$('.petra-collapse-nav > li.petra_parent_dropdown > a').each(function(){

  var self = $(this);

  self.on('click', function(e){

    e.preventDefault();

    var current = $(this).parent();

    if (current.hasClass('petra_dropnav-active')) {
      current.removeClass('petra_dropnav-active').closest('li').find('.petra-dropdown-menu').slideUp();
    } else {
      $.when(
          $('.petra_dropnav-active').removeClass('petra_dropnav-active').closest('li').find('.petra-dropdown-menu').slideUp().promise()
      ).done(function() {
          current.addClass('petra_dropnav-active').closest('li').find('.petra-dropdown-menu').delay(200).slideDown().promise()
      });
    }

  });
});