Use async forEach loop while fetching data from firestore - node.js

Question

I have firestore data somewhat like this:
"Support": {
"userid":"abcdxyz",
"message": "hello"
}
I am using nodejs to fetch my data and I also want to show the email address and name of the person who sent this message. So I am using following function:
database.collection("support").get().then(async function (collections) {
var data = [];
console.log("data collected");
collections.forEach(async function (collection) {
var temp = {};
var collectionData = collection.data()
var userInfo = await getUserDetails(collectionData.userId)
temp.name = userInfo.name
temp.supportMessage = collectionData.supportMessage
data.push(temp)
console.log("data pushed")
});
console.log("data posted")
return res.status(200).end(JSON.stringify({ status: 200, message: "Support Message fetched successfully.", data: data }))
}).catch(error => {
return res.status(500).end(JSON.stringify({ status: 500, message: "Error: " + error }))
});
Here the sequence of logs is following: data collected, data posted, data pushed
I want the sequence like this: data collected, data pushed (x times), data posted

Answer 1

Use following code:
database.collection("support").get().then(async function (collections) {
var data = [];
console.log("data collected");
for await(let collection of collections){
var temp = {};
var collectionData = collection.data()
var userInfo = await getUserDetails(collectionData.userId)
temp.name = userInfo.name
temp.supportMessage = collectionData.supportMessage
data.push(temp)
console.log("data pushed")
}
console.log("data posted")
return res.status(200).end(JSON.stringify({ status: 200, message: "Support Message fetched successfully.", data: data }))
}).catch(error => {
return res.status(500).end(JSON.stringify({ status: 500, message: "Error: " + error }))
});
OR
Use can use
var promise = Promise.all(collections.map((collection) =>{
...
return await ... //or a promise
}));
promise.then(() => {
console.log("posted");
return res.status(200).end(...);
})

Answer 2

I solved my answer with the help of #estus comment.
Credit: #estus
var data = [];
var tempCollection = [];
collections.forEach(collection => {
tempCollection.push(collection.data());
});
for (collection of tempCollection) {
var temp = {};
var userInfo = await getUserDetails(collection.userId)
temp.name = userInfo.name
temp.supportMessage = collection.supportMessage
data.push(temp)
}
It solved my problem very easily.

Answer 3

I know this might not the OP's exact use case but if you're interested in compiling the results of a collection query into an array, you can still use the .docs property of a QuerySnapshot to obtain the list of items:
...
const userId = <some-id>;
const usersRef = db.collection(`users`)
const usersSnapshot = await usersRef.where("id", "==", userId).get()
if (usersSnapshot.empty) {
console.log('found no matching user ', userId);
return;
}
console.log(`found ${usersSnapshot.size} user records`);
const userResults = []
// this block here doesn't construct the results array before the return statement
// because .foreach enumerator doesn't await: https://stackoverflow.com/q/37576685/1145905
// usersSnapshot.forEach((doc) => {
// // doc.data() is never undefined for query doc snapshots
// //console.log(doc.id, " => ", doc.data());
// userResults.push[doc.data()];
// });
for (user of usersSnapshot.docs) {
// console.log(user.id, " => ", user.data());
userResults.push(user.data());
}
...
A more detailed example is here