ECMAScript 6 compatibility table
kangax.github.io
kangax.github.io
And because typescript != javascript, we can't use any other tools, either. TS is duplicating the 6to5 efforts, with little to show for it.
If you use TS, right now you're stuck with es5. It's starting to itch.
I wish they'd prioritize the es6 features in es6 output mode and let me worry about converting that to es5.
The type check step should be available to run on its own. IMO they should not even worry about transpiling, just be a type checking engine.
The API for TS, last I used it, was extremely limited. It has always been viewed as a black box compiler by the authors- they need to expose more flexibility.
That is because io.js upgraded to a current, and maintained, version of Google V8. This was one of the reasons for the fork.
io.js: V8 4.1.x
node.js: V8 3.28.x
Writing tests for 'let' support, for instance, is harder than just testing that all the Array.prototype methods are now on TypedArrays, so those methods are worth twice that of let support, even though let is considerably more complicated to implement and game changing in its consequences.
And that's why we give different weight to different features. Smallest ones (Math methods, octal & binary literals, etc.) have a weight of 0.25. Medium ones (Map, Set, rest parameters, etc.) have a weight of 0.5. Finally, landmark features (arrow functions, classes, generators) have a weight of 1.
The final % score is calculated according to all this.
Modules are difficult to test (via regular means like `eval`) and the standard is still in the flux so we're trying to figure out the best way — https://github.com/kangax/compat-table/issues/316
Is this the only noteworthy ES6 feature which isn't tested?