How to get auto-generated ID of newly created document in a subcollection in Firestore Web V9? Javascript/React

Question

onClick I create a new document within a subcollection with a user's document.

Here's that function:

// Create a new checkout session in the subcollection inside this users document

const createCheckoutSession = async () => {
const collectionRef = collection(db, 'users', currentUser.uid, 'checkout_sessions');
const payload = {
  price: 'price_1JvjWLChfN4TVWbYw2LdDXZZ',
  success_url: window.location.origin,
  cancel_url: window.location.origin
};

await addDoc(collectionRef, payload);

// TODO – Get the newly created document's id. 

};

My goal is to get the newly created document's ID. To then get a field within that document to fire off a redirect to Stripe checkout.

In Firestore Web V8, I'm pretty certain I would use:

collectionRef.onSnapshot(async (snap) => {
  const { sessionId } = snap.data();
   if (sessionId) {
     // We have a session, let's redirect to Checkout
     // Init Stripe
     const stripe = await getStripe();
     stripe.redirectToCheckout({ sessionId });
   }
});

How can I get the newly created document's ID list as // TODO above?

Answer 1

The addDoc function returns a Promise<DocumentReference> to the newly added document. So you cna get the ID with:

const docRef = await addDoc(collectionRef, payload);

console.log(docRef.id);