symmetricDifferenceWith

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.

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),
];

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]