code: function _promiseAppendJQuery(obj) {
      const document = obj.document || obj;
      // append to body
      return Promise.resolve()
          .then(() => {
              if (JQUERY_SCRIPT) return JQUERY_SCRIPT;
              return fs.readFile(JQUERY_PATH, 'utf8');
          })
          .then(src => {
              JQUERY_SCRIPT = src;
              const el = document.createElement('script');
              el.type = 'text/javascript';
              el.innerHTML = src;
              el.className = 'jsdom-jquery';
              document.body.appendChild(el);
              return obj;
          });
  }
docs: Instead of appending a script tag with src attribute  (e.g. <script src="/script.js">); this reads the script file and inserts the code within a script tag. This is bec. we cannot know when a dynamically inserted script loads. see https://github.com/tmpvar/jsdom/issues/640#issuecomment-22216965