javascript 複選框，選與不選。

<input type=checkbox name=mm value=a οnclick="checkItem(this, 'mmAll')"><br>
<input type=checkbox name=mm value=b οnclick="checkItem(this, 'mmAll')"><br>
<input type=checkbox name=mm value=c οnclick="checkItem(this, 'mmAll')"><br>
<input type=checkbox name=mm value=d οnclick="checkItem(this, 'mmAll')"><br>
<input type=checkbox name=mm value=e οnclick="checkItem(this, 'mmAll')"><br><br>
<input type=checkbox name=mmAll οnclick="checkAll(this, 'mm')">全選與不全選的切換

<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>