选中dropdownlist，并且触发change()事件
------解决方案--------------------
- HTML code
<!DOCTYPE HTML>
<html>
<head>
<meta charset="gb2312" />
<title></title>
<script src="http://code.jquery.com/jquery-latest.js"></script>
<style>
</style>
</head>
<body>
<select>
<option value="1">1-1</option>
<option value="2">1-2</option>
<option value="3">1-3</option>
</select>
<script>
$('select').val(2).change(function(){
alert(123);
}).change()
</script>
</body>
</html>