能否简化一下这个js。
下面的js能否合成一个？
程序代码：<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
<TITLE> New Document </TITLE>
<META NAME="Generator" CONTENT="EditPlus">
<META NAME="Author" CONTENT="">
<META NAME="Keywords" CONTENT="">
<META NAME="Description" CONTENT="">
<style>
body {
font-family: "Verdana","宋体";
font-size:12px;
margin:0;
padding:0;
}
a,a:visited {
color:#666666;
text-decoration:none;
}
a:hover{
color:#ff0000;
text-decoration:none;
}
ul, li{
color:#999999;
line-height:20px;
}
ol{ margin-top:6px;
margin-left:16px;
padding:0;
list-style-type:none;
color:#666666;
}
table, td ,th{
margin:0;
padding: 0;
border:0;
font-size:12px;
}
img{ border:0;
padding:0;
margin:0;
}
.date{
float:right;
margin-right:12px;
}
#struct{
margin:auto;
width:1000px;
}
#left_bg{
background:url(../img/left_bg.jpg) #f4f4f4 repeat-x top left; }
.litop{ margin-top:10px;}
.view{ background:url(../img/view_bg1.jpg) no-repeat; padding-top:18px; padding-left:2px;}
.viewfont a{ color:#0b0b0b; font-size:11px; font-weight:bold;line-height:20px;}
.viewfont a:visited{ color:#0b0b0b; }
.viewfont a:hover{ color:#ff0000; }
.kuang_white{ border:1px #fff solid; background-color:#FFFFFF;}
</style>
</HEAD>
<BODY>
<table cellSpacing=0 cellPadding=0 align=center border=0 >
<tr>
<td class=left_bg vAlign=top width="24%">
<table cellSpacing=0 cellPadding=0 width="100%" border=0>
<tr>
<td class=bt onmouseover="this.className='bt_mouseover'" onclick=this.blur(); onmouseout="this.className='bt_mouseout'"><A href="#" onclick="showLayer(); return false;">报表下载、上报</A> </td>
</tr>
<tr>
<td vAlign=top>
<div class="zibt" id="aa" style="display:none">
<UL>
<LI><A href="#">隐患月报</A></LI>
<LI><A href="#">检查报表</A></LI>
<LI><A href="#">事故报表</A></LI></UL>
</div>
</td>
</tr>
<tr>
<td height=4></td>
</tr>
<tr>
<td class=bt onmouseover="this.className='bt_mouseover'" onclick=this.blur(); onmouseout="this.className='bt_mouseout'"><A href="#">组织台帐</A></td>
</tr>
<tr>
<td height=4></td>
</tr>
<tr>
<td class=bt onmouseover="this.className='bt_mouseover'" onclick=this.blur(); onmouseout="this.className='bt_mouseout'"><A href="#" onclick="showLayer2(); return false;">工作计划</A> </td>
</tr>
<tr>
<td vAlign=top>
<div class="zibt" id="bb" style="display:none">
<UL>
<LI><A href="#">年工作计划</A></LI>
<LI><A href="#">月工作计划</A></LI>
</UL>
</div>
</td>
</tr>
</table>
<script type="text/javascript">
var $ = function(id){return document.getElementById(id)}
function showLayer()
{
if($("aa").style.display == "none")
{
$("aa").style.display = "block"
}
else
{
$("aa").style.display = "none"
}
}
</script>
<script type="text/javascript">
var $ = function(id){return document.getElementById(id)}
function showLayer2()
{
if($("bb").style.display == "none")
{
$("bb").style.display = "block"
}
else
{
$("bb").style.display = "none"
}
}
</script>
</BODY>
</HTML>
