javascript应用：实现复选框全选/全不选切换

shaobo

 经常有人问起在网页里实现多选框的全选功能，今天我就写了这么一个DEMO
<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 >全选与不全选的切换
<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>