interface Item {
  category: string;
  value: number;
}

function sumByCategory(items: Item[]): Record<string, number> {
  // Tu código aquí
  return items.reduce( 
    (accumulativeValue, currentValue) => { 
      accumulativeValue[currentValue['category']] = 
        ( accumulativeValue[currentValue['category']] !== undefined 
            ? accumulativeValue[currentValue['category']]
            :  0 
        ) + currentValue['value']; 
        
    return accumulativeValue
    },{}
  );
}

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