Function to Find an Item by ID

Part of the Introduction To TypeScript section of Coddy's JavaScript journey — lesson 65 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
Various inventory items and updated inventory arrays

Create a generic function named findItemById that searches for an item in an inventory array by its ID.

The function should:

Use a generic type parameter T
Accept a parameter inventory of type InventoryItem<T>[]
Accept a parameter id of type number
Return the found item of type InventoryItem<T> or undefined if not found
Have an explicit return type annotation of InventoryItem<T> | undefined

Create test inventories:

Create mixedBookInventory as an array containing:
- An item with id: 10, quantity: 3, details: { title: "JavaScript Basics", author: "Alice Brown" }
- An item with id: 11, quantity: 7, details: { title: "React Fundamentals", author: "Bob Wilson" }
- An item with id: 12, quantity: 2, details: { title: "Node.js Guide", author: "Carol Davis" }
Create mixedElectronicInventory as an array containing:
- An item with id: 20, quantity: 5, details: { brand: "Samsung", model: "Galaxy S23" }
- An item with id: 21, quantity: 1, details: { brand: "Apple", model: "iPhone 15" }

Test your function and print the following outputs:

Find item with ID 11 in mixedBookInventory and print the result's details.title (or undefined if not found)
Find item with ID 20 in mixedElectronicInventory and print the result's details.brand (or undefined if not found)
Find item with ID 99 in mixedBookInventory and print the result (should be undefined)
Find item with ID 12 in mixedBookInventory and print the result's quantity (or undefined if not found)
Find item with ID 21 in mixedElectronicInventory and print the result's details.model (or undefined if not found)
Find item with ID 10 in mixedBookInventory and print the result's id (or undefined if not found)
Find item with ID 50 in mixedElectronicInventory and print the result (should be undefined)

Try it yourself

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

// Items from previous challenge
const bookItem: InventoryItem<{ title: string; author: string }> = {
  id: 1,
  quantity: 5,
  details: { title: "TypeScript Handbook", author: "John Doe" }
};

const electronicItem: InventoryItem<{ brand: string; model: string }> = {
  id: 2,
  quantity: 3,
  details: { brand: "TechCorp", model: "X100" }
};

const clothingItem: InventoryItem<{ size: string; color: string }> = {
  id: 3,
  quantity: 10,
  details: { size: "M", color: "Blue" }
};

// Generic function to add item to inventory
function addItem<T>(inventory: InventoryItem<T>[], newItem: InventoryItem<T>): InventoryItem<T>[] {
  return [...inventory, newItem];
}

// Create book inventory and new book
const bookInventory = [bookItem];
const newBook: InventoryItem<{ title: string; author: string }> = {
  id: 4,
  quantity: 2,
  details: { title: "Advanced TypeScript", author: "Jane Smith" }
};
const updatedBookInventory = addItem(bookInventory, newBook);

// Create electronic inventory and new electronic
const electronicInventory = [electronicItem];
const newElectronic: InventoryItem<{ brand: string; model: string }> = {
  id: 5,
  quantity: 1,
  details: { brand: "GadgetCorp", model: "Z500" }
};
const updatedElectronicInventory = addItem(electronicInventory, newElectronic);

// Print outputs
console.log(updatedBookInventory.length);
console.log(updatedBookInventory[1].details.title);
console.log(updatedBookInventory[1].details.author);
console.log(updatedElectronicInventory.length);
console.log(updatedElectronicInventory[1].details.brand);
console.log(updatedElectronicInventory[1].details.model);
console.log(updatedElectronicInventory[0].id);
console.log(updatedElectronicInventory[1].quantity);