for循环语句如何理解,请帮忙解释下下面这段语句的意思
for (var i = 0; i < oLi.length; i++)
{
oLi[i].index = i;
oLi[i].onmouseover = function ()
{
for (var n = 0; n < oLi.length; n++) oLi[n].className = '';
this.className = 'current';
for (var n = 0; n < oUl.length; n++) oUl[n].style.display = 'none';
oUl[this.index].style.display = 'block';
}
}