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>