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<html>
<head>
<script src="http://code.jquery.com/jquery-latest.js"></script>
</head>
<body>
<select id="type">
<option disabled selected>Выберите тип</option>
<option value="1">Тип 1</option>
<option value="2">Тип 2</option>
</select>
<script type="text/javascript">
$("#type").change(function(){
switch($('#type').val()) {
case "1": alert(1); break;
case "2": alert(2); break;
default: alert($('#type').val()); break;
}
});
</script>
</body>
</html>