superSet javascript Code Snippet in 2025

Checks if the first iterable is a superset of the second one, excluding duplicate values.

• Use the new Set() constructor to create a new Set object from each iterable.
• Use Array.prototype.every() and Set.prototype.has() to check that each value in the second iterable is contained in the first one.

const superSet = (a, b) => {
  const sA = new Set(a), sB = new Set(b);
  return [...sB].every(v => sA.has(v));
};

superSet(new Set([1, 2, 3, 4]), new Set([1, 2])); // true
superSet(new Set([1, 2, 3, 4]), new Set([1, 5])); // false