Did someone say unique values? It't time for `Set`! This is an exercise where ES6 can really shine, `Set` is made to store unique values, and that's exactly what we're asked to do here. Let's take it step-by-step.
This one is actually fairly easy, so this will be a short post. We'll do some basic array manipulation and make a `Map` for the DNA base pairs. This creates a mapping of each of the 4 letters to it's partner.