FacetWP - add a "Load more" button below results

functions.php

<?php

function fwp_load_more() {
?>
<script>
(function($) {
    $(function() {
        if ('object' != typeof FWP) {
            return;
        }

        wp.hooks.addFilter('facetwp/template_html', function(resp, params) {
            if (FWP.is_load_more) {
                FWP.is_load_more = false;
                $('.facetwp-template').append(params.html);
                return true;
            }
            return resp;
        });

        $(document).on('click', '.fwp-load-more', function() {
            $('.fwp-load-more').html('Loading...');
            FWP.is_load_more = true;
            FWP.paged = parseInt(FWP.settings.pager.page) + 1;
            FWP.soft_refresh = true;
            FWP.refresh();
        });

        $(document).on('facetwp-loaded', function() {
            if (FWP.settings.pager.page < FWP.settings.pager.total_pages) {
                if (! FWP.loaded && 1 > $('.fwp-load-more').length) {
                    $('.facetwp-template').after('<button class="fwp-load-more">Load more</button>');
                }
                else {
                    $('.fwp-load-more').html('Load more').show();
                }
            }
            else {
                $('.fwp-load-more').hide();
            }
        });
    });
})(jQuery);
</script>
<?php
}
add_action( 'wp_head', 'fwp_load_more', 99 );

No more need to write code to implement a load more button. The facetwp plugin added this functionality. You can just check this option in the plugin settings.