哪位大佬告诉我这一段讲了什么呀,很急
<script>
function $(id) {
return typeof id==='string'?document.getElementById(id):id;
}
var titles=$("notice-tit").getElementsByTagName("li");
var divs=$("notice-con").getElementsByTagName("div");
for(var i=0;i<titles.length;i++){
titles[i].index=i;
titles[i].onmouseover=function () {
for(var j=0;j<titles.length;j++){
titles[j].className="";
divs[j].style.display="none";
}
this.className="tab_current";
divs[this.index].style.display="block";
};
};
</script>