---
title: isContainedIn
tags: 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.

```js
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;
}
```

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