What I meant was that I haven't seen a method called "remove_"

That's the point of this kata (at least for JS version): extend array functionality with a new method. It doesn't exist, but you can write your own functions that extend a prototype (Array).

I don't understand the point of your question.

Do you know the whole JS documentation is available online? If I type js re into Google, the autocompletion immediately proposes me je remove element from array...