How can I get specific document data from firestore querysnapshot?

Question

I got a querysnapshot in a function. And want to bring the whole querysnapshot to another function (functionTwo). In functionTwo, I want to get a specific document in the qu

Answer 1

Theres an easy way to do this, each QuerySnapshot has a property docs which returns an array of QueryDocumentSnapshots. See QuerySnapshot documentation.

let citiesRef = db.collection('cities');
let query = citiesRef.where('capital', '==', true).get().then(snapshot => {
  snapshot.docs[0]; // => returns first document
});

Answer 2

let citiesRef = db.collection('cities');
let query = citiesRef.where('capital', '==', true).get()
  .then(snapshot => {
    if (snapshot.empty) {
      console.log('No matching documents.');
      return;
    }  

    snapshot.forEach(doc => {
      console.log(doc.id, '=>', doc.data());
    });
  })
  .catch(err => {
    console.log('Error getting documents', err);
  });

from https://firebase.google.com/docs/firestore/query-data/get-data

Answer 3

You can get an array of the document snapshots by using the docs property of a QuerySnapshot. After that you'll have to loop through getting the data of the doc snapshots looking for your doc.

const docSnapshots = querysnapshot.docs;

for (var i in docSnapshots) {
    const doc = docSnapshots[i].data();

    // Check for your document data here and break when you find it
}

Or if you don't actually need the full QuerySnapshot, you can apply the filter using the where function before calling get on the query object:

const dataKey_1 = "dataKey_1";    
const initialQuery = ref_serial_setting;
const filteredQuery = initialQuery.where('data_name', '==', dataKey_1);

filteredQuery.get()
    .then(querySnapshot => {
        // If your data is unique in that document collection, you should
        // get a query snapshot containing only 1 document snapshot here
    })

    .catch(error => {
        // Catch errors
    });