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30-seconds-of-code/snippets/symmetricDifferenceWith.md
30secondsofcode 96477cc692 Travis build: 1366
2018-01-24 10:01:27 +00:00

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### symmetricDifferenceWith
Returns the symmetric difference between two arrays, using a provided function as a comparator.
Use `Array.filter()` and `Array.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]
```