怎样取select option 中的值？

  <select name="test">
     <option value="">请选择</option>                
     <option value="1">123</option>                
     <option value="2">456</option>                
     <option value="3">789</option>
   </select>
   var selIndex = document.all.test.selectedIndex;
   var selText = document.all.test.options[selIndex].text;
   var selValue = document.all.test.options[selIndex].value;