[1]

Safari 9.0 (2015-11-04 23:31:31 +09:00 版) https://developer.apple.com/library/safari/releasenotes/General/WhatsNewInSafari/Articles/Safari_9.html#//apple_ref/doc/uid/TP40014305-CH9-SW27

The following ECMAScript 6 content is now supported by Safari:
Symbol Objects

[2] Write structured clone algorithm in terms of ECMAScript · whatwg/html@bfb960c (2016-03-02 16:45:03 +09:00 版) https://github.com/whatwg/html/commit/bfb960c938580c95e77365e614218b952f96375b

[3] Add the symbol type (domenic著, 2017-08-01 00:38:30 +09:00) https://github.com/heycam/webidl/commit/d6c3ddbfe74d4a6192aae98bcf03b6c323582e8d

[4] 27553 – Support Symbol (2017-08-02 17:07:27 +09:00) https://www.w3.org/Bugs/Public/show_bug.cgi?id=27553

[5] `any` type conversion does not take into account of symbols · Issue #301 · heycam/webidl (2017-08-02 17:08:07 +09:00) https://github.com/heycam/webidl/issues/301

[6] Add the symbol type by domenic · Pull Request #377 · heycam/webidl (2017-08-02 17:09:36 +09:00) https://github.com/heycam/webidl/pull/377

[7] Handle Symbols correctly in legacy platform object's [[DefineOwnPrope… (TimothyGu著, 2017-08-17 04:47:39 +09:00) https://github.com/heycam/webidl/commit/c062489e7289c1614f695599783af3f8dbe6ef9e