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symmetricDifferenceBy

JS TODO

Returns the symmetric difference between two arrays, after applying the provided function to each array element of both.

Create a Set by applying fn to each array's elements, then use Array.prototype.filter() on each of them to only keep values not contained in the other.

const symmetricDifferenceBy = (a, b, fn) => {
const sA = new Set(a.map((v) => fn(v))),
sB = new Set(b.map((v) => fn(v)));
return [
...a.filter((x) => !sB.has(fn(x))),
...b.filter((x) => !sA.has(fn(x))),
];
};
symmetricDifferenceBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [ 1.2, 3.4 ]