ECMAScript 2016+ 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)

			Compilers/polyfills					Desktop browsers																	Servers/runtimes					Mobile
Feature name	Current browser		Traceur	Babel 6 + core-js 2	Babel 7 + core-js 2	Babel 7 + core-js 3	Closure 2018.02	Closure 2018.10	Closure 2018.11	Closure 2018.12	Closure 2019.01	Closure 2019.01	Closure 2019.02	Closure 2019.03	Closure 2019.03	Type- Script + core-js 2	Type- Script + core-js 2	Type- Script + core-js 2	Type- Script + core-js 2	Type- Script + core-js 2	Type- Script + core-js 3	Type- Script + core-js 3	Type- Script + core-js 3	Type- Script + core-js 3	es7-shim	IE 11	Edge 15	Edge 16	Edge 17	Edge 18	Edge 19 Preview	FF 59	FF 60 ESR	FF 61	FF 62	FF 63	FF 64	FF 65	FF 66	FF 67	FF 68 Beta	FF 69 Nightly	OP 12.10	CH 67, OP 54	CH 68, OP 55	CH 69, OP 56	CH 70, OP 57	CH 71, OP 58	CH 72, OP 59	CH 73, OP 60	CH 74, OP 61	CH 75, OP 62	CH 76, OP 63	CH 77, OP 64	SF 10.1	SF 11	SF 11.1	SF 12	SF 12.1	SF TP	WK	PJS	Node 0.10 ^[1]	Node 0.12 ^[2]	Node 4 ^[2]	Node >=6.5 <7 ^[2]	Node 7.0-7.5 ^[2]	Node >=7.6 <8 ^[2]	Node >=8.0 <8.3 ^[2]	Node >=8.3 <8.7 ^[2]	Node >=8.7 <8.10 ^[2]	Node >=8.10 <9 ^[2]	Node >=10.0 <10.4 ^[2]	Node >=10.4 <10.9 ^[2]	Node >=10.9 <11 ^[2]	Node >=11 ^[2]	DUK 2.0	DUK 2.1	DUK 2.2	DUK 2.3	GraalVM 19.0.0 ^[3]	AN 4.4	AN 4.4.3	iOS >=10.3 <11	iOS 11	iOS 11.3	iOS 12	iOS 12.2	Samsung 6.4	Samsung 7.2	Samsung 8.2
2016 features
§exponentiation (**) operator	2/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	2/3	2/3	2/3	2/3	2/3	2/3	2/3	2/3	2/3	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	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	3/3	3/3	3/3	3/3	3/3	3/3	3/3	0/3	0/3	0/3	0/3	0/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	2/3	2/3	2/3	2/3	3/3	0/3	0/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3
§basic support	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	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	No	No	No	No	Flag^[4]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§assignment	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	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	No	No	No	No	Flag^[4]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§early syntax error for unary negation without parens	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	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	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Flag^[4]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§Array.prototype.includes	0/3	3/3	3/3	3/3	1/3	2/3	2/3	2/3	2/3	2/3	2/3	2/3	2/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	2/3	0/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	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	3/3	3/3	3/3	3/3	3/3	3/3	3/3	0/3	0/3	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	0/3	0/3	0/3	3/3	0/3	0/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3
§Array.prototype.includes	No	Yes^[5]	Yes^[5]	Yes^[5]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes	No	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	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§Array.prototype.includes is generic	No	Yes^[5]	Yes^[5]	Yes^[5]	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes	No	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	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§%TypedArray%.prototype.includes	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	No	No	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	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
2016 misc
§generator functions can't be used with "new" ^[7]	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	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	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§generator throw() caught by inner generator ^[8]	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	No	No	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	No	No	Flag	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§strict fn w/ non-strict non-simple params is error ^[10]	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	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	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§nested rest destructuring, declarations ^[11]	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	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	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§nested rest destructuring, parameters ^[12]	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	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	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§Proxy, "enumerate" handler removed ^[13]	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	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	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§Proxy internal calls, Array.prototype.includes	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	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	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
2017 features
§Object static methods	0/4	4/4	4/4	4/4	3/4	3/4	3/4	3/4	3/4	3/4	3/4	3/4	3/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	3/4	0/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	0/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	0/4	0/4	0/4	0/4	0/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	0/4	0/4	0/4	0/4	4/4	0/4	0/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4
