function groupByFirstLetter(words: string[]): Record<string, string[]> {
  const mimapa = new Map();

  for (const word of words) {
    const first = word[0].toLocaleLowerCase();
    mimapa.set(first, (mimapa.get(first) || []).concat(word));
  }

  return Object.fromEntries(mimapa.entries());
}

// No modificar: necesario para evaluar el resultado.
export { groupByFirstLetter };