React Js

What is Reactjs?

ReactJS is a component-based JavaScript library used to build dynamic and interactive user interfaces. It simplifies the creation of single-page applications (SPAs) with a focus on performance and maintainability.

• import React from 'react': Imports React to create components and use JSX.
• function App() { ... }: Defines a functional component called App.
• return ( ... ): Returns JSX that represents the UI (a div with an h1 tag displaying "Hello, World!").
• export default App: Exports the App component so it can be used elsewhere.

React Work ?

React operates by creating an in-memory virtual DOM rather than directly manipulating the browser’s DOM. It performs necessary manipulations within this virtual representation before applying changes to the actual browser DOM.

Here’s how the process works:

1. Actual DOM and Virtual DOM

• Initially, there is an Actual DOM(Real DOM) containing a div with two child elements: h1 and h2.
• React maintains a previous Virtual DOM to track the UI state before any updates.

2. Detecting Changes

• When a change occurs (e.g., adding a new h3 element), React generates a New Virtual DOM.
• React compares the previous Virtual DOM with the New Virtual DOM using a process called reconciliation.

3. Efficient DOM Update

• React identifies the differences (in this case, the new h3 element).
• Instead of updating the entire DOM, React updates only the changed part in the New Actual DOM, making the update process more efficient.