javascript应用：实现复选框全选/全不选切换

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 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>