code: function RejectPromise(promise, reason) {
    // Check promise status to confirm that this reject has an effect.
    // Call runtime for callbacks to the debugger or for unhandled reject.
    if (GET_PRIVATE(promise, promiseStateSymbol) === kPending) {
      var debug_is_active = DEBUG_IS_ACTIVE;
      if (debug_is_active ||
          !HAS_DEFINED_PRIVATE(promise, promiseHasHandlerSymbol)) {
        %PromiseRejectEvent(promise, reason, debug_is_active);
      }
    }
    FulfillPromise(promise, kRejected, reason, promiseRejectReactionsSymbol)
  }
docs: ES#sec-rejectpromise RejectPromise ( promise, reason )