jquery: check the current toggled class

So, this is my code

     $(".heart.fa").click(function() {
          $(this).toggleClass("fa-heart fa-heart-o");

//Wanna check here is its fa-heart or fa-heart-o

           var row = $(this).closest("i");
           var rowId = row.attr("id");
            alert(rowId);

        });

<div>
  <i id= '".$i."' class='heart fa fa-heart-o'></i>
</div>

Want to check inside this function if it's currently fa-heart-o or fa-heart