What does this log?

const s = new Set([2, "2", 2, { a: 1 }, { a: 1 }, NaN, NaN, NaN]);
console.log(s.size);

1. 3
2. 5
3. 8
4. 6

A Set has map, filter and sort methods, just like an array.

1. True
2. False

What does this log?

const a = new Set([1, 2, 3]);
const b = new Set([3, 4]);
console.log([...a.symmetricDifference(b)]);

1. [1, 2]
2. [1, 2, 3, 4]
3. [1, 2, 4]
4. [3]

What does this log?

const ws = new WeakSet();
const o = {};
ws.add(o);
console.log(ws.has(o), ws.has({}), ws.size);

1. true false 1
2. true false 0
3. true false undefined
4. true true 1

A regular Set keeps an object in memory even after the variable that referred to it is set to null, but a WeakSet does not.

1. True
2. False