how to convert this code to realtime data firestore, this code work well but is not realtime. i need realtime read for my datatable.

    useEffect(() => {
    setLoading(true)
    const date = new Date()
    const januari = new Date(date.getFullYear(), 0)
    const juni = new Date(date.getFullYear(), 5   1, 0)
    const tahunSekarang = date.getFullYear()
    const tahunSetelah = date.getFullYear()   1
    const tahunSebelum = date.getFullYear() - 1

    const pengunjungRef = firebase
        .firestore()
        .doc(
            date >= januari && date <= juni
                ? 'pengunjung/genap'
                : 'pengunjung/ganjil'
        )

    firebase
        .firestore()
        .collectionGroup(
            date >= januari && date <= juni
                ? `${tahunSebelum}_${tahunSekarang}`
                : `${tahunSekarang}_${tahunSetelah}`
        )
        .orderBy(firebase.firestore.FieldPath.documentId())
        .startAt(pengunjungRef.path)
        .endAt(pengunjungRef.path   '\uf8ff')
        .get()
        .then((querySnapshot) => {
            let list = []
            querySnapshot.forEach((doc) => {
                list.push({ id: doc.id, ...doc.data() })
            })
            setData(list)
            setLoading(false)
        })
        .catch((err) => {
            console.error('failed to execute query', err)
        })
}, [])

i try this with onSnapshot from firestore documentation but its not work and show error, i try onSnapshot on simple query its work, but when i try to this query group code its show error.

 firebase
        .firestore()
        .collectionGroup(
            date >= januari && date <= juni
                ? `${tahunSebelum}_${tahunSekarang}`
                : `${tahunSekarang}_${tahunSetelah}`
        )
        .orderBy(firebase.firestore.FieldPath.documentId())
        .startAt(pengunjungRef.path)
        .endAt(pengunjungRef.path   '\uf8ff')
        .onSnapshot((querySnapshot) => {
            let list = []
            querySnapshot.forEach((doc) => {
                list.push({ id: doc.id, ...doc.data() })
            })
            setData(list)
            setLoading(false)
        })
        .catch((err) => {
            console.error('failed to execute query', err)
        })

Error in the console:

firebase_compat_app__WEBPACK_IMPORTED_MODULE_15__.default.firestore(...).collectionGroup(...).orderBy(...).startAt(...).endAt(...).onSnapshot(...).catch is not a function

CodePudding user response：

The onSnapshot() does not return a Promise so you can't add a catch() there. The code should work after removing the .catch().