jQuery(document).ready(function () {
  jQuery('textarea[w3tc-data-validator="regexps"]').change(function () {
    var v = jQuery(this).val();
    var items = v.split("\n");

    for (var n = 0; n < items.length; n++) {
      var regexp = items[n].trim();
      if (regexp.length > 0) {
        try {
          new RegExp(regexp);
        } catch (e) {
          var error = "Contains invalid regexp " + regexp + ", please fix";
          console.log(error);
          jQuery(this)[0].setCustomValidity(error);
          return;
        }
      }
    }

    jQuery(this)[0].setCustomValidity("");
  });
});