javascript实现渐隐渐现上下循环滚动

在用jquery无缝自适应高度隔时上下滚动一文中我们实现了用jquery来实现一种较为华丽的网站信息或公告的上下滚动，本文介绍一种用javascript代码实现的上下循环滚动，滚动时还能让被显示的第一条信息渐现效果。(在dscuzX2中工作，请看下文演示，不知道在wordpress中是否正常)

<script type="text/javascript">
function H$(i) {return document.getElementById(i)}
function H$$(c, p) {return p.getElementsByTagName(c)}
var slider = function () {
function init (o) {
this.id = o.id;
this.at = o.auto ? o.auto : 3;
this.o = 0;
this.pos();
}
init.prototype = {
pos : function () {
clearInterval(this.__b);
this.o = 0;
var el = H$(this.id), li = H$$('li', el), l = li.length;
var _t = li[l-1].offsetHeight;
var cl = li[l-1].cloneNode(true);
cl.style.opacity = 0; cl.style.filter = 'alpha(opacity=0)';
el.insertBefore(cl, el.firstChild);
el.style.top = -_t + 'px';
this.anim();
},
anim : function () {
var _this = this;
this.__a = setInterval(function(){_this.animH()}, 20);
},
animH : function () {
var _t = parseInt(H$(this.id).style.top), _this = this;
if (_t >= -1) {
clearInterval(this.__a);
H$(this.id).style.top = 0;
var list = H$$('li',H$(this.id));
H$(this.id).removeChild(list[list.length-1]);
this.__c = setInterval(function(){_this.animO()}, 20);
//this.auto();
}else {
var __t = Math.abs(_t) - Math.ceil(Math.abs(_t)*.07);
H$(this.id).style.top = -__t + 'px';
}
},
animO : function () {
this.o += 2;
if (this.o == 100) {
clearInterval(this.__c);
H$$('li',H$(this.id))[0].style.opacity = 1;
H$$('li',H$(this.id))[0].style.filter = 'alpha(opacity=100)';
this.auto();
}else {
H$$('li',H$(this.id))[0].style.opacity = this.o/100;
H$$('li',H$(this.id))[0].style.filter = 'alpha(opacity='+this.o+')';
}
},
auto : function () {
var _this = this;
this.__b = setInterval(function(){_this.pos()}, this.at*1000);
}
}
return init;
}();
</script>
<script type="text/javascript">
new slider({id:'slider'})
</script>

你要做的就是在你想要该效果的地方增加<ul id="slider"><li>要滚动的信息</li></ul>