Capstone: typed inventory lookup

Everything so far comes together here: an interface for the shape of an item, a function whose return type is a union (Item | undefined, since a lookup might not find anything), and a generic helper that works regardless of what's in the array.

array.find(fn) returns the first item where fn returns true, or undefined if none match - which is exactly what an Item | undefined return type promises the caller: check before assuming you got a real item back.

Your task: define Item with id: number and name: string, write findItem(items, id) returning the matching item or undefined, and a generic count(arr) returning arr.length.

You'll practice:

Combining an interface with a union return type
Writing a generic helper that works on any array

interface Item {
  id: number;
  name: string;
}

// findItem returns the matching item, or undefined if no id matches.
function findItem(items: Item[], id: number): Item | undefined {

}

// count works on an array of any type.
function count<T>(arr: T[]): number {

}

const inventory: Item[] = [
  { id: 1, name: "Mouse" },
  { id: 2, name: "Keyboard" },
];

const found = findItem(inventory, 2);
const missing = findItem(inventory, 99);
const total = count(inventory);