JS: Set.prototype.keys

New in JS2015.

setObj.keys ( )

Return a Iterable Object (also is a Iterator) for the set instance setObj. Each yield of the iterator is a element of the set.

const ss = new Set([3, 4, "ok"]);

for (const e of ss.keys()) {
  console.log(e);
}
// prints
// 3
// 4
// ok

This example shows the result is iterator and iterable:

const ss = new Set([3, "yes"]);

console.log(ss.keys); // [Function: values]
// result is a function that returns a iterator object

// call it
console.log(ss.keys()); // SetIterator { 3, 'yes' }
// result is a iterator object

// is also a iterable
console.log(
  Symbol.iterator in (ss.keys()),
); // true

[see Symbol Tutorial]