Tu masz przykład z użycie Js i jQuery z mojej stronki.
$(window).scroll(function()
{
if((pageYOffset > 40)&&(window.innerWidth > 620))
{
$(".top-contact").css("display","none");
$(".menu").css({"position" : "fixed","top":"0","width":"100%","border":"1px solid black","box-shadow":"0px 4px 2px black"});
$(".background-images-container").css("margin-top","90px");
}
else if(window.innerWidth > 620 )
{
$(".top-contact").css("display","block");
$(".menu").css({"position":"static","border":"none"});
$(".background-images-container").css("margin-top","0");
}
});