Basic jQuery

Basic jQuery

last  2 child add class
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$('ul.menu>li').slice(-2).addClass('last-elements');

lenth 
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  if ($(".active").length) {
    $(".active").dropify();
  }

data background
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$("[data-background]").each(function () {
    $(this).css("background-image", "url(" + e(this).attr("data-background") + ")")
});

isotop active
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// filter items on button click
$('.portfolio-menu').on( 'click', 'button', function() {
  var filterValue = $(this).attr('data-filter');
  $grid.isotope({ filter: filterValue });
});	

// init Isotope
var $grid = $('.grid').isotope({
  itemSelector: '.grid-item',
  percentPosition: true,
  masonry: {
    // use outer width of grid-sizer for columnWidth
    columnWidth: '.grid-item',
  }
});

//for menu active class
$('.portfolio-menu button').on('click', function(event) {
	$(this).siblings('.active').removeClass('active');
	$(this).addClass('active');
	event.preventDefault();
});