como usar o intersectionBy no javascript es6

Returns a list of elements that exist in both arrays, after applying the provided function to each array element of both.

Create a Set by applying fn to all elements in b, then use Array.prototype.filter() on a to only keep elements, which produce values contained in b when fn is applied to them.

const intersectionBy = (a, b, fn) => {
  const s = new Set(b.map(fn));
  return a.filter(x => s.has(fn(x)));
};

intersectionBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [2.1]

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