[Firebase] Cloud Firestore — Add, Set, Update, Delete, Get data

2 min readMar 13, 2019

Set a document

When you use set() to create a document, you must specify an ID for the document to create.

// Add a new document in collection "cities"
db.collection("cities").doc("LA").set({
    name: "Los Angeles",
    state: "CA",
    country: "USA"
})db.collection('cities').doc('BJ').set({
    capital: true
}, { merge: true });

Specify that the data should be merged into the existing document.

db.collection('cities').doc('BJ').set({
    capital: true
}, { merge: true });

Add a document

Let Cloud Firestore auto-generate an ID.

// Add a new document with a generated id.
db.collection("cities").add({
    name: "Tokyo",
    country: "Japan"
});

.add(...) and .doc().set(...) are completely equivalent

// Add a new document with a generated id.
db.collection("cities").doc().set(data);

Update a document

// Set the "capital" field of the city 'DC'
db.collection("cities").doc("DC").update({
    capital: true
});

Update fields in nested objects

// Create an initial document to update.
var frankDocRef = db.collection("users").doc("frank");
frankDocRef.set({
    name: "Frank",
    favorites: { food: "Pizza", color: "Blue", subject: "recess" },
    age: 12
});// To update age and favorite color:
db.collection("users").doc("frank").update({
    "age": 13,
    "favorites.color": "Red"
});

Add server timestamps to your documents, when updating the field.

// Update the timestamp field with the value from the server
db.collection('objects').doc('some-id').update({
    timestamp: firebase.firestore.FieldValue.serverTimestamp()
});

Update elements in an array

var washingtonRef = db.collection("cities").doc("DC");// Atomically add a new region to the "regions" array field.
washingtonRef.update({
    regions: firebase.firestore.FieldValue.arrayUnion("greater_virginia")
});// Atomically remove a region from the "regions" array field.
washingtonRef.update({
    regions: firebase.firestore.FieldValue.arrayRemove("east_coast")
});

Get a document

db.collection("cities").doc("SF")
  .get()
  .then(function(doc) {
    if (doc.exists) {
      console.log("Document data:", doc.data());
    } else {
      // doc.data() will be undefined in this case
      console.log("No such document!");
    }
  }).catch(function(error) {
    console.log("Error getting document:", error);
  });

Get multiple documents from a collection

db.collection("cities").get()
  .then(function(querySnapshot) {
    querySnapshot.forEach(function(doc) {
      // doc.data() is never undefined for query doc snapshots
      console.log(doc.id, " => ", doc.data());
  });
});

Perform simple and compound queries

Simple queries

db.collection("cities").where("capital", "==", true);db.collection("cities").where("state", "==", "CA");db.collection("cities").where("population", "<", 100000);db.collection("cities").where("name", ">=", "San Francisco");db.collection("cities").where("regions", "array-contains", "west_coast");

Compound queries

db.collection("cities").where("state", ">=", "CA").where("state", "<=", "IN");
db.collection("cities").where("state", "==", "CA").where("population", ">", 1000000);