30-seconds-of-code/snippets/difference.md

title, tags, expertise, cover, firstSeen, lastUpdated

title	tags	expertise	cover	firstSeen	lastUpdated
Array difference	array	beginner	blog_images/interior-3.jpg	2017-12-17T16:41:31+02:00	2020-10-19T18:51:03+03:00

Calculates the difference between two arrays, without filtering duplicate values.

• Create a Set from b to get the unique values in b.
• Use Array.prototype.filter() on a to only keep values not contained in b, using Set.prototype.has().

const difference = (a, b) => {
  const s = new Set(b);
  return a.filter(x => !s.has(x));
};

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