CODEWITHSUNDEEP
javascriptreactjsfirebasegoogle-cloud-firestore
JS3
JS3

Reputation: 1829

How do I check if object exist?

I have this firestore document and I wanted to check if doses exist in the document since there are other documents that do not have the doses yet. Hence, retrieving the data inside the doses will cause an error.

enter image description here

This is how I retrieve the specific document:

  useEffect(() => {
    const unsubscribe = firestore
      .collection("users")
      .doc(uid)
      .onSnapshot((snapshot) => {
        const arr = [];
        arr.push({
          ...snapshot.data(),
        });

        setUsers(arr);
      });

    return () => {
      unsubscribe();
    };
  }, []);

To display the data inside the doses. This will only work if doses exist in the document. For other users that does not have this object yet, it would cause an error that says:

TypeError: Cannot read property 'selectedVaccine' of undefined

  {users && users.map((user) => {
             {user.doses.selectedVaccine}    
              })}

Upvotes: 0

Views: 52

Answers (1)

Viet
Viet

Reputation: 12787

You can use optional chaining to avoid this issue like this

{user.doses?.selectedVaccine}

Upvotes: 1

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