Function to Get Item Details

Part of the Introduction To TypeScript section of Coddy's JavaScript journey — lesson 67 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
Type aliases Book, Electronic, BookItem, and ElectronicItem
Inventory arrays bookStore and electronicStore

Create a function named getItemDetails that takes an InventoryItem<any> and uses type guards to determine what type of item it is, then prints appropriate information.

The function should:

Accept a parameter item of type InventoryItem<any>
Use the in operator to check if item.details has a title property
Use the in operator to check if item.details has a brand property
Print "Book: [title] by [author]" if it's a book
Print "Electronic: [brand] [model]" if it's an electronic
Print "Unknown item type" if it's neither
Have a return type of void

Create test items:

Create testBook of type InventoryItem<any> with:
- id: 300
- quantity: 6
- details: { title: "TypeScript Handbook", author: "Microsoft Team" }
Create testElectronic of type InventoryItem<any> with:
- id: 400
- quantity: 2
- details: { brand: "Dell", model: "XPS 13" }
Create unknownItem of type InventoryItem<any> with:
- id: 500
- quantity: 1
- details: { color: "Red", size: "Large" }

Test your function by calling getItemDetails with each test item:

Call getItemDetails(testBook)
Call getItemDetails(testElectronic)
Call getItemDetails(unknownItem)

Also test with items from your existing stores:

Use findItemById to find item with ID 100 in expandedBookStore, then call getItemDetails with the result
Use findItemById to find item with ID 200 in electronicStore, then call getItemDetails with the result

Try it yourself

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

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

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

// Create specific object types
type Book = {
  title: string;
  author: string;
};

type Electronic = {
  brand: string;
  model: string;
};

// Create type aliases for specific inventory items
type BookItem = InventoryItem<Book>;
type ElectronicItem = InventoryItem<Electronic>;

// Create concrete inventory items
const specificBook: BookItem = {
  id: 100,
  quantity: 8,
  details: { title: "Clean Code", author: "Robert Martin" }
};

const specificElectronic: ElectronicItem = {
  id: 200,
  quantity: 4,
  details: { brand: "Sony", model: "WH-1000XM4" }
};

// Create typed inventory arrays
const bookStore: BookItem[] = [specificBook];
const electronicStore: ElectronicItem[] = [specificElectronic];

// Create additional items and test type system
const anotherBook: BookItem = {
  id: 101,
  quantity: 3,
  details: { title: "Design Patterns", author: "Gang of Four" }
};

const expandedBookStore = addItem(bookStore, anotherBook);

// Print outputs
console.log(specificBook.details.title);
console.log(specificBook.details.author);
console.log(specificElectronic.details.brand);
console.log(specificElectronic.details.model);
console.log(expandedBookStore.length);
console.log(findItemById(expandedBookStore, 101)!.details.title);
console.log(findItemById(electronicStore, 200)!.quantity);
console.log(expandedBookStore[1].details.author);