§Object.values	No	Yes^[5]	Yes^[5]	Yes^[5]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes	No	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	No	No	No	No	Flag^[4]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§Object.entries	No	Yes^[5]	Yes^[5]	Yes^[5]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes	No	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	No	No	No	No	Flag^[4]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§Object.getOwnPropertyDescriptors	No	Yes^[5]	Yes^[5]	Yes^[5]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes	No	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	No	No	No	No	Flag^[4]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§Object.getOwnPropertyDescriptors doesn't provide undefined descriptors	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	No	No	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	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§String padding	0/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	0/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	0/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	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	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	0/2	0/2	0/2	0/2	2/2	0/2	0/2	2/2	2/2	2/2	2/2	2/2	0/2	2/2	2/2
§String.prototype.padStart	No	Yes^[5]	Yes^[5]	Yes^[5]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes	No	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	No	No	No	No	No	Flag^[4]	Flag^[4]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Flag^[4]	Yes	Yes
§String.prototype.padEnd	No	Yes^[5]	Yes^[5]	Yes^[5]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes	No	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	No	No	No	No	No	Flag^[4]	Flag^[4]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Flag^[4]	Yes	Yes
§trailing commas in function syntax	0/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	0/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	0/2	0/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	0/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	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	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	0/2	0/2	0/2	0/2	2/2	0/2	0/2	2/2	2/2	2/2	2/2	2/2	0/2	2/2	2/2
§in parameter lists	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	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	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes
§in argument lists	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	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	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes
§async functions	4/16	4/16	4/16	4/16	10/16	10/16	10/16	10/16	10/16	10/16	10/16	10/16	10/16	9/16	9/16	9/16	9/16	9/16	9/16	9/16	9/16	9/16	0/16	0/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	0/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	15/16	16/16	16/16	16/16	16/16	16/16	16/16	0/16	0/16	0/16	0/16	0/16	0/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	0/16	0/16	0/16	0/16	16/16	0/16	0/16	15/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16
§return	Yes	Yes^[14]	Yes^[14]	Yes^[14]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	No	No	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	No	No	No	No	No	Flag^[4]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§throw	?	?	?	?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	No	No	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	No	No	No	No	No	?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§no line break between async and function	?	?	?	?	No	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	No	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	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§no "prototype" property	?	?	?	?	No	No	No	No	No	No	No	No	No	No	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	No	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	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§await	Yes	Yes^[14]	Yes^[14]	Yes^[14]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	No	No	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	No	No	No	No	No	Flag^[4]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§await, rejection	?	?	?	?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	No	No	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	No	No	No	No	No	?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§must await a value	?	?	?	?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	?	?	?	?	?	?	?	?	?	No	No	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	No	No	No	No	No	?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§can await non-Promise values	?	?	?	?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	No	No	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	No	No	No	No	No	?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§cannot await in parameters	?	?	?	?	No	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	No	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	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§async methods, object literals	?	?	?	?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	No	No	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	No	No	No	No	No	?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§async methods, classes	?	?	?	?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	No	No	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	No	No	No	No	No	?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§async arrow functions in methods, classes	Yes	Yes^[14]	Yes^[14]	Yes^[14]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	No	No	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	No	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Flag^[4]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§async arrow functions	Yes	Yes^[14]	Yes^[14]	Yes^[14]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	Yes^[9]	No	No	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	No	No	No	No	No	Flag^[4]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§correct prototype chain	?	?	?	?	No	No	No	No	No	No	No	No	No	No	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	No	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	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§async function prototype, Symbol.toStringTag	?	