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 2018.11 Closure 2019.01 Closure 2019.02 Closure 2019.03 Closure 2019.03 Closure 2019.07 Closure 2019.10 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		 Type-
Script +
core-js 3		 Type-
Script +
core-js 3		 es7-shim IE 11 Edge 15 Edge 16 Edge 17 Edge 18 FF 60 ESR FF 63 FF 64 FF 65 FF 66 FF 67 FF 68 ESR FF 69 FF 70 FF 71 Beta FF 72 Nightly OP 12.10 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		 CH 78,
OP 65		 CH 79,
OP 66		 CH 80,
OP 67		 SF 11 SF 11.1 SF 12 SF 12.1 SF 13 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] Node 12.0-12.4[2] Node 12.5-12.8[2] Node 12.9-12.10[2] Node >=12.11 <13[2] Node 13.0+[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 iOS 13 Samsung 7.2 Samsung 8.2 Samsung 9.2 Samsung 9.4 Samsung 10.2
2016 features
§exponentiation (**) operator MDN (Mozilla Development Network) logo  2/3 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 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 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 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 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 Flag[4] 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
§assignment 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 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 Yes Yes Yes Yes Yes No No Yes Yes Yes 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 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 Flag[4] Yes Yes Yes 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 Yes Yes Yes
§Array.prototype.includes MDN (Mozilla Development Network) logo  0/3 3/3 3/3 3/3 1/3 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 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 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 3/3 3/3 3/3
§Array.prototype.includes MDN (Mozilla Development Network) logo  No Yes[5] Yes[5] Yes[5] 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 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 No No Yes No No Yes Yes Yes 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[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 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 No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§%TypedArray%.prototype.includes MDN (Mozilla Development Network) logo  No Yes[5] Yes[5] Yes[5] 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 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 No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
2016 misc
§generator functions can't be used with "new" MDN (Mozilla Development Network) logo [7] 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 Yes Yes Yes Yes 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 Yes Yes Yes
§generator throw() caught by inner generator MDN (Mozilla Development Network) logo [8] No No No No No 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 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 Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes 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 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 No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§nested rest destructuring, declarations MDN (Mozilla Development Network) logo [11] No 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 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 No No Yes No No Yes Yes Yes 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 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 Yes Yes Yes Yes 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 Yes Yes Yes
§Proxy, "enumerate" handler removed MDN (Mozilla Development Network) logo [13] 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 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
§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 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 No No Yes No No Yes Yes Yes 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 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 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 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 4/4 4/4 4/4
§Object.values MDN (Mozilla Development Network) logo  No Yes[5] Yes[5] Yes[5] 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 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 No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Object.entries MDN (Mozilla Development Network) logo  No Yes[5] Yes[5] Yes[5] 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 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 No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Object.getOwnPropertyDescriptors MDN (Mozilla Development Network) logo  No Yes[5] Yes[5] Yes[5] 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 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 No No Yes No No Yes Yes Yes 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 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 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 Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes 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 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 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 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 2/2 2/2 2/2 2/2 2/2 2/2
§String.prototype.padStart MDN (Mozilla Development Network) logo  No Yes[5] Yes[5] Yes[5] 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 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 Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§String.prototype.padEnd MDN (Mozilla Development Network) logo  No Yes[5] Yes[5] Yes[5] 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 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 Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§trailing commas in function syntax MDN (Mozilla Development Network) logo  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 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 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 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 2/2 2/2 2/2 2/2 2/2 2/2
§in parameter lists MDN (Mozilla Development Network) logo  No 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 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 Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§in argument lists MDN (Mozilla Development Network) logo  No 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 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 Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§async functions MDN (Mozilla Development Network) logo  4/16 4/16 4/16 4/16 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 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 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 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 16/16 16/16 16/16
