Any operation that would mutate a data structure in Immutable.js does not modify the original value.
But rather returns a new value.
An Iterable is a set of key/value entries that can be iterated (e.g. using .map(), .filter(), .reduce(), …)
All collections in Immutable.js, like Map and List, use Iterable as a base class.
Think of Map as an object.
.fromJS() This returns a given JS object as an Immutable.js representation,
Converting objects into Maps, and arrays into Lists.