I am going to continue to use var for everything, because I think let and const are stupid.
It is not cool or interesting to learn about new scoping rules introduced by let, and it is not cool or interesting that so many people — especially juniors, but not exclusively — are lulled into a false sense of security by believing const means the referenced value is immutable, which it isn't.
I am going to continue to write small JavaScript, like from The Good Parts.