What's the point of reimplementing a set though? It already comes with the language, and the language's implementation is probably miles better than what you'd

What's the point of reimplementing a set though? It already comes with the language, and the language's implementation is probably miles better than what you'd come up with anyway. I'd be more interested to know whether the candidate knows what a set is, and how it differs from an array or an object, and when might it come handy. But reimplementing what already comes with the language? A waste of time, and (hopefully) not representative of the work they'll be doing day to day.