js取select的text值和value值

<script language="javascript">
 function chk(){
  var obj = document.getElementById("sel");
  var str_text = obj.options[obj.selectedIndex].text;
  var str_value = obj.options[obj.selectedIndex].value;

  if (confirm("确定要选择"+strsel+"吗？")){
  }else{
  }
 }
</script>
<select name="sel" onchange="return chk()">
 <option value=1>a001</option>
 <option value=2>a002</option>
 <option value=3>a003</option>
</select>