# File lib/action_view/helpers/upload_progress_helper.rb, line 378
      def upload_progress_update_bar_js(percent=nil)
        progress = upload_progress
        percent ||= case 
          when progress.nil? || !progress.started? then 0
          when progress.finished? then 100
          else progress.completed_percent
        end.to_i

        # TODO do animation instead of jumping
        "$('#{progress_bar_id}').firstChild.firstChild.style.width='#{percent}%'"
      end