An example of an immutable transformation of a deep object.

DeepTransformation.js

const restaurant = {
  clientRequests: {
    "1": {
      "drinks": [
        {id: 3, name: "Beer", quantity: 4} 
      ]
    },
    "2": {
      "appetizers": [
        {id: 1, name: "Onion rings", quantity: 2},
        {id: 2, name: "Cheese and bacon fries", quantity: 1}
      ],
      "drinks": [
        {id: 3, name: "Beer", quantity: 3} 
      ]
    }
  },
  isOpen: true,
  totalTables: 7
}

// We want to add one more ration of fries for table number 2

const alteredRestaurant = {...restaurant, 
  clientRequests: {...restaurant.clientRequests,
    "2": { ...restaurant.clientRequests["2"],
      "appetizers": restaurant.clientRequests["2"]["appetizers"].map(appetizer => 
         (appetizer["id"] === 2) ? {...appetizer, quantity: appetizer.quantity+1} : appetizer)
    }
  }
}