How React JS Works Under the Hood?

React JS is a JavaScript library that works under the hood by using a virtual DOM (Document Object Model) and a reconciliation algorithm to update the user interface of web applications efficiently. Here is a more detailed overview of how React JS works under the hood:

1. Virtual DOM: React JS uses a virtual DOM, which is a lightweight copy of the real DOM. The virtual DOM is an in-memory representation of the user interface, which allows React to manage the state and appearance of the user interface more efficiently.
2. JSX Syntax: React JS uses a syntax called JSX, which is a combination of JavaScript and HTML-like syntax. JSX allows developers to write components in a more intuitive and efficient way, by combining the functionality of JavaScript and the structure of HTML.
3. Component-Based Architecture: React JS is based on a component-based architecture, where each component represents a part of the user interface. Components can be nested within each other to create more complex user interfaces.
4. State Management: React JS uses a state management system to manage the data and state of components. When the state of a component changes, React updates the virtual DOM to reflect the changes.
5. Reconciliation Algorithm: React JS uses a reconciliation algorithm to update the real DOM efficiently. When the state of a component changes, React compares the new virtual DOM to the previous virtual DOM and identifies the differences. It then updates the real DOM only for the parts that have changed, rather than updating the entire user interface.
6. React Fiber: React JS uses a new rendering engine called React Fiber, which is designed to improve the performance and efficiency of the virtual DOM. React Fiber uses a new algorithm for scheduling and managing updates, which makes it possible to handle large and complex user interfaces more efficiently.

In conclusion, React JS works under the hood by using a virtual DOM, JSX syntax, a component-based architecture, state management, a reconciliation algorithm, and a rendering engine called React Fiber. These technologies and algorithms allow React to manage the state and appearance of user interfaces more efficiently, making it an essential tool for modern web development.