code: function adjustDropdownHeight( $elem ) {
          var list = $elem.find( ".bselect-option-list" );
          var len = list.find( "li:visible" ).length;
  
          list.innerHeight( parseInt( list.css( "line-height" ), 10 ) * 1.5 * ( len < 5 ? len : 5 ) );
      }
docs: Adjusts the dropdown height of an bselect.