Most of the JavaScript developers I've encountered recently refuse to use Map, and if you dare use it, they will say that it's complicated code and premature optimisation before even making an attempt to understand it.

I feel like trying to add fast data structures into JavaScript is futile, I think at this point it would be better to make it easier for JavaScript and the browser to interface with faster languages.

The only thing I would add to JavaScript at this point is first class TypeScript support so that we can ditch the transpilers.