Vertically centering Bootstrap modal window

Question

I would like to center my modal on the viewport (middle) I tried to add some css properties

 .modal { position: fixed; top:50%; left:50%; }   

Answer 1

Based on Arany's answer, but also accounting for page scroll.

(function($) {
    "use strict";
    function positionModals(e) {
        var $this = $(this).css('display', 'block'),
            $window = $(window),
            $dialog = $this.find('.modal-dialog'),
            offset = ($window.height() - $window.scrollTop() - $dialog.height()) / 2,
            marginBottom = parseInt($dialog.css('margin-bottom'), 10);

        $dialog.css('margin-top', offset < marginBottom ? marginBottom : offset);
    }

    $(document).on('show.bs.modal', '.modal', positionModals);

    $(window).on('resize', function(e) {
        $('.modal:visible').each(positionModals);
    });
}(jQuery));