?	?	?	No	No	No	No	No	No	No	No	No	No	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	No	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	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§async function constructor	?	?	?	?	No	No	No	No	No	No	No	No	No	No	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	No	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	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§shared memory and atomics	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	17/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	17/17	17/17	17/17	17/17	17/17	17/17	17/17	17/17	17/17	17/17	16/17	12/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	0/17	17/17	17/17	17/17	0/17	0/17	17/17	17/17	0/17	0/17	0/17	0/17	17/17	0/17	0/17	16/17	12/17	0/17	0/17	0/17	0/17	0/17	0/17
§SharedArrayBuffer	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Flag^[15]	Yes	No^[16]	No^[16]	No^[16]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	No	No^[18]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No	No	No	No	Flag^[20]	Flag^[20]	Flag^[20]	Flag^[20]	Yes	Yes	Yes	No^[18]	No^[18]	Yes	Yes	No	No	No	No	Yes	No	No	Yes	No^[19]	No^[19]	No^[19]	No^[19]	Flag^[20]	Flag^[20]	No^[18]
§SharedArrayBuffer[Symbol.species]	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Flag^[15]	Yes	No^[16]	No^[16]	No^[16]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	No	No^[18]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No	No	No	No	No	No	No	No	Yes	Yes	Yes	No^[18]	No^[18]	Yes	Yes	No	No	No	No	Yes	No	No	Yes	No^[19]	No^[19]	No^[19]	No^[19]	No	No	No^[18]
§SharedArrayBuffer.prototype.byteLength	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Flag^[15]	Yes	No^[16]	No^[16]	No^[16]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	No	No^[18]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No	No	No	No	Flag^[20]	Flag^[20]	Flag^[20]	Flag^[20]	Yes	Yes	Yes	No^[18]	No^[18]	Yes	Yes	No	No	No	No	Yes	No	No	No	No^[19]	No^[19]	No^[19]	No^[19]	Flag^[20]	Flag^[20]	No^[18]
§SharedArrayBuffer.prototype.slice	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Flag^[15]	Yes	No^[16]	No^[16]	No^[16]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	No	No^[18]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No	No	No	No	No	No	No	No	Yes	Yes	Yes	No^[18]	No^[18]	Yes	Yes	No	No	No	No	Yes	No	No	Yes	No^[19]	No^[19]	No^[19]	No^[19]	No	No	No^[18]
§SharedArrayBuffer.prototype[Symbol.toStringTag]	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Flag^[15]	Yes	No^[16]	No^[16]	No^[16]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	No	No^[18]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No	No	No	No	Flag^[20]	Flag^[20]	Flag^[20]	Flag^[20]	Yes	Yes	Yes	No^[18]	No^[18]	Yes	Yes	No	No	No	No	Yes	No	No	Yes	No^[19]	No^[19]	No^[19]	No^[19]	Flag^[20]	Flag^[20]	No^[18]
§Atomics.add	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Flag^[15]	Yes	No^[16]	No^[16]	No^[16]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	No	No^[18]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No	No	No	No	Flag^[20]	Flag^[20]	Flag^[20]	Flag^[20]	Yes	Yes	Yes	No^[18]	No^[18]	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	No^[19]	No^[19]	No^[19]	Flag^[20]	Flag^[20]	No^[18]
§Atomics.and	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Flag^[15]	Yes	No^[16]	No^[16]	No^[16]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	No	No^[18]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No	No	No	No	Flag^[20]	Flag^[20]	Flag^[20]	Flag^[20]	Yes	Yes	Yes	No^[18]	No^[18]	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	No^[19]	No^[19]	No^[19]	Flag^[20]	Flag^[20]	No^[18]
§Atomics.compareExchange	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Flag^[15]	Yes	No^[16]	No^[16]	No^[16]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	No	No^[18]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No	No	No	No	Flag^[20]	Flag^[20]	Flag^[20]	Flag^[20]	Yes	Yes	Yes	No^[18]	No^[18]	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	No^[19]	No^[19]	No^[19]	Flag^[20]	Flag^[20]	No^[18]
§Atomics.exchange	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Flag^[15]	Yes	No^[16]	No^[16]	No^[16]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	No	No^[18]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No	No	No	No	Flag^[20]	Flag^[20]	Flag^[20]	Flag^[20]	Yes	Yes	Yes	No^[18]	No^[18]	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	No^[19]	No^[19]	No^[19]	Flag^[20]	Flag^[20]	No^[18]
§Atomics.wait	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Flag^[15]	Yes	No^[16]	No^[16]	No^[16]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	No	No^[18]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No	No	No	No	Flag^[20]	Flag^[20]	Flag^[20]	Flag^[20]	Yes	Yes	Yes	No^[18]	No^[18]	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	No^[19]	No^[19]	No^[19]	Flag^[20]	Flag^[20]	No^[18]
§Atomics.wake	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Flag^[15]	Yes	No^[16]	No^[16]	No^[16]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	No	No^[18]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No	No	No	No	Flag^[20]	Flag^[20]	Flag^[20]	Flag^[20]	Yes	Yes	Yes	No^[18]	No^[18]	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	No^[19]	No^[19]	No^[19]	Flag^[20]	Flag^[20]	No^[18]
§Atomics.isLockFree	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Flag^[15]	Yes	No^[16]	No^[16]	No^[16]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	No	No^[18]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No	No	No	No	Flag^[20]	Flag^[20]	Flag^[20]	Flag^[20]	Yes	Yes	Yes	No^[18]	No^[18]	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	No^[19]	No^[19]	No^[19]	Flag^[20]	Flag^[20]	No^[18]
