What is the React.js,JavaScript and JavaScript XML

What is the React.js ?
React is a library for building a user interfaces and open source platform.Its used for UI components based.The facebook and meta is created and maintain the React.
It is defined as the single page application.It is a declarative,efficient and flexible in JavaScript.when virtual DOM,which is a ligth weight memory.React is a faster and improve the performance.
Drawback.
1.Learning Curve
2.JSX is complexity
3.It is only used the library

What is the JS ?
JS- JavaScript is a programming language.It is a general-purpose scripting language primarily used to web development to add the interactivity and dynamic behavior to websites. It can be executed the directly web browser.

let dev= Hello;
console.log(dev);

What is a JSX ?
JSX-JavaScript XML is a syntax extension for JavaScript. It is allow the developer to write HTML like a code directly within JavaScript files. JSX is commonly used to liberies like React to describe the structure of user interface in a declarative way.
It is used to define the UI components.

let element=<h1>Hello</h2>;