What is React js for Beginners

React is a JavaScript library for building user interfaces. It was developed by Facebook in 2011 and is now maintained by a community of developers. One of the key features of React is its ability to declaratively describe the structure of a user interface using JSX, a syntax that combines HTML-like elements with JavaScript. This allows developers to create complex UI components in a way that is easy to understand and maintain. React also uses a virtual DOM (Document Object Model) to optimize updates to the UI. When the state of a React component changes, the virtual DOM is used to calculate the minimal set of changes that need to be made to the actual DOM in order to reflect the new state. This helps to improve the performance of React applications by reducing the number of DOM manipulations that need to be made. In addition to its core features, React also has a large ecosystem of supporting libraries and tools. These include libraries for state management (such as Redux and MobX), routing (such as React Router), and testing (such as Jest). React is widely used in the development of web applications, and it has also been used to build native mobile apps using frameworks like React Native. It is a popular choice for developers due to its performance, simplicity, and flexibility.