code: function _rollbarWindowOnError(client, old, args) {
    if (!args[4] && window._rollbarWrappedError) {
      args[4] = window._rollbarWrappedError;
      window._rollbarWrappedError = null;
    }
  
    globalNotifier.uncaughtError.apply(globalNotifier, args);
    if (old) {
      old.apply(window, args);
    }
  }
docs: Global window.onerror handler