Create a non-facet custom fSelect dropdown from any HTML select element

<?php

// Creates a non-facet fSelect from a <select> HTML element:
// <select class="custom-fselect"><option>your options</option></select>
// Add the attribute multiple to show checkboxes:
// <select class="custom-fselect" multiple="multiple"><option>your options</option></select>
// If there is already an fSelect facet on the page, leave out the two lines that include the CSS and JavaScript.    

add_action( 'wp_footer', function() {
  ?>
    <link href="/wp-content/plugins/facetwp/assets/vendor/fSelect/fSelect.css" rel="stylesheet" type="text/css">
    <script src="/wp-content/plugins/facetwp/assets/vendor/fSelect/fSelect.js"></script>
    <script>
      document.addEventListener('DOMContentLoaded', function() {
        fSelect('.custom-fselect');
      });
    </script>
  <?php
}, 100 );