module.js

(function () {
  const packs = new Map();
  let currentPack;

  function dynamicImport(path) {
    let pack = packs.get(path);
    if (!pack) {
      let load;
      const prom = new Promise((resolve) => load = resolve);
      pack = { path, load, prom };
      packs.set(path, pack);

      currentPack = pack;
      //console.warn('start loading', path, pack);
      import(path + '.js');
    }
    return pack.prom;
  }
  function dynamicExport(fun) {
    const pack = currentPack;
    currentPack = null;
    const prom = fun();
    //console.warn('dynamicExport', prom);
    const { load } = pack;
    pack.load = null;
    prom.then(res => load(res));
  }

  window.dynamicImport = dynamicImport;
  window.dynamicExport = dynamicExport
}());