.class:hover .subclass0 {display:none;}
.class:hover .subclass {display:block;}
var elements = document.querySelectorAll('.item');
elements.addEventListener('mouseenter', function() {
whatNeedToShow.style.display = 'block';
}, false);
elements.addEventListener('mouseleave', function() {
whatNeedToShow.style.display = 'none';
}, false);