enable sumbit if have file

<!DOCTYPE HTML>
<html lang=en>
<head>
    <title>Belajar Jquery dan Ajax</title>

    <style type="text/css">
    </style>

</head>
<body>
    <form action="#" method="post" enctype="multipart/form-data">
        <input type="file" />
        <input type="submit" id="bubmit" value="Upload" />
    </form>

     <script type="text/javascript" src="jquery.js"></script>
     <script type="text/javascript">
        $(document).ready(function(){
         $('input[type="file"]').change(function(){
          $(this).next().removeAttr('disabled');
         })
         .next().attr('disabled', 'disabled');

        });


    </script>

</body>
<html>