JAVASCRIPT 셀렉트박스 선택된 값 가져오기

var vElement = document.getElementById('tch_info');
var vIndex = vElement.selectedIndex;
 
opener.document.writeFrm.teacher_id.value = vElement.options[vIndex].value;
opener.document.writeFrm.teacher_name.value = vElement.options[vIndex].text;