It turns out `let` is usable in most browsers today, and in some older ones. The point is there's no extra opt in and no forked runtime semantics.
> Doesn't that happen all the time?
You're talking about new syntax bombing old browsers. That's not the issue. The issue is same syntax in old and new, works (for whatever value of "works") in old and new, but differs in meaning due to a "use sanity"; directive.
Fair enough. You have probably heard arguments similar to mine hundreds of times, thanks again for answering.
For what is worth, I never depend on the truthyness of falsyness of 0 and "", and always test for them explicitly, so it will not affect my code if in a distant future javascript starts treating them as truthy. Just, you know, in case you change your mind in the future.
> Doesn't that happen all the time?
You're talking about new syntax bombing old browsers. That's not the issue. The issue is same syntax in old and new, works (for whatever value of "works") in old and new, but differs in meaning due to a "use sanity"; directive.