javaScript checkbox 全选/反选及批量删除

<script type="text/javascript">
var a;
function CheckAll(){
if(a==1)
{
for(var i=0;i<window.document.form1.elements.length;i++)
{
var e = form1.elements[i];
e.checked =false;
}
a=0;
}
else
{
for(var i=0;i<window.document.form1.elements.length;i++)
{
var e = form1.elements[i];
e.checked =true;
}
a=1;
}
}
function CheckDel(){
var number=0;
for(var i=0;i<window.document.form1.elements.length;i++)
{
var e = form1.elements[i];
if (e.Name != "CheckBoxAll")
{
if(e.checked==true)
{
number=number+1;
}
}
}
if(number==0)
{
alert("请选择需要删除的项！");
return false;
}
if (window.confirm("你确认删除吗？"))
{
return true;
}
else
{
return false;
}
}
<asp:LinkButton ID="lbDelete" runat="server" OnClientClick="javascript：return CheckDel();" onclick="lbDelete_Click">
<img alt="" src="../images/del.gif" width="16" height="16" border="0" /> 删 除 </asp:LinkButton>
<input id="CheckBoxAll" type="checkbox" onclick="CheckAll()" />
<input id="CheckBox" name="MenuID" type="checkbox" value="<%#Eval("Menu_ID") %>" />

// 删除菜单信息
protected void lbDelete_Click(object sender, EventArgs e)
{
ZZTJ.BLL.SysMenuInfo list = new ZZTJ.BLL.SysMenuInfo();
list.Delete(Request.Form["MenuID"].ToString());
BindMenus();
}