/**

* JavaScript脚本实现回到页面顶部示例

* @param acceleration 速度

* @param stime 时间间隔 (毫秒)

**/

function gotoTop(acceleration,stime) {

   acceleration = acceleration || 0.1;

   stime = stime || 10;

   var x1 = 0;

   var y1 = 0;

   var x2 = 0;

   var y2 = 0;

   var x3 = 0;

   var y3 = 0; 

   if (document.documentElement) {

       x1 = document.documentElement.scrollLeft || 0;

       y1 = document.documentElement.scrollTop || 0;

   }

   if (document.body) {

       x2 = document.body.scrollLeft || 0;

       y2 = document.body.scrollTop || 0;

   }

   var x3 = window.scrollX || 0;

   var y3 = window.scrollY || 0;

 

   // 滚动条到页面顶部的水平距离

   var x = Math.max(x1, Math.max(x2, x3));

   // 滚动条到页面顶部的垂直距离

   var y = Math.max(y1, Math.max(y2, y3));

 

   // 滚动距离 = 目前距离 / 速度, 因为距离原来越小, 速度是大于 1 的数, 所以滚动距离会越来越小

   var speeding = 1 + acceleration;

   window.scrollTo(Math.floor(x / speeding), Math.floor(y / speeding));

 

   // 如果距离不为零, 继续调用函数

   if(x > 0 || y > 0) {

       var run = "gotoTop(" + acceleration + ", " + stime + ")";

       window.setTimeout(run, stime);

   }

}