We lived for so long in a world where Javascript was so flaky and non-standard that wise programmers stuck to a lowest-common-denominator style. But now you can really take advantage of the language.

I'm writing a compiler in JS that uses higher-order functions all over the place and I haven't been bitten yet by language inconsistency or performance gotchas. So I think you could go a long way showing how to do the sorts of metaprogramming tricks that used to be only attempted in Lisp or Haskell.