docs: function decamelcase(val, separator) {
      if (separator === void 0) { separator = '-'; }
      if (!is_1.isValue(val))
          return null;
      return val
          .replace(/([a-z\d])([A-Z])/g, '$1' + separator + '$2')
          .replace(/([A-Z]+)([A-Z][a-z\d]+)/g, '$1' + separator + '$2')
          .toLowerCase();
  }