Firestore, query and update with node.js

Question

I need a cloud function that triggers automatically once per day and query in my "users" collection where "watched" field is true and update all of them as false. I get "13:26 error Parsing error: Unexpected token MyFirstRef" this error in my terminal while deploying my function. I am not familiar with js so can anyone please correct function. Thanks.

const functions = require("firebase-functions");
const admin = require("firebase-admin");
const { snapshotConstructor } = require("firebase-functions/lib/providers/firestore");
admin.initializeApp();

exports.changeWatched = functions.pubsub.schedule("every 24 hours").onRun((context) => {
  const MyFirstRef = admin.firestore().collection("users")
  const queryRef = await MyFirstRef.where("watched", "==", true).get().then((snapshot) => {
    snapshot.docs.forEach( doc => {
      console.log("debug");
      const realId = doc.id
      const MyRef = await admin.firestore().collection("users").doc(realId)
      MyRef.update({watched: false})
    })
  })
});

Answer 1

There are several points to correct in your code:

• You need to return a Promise when all the asynchronous job is completed. See this doc for more details.
• If you use the await keyword, you need to declare the function async , see here .
• A QuerySnapshot has a forEach() method
• You can get the DocumentReference of a doc from the QuerySnapshot just by using the ref property.

The following should therefore do the trick:

exports.changeWatched = functions.pubsub.schedule("every 24 hours").onRun(async (context) => {  // <== See async
    const db = admin.firestore();
    const batch = db.batch();
    const snapshot = await db.collection("users").where("watched", "==", true).get();

    snapshot.forEach(doc => {
        batch.update(doc.ref, { watched: false });
    });

    return batch.commit();  // Here we return the Promise returned by commit()

});

Note that we use a batched write , which can contain up to 500 operations. In case you need to update more docs in one Cloud Function execution, use Promise.all() or cut the batch in several batches.

---

Promise.all() version:

exports.changeWatched = functions.pubsub.schedule("every 24 hours").onRun(async (context) => {  // <== See async
    const db = admin.firestore();

    const snapshot = await db.collection("users").where("watched", "==", true).get();

    return Promise.all(snapshot.docs.map(doc => doc.ref.delete());
    
});