Why is the data value not being assigned to the selector?

Question

JavaScript

I am writing my own slider. Here is the problem, in breadcrumbs the data-id attribute is assigned to the dots, the idea is that the value of this data-id is pulled up to the slide selector (for example, "slide c0", where c0 is the slide number, instead of conditional zero, the data-id value should be assigned, but this doesn't happen console.log says "I didn't find such a selector, go to hell"
https://jsfiddle.net/Nixtone/huz7790g/ Line 22 of JS On the checkout line

. without scrolling through the entire slider when going from the last to the first slide) Please.

Answer 1

Russian markings

c