​x
 
<html>
<head>
<script type="text/javascript">
function insertBeforeSelected()
  {
  var x=document.getElementById("mySelect");
  if (x.selectedIndex>=0)
    {
    var y=document.createElement('option');
    y.text='Kiwi';
    var sel=x.options[x.selectedIndex];  
    try
      {
      x.add(y,sel); // standards compliant
      }
    catch(ex)
      {
      x.add(y,x.selectedIndex); // IE only
      }
    }
  }
</script>
</head>
<body>
​
<form>
<select id="mySelect">
  <option>Apple</option>
  <option>Pear</option>
  <option>Banana</option>
  <option>Orange</option>
</select>
<input type="button" onclick="insertBeforeSelected()" value="Insert option before selected" />
</form>
​
</body>
</html>
​