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30-seconds-of-code/snippets/isContainedIn.md
30secondsofcode 164fad4f5e Travis build: 1705
2020-01-13 08:19:45 +00:00

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---
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
```