How to add a field in Firestore collection using Next.js? - reactjs

Question

I want to add a field in the DB collection after the user has created that is a boolean, like isAdmin: false. Creation of user and adding doc to the DB is working but I'm not sure if I should add it while adding the doc or use updateDoc. I tried this but not working:
await updateDoc(collection(firestore, "Users", User.id), {
isAdmin: false
});
I'm using Next.js and react-firebase-hooks. Thanks in advance for any help.
My current code that is working with user creation and adding the user to Firebase db:
const [signUpForm, setSignUpForm] = useState({
email: "",
password: "",
confirmPassword: "",
});
const [error, setError] = useState(false);
const [createUserWithEmailAndPassword, user, loading, userError] =
useCreateUserWithEmailAndPassword(auth);
const onSubmit = async (event) => {
try {
event.preventDefault();
if (error) setError("");
if (signUpForm.password !== signUpForm.confirmPassword) {
return setError("Password do not match");
}
createUserWithEmailAndPassword(signUpForm.email, signUpForm.password);
} catch (error) {
console.log("Error", error.msg);
}
};
//Sets inputs value in signUpForm useState
const onChange = (event) => {
setSignUpForm((prev) => ({
...prev,
[event.target.name]: event.target.value,
}));
};
//Adds the user to Firebase db
const createUserDocument = async (User) => {
await addDoc(
collection(firestore, "Users"),
JSON.parse(JSON.stringify(User))
);
};
useEffect(() => {
if (user) {
createUserDocument(user.user);
console.log(user);
}
}, [user]);

Answer 1

Collections have no fields. Collections have documents. You have mistake in updateDoc() function.
Here is how you should update documents:
await updateDoc(doc(firestore, "Users", user.uid), {
isAdmin: false
});
In your arrow function, you have another mistake. You're creating a document with random ID. You should use setDoc() instead of addDoc() function.
const createUserDocument = async (user) => {
await setDoc(
doc(firestore, "Users", user.uid),
JSON.parse(JSON.stringify(User))
);
};
Edit:
Assuming your user object is a User not UserCredential it has .uid field not .id. If it is a UserCredential you need first take a user so: user.user.uid