iterum library provides a class for handling iterable transformations inspired in Array methods and lodash/fp functions. This library also supplies combinatorial functions like permutations, combinations, variations, product, power and powerSet that has a high computational cost but this library is able to support taking advantage of lazy evaluation.Then, obj can be processed as an ordered list of values. However, unlike built-in iterables (Array, Set, Map, String, etc), obj is a lazy iterable. It means that, thanks to generators, obj does not store the computed values in memory and its values are computed just when are required. These are the essential features for implementing lazy evaluation.