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ES4 Implementation Update

DZone's Guide to

ES4 Implementation Update

· Web Dev Zone ·
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Deploying code to production can be filled with uncertainty. Reduce the risks, and deploy earlier and more often. Download this free guide to learn more. Brought to you in partnership with Rollbar.

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.

Deploying code to production can be filled with uncertainty. Reduce the risks, and deploy earlier and more often. Download this free guide to learn more. Brought to you in partnership with Rollbar.

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