Allen Wirfs-Brock (2015-05-11T23:31:56.000Z)
d at domenic.me (2015-05-14T17:22:16.047Z)
The single formal design decision was made when ES5 was being developed. It practice, it some seem to have been accepted just fine. Replacing the current single FormalParameter (which allows for the possibility of a default value initializer) with an alternative production that didn't allow a default value would just be creating a different inconsistency as it would be the only place a formal parameter could have have a default value initializer. Regardless, ES6 and the syntax is set.