javascript로 가져온 값 비교해서 selected시키기

<script>
function chk(frm)
{
for (i=0;i < window.frm.aa.length ;i++ )
 {
 if(window.frm.aa.options[i].value == '02')
  {   
   window.frm.aa.options[i].selected = 'selected';
  }
 }
}
</script>