Add data to Cloud Firestore code example
Example: document.set() firebasefirestore java
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")});