React

React is an open-source JavaScript library for building user interfaces, created by Meta (Facebook). Interfaces are built from reusable components, each a function that returns what the UI should look like for the current data, usually written in JSX, an HTML-like syntax inside JavaScript.

When data (state) changes, React updates only the parts of the page that need to change. React is used for single-page web apps, and with frameworks such as Next.js for server-rendered and static websites; React Native uses the same ideas for mobile apps.

import { useState } from "react";

function Counter() {
  const [count, setCount] = useState(0);
  return <button onClick={() => setCount(count + 1)}>Clicked {count} times</button>;
}