function ctype_digit (text) {
  // http://kevin.vanzonneveld.net
  // +   original by: Brett Zamir (http://brett-zamir.me)
  // -    depends on: setlocale
  // *     example 1: ctype_digit('150');
  // *     returns 1: true
  if (typeof text !== 'string') {
    return false;
  }
  // BEGIN REDUNDANT
  this.setlocale('LC_ALL', 0); // ensure setup of localization variables takes place
  // END REDUNDANT
  return text.search(this.php_js.locales[this.php_js.localeCategories.LC_CTYPE].LC_CTYPE.dg) !== -1;
}

ctype_digit('150');

true