Make multiple firestore queries in a cloud function - node.js

Question

I want to create a scheduled cloud function that is generating employees bonus at the end of each month.
To do that, i need a list of all employees, of all invoices of that user and of all existing bonus, all contained in firestore collections.
So i need 3 firestore collections but can't find any solution on how to do query that in a cloud function.
i tried this for now :
exports.generateBonus = functions.https.onRequest(async (req, res) => {
var listEmployee = [];
var listInvoice = [];
const employeeRef = admin.firestore().collection('employee');
const invoiceRef = admin.firestore().collection('invoice');
const promiseFacture = new Promise((resolve,reject)=>{
return factureRef.get();
})
.then(list_invoice => {
listInvoice = list_invoice.docs.map(doc => {
return doc.data();
});
})
.catch(error => {
console.log("got an error",error);
});
const promiseEmployee = new Promise((resolve,reject)=>{
return employeeRef.get();
})
.then(list_employee => {
listEmployee = list_user.docs.map(doc => {
return doc.data();
});
})
.catch(error => {
console.log("got an error",error);
});
Promise.all([promiseInvoice, promiseEmployee])
.then((values) => {
console.log(values);
return res.send('ok');
})
.catch(error => {
console.log(error);
})
});
But it return me two empty arrays in 1 sec
Does anyone know how to do this ? Thank you

Answer 1

The following, using destructuring assignment syntax, should do the trick:
exports.generateBonus = functions.https.onRequest(async (req, res) => {
const employeesRef = admin.firestore().collection('employee');
const invoicesRef = admin.firestore().collection('invoice');
const [employeesSnapshot, invoicesSnapshot] = await Promise.all([employeesRef.get(), invoicesRef.get()]);
const listEmployees = employeesSnapshot.docs;
const listInvoices = invoicesSnapshot.docs;
//Logging
listEmployees.forEach(snap => {
console.log(snap.data());
});
listInvoices.forEach(snap => {
console.log(snap.data());
});
//...
res.status(200).send(...); //Adapt the ... to a meaningful value
});
Note that the get() method returns a Promise, so you don't need to wrap it in another Promise.
(note that I have added an s to all the collections/snapshots variables names).