All JS checkbox Select/Reverse and bulk Delete

Delete Menu Information
protected void Lbdelete_click (object sender, EventArgs e)
{
Zztj. Bll. Sysmenuinfo list = new ZZTJ. Bll. Sysmenuinfo ();
List. Delete (request.form["MenuID"). ToString ());
Bindmenus ();
}

<script type= "Text/javascript Tutorial" >
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 ("Please select the item you want to delete!") ");
return false;
}
if (window.confirm) ("Do you confirm deletion?") "))
{
return true;
}
Else
{
return false;
}
}
<asp Tutorial: LinkButton id= "Lbdelete" runat= "Server" onclientclick= "Javascript:return Checkdel ();" Onclick= "Lbdelete_ Click ">
Delete </asp:LinkButton>
<input id= "Checkboxall" type= "checkbox" onclick= "Checkall ()"/>
<input id= "checkbox" Name= "MenuID" type= "checkbox" Value= "<% #Eval (" menu_id ")%>"/> "