https://kangax.github.io/compat-table/es6/
That said, it will be a long time before you can write vanilla ES6 without transpilation and publish it, for the same reason that many sites still sadly support IE<=8.
Apple recognizes that the Web poses a threat to their business model (although I think it's not as big as they fear, after all, how much of their profits come from the app store). This is why I am skeptical they will support WebAssembly in the end. After all, it will be possible to compile ES6 to WebAssembly just as much as any other language.
I'm open to other suggestions for why Safari has become essentially the IE6 of our time, but pure business strategy is the only one I can come up with (which is fair, since Apple is a business after all).
WebAssembly is listed as in development.
Supposedly the STP version is getting updated every 2 weeks, so lets hope that that also transitions to the non-developer version of Safari.
Actually Safari (well, Webkit), in beta, is the closest to full ES6 support of all current browsers -- down to 98% or so.
It's just that Safari has a release only once or twice a year. But when it has, suddenly everybody on OS X/iOS using Safari would get all that stuff at once.
(And recently they started a public beta builds program that might see them releasing new versions much sooner).
>Apple recognizes that the Web poses a threat to their business model
And with that information above, can we put this age old conspiracy theory to rest?
Apple had long had the best mobile browser when Android still had the horrible "Android Browser". They regularly added all kinds of features that benefit apps (e.g. the canvas, css animations, several API to access native mobile features, etc.), and they continuously improve it (see this 98% ES6 support).
For a company that "fears web apps" Apple not only promoted them to developers (before and after they created their native app frameworks and app store), not only has extensive documentation and how to's for best mobile experiences on their dev pages, but also has seen that Safari webkit based apps have traditionally been a better experience than Chrome based web apps on Android.
Even today, it's faster, and more memory/cpu/battery efficient on mobile than Chrome is on Android.
https://blog.runspired.com/2016/03/25/the-chrome-distortion-...
Safari was only held back because it's not a huge priority for Apple -- not because of some fear that web apps will eat their app store lunch.
After all, web apps are difficult to monetize (no credit cards at hand), people expect most of them to be free, have a subpar experience for anything more demanding compared to bare metal languages, and don't integrate that well with native APIs anywhere (iOS, Android, Desktop, etc), as they have to run in a more restricted sandbox than native apps do (and of course somebody has to continuously porting all the native APIs, and at a great common denominator at that, since they also need to be portable).
And hey, for whatever reason, Apple has earned my eternal gratitude (and my consumer dollar) over the past few months by being one of the only entities in this country capable and willing to stand up to government bullying and surveillance. Web standard are great for me in my job, and I believe they're important for the future of online communication. But standing up to government overreach is of critical importance to all of us. I'm an Android user myself, but wife uses iPhone so I'm already getting ready to buy her a new iPhone 7 when they come out.
I'm curious: how much have "evergreen" browsers changed this? Do developers typically target Chrome from a few months ago? Two years ago? Just "today"?
Maybe a better way to put it: if you only cared about Chrome, how long would you wait after a new feature was introduced to start using it?
IE9 is the oldest browser we support, and soon we won't support it either.
Few devs care for older support unless they're working on enterprise, are masochists, or really really really care about supporting 0.00000001% [0] of their users because they care that much (and more power to them!!)
Most devs can point to Microsoft and say "Look, even the guys who created it are no longer supporting it." as an excuse to not support it themselves. I frequently do this when asked to support Safari 5... on Windows. Apple doesn't support it - neither do I.
If you work with say.. Healthcare clients you often need to support back to IE7 or even IE6 because that is what they use internally....
[0] I mean to say "practically zero, but not zero percent".