Slick slider progress bar?

Question

JavaScript

Guys, there is an example of slick progress bar. I can’t remake a little for myself, it is necessary that initially on the bar itself, the first slide be marked. That is, the page has loaded, our bar is already filled with a black bar for one slide

https://codepen.io/mjtweaver/pen/pEkYgQ

Answer 1

https://jsfiddle.net/qd8Lab7f/