Generic Functions

👨‍💼 We have utility functions that work with arrays, but they're limited to specific types. Let's make them generic so they work with any type.

The syntax for generic functions:

function functionName<Value>(param: Value): Value {
	return param
}

The <Value> declares a type parameter. When you call the function, TypeScript infers (or you specify) what Value is:

identity<string>('hello') // Explicit: Value is string
identity(42) // Inferred: Value is number

🐨 Open

index.ts

and:

Create a generic identity function that takes a value and returns the same value (preserving its type)
Create a generic last function that takes an Array<Item> and returns Item | undefined (the last element, or undefined for an empty array)
Export identity and last by name

Completion criteria

Named exports: identity, last
identity returns the same value for strings, numbers, booleans, and null
last([1, 2, 3]) → 3; last(['a', 'b', 'c']) → 'c'; last([]) → undefined

💰 Use a type parameter to make the array function work with any type.