javascript object 파라미터로 사용하기

<script type="text/javascript">
function changeSelect(obj1,obj2) {
    obj1.onchange=function() {}
    if (obj2.name=="big") {
        obj2.onchange=function() { changeSelect(obj2,document.all.namedItem("medium")); }
    } else if (obj2.name=="medium") {
        obj2.onchange=function() { changeSelect(obj2,document.all.namedItem("third")); }
    } else if (obj2.name=="third") {
        obj2.onchange=function() { changeSelect(obj2,document.all.namedItem("forth")); }
    } else if (obj2.name=="forth") {
        obj2.onchange=function() { changeSelect(obj2,document.all.namedItem("big")); }
    }
    for (var i=1; i<obj1.options.length; i++) {
        if (i!=obj1.selectedIndex) {
            obj2.options.appendChild(obj1.options[i].cloneNode(true));
        }
    }
}
</script>
<SELECT name=big onChange="changeSelect(this,document.all.namedItem('medium'))">
    <OPTION>첫번째
    <OPTION value=cost>비용
    <OPTION value=time>시간
    <OPTION value=info selected>정보
    <OPTION value=service>서비스</OPTION></SELECT>
<SELECT name=medium> <OPTION selected>두번째</OPTION></SELECT>
<SELECT name=third> <OPTION selected>세번째</OPTION></SELECT>
<SELECT name=forth> <OPTION selected>네번째</OPTION></SELECT>