How to save the content of a div required styles as html file using jquery

I need to a save certain part of my web page as an html package. I can only download the plain html but I don't have any idea how to include external style sheets and images along with it. See my code below.

function downloadInnerHtml(filename, elId, mimeType) {
  var elHtml = document.getElementById(elId).innerHTML;
  var link = document.createElement('a');
  mimeType = mimeType || 'text/plain';
  link.setAttribute('download', filename);
  link.setAttribute('href', 'data:' + mimeType + ';charset=utf-8,' + encodeURIComponent(elHtml));
  link.click();
}

Thanks in advance.