What language is React built-in?

React is a JavaScript library for building user interfaces. It was developed by Facebook and is often used for building web applications.

React is built using a combination of JavaScript and JSX, a syntax extension for JavaScript. JSX allows developers to write HTML-like code in their JavaScript files, which makes it easier to build and style components in a declarative way.

While React itself is written in JavaScript, it can be used with a variety of other languages and technologies. For example, it is often used with libraries like Redux for managing application state, or with server-side rendering frameworks like Next.js.

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