I frequently see members of the Firefox, Chrome, and Edge teams at various JavaScript Meetups (in the Bay Area) as well as conferences, though I've yet to meet someone from the Safari team.
Perhaps this is due to the secretive nature of Apple, and as a result I'm always surprised when new Safari features come out. By the time a feature lands in a different browser, we already know it's coming.
I wish they would be more flexible with their secrecy. The open-source pieces of Apple (the CLI-stuff in OS X, Safari, etc) would gain much by being less secretive.
(and it wouldn't hinder them from being gold silent on other matters; hardware, business, etc)
I expect some of it is just down to comparative size: Apple nowadays have pretty few people working on WebKit (and the JavaScriptCore team is really small—though I doubt V8 people, now mostly in Munich, appear in the Bay Area often!).
I find the title quite misleading as I was expecting support of ES6 modules syntax, which is one of the most important change that came with ES6. But it looks like it's still work in progress (see https://bugs.webkit.org/show_bug.cgi?id=147340 ).
Chrome Canary with experimental JS features enabled fails two tests: "Array.prototype.values" and "no assignments allowed in for-in head". First one on purpose to maintain web compatibility (https://bugs.chromium.org/p/chromium/issues/detail?id=615873). Wondering what is the reason behind the second missing feature?
Actually it exists since Android v3.0 I don't know the exact date because neither Google Play Store nor the release notes from Samsung [0] log version dates.
The final piece to the JavaScript puzzle is ES7's async and await. Whilst this is awesome news, if it included async and await then the circle would be complete.
Unfortunately, async and await didn't make it into ES7. ES2016 (ES7) was finalized with Array.prototype.includes and the exponentiation operator [0]. We'll have to wait for ES2017 at the earliest for async/await to make it into the official spec [1][2].
Perhaps this is due to the secretive nature of Apple, and as a result I'm always surprised when new Safari features come out. By the time a feature lands in a different browser, we already know it's coming.