Array Utilities

function first<T>(items: T[]): T | undefined {
  return items[0];
}

function unique<T>(items: T[]): T[] {
  return [...new Set(items)];
}

function groupBy<T, K extends string | number>(items: T[], getKey: (item: T) => K): Record<K, T[]> {
  return items.reduce(
    (groups, item) => {
      const key = getKey(item);
      groups[key] = groups[key] ?? [];
      groups[key].push(item);
      return groups;
    },
    {} as Record<K, T[]>,
  );
}

const names = ["Ali", "Sara", "Ali", "Noura"];
const scores = [82, 91, 82, 75];

console.log(first(names));
console.log(unique(scores));
console.log(groupBy(names, (name) => name.length));