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unionWith

TS JS Deno

Returns every element that exists in any of the two arrays once, using a provided comparator function.

Create a Set with all values of a and values in b for which the comparator finds no matches in a, using Array.prototype.findIndex().

typescript
const unionWith = (a: any[], b: any[], comp: Predicate) =>
Array.from(
new Set([...a, ...b.filter((x) => a.findIndex((y) => comp(x, y)) === -1)])
);
typescript
unionWith(
[1, 1.2, 1.5, 3, 0],
[1.9, 3, 0, 3.9],
(a, b) => Math.round(a) === Math.round(b)
); // [1, 1.2, 1.5, 3, 0, 3.9]