/**
 * 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);
    }
 }