Js返回顶部的方法

 1 if (window.addEventListener) {
 2     window.addEventListener('load', goTopEx);
 3 } else if (window.attachEvent) {
 4     window.attachEvent('onload', goTopEx);
 5 } else {
 6     window.onload = goTopEx;
 7 }
 8 function goTopEx() {
 9     var obj = document.getElementById("goTopBtn");
10     getScrollTop() > 0 ? obj.style.display = "": obj.style.display = "none";
11     function getScrollTop() {
12         return document.documentElement.scrollTop + document.body.scrollTop;
13     }
14     function setScrollTop(value) {
15         if (document.documentElement.scrollTop) {
16             document.documentElement.scrollTop = value;
17         } else {
18             document.body.scrollTop = value;
19         }
20     }
21     window.onscroll = function() {
22         getScrollTop() > 0 ? obj.style.display = "": obj.style.display = "none";
23     }
24     obj.onclick = function() {
25         var goTop = setInterval(scrollMove, 10);
26         function scrollMove() {
27             setScrollTop(getScrollTop() / 1.1);
28             if (getScrollTop() < 1) clearInterval(goTop);
29         }
30     }
31 }