code: function download(dataUrl, extension, filename) {
  
      // Anchor
      var anchor = document.createElement('a');
      anchor.setAttribute('href', dataUrl);
      anchor.setAttribute('download', filename || 'graph.' + extension);
  
      // Click event
      var event = document.createEvent('MouseEvent');
      event.initMouseEvent('click', true, false, window, 0, 0, 0 ,0, 0,
        false, false, false, false, 0, null);
  
      anchor.dispatchEvent(event);
      delete anchor;
    }
docs: Utilities