30-seconds-of-code/snippets/js/s/subset.md

title, type, language, tags, cover, dateModified

title	type	language	tags	cover	dateModified
Subset of iterable	snippet	javascript	array	citrus-drink	2020-10-22T20:24:30+03:00

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

• Use the 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 first iterable is contained in the second one.

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

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