JS syntax future-proofing, Macros, the "Reader" (was: Performance concern with let/const)

[François REMY]

|  But if we have macros, then many progressive
|  enhancement and anti-regressive polyfill approaches can be done, even
|  with new syntax (not just with APIs).

Seems like another good way of fixing the issue :-) However, this seems to 
require some form of conditionnal compilation to work , right? [1]

[1] http://www.javascriptkit.com/javatutors/conditionalcompile.shtml