返回顶部的js实现

(function() {
var backToTopTxt = "返回顶部", backToTopEle = $('<div class="backToTop tops"></div>').appendTo($("body"))
.text(backToTopTxt).attr("title", backToTopTxt).click(function() {
$("html, body").animate({ scrollTop: 0 }, 520);
}), backToTopFun = function() {
var st = $(document).scrollTop(), winh = $(window).height();
(st > 0)? backToTopEle.show(): backToTopEle.hide();
//IE6下的定位
if (!window.XMLHttpRequest) {
backToTopEle.css("top", st + winh - 60);
}
};
$(window).bind("scroll", backToTopFun);
$(function() { backToTopFun(); });
})();