​x
 
<html>
<head>
<script type="text/javascript">
function getIndex()
  {
  var x=document.getElementById("mySelect")
  alert(x.selectedIndex)
  }
</script>
</head>
<body>
​
<form>
Select your favorite fruit:
<select id="mySelect">
  <option>Apple</option>
  <option>Orange</option>
  <option>Pineapple</option>
  <option>Banana</option>
</select>
<br /><br />
<input type="button" onclick="getIndex()"
value="Alert index of selected option">
</form>
​
</body>
</html>
​