Pedro Maciel Xavier

What is a skip list? I think you should give a very short description about what it is and what are the advantages with regard to, say, red-black trees or other deterministic data structures...

Claudio Esperança

I would start with an empty list defined in the block itself. Like so (see below).

What does Search return?
Also, ordinarily I think methods should start with lowercase letters rather than uppercase, which should be reserved for classes... But it's just a style preference.

I've written in lowercase before but there was a conflict with the js keyword `delete`. Switching to uppercase sounded the nearest workaround to me.