Small jQuery script that notices the user when leaving the page without saving after updating a form

form.html

<form action="..." data-unsaved-warning>
    <!-- Something something the form -->
</form>

unsaved-changes.js

$(document).ready(function() {
    $('body').on(
        'change',
        'form[data-unsaved-warning] select, form[data-unsaved-warning] input, form[data-unsaved-warning] textarea',
        function(e) {
            $(e.target).parents('form').attr('data-unsaved-changes', '1');
        }
    );

    $('body').on('submit', 'form[data-unsaved-warning]', function(e){
        $(e.target).data('submitting', '1');
        $(e.target).data('unsaved-changes', '0');
    })

    $(window).bind('beforeunload', function(e){
        var error = '';
        $('form[data-unsaved-changes="1"]').each(function(i, form) {
            if ($(form).data('submitting') !== '1') {
                error = "Warning : you did not save your form !";
            }
        })

        if (error != '') {
            return error;
        }
    });
});