§return Yes Yes[14] Yes[14] Yes[14] 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 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 Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§throw ? ? ? ? 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 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 Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes 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 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 Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes 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 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 Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§await MDN (Mozilla Development Network) logo  Yes Yes[14] Yes[14] Yes[14] 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 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 Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§await, rejection ? ? ? ? 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 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 Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§must await a value ? ? ? ? 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 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 Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§can await non-Promise values ? ? ? ? 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 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 Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§cannot await in parameters ? ? ? ? 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 ? Yes Yes 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 Yes Yes Yes
§async methods, object literals ? ? ? ? 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 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 Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§async methods, classes ? ? ? ? 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 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 Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes 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[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 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 Yes Yes Yes Yes Yes No No No No Yes No No No Yes Yes Yes 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[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 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 Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes 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 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 Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes 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 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 Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes 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 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 Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes 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 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 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 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 0/17 17/17 17/17 17/17 0/17 0/17 17/17 17/17 17/17 17/17 17/17 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 0/17 0/17 17/17
§SharedArrayBuffer MDN (Mozilla Development Network) logo  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] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] No[18] No[18] No[18] No[18] No No No No Flag[19] Flag[19] Flag[19] Flag[19] Yes Yes Yes No[20] No[20] Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No Yes No[18] No[18] No[18] No[18] No[18] Flag[19] No[20] No[20] No[20] Yes
§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 Flag[15] Yes 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] No[18] No[18] No[18] No[18] No No No No No No No No Yes Yes Yes No[20] No[20] Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No Yes No[18] No[18] No[18] No[18] No[18] No No[20] No[20] No[20] Yes
§SharedArrayBuffer.prototype.byteLength MDN (Mozilla Development Network) logo  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] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] No[18] No[18] No[18] No[18] No No No No Flag[19] Flag[19] Flag[19] Flag[19] Yes Yes Yes No[20] No[20] Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No[18] No[18] No[18] No[18] No[18] Flag[19] No[20] No[20] No[20] Yes
§SharedArrayBuffer.prototype.slice MDN (Mozilla Development Network) logo  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] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] No[18] No[18] No[18] No[18] No No No No No No No No Yes Yes Yes No[20] No[20] Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No Yes No[18] No[18] No[18] No[18] No[18] No No[20] No[20] No[20] Yes
§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 Flag[15] Yes 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] No[18] No[18] No[18] No[18] No No No No Flag[19] Flag[19] Flag[19] Flag[19] Yes Yes Yes No[20] No[20] Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No Yes No[18] No[18] No[18] No[18] No[18] Flag[19] No[20] No[20] No[20] Yes
§Atomics.add MDN (Mozilla Development Network) logo  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] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] No[18] No[18] No[18] No No No No Flag[19] Flag[19] Flag[19] Flag[19] Yes Yes Yes No[20] No[20] Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes No[18] No[18] No[18] No[18] Flag[19] No[20] No[20] No[20] Yes
§Atomics.and MDN (Mozilla Development Network) logo  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] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] No[18] No[18] No[18] No No No No Flag[19] Flag[19] Flag[19] Flag[19] Yes Yes Yes No[20] No[20] Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes No[18] No[18] No[18] No[18] Flag[19] No[20] No[20] No[20] Yes
§Atomics.compareExchange MDN (Mozilla Development Network) logo  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] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] No[18] No[18] No[18] No No No No Flag[19] Flag[19] Flag[19] Flag[19] Yes Yes Yes No[20] No[20] Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes No[18] No[18] No[18] No[18] Flag[19] No[20] No[20] No[20] Yes
§Atomics.exchange MDN (Mozilla Development Network) logo  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] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] No[18] No[18] No[18] No No No No Flag[19] Flag[19] Flag[19] Flag[19] Yes Yes Yes No[20] No[20] Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes No[18] No[18] No[18] No[18] Flag[19] No[20] No[20] No[20] Yes
§Atomics.wait MDN (Mozilla Development Network) logo  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] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] No[18] No[18] No[18] No No No No Flag[19] Flag[19] Flag[19] Flag[19] Yes Yes Yes No[20] No[20] Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes No[18] No[18] No[18] No[18] Flag[19] No[20] No[20] No[20] Yes
§Atomics.wake MDN (Mozilla Development Network) logo  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] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] No[18] No[18] No[18] No No No No Flag[19] Flag[19] Flag[19] Flag[19] Yes Yes Yes No[20] No[20] Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes No[18] No[18] No[18] No[18] Flag[19] No[20] No[20] No[20] Yes
§Atomics.isLockFree MDN (Mozilla Development Network) logo  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] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] No[18] No[18] No[18] No No No No Flag[19] Flag[19] Flag[19] Flag[19] Yes Yes Yes No[20] No[20] Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes No[18] No[18] No[18] No[18] Flag[19] No[20] No[20] No[20] Yes
§Atomics.load MDN (Mozilla Development Network) logo  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] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] No[18] No[18] No[18] No No No No Flag[19] Flag[19] Flag[19] Flag[19] Yes Yes Yes No[20] No[20] Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes No[18] No[18] No[18] No[18] Flag[19] No[20] No[20] No[20] Yes
§Atomics.or MDN (Mozilla Development Network) logo  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] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] No[18] No[18] No[18] No No No No Flag[19] Flag[19] Flag[19] Flag[19] Yes Yes Yes No[20] No[20] Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes No[18] No[18] No[18] No[18] Flag[19] No[20] No[20] No[20] Yes
