The post says:

  In javascript, everything is mutable, but w/ new es7
  spread/rest syntax it is increasingly easy to just do
  immutable anyway. E.g. instead of myobj.x = newx you can
  do myobj = {...myobj, x: newx} and everything is immutable
  & persistant!

But if I'm reading this right:

https://github.com/sebmarkbage/ecmascript-rest-spread

They will be neither immutable nor persistent.