$(document).on('show.bs.modal', '.modal', function () {
    var zIndex = 1040 + (10 * $('.modal:visible').length);
    $(this).css('z-index', zIndex);
    setTimeout(function() {
        $('.modal-backdrop').not('.modal-stack').css('z-index', zIndex - 1).addClass('modal-stack');
    }, 0);
});

$(document).on('hidden.bs.modal', '.modal', function () {
    $('.modal:visible').length && $(document.body).addClass('modal-open');
});

