<script language="javascript">
//这个循环实现了原先document.all.formN.id="hoho"; 想要做的事情
for(var i=0;i<document.all.formN.attributes.length;i++){
    if(document.all.formN.attributes[i].name == "id"){
        //alert(document.all.formN.attributes[i].name);
        document.all.formN.attributes[i].value = "hoho";
        }
}

hoho.submit();
</script>

document.all.formN.getAttributeNode("id")

document.all.formN.setAttribute("id","hoho")