Im trying to make sure that the post request doest happen if the body doesn't contain a subscription object. This is for a shopping cart that allows both one-time payments and subscriptions. The problem is when a user that has a subscription come back to the site to buy a one-time payment item this functions will replace the value in the database with "null" because it creates a new object everything the user checkouts. This is stripe based and trying to avoid using webhooks.

frontend

    let { data, error } = useSWR(
        router.query.session_id
          ? `/api/checkout_sessions/${router.query.session_id}`
          : null,
        fetchGetJSON
      );

      if (error) return <div>failed to load</div>;

      if (state && state.token) {
        const submitStripInfo = async () => {
          if (data == undefined) {
            return;
          }
          const token = JSON.parse(localStorage.getItem("auth")!);
          // console.log("token", );

          axios({
            method: "post",
            url: `${baseUrl}`,
            data: data,
            headers: {
              "Access-Control-Allow-Origin": "*",
              "Access-Control-Allow-Methods": "GET,PUT,POST,DELETE,PATCH,OPTIONS",
              Authorization: "Bearer " + token.token,
            },
          })
            .then((res) => {
              console.log("response", res.data.result);
              data = undefined;
              alert(res.data.result);
            })
            .catch((error) => {
              console.log("error", error);
            });

          if (state.user) {
            console.log("user is here");
            console.log(data);
          }
        };

        submitStripInfo();
      }

Backend code(NODE)

    export const createSubscription = async (req, res) => {
      // console.log("req_data", JSON.stringify(req.body));
      try {
        const subscriptions = JSON.stringify(req.body.subscription, null, 4);
        console.log(subscriptions)
        const user = await User.findByIdAndUpdate(req.user._id, {
          subscriptions: {subscriptions}, 
        },

        

      );
      
        if (!user)
          return res
            .status(400)
            .send("User not found")

            .save();
        console.log("success");
        return res.json({subscriptions,
          result: 'successfuls'});
      } catch (error) {
        console.log(error);
      }
    };