Javascript prompt and submit

i want to get a value from JavaScript prompt and pass it to input for finally submit it

<form id="createdirForm"><input type="text" name="" id="createdir"/><form>
        <script type="text/javascript">
        function createdir(){
            var newdiame;
            newdiame = prompt('Please input the directory name:', '');
            if (!newdiame) retu;
            $('createdir').newdiame.value = newdiame;
            $('createdirForm').submit();
        }
        </script>