add a field to a firebase collection programmatically 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: 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")});