复选框的全选，多选，全不选，反选

<form name=hrong>
  <input type=checkbox name=All onclick="checkAll('mm')">
  全选
  <br/>
  <input type=checkbox name=mm onclick="checkItem('All')">
  <br/>
  <input type=checkbox name=mm onclick="checkItem('All')">
  <br/>
  <input type=checkbox name=mm onclick="checkItem('All')">
  <br/>
  <input type=checkbox name=mm onclick="checkItem('All')">
  <br/>
  <input type=checkbox name=mm onclick="checkItem('All')">
  <br/>
  <br/>
  <input type=checkbox name=All2 onclick="checkAll('mm2′)">
  全选
  <br/>
  <input type=checkbox name=mm2 onclick="checkItem('All2′)">
  <br/>
  <input type=checkbox name=mm2 onclick="checkItem('All2′)">
  <br/>
  <input type=checkbox name=mm2 onclick="checkItem('All2′)">
  <br/>
  <input type=checkbox name=mm2 onclick="checkItem('All2′)">
  <br/>
  <input type=checkbox name=mm2 onclick="checkItem('All2′)">
  <br/>
</form>
<script LANGUAGE="JavaScript">
 function checkAll(str)
 {
   var a = document.getElementsByName(str);
   var n = a.length;
   for (var i = 0; i < n; i++) a[i].checked = window.event.srcElement.checked;
 }
 function checkItem(str)
 {
   var e = window.event.srcElement;
   var all = eval("document.hrong." + str);
   if (e.checked)
   {
     var a = document.getElementsByName(e.name);
     all.checked = true;
     for (var i = 0; i < a.length; i++)
     {
       if (!a[i].checked)
       {
         all.checked = false;
         break;
       }
     }
   }
   else all.checked = false;
 }
</script>