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(); 
}