What Is React?

React is an open-source JavaScript library for building user interfaces, originally developed by Facebook (now Meta). It is used to build web applications and is especially well suited to single-page applications (SPAs).

React takes a component-based approach. The parts of an application — its interface elements — are components that can be built, managed and combined independently. This keeps the code modular and easier to maintain.

One of React's key features is the virtual DOM (Document Object Model). Instead of manipulating the real DOM directly, React works on a virtual DOM and updates only the parts that changed, which improves performance.

React is also based on one-way data flow: data moves through the application in one direction (usually from parent to child), which makes the application's behaviour more predictable.

React has a large community and ecosystem and is used by many major projects. Thanks to its sibling project React Native, the same component-based approach can also be used to build mobile apps.