this seems very uneficient

Is this not considered kind of cheap though by using hardcoded entries for multi-symbol values like IV, IX, XL, etc.? I thought that the "proper" solution would only use what was shown in the challenge prompt as hardcoded symbol/value pairs.

Idk about my solution compare to this one, probably mine is worst like 80% of the time (I'm starting in js);

This is so clever solution, I just create array 2 arrays and check it.

should not with 900&400&90&40....so i think it not a good answer