javascript - Firebase: doc.data() returns empty object - Stack Overflow

I am working on a Firebase Cloud Function to take all the data in a Firestore collection and put it into the Firebase Realtime Database.

When I run my code (at the bottom of the post) in the Firebase functions emulator, the console.log on line 9 prints a bunch of keys paired to a bunch of empty objects, like so (actual IDs redacted):

{ 
 '<some id>': {},
 '<some other id>': {},
 <bunch of other entries>...
}

This doesn't make sense to me, as the documentation doesn't say why it should return an empty object. My documents do exist, so why can't I get their data?

Here is the source code with the problematic segment mented:

 exports.generateCache = functions.https.onRequest((req, res) => {
    admin.firestore().collection('parts').select().get()
    .then(snapshot => snapshot.docs)
    .then(docs => {
        // this is the problematic segment of code
        var cache = {}
        docs.forEach(doc => {
            cache[doc.id] = doc.data()
        })
        console.log(cache)
        return cache
    })
    .then(cachedData => storeCachedData(cachedData))
    .then(() => {
        res.send('done!')
        res.end()
    })
})

I am working on a Firebase Cloud Function to take all the data in a Firestore collection and put it into the Firebase Realtime Database.

When I run my code (at the bottom of the post) in the Firebase functions emulator, the console.log on line 9 prints a bunch of keys paired to a bunch of empty objects, like so (actual IDs redacted):

{ 
 '<some id>': {},
 '<some other id>': {},
 <bunch of other entries>...
}

This doesn't make sense to me, as the documentation doesn't say why it should return an empty object. My documents do exist, so why can't I get their data?

Here is the source code with the problematic segment mented:

 exports.generateCache = functions.https.onRequest((req, res) => {
    admin.firestore().collection('parts').select().get()
    .then(snapshot => snapshot.docs)
    .then(docs => {
        // this is the problematic segment of code
        var cache = {}
        docs.forEach(doc => {
            cache[doc.id] = doc.data()
        })
        console.log(cache)
        return cache
    })
    .then(cachedData => storeCachedData(cachedData))
    .then(() => {
        res.send('done!')
        res.end()
    })
})

• javascript
• firebase
• google-cloud-firestore
• google-cloud-functions

Share Improve this question Follow edited Aug 16, 2018 at 5:44 Frank van Puffelen 601k8585 gold badges890890 silver badges860860 bronze badges asked Aug 16, 2018 at 5:06 Aditya RAditya R 56744 silver badges1717 bronze badges

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2 Answers 2

Sorted by: Reset to default 3

If you check here of the firebase docs. The code sample for querying multiple docs in a collection is:

db.collection("cities").where("capital", "==", true)
.get()
.then(function(querySnapshot) {
    querySnapshot.forEach(function(doc) {
        // doc.data() is never undefined for query doc snapshots
        console.log(doc.id, " => ", doc.data());
    });
})
.catch(function(error) {
    console.log("Error getting documents: ", error);
});

So in your case, try changing this:

.then(snapshot => snapshot.docs)
.then(docs => {
    // this is the problematic segment of code
    var cache = {}
    docs.forEach(doc => {
        cache[doc.id] = doc.data()
    })

to this

.then(snapshot => {

    var cache = {}
    snapshot.forEach(doc => {
        cache[doc.id] = doc.data()
    })

Firestore Snapshot To Object:

db.collection('collection').then(snapshot =>
    const docsDictionary = (snapshot.docs || []).reduce((prev, doc) => ({ ...prev, [doc.id]: doc.data() }), {})
    // ...do stuff
)