Pulling a variable out of Promise when querying data from Firestore Firebase database - Javascript

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let savedArrayUID = []; let savedArrayEmails = [];

function pullIt(emailSearch) {

    db.collection(collectionName).where('email', '==', emailSearch).get()
        .then((querySnapshot) => {
            querySnapshot.forEach((doc) => {
                savedArrayUID.push(doc.id);
                savedArrayEmails.push(doc.data());
                // doc.data() is never undefined for query doc snapshots

                console.log(doc.id, " => ", doc.data());
                // saved.   push(doc.id);
                return savedArrayUID; 
            })
        });
}

I can query the data from the database but cannot pull the variable out of the scope of the function. I want to use this function to pass through emails to find info of their profile saved in my Database.

I really struggle to understand how Promiseses can help here. I have a feeling this is already solved, but I could not find an answer anywhere.

google-cloud-firestore firebase javascript
1 Answers

There's two steps to this:

  1. Ensure that your data makes it out of your pullIt (as a promise).
  2. Then call that pullIt correctly, waiting for the promise to resolve.

In code, you're missing a top-level return the pullIt code:

function pullIt(emailSearch) {
    // 
    return db.collection(collectionName).where('email', '==', emailSearch).get()
        .then((querySnapshot) => {
            querySnapshot.forEach((doc) => {
                savedArrayUID.push(doc.id);
                savedArrayEmails.push(doc.data());
            })
            return savedArrayUID; // 
        });
}

And then when calling pullIt, you'll need to use either await or then, to ensure pullIt completed before you try to access the result.

So either:

pullIt("yourSearchTeam").then((results) => {
  // TODO: use your results here
})

Or (in an async context):

const results = await pullIt("yourSearchTeam")

// TODO: use your results here
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