Firebase Firestore get() async/await

Question

can anyone help me to "translate" this example in Typescript with async/await

console.log("start") 
var citiesRef = db.collection('cities');
var allCities = citiesRef.get()
    .then(snapshot => {
        snapshot.forEach(doc => {
            console.log(doc.id, '=>', doc.data().name);
        });
        console.log("end")
    })
    .catch(err => {
        console.log('Error getting documents', err);
    });

I tested some code but i think i do something wrong with the 'forEach' loop.

The result i want in console:

start
Key1 => city1
Key2 => city2
end

Result i get in some of my tests:

start
end
Key1 => city1
Key2 => city2

Thx in advance

score 13 · Accepted Answer · answered Nov 21 '17 at 08:46

Without knowing the types, I assumed base on their usage that they conform to the following interface:

var db: {
    collection(name: 'cities'): {
        get(): Promise<Array<{
            id: string;
            data(): { name: string }
        }>>
    }
};

Given that declaration, an async/await version of the code would be

async function foo() {
    console.log("start")
    var citiesRef = db.collection('cities');
    try {
        var allCitiesSnapShot = await citiesRef.get();
        allCitiesSnapShot.forEach(doc => {
            console.log(doc.id, '=>', doc.data().name);
        });
        console.log("end")
    }
    catch (err) {
        console.log('Error getting documents', err);
    }
}

I want to return a value after `var allCitiesSnapShot = await citiesRef.get();` I m writing in console which working fine but cannot return a value. — Musaddiq Khan, Oct 17 '18 at 10:35
For this answer if I wanted to await `.onSnapshot()` how would the above need to be changed? — virtualLast, May 16 '19 at 15:00

Balaji · Answer 2 · 2021-08-04T18:30:27.833

async/await

async function  allData_firestore(){ <---async
  var db = firebase.firestore();

var allCities = await  db.collection('cities').get(); //<----await

 for(const doc of allCities.docs){
console.log(doc.id, '=>', doc.data());
  }
 
 return allCities 

}

Or promise function

function allData_firestore(){
     return db.collection('cities').doc('0gUdiWNEHiPMZStV9G').get().then(function (doc) {
            if (doc.exists) return doc.data();
            return Promise.reject("No such document");
        }

}

Firebase Firestore get() async/await

2 Answers2

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