Typescript Set Functions

sets.ts

export const union = <T>(a: Set<T>, b: Set<T>) => new Set([...a, ...b]);
export const intersection = <T>(a: Set<T>, b: Set<T>) => new Set([...a].filter(x => b.has(x)));
export const difference = <T>(a: Set<T>, b: Set<T>) => new Set([...a].filter(x => !b.has(x)));
export const symmetric = <T>(a: Set<T>, b: Set<T>) => union(difference(a, b), difference(b, a));
export const isSubsetOf = <T>(a: Set<T>, b: Set<T>) => [...b].every(x => a.has(x));
export const isSupersetOf = <T>(a: Set<T>, b: Set<T>) => [...a].every(x => b.has(x));
export const isDisjointFrom = <T>(a: Set<T>, b: Set<T>) => !intersection(a, b).size;