var setA = new Set([1, 9, 11]); console.log('Set A =>', [...setA]); var setB = new Set([1, 4, 8, 9, 11]); console.log('Set B =>', [...setB]); function isSubset(subset, set) { for (let elem of subset) { if (!set.has(elem)) { return false; } } return true; } console.log('is A subset of B=>', isSubset(setA, setB));