先上示例动图

熟肉核心代码
scroll(function(direction) {
if (direction == "up") {
jQuery(".scrollcircle").addClass("scroll_up");
} else {
jQuery(".scrollcircle").addClass("scroll_down");
}
});
var cssend = document.querySelector(".scrollcircle");
cssend.addEventListener("webkitAnimationEnd", function() {
jQuery(".scrollcircle").removeClass("scroll_up").removeClass("scroll_down");
}, false);
function scroll(fn) {
var beforeScrollTop = document.body.scrollTop, fn = fn || function() {
};
window.addEventListener("scroll", function() {
var afterScrollTop = document.body.scrollTop, delta = afterScrollTop - beforeScrollTop;
if (delta === 0) {
return false;
}
fn(delta > 0 ? "down" : "up");
beforeScrollTop = afterScrollTop;
}, false);
};
全部代码详见
http://www.dyniao.com/use-javascript-and-css3-add-scroll-effect/