window_send_prop.jsx

function Parent () {
  function save (text) {
    server.save(text); // save text on server
  }

  return <Window onSave={(text) => save(text)}} />;
}

function Window ({ onSave }) {
  const [text, setText] = useState('');

  return <div>
          <label>Text:</label>
          <input type="text" value={text} onChange={(e) => setText(e.target.value)} />
          <button onClick={() => onSave(text)}>Save</button>
      </div>;
}