ECMAScript Next compatibility table

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V8 SpiderMonkey JavaScriptCore Chakra Other
⬤ Minor difference (1 point) ⬤ Small feature (2 points) ⬤ Medium feature (4 points) ⬤ Large feature (8 points)

Feature name	Current browser		Traceur	Babel + core-js ^[2]	Closure	Type- Script + core-js	es7-shim	IE 9	IE 10	IE 11	Edge 12 ^[3]	Edge 13 ^[3]	Edge 14 ^[3]	Edge 15 ^[3]	FF 38 ESR	FF 42	FF 43	FF 44	FF 45 ESR	FF 46	FF 47	FF 48	FF 49	FF 50	FF 51 Beta	FF 52 Aurora	FF 53 Nightly	CH 46, OP 33 ^[1]	CH 47, OP 34 ^[1]	CH 48, OP 35 ^[1]	CH 49, OP 36 ^[1]	CH 50, OP 37 ^[1]	CH 51, OP 38 ^[1]	CH 52, OP 39 ^[1]	CH 53, OP 40 ^[1]	CH 54, OP 41 ^[1]	CH 55, OP 42 ^[1]	CH 56, OP 43 ^[1]	CH 57, OP 44 ^[1]	SF 5.1	SF 6	SF 6.1, SF 7	SF 7.1, SF 8	SF 9	SF 10	SF TP	WK	PJS	Node 0.10 ^[4]	Node 0.12 ^[4]	io.js ^[4]	Node 4 ^[4]	Node 5 ^[4]	Node 6.0-6.4 ^[4]	Node 6.5 ^[4]	Node 7 ^[4]	AN 4.0	AN 4.1	AN 4.2	AN 4.3	AN 4.4	AN 5.0	AN 5.1	iOS 5.1	iOS 6	iOS 7	iOS 8
2016 features
§exponentiation (**) operator	2/3	3/3	3/3	2/3	0/3	0/3	0/3	0/3	0/3	0/3	3/3	3/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	3/3	3/3	0/3	0/3	0/3	0/3	0/3	0/3	3/3	3/3	3/3	3/3	3/3	3/3	0/3	0/3	0/3	0/3	0/3	0/3	3/3	3/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	3/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3
§basic support	Yes	Yes	Yes	Yes	No	No	No	No	No	Flag	Yes	Yes	No	No^[5]	No^[5]	No^[5]	No^[5]	No^[5]	No^[5]	No^[5]	No^[5]	No^[5]	No^[5]	Yes	Yes	No	No	No	No	No	Flag	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	Flag	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No
§assignment	Yes	Yes	Yes	Yes	No	No	No	No	No	Flag	Yes	Yes	No	No	No	No	No	No	No	No^[5]	No^[5]	No^[5]	No^[5]	Yes	Yes	No	No	No	No	No	Flag	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	Flag	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No
§early syntax error for unary negation without parens	No	Yes	Yes	No	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	Flag	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	Flag	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No
§Array.prototype.includes	0/3	3/3	0/3	3/3	2/3	0/3	0/3	0/3	0/3	0/3	3/3	3/3	0/3	0/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	0/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	0/3	0/3	0/3	0/3	2/3	3/3	3/3	3/3	0/3	0/3	0/3	0/3	0/3	0/3	3/3	3/3	3/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	2/3	3/3
§Array.prototype.includes	No	Yes	No	Yes^[6]	Yes	No	No	No	No	No	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes
§Array.prototype.includes is generic	No	Yes	No	Yes^[6]	Yes	No	No	No	No	No	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes
§%TypedArray%.prototype.includes	No	Yes	No	Yes^[6]	No	No	No	No	No	No	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	Yes
2016 misc
§generator functions can't be used with "new"^[7]	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	Yes
§generator throw() caught by inner generator ^[8]	No	No	Yes	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes	Yes	Yes	No	No	Flag	Flag	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	Yes	No	No	No	No	No	Yes
§strict fn w/ non-strict non-simple params is error ^[9]	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	Yes
§nested rest destructuring, declarations ^[10]	No	Yes	Yes	Yes	No	No	No	No	No	Flag	Yes	Yes	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No
§nested rest destructuring, parameters ^[11]	No	Yes	Yes	Yes	No	No	No	No	No	Flag	Yes	Yes	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No
§Proxy, "enumerate" handler removed ^[12]	No	No	No	No	No	No	No	No	No	No	No	Yes	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	Yes
§Proxy internal calls, Array.prototype.includes	No	No	No	No	No	No	No	No	No	No	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	Yes
2017 features
§Object.values	No	Yes	No	Yes^[6]	Yes	No	No	No	No	No	Yes	Yes	No	No	No	No	No^[5]	No^[5]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Flag	Flag	Flag	Yes	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	Flag	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No
