Generics

Without generics, a "return the first element" function would need typing per array type: one for number[], another for string[]. A generic function instead declares a placeholder type name - conventionally T - right after its own name, then uses T anywhere a real type would go:

function first<T>(arr: T[]): T {
  return arr[0];
}

T isn't a real type - it's filled in per call. first([10, 20, 30]) fills T with number; first(["a", "b"]) fills it with string. The body never needs to know which - arr[0] works identically either way.

Your task: write first(arr) so it returns the first element of any array, typed generically.

You'll practice:

Declaring a generic type parameter with <T>
Using T in a parameter and return type

// Write first<T>(arr: T[]): T, returning the first element of any array.
function first<T>(arr: T[]): T {

}

const firstNum = first([10, 20, 30]);
const firstWord = first(["a", "b", "c"]);