I'm looking for a way to have a small array with big hols between the values. E.g.

var list = List([1, 2]);
list = list.set(10000, 3);
list.forEach( x => {
    console.log(x)
});

Expected output should be:

1
2
undefined (printed out once, not 10000)
3

Right now I get the undefined value printed 10000 times. I would like to be still aware that there are holes when traversing the list, but not store all 10000 undefined values inside the Array.

Maybe I would be able to achieve this using another data structure? As I understand it Immutable.js treats lists as trees. When inserting a new value I don't want all the leafs in between. Reversing it should also work.