原生

1.function getScrollTop() {

var scrollTop = 0;

if (document.documentElement && document.documentElement.scrollTop) {

scrollTop = document.documentElement.scrollTop;

} else if (document.body) {

scrollTop = document.body.scrollTop;

}

return scrollTop;

}

jQuery

2.$(window).scroll(function(){

var $scroll_height = $(document).scrollTop();

if($scroll_height > 10){

$("#header").css("background","rgba(0,0,0,.95)")

} else {

$("#header").css("background","")

}

})