function reduce(map, callback, initialValue) { if (initialValue == null && map.size === 0) { throw new TypeError('Reduce of empty map with no initial value'); } let accumulator = initialValue; for (const [key, value] of map) { if (accumulator == null) { accumulator = value; } else { accumulator = callback(accumulator, value, key, map); } } return accumulator; } export { reduce };