Training tasks on the topic Recursion and Closures?

Question

JavaScript

In search of practical tasks on the topics: Recursion and Closures (Javascript).
Offer tasks as close as possible to the practical application of these two techniques in real Javascript development.

Answer 1

Organize a chain of method calls using currying (similar to, for example, lodash/underscrore).
In general, for closures, any task with collection traversal through map / reduce, for example, implement map through reduce or filter through reduce.
Separately, for closures - hiding the implementation of some service - only interface functions are exported from the module,
recursion is usually a traversal of graphs and collections, the classic task of implementing a binary search or some kind of sorting is not much in demand in practice ... Of course, you can propose to implement the function validation of some object with links...