§Atomics.load	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Flag^[15]	Yes	No^[16]	No^[16]	No^[16]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	No	No^[18]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No	No	No	No	Flag^[20]	Flag^[20]	Flag^[20]	Flag^[20]	Yes	Yes	Yes	No^[18]	No^[18]	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	No^[19]	No^[19]	No^[19]	Flag^[20]	Flag^[20]	No^[18]
§Atomics.or	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Flag^[15]	Yes	No^[16]	No^[16]	No^[16]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	No	No^[18]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No	No	No	No	Flag^[20]	Flag^[20]	Flag^[20]	Flag^[20]	Yes	Yes	Yes	No^[18]	No^[18]	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	No^[19]	No^[19]	No^[19]	Flag^[20]	Flag^[20]	No^[18]
§Atomics.store	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Flag^[15]	Yes	No^[16]	No^[16]	No^[16]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	No	No^[18]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No	No	No	No	Flag^[20]	Flag^[20]	Flag^[20]	Flag^[20]	Yes	Yes	Yes	No^[18]	No^[18]	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	No^[19]	No^[19]	No^[19]	Flag^[20]	Flag^[20]	No^[18]
§Atomics.sub	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Flag^[15]	Yes	No^[16]	No^[16]	No^[16]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	No	No^[18]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No	No	No	No	Flag^[20]	Flag^[20]	Flag^[20]	Flag^[20]	Yes	Yes	Yes	No^[18]	No^[18]	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	No^[19]	No^[19]	No^[19]	Flag^[20]	Flag^[20]	No^[18]
§Atomics.xor	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Flag^[15]	Yes	No^[16]	No^[16]	No^[16]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	Flag^[17]	No	No^[18]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No^[19]	No^[19]	No^[19]	No^[19]	No^[19]	No	No	No	No	Flag^[20]	Flag^[20]	Flag^[20]	Flag^[20]	Yes	Yes	Yes	No^[18]	No^[18]	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	No^[19]	No^[19]	No^[19]	Flag^[20]	Flag^[20]	No^[18]
2017 misc
§Proxy "ownKeys" handler, duplicate keys for non-extensible targets (ES 2017 semantics) ^[21]	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	Yes	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	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	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	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	No	Yes	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	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	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
2017 annex b
§Object.prototype getter/setter methods	0/16	16/16	16/16	16/16	0/16	0/16	0/16	0/16	0/16	0/16	0/16	0/16	0/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	0/16	8/16	12/16	14/16	14/16	14/16	14/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	12/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	16/16	12/16	0/16	10/16	10/16	10/16	10/16	10/16	12/16	12/16	12/16	16/16	16/16	16/16	16/16	16/16	0/16	0/16	16/16	16/16	16/16	6/16	6/16	16/16	16/16	16/16	16/16	16/16	10/16	12/16	16/16
§__defineGetter__	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	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	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§__defineGetter__, symbols	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	No	No	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	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Flag^[4]	Flag^[4]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§__defineGetter__, ToObject(this)	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	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	No	No	No	No	No	No	No	Flag^[22]	Flag^[22]	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	No	No	Yes
§__defineSetter__	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	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	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§__defineSetter__, symbols	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	No	No	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	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Flag^[4]	Flag^[4]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§__defineSetter__, ToObject(this)	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	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	No	No	No	No	No	No	No	Flag^[22]	Flag^[22]	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	No	No	Yes
§__lookupGetter__	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	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	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§__lookupGetter__, prototype chain	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	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	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§__lookupGetter__, symbols	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	No	No	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	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Flag^[4]	Flag^[4]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§__lookupGetter__, ToObject(this)	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	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	No	No	No	No	No	No	No	Flag^[22]	Flag^[22]	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	No	No	Yes
§__lookupGetter__, data properties can shadow accessors	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	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	Yes	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes
