1let initialData = {
2  name: 'Frank',
3  age: 12,
4  favorites: {
5    food: 'Pizza',
6    color: 'Blue',
7    subject: 'recess'
8  }
9};
10
11let updateNested = db.collection('users').doc('Frank').update({
12  age: 13,
13  'favorites.color': 'Red'
14});