Lazy Loading & Code Splitting

What approach should be used for loading polyfills in a code-split application?
async function loadApp() {
  if (!window.IntersectionObserver) {
    await import('intersection-observer');
  }
  if (!window.fetch) {
    await import('whatwg-fetch');
  }
  const app = await import('./app');
  app.init();
}
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