unique elements in a Set (by definition) or making Array elements unique

uniqueSets.js

//immutable:
const { List } = require('immutable');
const someList = List([1,2,3,4,4,4,4]);
const uniqueList = someList.toSet();

//ES6:
const someArr = [1,2,3,4,4,4,4]; 
const uniqueSet = new Set(someArr); //==> {1,2,3,4} uniqueSet.constructor is a Set; typeof uniqueSet = "object"
const uniqueArr  = [...uniqueSet];	//==> [1,2,3,4] uniqueList.constructor is an Array; typeof uniqueList = "object"
const uniqueArr2 = Array.from(uniqueSet); //ALT to above line