通过iframe 实现upload file无刷新
<html>
<head>
</head>
<body>
<form encType="multipart/form-data" method="post" target="hidden_frame">
<input type="file" id="file" name="file"/>
<input type="submit" value="upload file"/>
<br/>
<iframe name="hidden_frame" id="hidden_frame" />
</form>
</body>
</html>
