Array is contained in other array

JavaScript, Array · Oct 22, 2020

Checks if the elements of the first array are contained in the second one regardless of order.

  • 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 number of occurrences 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

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