What is React js?

            React.js is a popular JavaScript library for building user interfaces. It was developed by Facebook and is now maintained by a large community of developers.              React is known for its ability to create reusable, composable, and easily maintainable components, which makes it a great choice for building large and complex web applications. One of the key features of React is the Virtual DOM. The Virtual DOM is a lightweight representation of the actual DOM, which allows for efficient updates and minimal re-rendering.   React uses the Virtual DOM to determine which components need to be updated when the state of your application changes. This makes React apps fast and responsive, even when dealing with large amounts of data. Another great feature of React is its ability to create reusable components.  React components are small, self-contained units of code that can be easily reused throu...