Execute code only after a non-thenable, asynchronous function completes

Question

I want to execute my code only after flexslider() function completes. The problem is that flexslider() does not return a promise or other thenable.

So I applied this nasty workaround with setTimeout that I want to get rid of. How can I refactor this and execute my code only after flexslider is initialized?

(function($) {
    $('.flexslider').flexslider({
        animation: "slide",
        controlNav: false
    });
    setTimeout(function() {
        var $navBar = $('.primary-nav');
        var navbarPosition = $navBar.offset().top;
        $(window).scroll(function() {
            var scrollPosition = $(this).scrollTop();

            if (scrollPosition >= navbarPosition) {
                $navBar.addClass('navbar-fixed');
            } else {
                $navBar.removeClass('navbar-fixed');
            }
        });
    }, 1000);
})(jQuery);   

Answer 1

How about using start:

$('.flexslider').flexslider({
  animation: "slide",
  controlNav: false,
  start: function(){
    // do something....
  }
});

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