[Offler]

Today https://github.com/google/traceur-compiler

[coldtea]

That's not using those features. That's using a bizarro extra step to the workflow to get a non native implementation.

[eddyb]

traceur-compiler can preserve ES6 syntax (without desugaring it), it's only missing automated feature detection at runtime (which I wanted to add more than an year ago, but was busy with other things).