const uniqueSymmetricDifference = (a, b) => [
…new Set([
…a.filter(v => !b.includes(v)),
…b.filter(v => !a.includes(v)),
]),
];
uniqueSymmetricDifference([1, 2, 3], [1, 2, 4]); // [3, 4]
uniqueSymmetricDifference([1, 2, 2], [1, 3, 1]); // [2, 3]
Массивы и объекты JavaScript
JavaScript