In JavaScript, keys can be any type... because of course they can. This is JavaScript, after all. But just because you can, doesn't mean you should... if you're a sicko, you might be wondering if this works:
const map = new Map();
map.set(["hello", "there"], "general kenobi");
console.log(map.get(["hello", "there"]));
// undefined
It actually doesn't. Ha! The key is an array, but it's a different array than the one we used to set the value. Sure, the contents are the same, but what matters when comparing keys is that the reference to the object (or array) in memory is the same. So, unfortunately, if we use a single named variable, it does work:
const map = new Map();
const greetingKey = ["hello", "there"];
map.set(greetingKey, "general kenobi");
console.log(map.get(greetingKey));
// general kenobi
That said, this still makes me sick to look at... in 99% of cases, you should just use strings or numbers as keys.
Complete the createUserMap function. It takes an array of user objects (each having fname and lname properties) and returns a Map.