I don’t see that your code is returning the correct results.
You are failing the first 4 tests - these:
frankenSplice([1, 2, 3], [4, 5], 1)should return [4, 1, 2, 3, 5].
frankenSplice([1, 2], ["a", "b"], 1)should return ["a", 1, 2, "b"].
frankenSplice(["claw", "tentacle"], ["head", "shoulders", "knees", "toes"], 2)should return ["head", "shoulders", "claw", "tentacle", "knees", "toes"].
All elements from the first array should be added to the second array in their original order.
I think the issue is that the built in “fake” console that FCC provides isn’t showing you what is really happening, mainly because it doesn’t show array brackets for some strange reason. When I run this in codepen, I get:
[4, 1, 2, 3, [5]]
which isn’t the same as what they want:
[4, 1, 2, 3, 5]
Unfortunately, in the FCC console, those both render as the same thing.