how to access an outside variable inside a forEach loop

Question

I'm trying to set an value to a variable declared outside from a forEach loop but I'm getting this warn: Identifier 'arr' is never reassigned; use 'const' instead of 'let'.tslint(prefer-const)... When i deploy my code I just get an empty variable

import * as functions from "firebase-functions"
import * as admin from "firebase-admin"

admin.initializeApp()

export const test = functions.https.onRequest(async (req, res) => {

    const stores = await admin.firestore().collection('stores').get()

    let arr: boolean[] = []

    // tslint:disable-next-line: no-void-expression
    await stores.forEach(async (store) => {
        const sales = await store.ref.collection('sales').get()
        arr.push(sales.empty)
    })

    console.log(arr);

    res.status(200).send({
    arr: arr
    })
})

forEach isn't an async function, so you can't await it. You also can't pass an async function to it and expect it to wait on promises within the function. — Doug Stevenson
Actually that await was an desperate attempt to make it work? What is the correct approach to do that Doug? — Caio Reis
Collect all the promises into an array and use Promise.all to wait for all of the results. — Doug Stevenson

Caio Reis Caio Reis · Accepted Answer · 2019-02-13T19:56:02

got the expected results with this code:

export const test = functions.https.onRequest(async (req, res) => {

    const fetchStores = await admin.firestore().collection('stores').get()
    const arr = []

    for (const store of fetchStores.docs) {
        const sales = await store.ref.collection('sales').get()
        arr.push(sales.empty)
    }

    res.status(200).send({arr: arr})

})

how to access an outside variable inside a forEach loop

1 Answers