js基础练习---简单划过显示事件

<script type="text/javascript">
var Oli=document.getElementById("lia");
var Odiv=document.getElementById("sub");
var otimer=null;//空的变量
Oli.onmouseover=Odiv.onmouseover=function()
{
Odiv.style.display="block";
clearTimeout(otimer);//清除延时器
};
Oli.onmouseout=Odiv.onmouseout=function()
{
otimer=setTimeout(function()//添加延时器
{
Odiv.style.display="none";
},300)
};
</script>

<div><a href="#" id="lia"></a></div>

<div class="n_subnav" id="sub">
<a href="#"></a>
<a href="#"></a>
</div>