astro/examples/framework-multiple/src/components/ReactCounter.jsx

import React, { useState } from 'react';

/** a counter written in React */
export function Counter({ children }) {
  const [count, setCount] = useState(0);
  const add = () => setCount((i) => i + 1);
  const subtract = () => setCount((i) => i - 1);

  return (
    <>
      <div className="counter">
        <button onClick={subtract}>-</button>
        <pre>{count}</pre>
        <button onClick={add}>+</button>
      </div>
      <div className="children">{children}</div>
    </>
  );
}