滚动返回页面顶部的JS特效

实现动态滚动的步骤：

（1）加入JS代码：

<script language="javascript">

var goto_top_type = -1;

var goto_top_itv = 0;

function goto_top_timer() {

var y = goto_top_type == 1 ? document.documentElement.scrollTop : document.body.scrollTop;

var moveby = 15;

y -= Math.ceil(y * moveby / 100);

if (y < 0) {

y = 0;

}

if (goto_top_type == 1) {

document.documentElement.scrollTop = y;

}

else {

document.body.scrollTop = y;

}

if (y == 0) {

clearInterval(goto_top_itv);

goto_top_itv = 0;

}

}

function goto_top() {

if (goto_top_itv == 0) {

if (document.documentElement && document.documentElement.scrollTop) {

goto_top_type = 1;

}

else if (document.body && document.body.scrollTop) {

goto_top_type = 2;

}

else {

goto_top_type = 0;

}

if (goto_top_type > 0) {

goto_top_itv = setInterval('goto_top_timer()', 50);

}

}

}

</script>

（2）加入链接：

<a href="javascript:void(0)" onclick="goto_top()">【返回顶部】</a>