You can see the latest proposals on the tc39/ecma262 GitHub repository.
A channel for feedback on ECMAScript standards is es-discuss.
These ES2016 features are implemented:
These ES2017 features are implemented:
- Async Functions
- Trailing commas in function parameter lists (Firefox 52)
Experimental new features
The following features are already implemented, but only available in the Firefox Nightly channel and not yet included in a draft edition of an ECMAScript specification.
Additions to the
New TypedObject objects
- Based on Typed Objects draft, and exposed via a global
TypedObject.ArrayType. This feature is non-standard and not documented.