§Object.entries	No	Yes	No	Yes^[6]	Yes	No	No	No	No	No	Yes	Yes	No	No	No	No	No^[5]	No^[5]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Flag	Flag	Flag	Yes	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	Flag	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No
§Object.getOwnPropertyDescriptors	0/2	1/2	0/2	1/2	1/2	0/2	0/2	0/2	0/2	0/2	0/2	2/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	2/2	2/2	2/2	2/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	2/2	2/2	2/2	2/2	0/2	0/2	0/2	0/2	0/2	1/2	2/2	2/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	2/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	1/2
§basic support	No	Yes	No	Yes^[6]	Yes	No	No	No	No	No	No	Yes	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	No	Flag	Flag	Flag	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	Flag	Yes	No	No	No	No	No	No	No	No	No	No	No	No	Yes
§doesn't provide undefined descriptors	No	No	No	No	No	No	No	No	No	No	No	Yes	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	No	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No
§String padding	0/2	2/2	0/2	2/2	2/2	0/2	0/2	0/2	0/2	0/2	0/2	2/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	2/2	2/2	2/2	2/2	2/2	2/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	2/2	2/2	2/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	2/2
§String.prototype.padStart	No	Yes	No	Yes^[6]	Yes	No	No	No	No	No	Flag	Yes	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	Flag	Flag	Flag	Flag	Flag	Flag	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	No	Flag	No	No	No	No	No	No	No	No	No	No	No	No	Yes
§String.prototype.padEnd	No	Yes	No	Yes^[6]	Yes	No	No	No	No	No	Flag	Yes	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	Flag	Flag	Flag	Flag	Flag	Flag	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	No	Flag	No	No	No	No	No	No	No	No	No	No	No	No	Yes
§trailing commas in function syntax	0/2	2/2	0/2	2/2	0/2	0/2	0/2	0/2	0/2	0/2	2/2	2/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	2/2	2/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	2/2	2/2	2/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	2/2
§in parameter lists	No	Yes	No	Yes	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	Flag	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes
§in argument lists	No	Yes	No	Yes	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	Flag	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes
§async functions	3/3	3/3	3/3	2/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	3/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	3/3	3/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	3/3	3/3	3/3	0/3	0/3	0/3	0/3	0/3	0/3	3/3	3/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3
§basic support	Yes	Yes^[13]	Yes	Yes^[14]	No	No	No	No	No	Flag	Flag	Yes	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	Flag	Flag	Flag	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	No	Flag	No	No	No	No	No	No	No	No	No	No	No	No	No
§await support	Yes	Yes^[13]	Yes	Yes^[14]	No	No	No	No	No	Flag	Flag	Yes	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	Flag	Flag	Flag	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	No	Flag	No	No	No	No	No	No	No	No	No	No	No	No	No
§arrow async functions	Yes	Yes^[13]	Yes	No	No	No	No	No	No	Flag	Flag	Yes	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	Flag	Flag	Flag	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	No	Flag	No	No	No	No	No	No	No	No	No	No	No	No	No
2017 misc
§class extends null	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	2/2	2/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2	0/2
§proper default constructor	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No
§proper "this" binding	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No
§Proxy "ownKeys" handler, duplicate keys for non-extensible targets	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	Yes
§RegExp "u" flag, case folding	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes
§arguments.caller removed	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No
2017 annex b
