed. I..

App.js code : import { useEffect, useState } from 'react'; import './App.css'; import B from './components/B'; import A from './components/A'; function App() { const [value, setValue] = useState(''); const [posts, setPosts] = useState([]); useEffect(() => { fetch('https://jsonplaceholder.typicode.com/posts') .then((res) => res.json()) .then((posts) => setPosts(posts)); }, []); return ( setValue(..