This script makes sure that a Salsa upload page has both a file and a file name before the upload is submitted. An alert is displayed if the file is missing. If the file is missing and the name is empty, then the script uses the basename of the file as the name.

upload_validation.html

<!-- Add client-side validation and defaulting to any upload page. -->
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script type="text/javascript">
    $(document).ready(function() {
        if (/upload_page_KEY=\d+/.test(window.location.href)) {
            $('#upload_page').submit(function () {
                var file = $('*[name=file]').val();
                if (file.length == 0 || file == 'No file selected.') {
                    alert('Please click the Browser button to choose a file before submitting this form.');
                    return(false);
                }
                var name = $('*[name=name]').val();
                if (name.length == 0) {
                    name = file.split('/').reverse()[0];
                    $('*[name=name]').val(name);
                    alert("We've suggested a filename for your file.  Please confirm that the filename is okay, then click the \"Upload File\" button.");
                    return(false);
                }
                return(true);
            })
        }
    });
</script>