垃圾checkbox

<input type="checkbox" value="1" id="id">编号1

<input type="checkbox" value="2" id="id">编号2

<input type="checkbox" value="3" id="id">编号3

<button id="btnTest" onclick="return t()">testCount</button>
<button id="btnTest" onclick="return showAllChk('id')">showAll</button>
<button id="btnTest" onclick="return myCheckAll('id')">全选ID</button>
<button id="btnTest" onclick="return unCheckAll('id')">全不选ID</button>
<button id="btnTest" onclick="return checkId('id')">检查ID</button>
<input type="checkbox" value="" id ="ALL" name="ALL" onClick = "checkAll('ALL','id')"/><label for="ALL">全选</label>

<script type="text/javascript">
 function t(){
  alert(document.all.id.length);
 }

 function showAllChk(chkId)
 {
  var chkobj = eval("document.all." + chkId);
  for(var i=0;i<chkobj.length;i++){
   alert(chkobj[i].value);
  }
 }
 
 function checkAll(allChkId,chkId){
  var chkObj = eval("document.all." + chkId);
  var chkAllObj = eval("document.all." + allChkId);
  for (var i=0;i<chkObj.length;i++){
   chkObj[i].checked = chkAllObj.checked;
  }
 }

 function myCheckAll(chkId)
 {
  var chkobj = eval("document.all." + chkId);
  for(var i=0;i<chkobj.length;i++){
   chkobj[i].checked = true;
  }
 }

 function unCheckAll(chkId)
 {
  var chkobj = eval("document.all." + chkId);
  for(var i=0;i<chkobj.length;i++){
   chkobj[i].checked = false;
  }
 }
 
 function checkId(chkId)
 {
  var chkobj = eval("document.all." + chkId);
  var result = false;
  for(var i=0;i<chkobj.length;i++){
   if (chkobj[i].checked){
    result = true;
    break;
   }
  }
  if (!result){
   alert("请至少选一个编号");
   chkobj[0].focus();
  }
  return result;

 }
</script>