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')
});

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")});