✅ Memo in ReactJS

In ReactJS, React.memo() is a higher-order component (HOC) used to optimize functional components by preventing unnecessary re-renders. It memoizes (remembers) the result of a component and re-renders it only if its props change.

📌 Why Use React.memo()?

• Prevents Unnecessary Re-Renders: If a component receives the same props, it won’t re-render.

• Improves Performance: Especially useful for large applications with complex UI.

• Efficient State Management: Reduces resource consumption by optimizing component rendering.

📌 Syntax

jsx
<h1>{value}<div>      import React, { useState } from 'react';const Child = React.memo(({ value }) => {  <h1>{value}<div>      import React, { useState, useCallback } from 'react';const Child = React.memo(({ onClick }) => {  <button <div>      <p>Count: {count}</p>      <Child onClick={handleClick} />      <button onClick={() => setCount(count + 1)}>Increment</button>    </div>  );};export default App;

🛠 Explanation:

• useCallback() → Memoizes the function to prevent unnecessary renders.

• React.memo() → Ensures the Child component does not re-render when the parent re-renders.

📌 When to Use React.memo()?

• Components that receive the same props frequently.

• Large lists or grids with numerous child components.

• Components performing complex calculations or data manipulations.

• Components that don't rely on global state changes.

📌 When Not to Use React.memo()?

• Components that already re-render very quickly.

• Components that frequently change state or props.

• Components that rely on context or use React hooks without optimizations.

✅ Final Thoughts

• Use React.memo() to prevent unnecessary renders.

• Combine it with useCallback for function memoization.

• Always check the component’s performance before using React.memo().