React JS is a JavaScript library used to build user interfaces (UI) for websites and web applications.

It was developed by Facebook (now Meta).

Example:

websites and apps that use React include Facebook and Instagram.
Why do we use React JS?

• To build interactive websites.
• To create reusable UI components.
• To update webpage content efficiently.
• To manage user interactions, like button clicks.

React JS Example:

function App() {
return (

Hello Sathish!

Welcome to React JS.

);
}

export default App;

Output:

Hello Sathish!
Welcome to React JS.

Here:

• function App() — creates a React component.
• return — specifies the UI to display.

• — displays a heading.

• export default App — allows the component to be imported into another file.