Set
by applying fn
to each element in b
.Array.prototype.map()
to apply fn
to each element in a
.Array.prototype.filter()
in combination with fn
on a
to only keep values not contained in b
, using Set.prototype.has()
.const differenceBy = (a, b, fn) => {
const s = new Set(b.map(fn));
return a.map(fn).filter(el => !s.has(el));
};
differenceBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [1] differenceBy([{ x: 2 }, { x: 1 }], [{ x: 1 }], v => v.x); // [2]
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