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

title, tags

title	tags
isContainedIn	array,intermediate

Returns true if the elements of the first array are contained in the second one regardless of order, false otherwise.

Use a for...of loop over a Set created from the first array. Use Array.prototype.some() to check if all distinct values are contained in the second array, use Array.prototype.filter() to compare the amount of occurences of each distinct value in both arrays. Return false if the count of any element is greater in the first array than the second one, true otherwise.

const isContainedIn = (a, b) => {
  for (const v of new Set(a)) {
    if (
      !b.some(e => e === v) ||
      a.filter(e => e === v).length > b.filter(e => e === v).length
    )
      return false;
  }
  return true;
};

isContainedIn([1, 4], [2, 4, 1]); // true