$el
   .doThis
   .end()
   .find( "a" ).first().removeClass( someClass );

$el
   .doThis
   .end()
   .find( "a" ).first().toggleClass( someClass , ( o.direction == "horizontal" ? !isCollapse : event ) );

$el
   .doThis
   .end()
   .find( "a" ).first()[o.direction == 'horizontal' ? 'toggleClass':'removeClass']( someClass )

<div data-direction="horizontal">

if(element.getAttribute("data-direction") == "horizontal")
{
 //TODO: remove or toggle
}

element.setAttribute("data-direction","state");

.toggleClass( someClass , ( o.direction == "horizontal" ? !isCollapse : false ) )