Manually replace sort box with fSelect

test.html

<link href="path/to/fSelect.css" rel="stylesheet" type="text/css">
<script src="path/to/fSelect.js">
<script>
(function($) {
  $(document).on('facetwp-loaded', function() {
    $('.facetwp-sort-select').fSelect();
  });
})(jQuery);
</script>

E.g.

    $(document).on('fs:closed', function(e, wrap) {
        var is_facet = $(wrap).closest('.facetwp-facet').length > 0;

        if (is_facet && ! wrap.classList.contains('multiple')) {
            FWP.autoload();
        }
    });