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30-seconds-of-code/snippets/symmetricDifferenceWith.md
Angelos Chalaris 611729214a Snippet format update
To match the starter (for the migration)
2019-08-13 10:29:12 +03:00

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---
title: symmetricDifferenceWith
tags: array,function,intermediate
---
Returns the symmetric difference between two arrays, using a provided function as a comparator.
Use `Array.prototype.filter()` and `Array.prototype.findIndex()` to find the appropriate values.
```js
const symmetricDifferenceWith = (arr, val, comp) => [
...arr.filter(a => val.findIndex(b => comp(a, b)) === -1),
...val.filter(a => arr.findIndex(b => comp(a, b)) === -1)
];
```
```js
symmetricDifferenceWith(
[1, 1.2, 1.5, 3, 0],
[1.9, 3, 0, 3.9],
(a, b) => Math.round(a) === Math.round(b)
); // [1, 1.2, 3.9]
```