下拉框禁止编辑权限

1、实现源码
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>下拉框禁止编辑权限</title>
<script type="text/javascript" src="jquery-1.12.3.js"></script>
<style type="text/css">
    #sel{
		200px;
		height:30px;
	}
</style>
<script type="text/javascript">
    $(document).ready(function(e) {
        var sel = $("#sel option:selected").val();
		alert(sel);
    });
</script>
</head>

<body>
   <select id="sel" tabindex="0" disabled="disabled">
        <optgroup>
             <option value="1">石头</option>
             <option value="2">沙子</option>
             <option value="3">木材</option>
        </optgroup>
   </select>
</body>
</html>
2、实现结果