Thank you. I just reread it and I did miss that I needed to return a linked list instead of an array.

You must return a new linked list (using the Node constructor). Currently you are returning an array of filtered nodes data. If you are not familiar with that, you should train on other easier katas using linked list and come back to this after, you'll see it's not hard actually.

I'm running this Kata under Node 8.1.3, and every time I return anything it tells me that I've returned [undefined], even when I return a test string. I've even manually returned [1,2,3] and it tells me that I've returned []. So I don't know what I'm doing wrong. I feel that my logic is well done and should work, but something seems to be wrong with the enviroment?