체크박스 전체선택,해제

<script language="javascript">
function checkAll()
{
 if(document.all.checkbx.checked == 1)
 {
 
  if(document.all.delseq!=null){
   clearAll();
   if(document.all.delseq.length>0){
    document.all.checkbx.checked = 1;
    for(x=0;x<document.all.delseq.length;x++)
    {
     document.all.delseq[x].checked = 1;
    }
   }else{
    document.all.checkbx.checked = 1;
    document.all.delseq.checked = 1;
   }
  }
 }
 else
 {
  if(document.all.delseq!=null){
   if(document.all.delseq.length>0){
    document.all.checkbx.checked = 0;
    for(x=0;x<document.all.delseq.length;x++)
    {
     document.all.delseq[x].checked = 0;
    }
   }else{
    document.all.delseq.checked = 0;
   }
  }
 }
}

function clearAll()
{
 if(document.all.delseq.length>0){
  for(x=0;x<document.all.delseq.length;x++)
  {
   if(document.all.delseq[x].checked == 1)
   {
    document.all.delseq[x].checked = 0;
   }
  }
 }else{
  document.all.delseq.checked = 0;
 }
}
</script>

<input type="checkbox" name="checkbx" value="" onclick="checkAll();">