Explain new features of React Memo in React v16.6 ?

React memo is a Higher Order Component (HOC) introduced in React v16.6. As the name suggests, Memo API uses the memoization technique to optimize performance and make the application faster. The Memo API avoids unnecessary re-renders in functional components thereby optimizing the performance of the application.

We will see two different examples mentioned below:

Prerequisites:

• NodeJS or NPM
• ReactJS

Syntax:

const MeomizedComponent = React.memo(function MyAnotherComponent(props) {});

Steps to Create the React Application:

Step 1: Create a React App using the following command

npx create-react-app react-memo-tutorial

Step 2: After creating the project (i.e. react-memo-tutorial), move to it by using the following command.

cd react-memo-tutorial

Step 3: Create a file named Header.js in the src directory. 

Project Structure:

Approach 1: Without Using Memo

In this approach we will use a simple form to illustrate component re-rendering works without using React.memo In the Header.js we are simply rendering the Header component with props that displays the props passed from the Parent component.

Example: This example implements the above-mentioned approach

//Header.js
import React from "react";
const Header = (props) => {
    console.log("Rendering header");
    return <div>{props.title}</div>;
};
export default Header;

//App.js
import React, { useState } from "react";
import "./App.css";
import Header from "./Header";
const App = () => {
    console.log("Rendering Form");
    const [name, setName] = useState("");
    return (
        <div className="App">
            <Header title="Input Field" />
            <input
                type="text"
                value={name}
                onChange={(e) => setName(e.target.value)}
            />
        </div>
    );
};
export default App;

Output: Now open http://localhost:3000

Approach 2: Using Memo

Here, the <Header/> component is rendered only once on startup. It is not re-rendered whenever the state changes in the <App/> component. Since we are wrapping up the Header component inside the memo, it is not re-rendering the component when the prop doesn’t change.

Example: This example implements the above-mentioned approach

import React from "react";
const Header = (props) => {
    console.log("Rendering header");
    return <div>{props.title}</div>;
};

// wrapping the component inside memo
export default React.memo(Header); 

Output: Now open http://localhost:3000