麻烦各位看个这么一段JS代码

getElementById() 不能返回对象集合．
getElementsByName() 才可以．
但是<div>标签没有name属性的．

解决方案 »

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replycount = reply.length;
是这个
replycount = reply.innerHTML.length;
?
变通一下处理:<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>无标题文档</title>
</head><body onload="GetReply()">
<script type="text/javascript">
var replycount = 0;

function GetReply()
{
var replys = document.getElementsByTagName("div");
for(var i = 0;i < replys.length;i++) if(replys[i].id == "reply") replycount++
alert(replycount);
} function Show(aid)
{
for ( i=0 ; i <replycount ; i++ )
{
if(aid==i) reply[aid].style.display="";
else reply[i].style.display="none";
}
}
</script>
<form>
<div id="book1">留言1内容    <a href="#" id="0" onMouseMove="Show(this.id)">回复 </a> </div>
<div id="reply" style="display:none">回复1 </div>
<div id="book2">留言2内容    <a href="#" id="1" onMouseMove="Show(this.id)">回复 </a> </div>
<div id="reply" style="display:none">回复2 </div>
</form>
</body>
</html>
<html><head>
<meta http-equiv="Content-Type" content="text/html; charset=shift_jis">
<title>新しいページ 1</title>
<script type="text/javascript">
var replycount;
function GetReply()
{
var reply = document.getElementById("reply");
alert(reply.innerHTML)
replycount = reply.length;
alert(replycount);
} function Show(aid)
{
for ( i=0 ; i <replycount ; i++ )
{
if(aid==i)
reply[aid].style.display="";
    else
reply[i].style.display="none";
}
}
</script>
<BODY onload="GetReply()">
<form>
<div id="book1">留言1内容    <a href="#" id="0" onMouseMove="Show(this.id)">回复 </a> </div>
    <div id="reply">1 </div> <div id="book2">留言2内容    <a href="#" id="1" onMouseMove="Show(this.id)">回复 </a> </div>
    <div id="reply">2 </div>
</form>
</BODY>你看看这个
就明白了
哥们
问题还没解决function Show(aid)
{
    for ( a=0 ; a <replycount ; a++ )
    {
        if(aid==a)
{
reply[aid].style.display="";
document.getElementById("book" + aid).style.display="none";
}else{
    reply[a].style.display="none";
}
    }
} 我的意思是说
    <div id="book1">留言1内容<a href="#" id="0" onMouseMove="Show(this.id)">回复 </a> </div>
    <div id="reply" style="display:none">回复1 </div>
    <div id="book2">留言2内容    <a href="#" id="1" onMouseMove="Show(this.id)">回复 </a> </div>
    <div id="reply" style="display:none">回复2 </div> 当鼠标放到 “回复”上的时候
这个时候
相对应的只显示“回复1” id=book1 的DIV 要隐藏可目前的效果是 “回复1"显示出来了
可是 ID=BOOK1 的div 内容也依然存在
看看这个<html>
<head>
<script type="text/javascript">
function Show(o1,o2)
{
var   obj1=document.getElementById(o1);
var   obj2=document.getElementById(o2);
obj1.style.display='none';
obj2.style.display='block';
}
function resetback(ob){document.getElementById(ob).style.display='block';
}
</script>
</head>
<BODY>
<form>
<div id="book1" onmouseover="Show('book1','book2');"   onmouseout="resetback('book1');">留言1内容    <a href="#" id="0">回复 </a> </div>
<br><br><br><br><br><br>
<div id="book2" onmouseover="Show('book2','book1');"   onmouseout="resetback('book2');">留言2内容    <a href="#" id="1">回复 </a> </div>
</form>
</BODY>
</html>
以下测试通过:<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>无标题文档</title>
</head><body onload="GetReply()">
<script type="text/javascript">
var replycount = 0;

function GetReply()
{
var replys = document.getElementsByTagName("div");
for(var i = 0;i < replys.length;i++) if(replys[i].id == "reply") replycount++
alert(replycount);
} function Show(aid)
{
for (i = 0;i <replycount;i++)
{
if(aid==i)
{
reply[aid].style.display = "";
document.getElementById("book" + (i + 1)).style.display = "none";
}
else
{
reply[i].style.display="none";
document.getElementById("book" + (i + 1)).style.display = "";
}
}
}
</script>
<form>
<div id="book1">留言1内容    <a href="#" id="0" onMouseMove="Show(this.id)">回复 </a> </div>
<div id="reply" style="display:none">回复1 </div>
<div id="book2">留言2内容    <a href="#" id="1" onMouseMove="Show(this.id)">回复 </a> </div>
<div id="reply" style="display:none">回复2 </div>
</form>
</body>
</html>
你的两个DIV靠的太近，感觉不出效果，我加了几个换行。