Bookmarkletで任意のJSライブラリをページに埋め込みつつ使いたいとき

bookmarklet_sweatalert.js

javascript: (function () {
  const libs = ["https://cdnjs.cloudflare.com/ajax/libs/sweetalert/2.1.2/sweetalert.min.js"];
  function import_script(urls){
    return Promise.all(urls.map(function(url){
      return new Promise(function(resolve,reject){
        var script = document.createElement('script');
        script.src = url;
        script.onload = resolve;
        document.head.appendChild(script);
      });
    }));
  }
  import_script(libs).then(function(){
    swal("テスト");
  });
})();