"unwise to use features like these which you wouldn't expect other people to know" I understand what you mean, but most of the described features has been in t

"unwise to use features like these which you wouldn't expect other people to know" I understand what you mean, but most of the described features has been in the language for ages, some of them more than 20 years. I think the reason why so many aren't aware of the features, is because they learn the language by looking at code written by others or from simplified tutorials, and never look at the formal specification. I remember how I struggled back in the late 90's to find good information, and how I read the ECMA-262 specification when I found it. Whenever a new specification is released I download it and read though it to see all new features, and also refresh my memory about the old.