how to update a field value firestore code example
Example 1: firestore set a document
let data = {
name: 'Los Angeles',
state: 'CA',
country: 'USA'
};
// Add a new document in collection "cities" with ID 'LA'
let setDoc = db.collection('cities').doc('LA').set(data);
Example 2: firestore update array
let washingtonRef = db.collection('cities').doc('DC');
// Atomically add a new region to the "regions" array field.
let arrUnion = washingtonRef.update({
regions: admin.firestore.FieldValue.arrayUnion('greater_virginia')
});
// Atomically remove a region from the "regions" array field.
let arrRm = washingtonRef.update({
regions: admin.firestore.FieldValue.arrayRemove('east_coast')
});