Create Specific Inventory Type

Part of the Introduction To TypeScript section of Coddy's JavaScript journey — lesson 66 of 73.

Challenge

Easy

You are provided with the following from the previous challenge:

The generic interface InventoryItem<T> with properties id, quantity, and details
The generic function addItem that adds items to inventory arrays
The generic function findItemById that searches for items by ID

Create two specific object types and their corresponding inventory item type aliases:

Create a type alias Book with properties:
- title of type string
- author of type string
Create a type alias Electronic with properties:
- brand of type string
- model of type string

Create type aliases for specific inventory items:

Create BookItem as InventoryItem<Book>
Create ElectronicItem as InventoryItem<Electronic>

Create concrete inventory items using your new type aliases:

Create specificBook of type BookItem with:
- id: 100
- quantity: 8
- details: { title: "Clean Code", author: "Robert Martin" }
Create specificElectronic of type ElectronicItem with:
- id: 200
- quantity: 4
- details: { brand: "Sony", model: "WH-1000XM4" }

Create typed inventory arrays:

Create bookStore of type BookItem[] containing specificBook
Create electronicStore of type ElectronicItem[] containing specificElectronic

Create additional items and test your type system:

Create anotherBook of type BookItem with:
- id: 101
- quantity: 3
- details: { title: "Design Patterns", author: "Gang of Four" }
Use addItem to add anotherBook to bookStore and store in expandedBookStore

Print the following outputs:

Print specificBook.details.title
Print specificBook.details.author
Print specificElectronic.details.brand
Print specificElectronic.details.model
Print the length of expandedBookStore
Use findItemById to find item with ID 101 in expandedBookStore and print the result's details.title
Use findItemById to find item with ID 200 in electronicStore and print the result's quantity
Print expandedBookStore[1].details.author

Try it yourself

// Generic interface from previous challenge
interface InventoryItem<T> {
  id: number;
  quantity: number;
  details: T;
}

// Generic function from previous challenge
function addItem<T>(inventory: InventoryItem<T>[], item: InventoryItem<T>): InventoryItem<T>[] {
  return [...inventory, item];
}

// Create the generic findItemById function
function findItemById<T>(inventory: InventoryItem<T>[], id: number): InventoryItem<T> | undefined {
  return inventory.find(item => item.id === id);
}

// Create test inventories
const mixedBookInventory: InventoryItem<{ title: string; author: string }>[] = [
  { id: 10, quantity: 3, details: { title: "JavaScript Basics", author: "Alice Brown" } },
  { id: 11, quantity: 7, details: { title: "React Fundamentals", author: "Bob Wilson" } },
  { id: 12, quantity: 2, details: { title: "Node.js Guide", author: "Carol Davis" } }
];

const mixedElectronicInventory: InventoryItem<{ brand: string; model: string }>[] = [
  { id: 20, quantity: 5, details: { brand: "Samsung", model: "Galaxy S23" } },
  { id: 21, quantity: 1, details: { brand: "Apple", model: "iPhone 15" } }
];

// Test the function and print outputs
const result1 = findItemById(mixedBookInventory, 11);
console.log(result1 ? result1.details.title : undefined);

const result2 = findItemById(mixedElectronicInventory, 20);
console.log(result2 ? result2.details.brand : undefined);

const result3 = findItemById(mixedBookInventory, 99);
console.log(result3);

const result4 = findItemById(mixedBookInventory, 12);
console.log(result4 ? result4.quantity : undefined);

const result5 = findItemById(mixedElectronicInventory, 21);
console.log(result5 ? result5.details.model : undefined);

const result6 = findItemById(mixedBookInventory, 10);
console.log(result6 ? result6.id : undefined);

const result7 = findItemById(mixedElectronicInventory, 50);
console.log(result7);