§__lookupSetter__	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	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	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§__lookupSetter__, prototype chain	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	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	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§__lookupSetter__, symbols	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	No	No	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	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Flag^[4]	Flag^[4]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§__lookupSetter__, ToObject(this)	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	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	No	No	No	No	No	No	No	Flag^[22]	Flag^[22]	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	No	No	Yes
§__lookupSetter__, data properties can shadow accessors	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	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	Yes	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	No	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	0/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	0/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	0/4	0/4	0/4	0/4	0/4	2/4	2/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	0/4	0/4	0/4	0/4	4/4	0/4	0/4	4/4	4/4	4/4	4/4	4/4	2/4	4/4	4/4
§__defineGetter__	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	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	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§__defineSetter__	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	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	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§__lookupGetter__	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	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	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes
§__lookupSetter__	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	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	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes
§assignments allowed in for-in head in non-strict mode	Yes	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	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	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
2018 features
§object rest/spread properties	0/2	2/2	2/2	2/2	2/2	1/2	1/2	1/2	1/2	0/2	0/2	0/2	0/2	0/2	2/2	2/2	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	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	0/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	0/2	0/2	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	2/2	2/2	2/2	2/2	2/2	2/2	2/2	0/2	0/2	0/2	0/2	2/2	0/2	0/2	0/2	0/2	2/2	2/2	2/2	0/2	0/2	2/2
§object rest properties	No	Yes	Yes	Yes	Yes	No^[23]	No^[23]	No^[23]	No^[23]	No^[23]	No^[23]	No^[23]	No^[23]	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	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	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	Flag^[4]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	Yes	Yes	Yes	No	Flag^[4]	Yes
§object spread properties	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No^[23]	No^[23]	No^[23]	No^[23]	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	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	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	Flag^[4]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	Yes	Yes	Yes	No	Flag^[4]	Yes
§Promise.prototype.finally	0/3	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	3/3	3/3	3/3	3/3	3/3	3/3	0/3	0/3	0/3	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	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	3/3	3/3	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	3/3	3/3	3/3	3/3	0/3	0/3	0/3	0/3	3/3	0/3	0/3	0/3	0/3	3/3	3/3	3/3	0/3	0/3	3/3
§basic support	No	Yes^[5]	Yes^[5]	Yes^[5]	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	No	No	No	No	No	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	No	No	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No^[24]	No^[24]	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	Yes	Yes	Yes	No	No	Yes
§don't change resolution value	No	Yes^[5]	Yes^[5]	Yes^[5]	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	No	No	No	No	No	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	No	No	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No^[24]	No^[24]	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	Yes	Yes	Yes	No	No	Yes
§change rejection value	No	Yes^[5]	Yes^[5]	Yes^[5]	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	No	No	No	No	No	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	No	No	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No^[24]	No^[24]	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	Yes	Yes	Yes	No	No	Yes
§s (dotAll) flag for regular expressions	?	Yes	Yes	Yes	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	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	No	?	?	?	?	?	?	?	Flag^[22]	Flag^[22]	Yes	Yes	Yes	Yes	Yes	?	?	No	No	Yes	?	?	No	No	Yes	Yes	Yes	?	?	Yes
§RegExp named capture groups	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	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	Flag^[22]	Flag^[22]	Flag^[22]	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	Yes	Yes	Yes	No	No	Flag^[22]
§RegExp Lookbehind Assertions	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	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	Flag^[22]	Flag^[22]	Flag^[22]	Flag^[22]	Flag^[22]	Flag^[22]	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	No	No	No	Flag^[22]	Flag^[22]	Yes
§RegExp Unicode Property Escapes	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	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	Flag^[22]	Flag^[22]	Flag^[22]	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	Yes	Yes	Yes	No	Flag^[22]	Flag^[22]
§Asynchronous Iterators	0/2	2/2	2/2	2/2	0/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	0/2	2/2	2/2	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	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	0/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	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	0/2	0/2	0/2	2/2	2/2	2/2	2/2	0/2	0/2	0/2	0/2	2/2	0/2	0/2	0/2	0/2	0/2	2/2	2/2	0/2	0/2	2/2
