That section seems to have an assumption you already have a complete understanding of es5 and feels like it should be one of the later sections, am I crazy? am i doing it wrong?
A lot of people have this impression, you can return to it later or use it as an occasion to improve your research skills through the documentation
It looks that way to me too. As far as I’ve been able to tell so far, it looks like the ES6 course assumes you know stuff that is first introduced later (as the course sequence exists now) in the Basic Data Structures course, in the Functional Programming course (e.g. the map, filter, and reduce methods), and perhaps elsewhere. It was kind of disorienting until I realized that. Still seems odd.