// Tested in both Node 22 and latest Edge

const m = new Map([[1, 2], [3, 4]]);
const keys = m.keys(); // IterableIterator<number>
const iter = keys.map(n => n * 100);
// Property 'map' does not exist on type 'IterableIterator<number>'.ts(2339)

const val = iter.next();
console.log(val);
// {value: 100, done: false}