How to pause Javascript MAP until Firebase Firestore is done? Promise, Async/Await or both

Question

I need to be able to map (or if need be, foreach) over an array of accounts. I want to verify whether or not the account exists in Firebase Firestore before I either update it or add it as a new account. The problem is that the map keeps running and then the Firebase Firestore function finally run. I tried wrapping the Firestore in its own promise but it didn't work. I need everything to run in order. I know my Promise and/or Async/Await are in the wrong places. I'm still learning how to properly use promises and async/await.

    let db = admin.firestore();

    (async () => {
        const accountInfo = [{ accountNumber: 'a' }, { accountNumber: 'b' }, { accountNumber: 'c' }];
        for (let i = 0, j = accountInfo.length; i < j; i++) {
            console.log("i: ", i);
            await Promise.all(
                accountInfo
                    .map(account => {

                        const {accountNumber} = account;
                        console.log(accountNumber);

                        // Firebase - Firestore
                        let docRef = db.collection('accounts').doc(accountNumber);

                        docRef.get().then(function (doc) {

                            console.log("doc.exists ", doc.exists)

                            if (doc.exists) {
                               firebaseUpate();
                            }
                            else {
                               firebaseAdd();
                            }
                        })
                    })
            )
        }
    })();

The results I'm getting:

[0] i:  0
[0] a
[0] b
[0] c
[0] i:  1
[0] a
[0] b
[0] c
[0] i:  2
[0] a
[0] b
[0] c
[0] doc.exists  false
[0] doc.exists  false
[0] doc.exists  false
[0] doc.exists  false
[0] doc.exists  false
[0] doc.exists  false
[0] doc.exists  false
[0] doc.exists  false
[0] doc.exists  false

The results I need: Console.log()

[0] i:  0
[0] a
[0] doc.exists  false
[0] i:  1
[0] b
[0] doc.exists  false
[0] i:  2
[0] c
[0] doc.exists  false

marzelin marzelin · Accepted Answer · 2019-10-28T13:53:36

Remove Promise.all, and just await for doc in for loop:

let db = admin.firestore();

(async () => {
  const accountInfo = [
    { accountNumber: "a" },
    { accountNumber: "b" },
    { accountNumber: "c" }
  ];
  for (let i = 0, j = accountInfo.length; i < j; i++) {
      console.log("i: ", i);
      const { accountNumber } = accountInfo[i];
      console.log(accountNumber);

      // Firebase - Firestore
      let docRef = db.collection("accounts").doc(accountNumber);

      const doc = await docRef.get();

      console.log("doc.exists ", doc.exists);

      if (doc.exists) {
        firebaseUpate();
      } else {
        firebaseAdd();
      }
  }
})();

How to pause Javascript MAP until Firebase Firestore is done? Promise, Async/Await or both

1 Answers