Ok so my question is not actually on the challenge itself, but on the concat portion of it.
I have been going through the circular in order order, and do not remember this ever being used in previous lessons. Then in this lesson it is tossed in as if it should be a know factor.
It’s easy enough to check a reference page to see what the function does, but I want to make sure that I am taking the lessons in the correct order.
This is part of the ES6 lesson plan which is listed directly after the Basic JS lesson plan.