2 · Model and build · 8 MIN

Keep a type relationship

Arrays store values in order, starting at index zero.

A generic preserves a relationship between an input type and output type. T[] contains T values, so first returns T or null for an empty list.

A row of numbered lockers starts at locker 0 in JavaScript.

Read the example

function first<T>(items: T[]): T | null {
  return items.length ? items[0] : null;
}
console.log(first([2, 4]));

2

Your challenge

Return the first item of the input array. Return null if the array is empty.

Common trap

The last index is length - 1, not length.