jQuery弹出(alert)select选择的值

<script src="jquery-1.9.1.js"></script>
<script type="text/javascript">
$(function () {
$('#btn').click(function () {
alert($('#s option:selected').val());
})
})
</script>
</head>
<body>
<select id="s" multiple="multiple">
<option value="1">商</option>
<option value="2">炳</option>
<option value="3">奇</option>
</select>
<input type="button" id="btn" value="获取" /><br />
</body>