intersection

Returns a list of elements that exist in both arrays.

Create a Set from b, then use Array.prototype.filter() on a to only keep values contained in b.

typescript

const intersection = (a: any[], b: any[]) => {
  const s = new Set(b);
  return [...new Set(a)].filter((x) => s.has(x));
};

typescript

intersection([1, 2, 3], [4, 3, 2]); // [2, 3]