How do you convert a Set to an array?

Two ways, both one line and equivalent in practice:

const set = new Set([3, 1, 2]);

const a = [...set];            // spread
const b = Array.from(set);     // Array.from

Use spread for brevity. Array.from is worth preferring in two cases: it takes a mapping function as a second argument, and it also accepts array-likes that have a length but are not iterable.

Array.from(set, (x) => x * 2);   // map while converting, no intermediate array

Order is preserved — a Set iterates in insertion order, so the result matches the order values were added, not sorted order.

Going the other way

const back = new Set(array);

The idiom this enables

Round-tripping through a Set is the standard way to remove duplicate primitives:

const unique = [...new Set([1, 2, 2, 3])];   // [1, 2, 3]

It compares with SameValueZero, so NaN deduplicates correctly and +0/-0 collapse into one. But it only works for primitives — objects compare by reference, so [...new Set([{a:1}, {a:1}])] still has two entries. Key by an id instead:

const uniqueUsers = [...new Map(users.map((u) => [u.id, u])).values()];

Why convert at all

A Set has no map, filter, sort or index access, so converting is how you reach array methods. If you only need to loop, you do not have to convert — for...of and forEach work directly on a Set, and skipping the copy avoids allocating a second structure for nothing.