Ordered sets

When you convert sets to lists, you run the risk of adding values to the list out of order. Sets have no defined order, because they're not indexed collections. Immutable.js has an OrderedSet collection type that acts like anOrderedMap. It preserves the insertion order of its values. Other than that, it is just like a regular set.

Note

Internally, Set uses Map to store its values as map keys. OrderedSet uses the OrderedMap keys.

Sorting sets

You can use ordered sets to remove duplicate values and maintain the value insertion order. This means that you can do things such as converting a list to an ordered set, sorting the set, and then converting it back to a list. Examine the following:

const myList = List.of(
  1, 3, 1, 2, 3, 4, 1, 5,
  2, 4, 6, 1, 5, 2, 7, 1,
  8, 3, 7, 1, 4, 2, 8, 9
);
const myUniqueList = myList
  .toOrderedSet()
  .sort()
  .reverse()
  .toList();

console.log('myList', myList.toJS());
// -> myList [ 1, 3, 1, 2, 3, 4, 1, 5, 2, 4, 6,
// ->          1, 5...