§Object.prototype getter/setter methods	0/16	16/16	0/16	16/16	0/16	0/16	0/16	8/16	12/16	12/16	12/16	12/16	14/16	14/16	14/16	14/16	14/16	14/16	14/16	16/16	16/16	16/16	16/16	16/16	16/16	10/16	10/16	10/16	10/16	10/16	10/16	10/16	10/16	10/16	10/16	10/16	10/16	12/16	12/16	12/16	12/16	16/16	16/16	16/16	16/16	12/16	0/16	10/16	10/16	10/16	10/16	10/16	10/16	10/16	10/16	10/16	10/16	10/16	6/16	6/16	10/16	8/16	12/16	12/16	12/16	16/16	16/16
§__defineGetter__	No	Yes	No	Yes^[6]	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§__defineGetter__, symbols	No	Yes	No	Yes^[6]	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	No	No	No	No	Yes	Yes
§__defineGetter__, ToObject(this)	No	Yes	No	Yes^[6]	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes
§__defineSetter__	No	Yes	No	Yes^[6]	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§__defineSetter__, symbols	No	Yes	No	Yes^[6]	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	No	No	No	No	Yes	Yes
§__defineSetter__, ToObject(this)	No	Yes	No	Yes^[6]	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes
§__lookupGetter__	No	Yes	No	Yes^[6]	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§__lookupGetter__, prototype chain	No	Yes	No	Yes^[6]	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§__lookupGetter__, symbols	No	Yes	No	Yes^[6]	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	No	No	No	No	Yes	Yes
§__lookupGetter__, ToObject(this)	No	Yes	No	Yes^[6]	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes
§__lookupGetter__, data properties can shadow accessors	No	Yes	No	Yes^[6]	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes
§__lookupSetter__	No	Yes	No	Yes^[6]	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§__lookupSetter__, prototype chain	No	Yes	No	Yes^[6]	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§__lookupSetter__, symbols	No	Yes	No	Yes^[6]	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	No	No	No	No	Yes	Yes
§__lookupSetter__, ToObject(this)	No	Yes	No	Yes^[6]	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes
§__lookupSetter__, data properties can shadow accessors	No	Yes	No	Yes^[6]	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes
§Proxy internal calls, getter/setter methods	0/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	2/4	4/4	4/4	2/4	2/4	2/4	2/4	2/4	2/4	2/4	2/4	4/4	4/4	4/4	4/4	4/4	0/4	0/4	0/4	0/4	0/4	0/4	2/4	2/4	2/4	2/4	2/4	2/4	0/4	0/4	0/4	0/4	0/4	4/4	4/4	4/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	2/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	4/4
§__defineGetter__	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	No	Yes	No	No	No	No	No	No	No	No	No	No	No	No	Yes
§__defineSetter__	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	No	Yes	No	No	No	No	No	No	No	No	No	No	No	No	Yes
§__lookupGetter__	No	No	No	No	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes
§__lookupSetter__	No	No	No	No	No	No	No	No	No	No	Yes	Yes	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes
§assignments allowed in for-in head in non-strict mode	Yes	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No

^[1] Flagged features have to be enabled via "Experimental Javascript features" flag

^[2] Flagged features require an optional transformer setting.

^[3] Flagged features have to be enabled via "Enable experimental Javascript features" setting under about:flags

^[4] Flagged features have to be enabled via --harmony or --es_staging flag

^[5] The feature is enabled by default only in Firefox Nightly.

^[6] This feature is supported when using TypeScript with core-js, or when a native ES6 host is used.

^[7] TC39 meeting notes from July 28, 2015.

^[8] 'Semantics of yield* in throw case' GitHub issue in ECMA-262 repo.

^[9] TC39 meeting notes from July 29, 2015.

^[10] TC39 meeting notes from July 28, 2015.

^[11] TC39 meeting notes from July 28, 2015.

^[12] 'Normative: Remove [[Enumerate]] and associated reflective capabilities' GitHub Pull Request in ECMA-262 repo.

^[13] This feature requires native generators or regenerator-runtime, it's a part of babel-polyfill or babel-runtime.

^[14] TypeScript async / await requires native generators support.