ES4 Implementation Update

The development of ECMAScript 4 is moving into an important phase: the implementors are making good on their word and are starting to implement the ECMAScript 4 proposals. Many of the features have been well thought out by this point and the implementors are working hard to integrate the necessary changes into their engines.

A couple important pieces are coming along but the most critical of which is the ECMAScript 4 Reference Implementation. They’ve released a second milestone release. You can find a copy of the implementation on the ECMAScript download page.

An important list of features is starting to become available in the reference implementation:

Implemented, may have bugs:

  • classes and interfaces
  • namespaces
  • pragmas
  • let, const, let-const
  • iterators
  • enumerability control
  • type expressions / definitions / annotations
  • runtime type checks (“standard mode”)
  • nullability
  • destructuring assignment
  • slice syntax
  • hashcode
  • catchalls
  • map & vector
  • date & time improvements
  • meta objects
  • static generics
  • string trim
  • typeof
  • globals
  • expression closures
  • name objects
  • type operators (is / to / cast / wrap)

Implemented and partly working, but still in flux / work to do:

  • inheritance checking
  • strict mode
  • type parameters
  • structural types
  • numbers & decimal
  • getters & setters (structural part is incomplete)
  • packages

Now a full feature list is also being worked on by all of the implementors (as I mentioned previously). This list is going to serve as the starting point for many implementors especially when they decide which features to implement.

Adobe has also taken a step and has outlined (note the column with green/red/etc.) where they stand on all of the ECMAScript 4 proposals. They also took the time to outline their position on the proposals that they’re (currently) declining to implement.

This is a really important step in the development of the language. The implementors are staking their ground and are working hard to make sure that a solid language comes out at the end – especially one that is universally implemented. Both Google and Apple have also been participating the ECMAScript 4 mailing list, asking a lot of good questions, as they look towards creating their own ES4 implementations (in Rhino and WebKit, respectively).

Pretty much everyone can agree that a lack of dialog between implementors would surely cause problems – but that does not appear to be the case, here. Because of this openness and solid dialog ECMAScript 4 looks to have a strong future.

Posted: February 27th, 2008

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