Match the secondar list scroll to main list

app.js

function articleMenuScroll(direction, target){

    var liHeight = 0;
    $('#sidebar-posts li').each(function(index) {
      if($(this).attr('data-id') === target.attr('data-id')){
        return false;
      } else {
        liHeight = liHeight + ($(this).height() + 20);
      }
    });

    if(direction === 'down'){
      $('.intro').scrollTop(liHeight);
    }

    if(direction === 'up'){
      $('.intro').scrollTop('-' + liHeight);
    }
  }