JavaScript Applications: Implementing check box selection/all switch

check box

<input Type=checkbox name=mm value=a ><br>
<input Type=checkbox name=mm value=b ><br>
<input Type=checkbox name=mm value=c ><br>
<input Type=checkbox name=mm Value=d ><br>
<input Type=checkbox name=mm value=e ><br><br>
<input Type=checkbox Name=mmall > Full selection and optional switching

<script language=javascript>
function Checkall (e, ItemName)
{
var AA = Document.getelementsbyname (itemname);
for (var i=0; i<aa.length; i++)
aa[i].checked = e.checked;
}
function Checkitem (e, Allname)
{
var all = Document.getelementsbyname (Allname) [0];
if (!e.checked) all.checked = false;
Else
{
var AA = Document.getelementsbyname (e.name);
for (var i=0; i<aa.length; i++)
if (!aa[i].checked) return;
All.checked = true;
}
}
</script>

PS: (Of course, if the full selection of the box is another control such as a button, or a link to anything, the checkbox in the Checkitem Click event can be removed to avoid errors)