§async generators	No	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	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	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	Flag^[22]	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	No	Yes	Yes	No	No	Yes
§for-await-of loops	No	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	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	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	Flag^[22]	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	No	Yes	Yes	No	No	Yes
2018 misc
§template literal revision	No	No	No	No	No	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	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	Flag^[22]	Flag^[22]	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	Yes	Yes	Yes	Yes	No	Flag^[22]	Yes
2019 features
§Object.fromEntries	No	No	No	Yes^[5]	No	No	No	No	No	No	No	No	Yes	No^[25]	No^[25]	No^[25]	No^[25]	No^[25]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	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	Yes	No	No	No	No	No	No	Yes	No	No	No
§string trimming	0/4	4/4	4/4	4/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	0/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	2/4	0/4	2/4	2/4	2/4	2/4	2/4	2/4	2/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	0/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	4/4	2/4	2/4	2/4	4/4	4/4	4/4	4/4	2/4	2/4	2/4	2/4	2/4	2/4	2/4	2/4	2/4	2/4	2/4	4/4	4/4	4/4	4/4	0/4	0/4	0/4	0/4	4/4	2/4	2/4	2/4	2/4	2/4	4/4	4/4	2/4	2/4	2/4
§String.prototype.trimLeft	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes	No	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	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§String.prototype.trimRight	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes	No	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	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§String.prototype.trimStart	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No^[26]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	No	No	No	No	No	No	No	No	Flag^[27]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	No	Yes	Yes	No	No	No
§String.prototype.trimEnd	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No^[28]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	No	No	No	No	No	No	No	No	Flag^[27]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	No	Yes	Yes	No	No	No
§Array.prototype.{flat, flatMap}^[29]	0/3	1/3	1/3	3/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	2/3	2/3	1/3	1/3	1/3	1/3	1/3	3/3	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	2/3	2/3	2/3	2/3	2/3	3/3	3/3	3/3	0/3	0/3	0/3	2/3	2/3	2/3	2/3	3/3	3/3	3/3	3/3	3/3	0/3	0/3	0/3	2/3	2/3	2/3	2/3	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	2/3	0/3	0/3	0/3	0/3	3/3	0/3	0/3	0/3	0/3	0/3	2/3	2/3	0/3	0/3	0/3
§Array.prototype.flat	No	No	No	Yes^[5]	No	No	No	No	No	No	No	Yes	Yes	No^[25]	No^[25]	No^[25]	No^[25]	No^[25]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	No	No	No	No	No	No	No	No^[30]	No^[30]	No^[30]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	No	No	No	No	Yes	No	No	No	No	No	Yes	Yes	No	No	No
§Array.prototype.flatMap	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	Yes	Yes	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	No	No	No	No	No	No	No	Flag^[27]	Flag^[27]	Flag^[27]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	No	No	No	No	Yes	No	No	No	No	No	Yes	Yes	No	No	No
§flat and flatMap in Array.prototype[@@unscopables]	No	No	No	Yes^[5]	No	No	No	No	No	No	No	No	No	No^[25]	No^[25]	No^[25]	No^[25]	No^[25]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	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	Yes	Yes	Yes	Yes	Yes	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	No	No	No	No	No	No	No	No	No	No
2019 misc
§optional catch binding	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	0/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	0/3	0/3	0/3	0/3	0/3	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	3/3	3/3	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	3/3	3/3	3/3	3/3	0/3	0/3	0/3	0/3	3/3	0/3	0/3	0/3	0/3	3/3	3/3	3/3	0/3	0/3	0/3
§basic	No	No	Yes	Yes	No	No	No	No	No	No	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	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	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	Yes	Yes	Yes	No	No	No
§await	No	No	Yes	Yes	No	No	No	No	No	No	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	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	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	Yes	Yes	Yes	No	No	No
§yield	No	No	Yes	Yes	No	No	No	No	No	No	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	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	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	Yes	Yes	Yes	No	No	No
§Symbol.prototype.description	0/3	0/3	0/3	3/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3	2/3	2/3	0/3	0/3	0/3	0/3	0/3	3/3	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	3/3	3/3	3/3	3/3	3/3	3/3	3/3	0/3	0/3	0/3	0/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	3/3	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	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	3/3	0/3	0/3	0/3	0/3	0/3	2/3	3/3	0/3	0/3	0/3
§basic	No	No	No	Yes^[5]	No	No	No	No	No	No	No	Yes	Yes	No^[25]	No^[25]	No^[25]	No^[25]	No^[25]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	Flag^[22]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	No	No	No	No	Yes	No	No	No	No	No	Yes	Yes	No	No	No
§empty description	No	No	No	Yes^[5]	No	No	No	No	No	No	No	Yes	Yes	No^[25]	No^[25]	No^[25]	No^[25]	No^[25]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	Flag^[22]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	No	No	No	No	Yes	No	No	No	No	No	Yes	Yes	No	No	No
