全选 、反选、javascript代码

<form name=aa>
<input type=checkbox>
<input type=checkbox>
<input type=checkbox>
<input type=checkbox>
<input type=checkbox>
<input type=checkbox>
<input type=button value="all" onclick=selectAll(document.aa)>
<input type=button value="other" onclick=selectOther(document.aa)>
<input type=reset value="reset">
<script>
function selectAll(obj)
{
for(var i = 0;i<obj.elements.length;i++)
if(obj.elements[i].type == "checkbox")
obj.elements[i].checked = true;
}
function selectOther(obj)
{
for(var i = 0;i<obj.elements.length;i++)
if(obj.elements[i].type == "checkbox" )
{
if(!obj.elements[i].checked)
obj.elements[i].checked = true;
else
obj.elements[i].checked = false;

}
}
</script>