run "npm create vite@latest" then replace App.tsx with contents below && npm run dev.

App.tsx

import { useEffect, useState } from "react";

interface MusicKitInstance {
  stuff: string;
}

declare global {
  interface Window {
    MusicKit?: {
      configure: () => Promise<void>;
      getInstance: () => MusicKitInstance | null;
    };
  }
}

const useMusic = () => {
  const [instance, setInstance] = useState(window.MusicKit?.getInstance());

  useEffect(() => {
    if (instance) return;

    (async () => {
      await window.MusicKit?.configure().then(() => {
        setInstance(window.MusicKit?.getInstance());
      });
    })();
  }, []);

  return instance;
};

function App() {
  // lies ftw
  window.MusicKit = {
    configure: () =>
      new Promise((resolve) => {
        setTimeout(() => resolve(), 2000);
      }),
    getInstance: () => ({ stuff: "hello world" }),
  };

  const music = useMusic();

  return (
    <div>{music?.stuff ? <div>{music.stuff}</div> : <div>nothing</div>}</div>
  );
}

export default App;