Good question. First - this is _not_ my guide. MDN is a wiki and anyone can edit it. - NaN is just a number type . You have NaN in Java or C++ too. It's a way

Good question. First - this is _not_ my guide. MDN is a wiki and anyone can edit it. - NaN is just a number type . You have NaN in Java or C++ too. It's a way to represent "a number we can't represent" - Good catch on strings, I'll edit it in.