§undefined description	No	No	No	Yes^[5]	No	No	No	No	No	No	No	No	No	No^[25]	No^[25]	No^[25]	No^[25]	No^[25]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	Flag^[22]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Yes	No	No	No	No	Yes	No	No	No	No	No	No	Yes	No	No	No
§Function.prototype.toString revision	0/7	0/7	0/7	0/7	0/7	0/7	0/7	0/7	0/7	0/7	0/7	0/7	0/7	0/7	0/7	0/7	0/7	0/7	0/7	0/7	0/7	0/7	0/7	1/7	4/7	4/7	4/7	4/7	4/7	7/7	7/7	7/7	7/7	7/7	7/7	7/7	7/7	7/7	7/7	7/7	0/7	7/7	7/7	7/7	7/7	7/7	7/7	7/7	7/7	7/7	7/7	7/7	4/7	4/7	4/7	4/7	4/7	4/7	4/7	1/7	0/7	0/7	4/7	4/7	4/7	4/7	4/7	4/7	4/7	4/7	7/7	7/7	7/7	7/7	1/7	1/7	1/7	1/7	7/7	0/7	0/7	4/7	4/7	4/7	4/7	4/7	4/7	4/7	4/7
§functions created with the Function 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	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	No	No	No	No	No	No	No	No	No	No	Flag^[22]	Flag^[22]	Flag^[22]	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	No	No	No	No	Flag^[22]	Flag^[22]
§arrows	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	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	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§[native code]	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	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	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§class expression with implicit 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	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	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§class expression with explicit 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	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	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
§unicode escape sequences in identifiers	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	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	No	No	No	No	No	No	No	No	No	No	Flag^[22]	Flag^[22]	Flag^[22]	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	No	No	No	No	Flag^[22]	Flag^[22]
§methods and computed property names	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	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	No	No	No	No	No	No	No	No	No	No	Flag^[22]	Flag^[22]	Flag^[22]	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	No	No	No	No	Flag^[22]	Flag^[22]
§JSON superset	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	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	0/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	2/2	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	0/2	0/2	0/2	2/2	2/2	2/2	2/2	0/2	0/2	0/2	0/2	2/2	0/2	0/2	0/2	0/2	0/2	2/2	2/2	0/2	0/2	0/2
§LINE SEPARATOR can appear in string literals	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	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	No	Yes	Yes	No	No	No
§PARAGRAPH SEPARATOR can appear in string literals	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	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	Yes	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	No	Yes	Yes	No	No	No
§Well-formed JSON.stringify	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	Yes	Yes	Yes	No	No	No	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	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	Yes	No	No	No	No	No	No	Yes	No	No	No
2020 features
§String.prototype.matchAll	No	Yes^[5]	Yes^[5]	Yes^[5]	No	No	No	No	No	No	No	No	No	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	Yes^[6]	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Flag^[27]	Yes	Yes	Yes	No	No	Flag^[22]	Flag^[22]	Flag^[22]	Flag^[22]	Flag^[22]	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	No	Flag^[22]	Flag^[22]	No	No	No	No	Yes	No	No	No	No	No	No	No	No	No	No
§BigInt	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	8/8	8/8	0/8	0/8	8/8	8/8	8/8	8/8	8/8	8/8	8/8	8/8	8/8	8/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	8/8	8/8	8/8	0/8	0/8	0/8	0/8	8/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8	0/8
§basic functionality	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	Flag^[31]	Yes	Yes	No	No	Yes	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	No	No	No	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	No	No	No	No	No	No
§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	Flag^[31]	Yes	Yes	No	No	Yes	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	No	No	No	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	No	No	No	No	No	No
§BigInt.asUintN	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	Flag^[31]	Yes	Yes	No	No	Yes	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	No	No	No	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	No	No	No	No	No	No
§BigInt.asIntN	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	Flag^[31]	Yes	Yes	No	No	Yes	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	No	No	No	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	No	No	No	No	No	No
§BigInt64Array	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	Yes	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	No	No	No	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	No	No	No	No	No	No
§BigUint64Array	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	Yes	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	No	No	No	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	No	No	No	No	No	No
§DataView.prototype.getBigInt64	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	Flag^[31]	Yes	Yes	No	No	Yes	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	No	No	No	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	No	No	No	No	No	No
§DataView.prototype.getBigUint64	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	Flag^[31]	Yes	Yes	No	No	Yes	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	No	No	No	Yes	Yes	Yes	No	No	No	No	Yes	No	No	No	No	No	No	No	No	No	No

