runTransaction firebase async await return undefined

November 6, 2022

with FirebaseFirestoreService I wrote this function to get and update at collection "setting"

export const handleGetOrderId = async () => {
  const settingDocRef = doc(db, "restaurant", "9NmmWP99jNciAqVqLROy", "setting", "9NmmWP99jNciAqVqLROy");

  try {
    await runTransaction(db, async (transaction) => {
      const sfDoc = await transaction.get(settingDocRef);
      if (sfDoc.exists()) {
        transaction.update(settingDocRef, { orderId: increment(1) });

        if (sfDoc?.data().orderId) {
          const new_id = parseFloat(sfDoc?.data().orderId) + 1;
          return String(new_id).padStart(6, "0");
        } else {
          return "000001";
        }
      }
    });
  } catch (e) {
    console.error(e);
  }
};

At frontend side I invoke "handleGetOrderId" like this

const orderId: any = await handleGetOrderId();

But it return "undefined" and I want to see a type of string just like auto-generated-ID of firebase – I was tried so many way to resolve but nothing changed. Someone please tell me where I wrong.

>Solution :

You are not returning anything from handleGetOrderId() function. The resolved promise of runTransaction is the data returned from transaction. Try refactoring the code as shown below:

export const handleGetOrderId = async () => {
  const settingDocRef = doc(db, "restaurant", "9NmmWP99jNciAqVqLROy", "setting", "9NmmWP99jNciAqVqLROy");

  try {
    const trasactionResult = await runTransaction(db, async (transaction) => {
      const sfDoc = await transaction.get(settingDocRef);
      if (sfDoc.exists()) {
        transaction.update(settingDocRef, {
          orderId: increment(1)
        });

        if (sfDoc?.data().orderId) {
          const new_id = parseFloat(sfDoc?.data().orderId) + 1;
          return String(new_id).padStart(6, "0");
        } else {
          return "000001";
        }
      }
    });

    // Add return here
    return transactionResult
  } catch (e) {
    console.error(e);
  }
};

Checkout passing information out of transaction part in the documentation.