Mastering Immutable.js

List supersets

The other approach is to use the isSuperset() method, which determines if the argument is a subset of the collection where we're calling the method:

const myList = List.of(  List.of(1, 2, 3),  List.of(4, 5, 6),  List.of(7, 8, 9));const isSuperset = myList  .flatten()  .isSuperset(List.of(2, 5, 8));console.log('isSuperset', isSuperset);// -> isSuperset true

As you can see, this is just another way of getting the same result as the prior example.

As a rule of thumb, if a collection is a subset of another collection, then the other collection is a superset. If a collection is a superset of another collection, then the other collection is a subset.