^[1] Flagged features have to be enabled via --harmony flag

^[2] Flagged features have to be enabled via --harmony or --es_staging flag

^[3] Executed in Node.js/JVM mode via graalvm/bin/node --jvm.

^[4] The feature have to be enabled via "Experimental Javascript features" setting under about:flags

^[5] This feature is supported when using Babel with core-js.

^[6] This feature is supported when using TypeScript with core-js.

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

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

^[9] Requires the downlevelIteration compile option.

^[10] TC39 meeting notes from July 29, 2015.

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

^[12] TC39 meeting notes from July 28, 2015.

^[13] 'Normative: Remove [[Enumerate]] and associated reflective capabilities' GitHub Pull Request in ECMA-262 repo.

^[14] This feature requires native generators or regenerator-runtime, it's a part of babel-polyfill or babel-runtime.

^[15] Flagged features have to be enabled via "Enable experimental Javascript features" setting under about:flags

^[16] The feature was temporarily disabled to mitigate the Meltdown and Spectre CPU bugs.

^[17] The feature was temporarily disabled to mitigate the Meltdown and Spectre CPU bugs. It can be enabled via javascript.options.shared_memory setting under about:config

^[18] The feature was temporarily disabled to mitigate the Meltdown and Spectre CPU bugs.

^[19] The feature was temporarily disabled to mitigate the Meltdown and Spectre CPU bugs.

^[20] The feature have to be enabled via "Experimental enabled SharedArrayBuffer support in JavaScript." setting under about:flags

^[21] The behaviour of the Proxy “ownKeys” handler in presence of duplicate keys has been modified later.

^[22] The feature have to be enabled via --js-flags="--harmony" flag

^[23] Requires native support for Object.assign

^[24] The feature is considered unstable, but can be enabled via --js-flags="--harmony-promise-finally" flag

^[25] TypeScript's compiler will accept code using this feature if the --target ES6 flag is set, but passes it through unmodified and does not supply a runtime polyfill.

^[26] Requires native support for String.prototype.trimLeft.

^[27] The feature is available only in Firefox Nightly builds.

^[28] Requires native support for String.prototype.trimRight.

^[29] Name of Array.prototype.flatten() changed to Array.prototype.flat() due to web compatibility issues.

^[30] Older Firefox Nightly builds support only the obsolete draft function name Array.prototype.flatten().

^[31] The feature have to be enabled via javascript.options.bigint setting under about:config.