<html>
<head>
<script>
function displayResult()
{
var x=document.getElementById("mySelect").form.id;
alert(x);
}
</script>
</head>
<body>
<form id="form1">
Select your favorite fruit:
<select id="mySelect">
<option>Apple</option>
<option>Orange</option>
<option>Pineapple</option>
<option>Banana</option>
</select>
</form>
<button type="button" onclick="displayResult()">Display id of container form</button>
</body>
</html>