Dynamic importmap

gistfile1.txt

if (HTMLScriptElement.supports && HTMLScriptElement.supports('importmap')) {
  // https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script/type/importmap
  const importMap = {
    imports: {
      lazyload: 'IntersectionObserver' in window
        ? './lazyload.js'
        : './lazyload-fallback.js',
    },
  };

  const im = document.createElement('script');
  im.type = 'importmap';
  im.textContent = JSON.stringify(importMap);
  document.currentScript.after(im);
}