There are three curves. Big O is simply the average best fit. You also have max worst and min best. JavaScript does (unless I'm wrong) a layer of variable look

There are three curves. Big O is simply the average best fit. You also have max worst and min best. JavaScript does (unless I'm wrong) a layer of variable lookup, so the time is far off from O(1). So, you are right on technical terms, and on interview terms, it depends. When I was just out of university I'd have probably went for the job. As I'm getting more senior, I'd still be polite and explain them where they are wrong, but stand my ground with the recruiter afterwards and tell him the interviewer was out of his depth, and checking off questions he probably googled somewhere. I'd then ask him to give me more serious companies to be considered by. Stuff like your story have more to do with team skills then technical skills. Who cares if you answer right or wrong on the question, when you are the guy you are supposed to work with get pissed off with each other after few minutes technical discussion. General advice: go for where you are celebrated and not for where you are tolerated. A bit of synergy can go a long way.