Javascript confirm dialog (jquery).js

//Requires jquery and bootsteap 3.2+

var modal_ok = 'Confirm';
var modal_abort = 'Abort';
var ok_text = '';
var modals = 0;
function ModalAlert(title, message, confirm, success_function, size, init_ok_disabled, ok_text) {
    modals++;
    var is_confirm_modal = (confirm !== undefined && confirm != null && confirm === true) ? true : false;
    var size = (size !== undefined && size != null) ? ' ' + size : '';
    var ok_disabled = (init_ok_disabled !== undefined && init_ok_disabled != null) ? init_ok_disabled : false;
    var ok_text = ok_text == null ? modal_ok : ok_text;
    jQuery('body').append('<div class="overlay"></div>');
    jQuery('body').append('<div class="overlay-modal"><div class="modal"><div class="modal-dialog' + size + '"><div class="modal-content"><div class="modal-header"><button type="button" class="close" data-dismiss="modal" aria-hidden="true">&times;</button><h4 class="modal-title">' + title + '</h4></div><div class="modal-body"><p>' + message + '</p></div><div class="modal-footer"><button type="button" class="btn btn-default close-modal-alert" data-dismiss="modal">' + ((is_confirm_modal) ? modal_abort : ok_text) + '</button>' + ((is_confirm_modal) ? '<button type="button" class="btn btn-primary confirm-modal-alert"' + ((ok_disabled) ? ' disabled="disabled" ' : '') + '>' + modal_accept + '</button>' : '') + '</div></div></div></div></div>');
    $('.overlay').css({
        "width": "100%",
        "height": "100%",
        "position": "fixed",
        "top": "0",
        "left": "0",
        "z-index": "1000",
        "background-color": "#626262",
        "opacity": "0.5",
        "filter:": "alpha(opacity=50);"
    });

    $('.overlay-modal .modal').show();

    $('.close-modal-alert').on('click', function () {
        modals--;
        if (success_function != null && confirm == false) {
            success_function();
        }
        $(".overlay").eq(modals).hide().remove();
        $(".overlay-modal").eq(modals).hide().remove();
        return false;
    });

    $('.modal-header .close').on('click', function () {
        modals--;
        $(".overlay").eq(modals).hide().remove();
        $(".overlay-modal").eq(modals).hide().remove();
        return false;
    });

    $('.confirm-modal-alert').on('click', function (e) {
        e.preventDefault();
        modals--;
        $(".overlay").eq(modals).hide().remove();
        $(".overlay-modal").eq(modals).hide().remove();
        success_function();
        return false;
    });

    $('.overlay').on('click', function () {
        $(this).hide();
        $(".overlay-modal").hide();
    });
}

//USE Yes/No
ModalAlert("Delete user?", "Are you sure you want to delete this user", true, function () {
  //Run any javascript here.
});

//Use OK
ModalAlert("Not allowed!", "You dont have access to this page", false, function () {
  //Run any javascript here.
}, 'modal-sm');