03-ES2015Set.js

const set = new Set();

set.add(1);
console.log(set.values()); // outputs @Iterator
console.log(set.has(1)); // outputs true
console.log(set.size); // outputs 1

set.add(2);
console.log(set.values()); // outputs [1, 2]
console.log(set.has(2)); // true
console.log(set.size); // 2

set.delete(1);
console.log(set.values()); // outputs [2]

set.delete(2);
console.log(set.values()); // outputs []

const setA = new Set();
setA.add(1);
setA.add(2);
setA.add(3);

const setB = new Set();
setB.add(2);
setB.add(3);
setB.add(4);

// --------- Union ----------
const union = (set1, set2) => {
  const unionAb = new Set();
  set1.forEach(value => unionAb.add(value));
  set2.forEach(value => unionAb.add(value));
  return unionAb;
};
console.log(union(setA, setB));

console.log(new Set([...setA, ...setB]));

// --------- Intersection ----------
const intersection = (set1, set2) => {
  const intersectionSet = new Set();
  set1.forEach(value => {
    if (set2.has(value)) {
      intersectionSet.add(value);
    }
  });
  return intersectionSet;
};
console.log(intersection(setA, setB));

console.log(new Set([...setA].filter(x => setB.has(x))));

// alternative - works on FF only
// console.log(new Set([x for (x of setA) if (setB.has(x))]));

// --------- Difference ----------
const difference = (set1, set2) => {
  const differenceSet = new Set();
  set1.forEach(value => {
    if (!set2.has(value)) {
      differenceSet.add(value);
    }
  });
  return differenceSet;
};
console.log(difference(setA, setB));

console.log(new Set([...setA].filter(x => !setB.has(x))));

// alternative  - works on FF only
// console.log(new Set([x for (x of setA) if (!setB.has(x))]));