except for the last one, all of those should be part of the language you are using, and well thought out + researched. I guess I should have been more specific: third party dependencies.
> - ubiquitous things, like data structures
There are a few basic data structures in JS, but almost everything else is in user-land.
> - hard to get right things, like time
Date is a notoriously bad API in JavaScript.
- implementations of specs, like Unicode
We just get a String type in JavaScript which is UTF-16, so...
Well, no, we aren't. We are talking about the Elm language, which compiles to JavaScript.
There are also other excellent languages that target JavaScript that have these things.