How we built it

Array subclassing and Symbol.species support

ES2015 changes the semantics of Arrays and certain other classes to create subclass instances from certain methods, and allow a new interception point, Symbol.species, to control whether it's actually the subclass or another class which is instantiated. For example, Array.prototype.map constructs instances of the subclass as its output, with the option to customize this by changing Symbol.species

Documentation

Specification

Established standard

Status in Chromium

Enabled by default (launch bug) in:

  • Chrome for desktop release 51
  • Opera release 38
  • Opera for Android release 38

Consensus & Standardization

Owner

Last updated on 2016-04-01