§Atomics.store MDN (Mozilla Development Network) logo  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] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] No[18] No[18] No[18] No No No No Flag[19] Flag[19] Flag[19] Flag[19] Yes Yes Yes No[20] No[20] Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes No[18] No[18] No[18] No[18] Flag[19] No[20] No[20] No[20] Yes
§Atomics.sub MDN (Mozilla Development Network) logo  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] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] No[18] No[18] No[18] No No No No Flag[19] Flag[19] Flag[19] Flag[19] Yes Yes Yes No[20] No[20] Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes No[18] No[18] No[18] No[18] Flag[19] No[20] No[20] No[20] Yes
§Atomics.xor MDN (Mozilla Development Network) logo  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] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] Flag[17] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] No[18] No[18] No[18] No No No No Flag[19] Flag[19] Flag[19] Flag[19] Yes Yes Yes No[20] No[20] Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes No[18] No[18] No[18] No[18] Flag[19] No[20] No[20] No[20] Yes
2017 misc
§Proxy "ownKeys" handler, duplicate keys for non-extensible targets (ES 2017 semantics) MDN (Mozilla Development Network) logo [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 Yes Yes Yes No No No No No No No No No No No No Yes Yes Yes Yes Yes No No No No No No Yes Yes Yes Yes No No No No No No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes No 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 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 Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§arguments.caller removed MDN (Mozilla Development Network) logo  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 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 Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes 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 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 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 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 16/16 12/16 16/16 16/16 16/16 16/16
§__defineGetter__ MDN (Mozilla Development Network) logo  No Yes[5] Yes[5] Yes[5] 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 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 Yes Yes Yes
§__defineGetter__, symbols No Yes[5] Yes[5] Yes[5] 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 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 Yes Yes Yes Yes Yes No No Yes Yes Yes Flag[4] Flag[4] Yes Yes Yes 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 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 No No No No No No No Flag[22] Flag[22] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes No No Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes
§__defineSetter__ MDN (Mozilla Development Network) logo  No Yes[5] Yes[5] Yes[5] 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 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 Yes Yes Yes
§__defineSetter__, symbols No Yes[5] Yes[5] Yes[5] 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 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 Yes Yes Yes Yes Yes No No Yes Yes Yes Flag[4] Flag[4] Yes Yes Yes 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 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 No No No No No No No Flag[22] Flag[22] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes No No Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes
§__lookupGetter__ MDN (Mozilla Development Network) logo  No Yes[5] Yes[5] Yes[5] 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 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 Yes Yes Yes
§__lookupGetter__, prototype chain No Yes[5] Yes[5] Yes[5] 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 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 Yes Yes Yes
§__lookupGetter__, symbols No Yes[5] Yes[5] Yes[5] 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 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 Yes Yes Yes Yes Yes No No Yes Yes Yes Flag[4] Flag[4] Yes Yes Yes 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 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 No No No No No No No Flag[22] Flag[22] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes No No Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes
§__lookupGetter__, data properties can shadow accessors No Yes[5] Yes[5] Yes[5] 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 Yes Yes Yes Yes Yes Yes Yes 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 Yes Yes Yes Yes Yes No No Yes Yes Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§__lookupSetter__ MDN (Mozilla Development Network) logo  No Yes[5] Yes[5] Yes[5] 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 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 Yes Yes Yes
§__lookupSetter__, prototype chain No Yes[5] Yes[5] Yes[5] 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 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 Yes Yes Yes
§__lookupSetter__, symbols No Yes[5] Yes[5] Yes[5] 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 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 Yes Yes Yes Yes Yes No No Yes Yes Yes Flag[4] Flag[4] Yes Yes Yes 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 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 No No No No No No No Flag[22] Flag[22] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes No No Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes
§__lookupSetter__, data properties can shadow accessors No Yes[5] Yes[5] Yes[5] 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 Yes Yes Yes Yes Yes Yes Yes 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 Yes Yes Yes Yes Yes No No Yes Yes Yes No No Yes Yes Yes Yes Yes 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 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 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 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 4/4 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 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 Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes 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 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 Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes 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 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 Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 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 Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§assignments allowed in for-in head in non-strict mode MDN (Mozilla Development Network) logo  Yes 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 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 Yes Yes Yes
2018 features
§object rest/spread properties 0/2 2/2 2/2 2/2 2/2 1/2 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 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 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 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 2/2 0/2 0/2 0/2 0/2 2/2 2/2 2/2 2/2 0/2 2/2 2/2 2/2 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 Yes Yes Yes Yes Yes Yes Yes Yes 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 Flag[4] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No Yes Yes Yes Yes Flag[4] Yes Yes Yes Yes
§object spread properties No Yes Yes Yes Yes Yes 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 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 Flag[4] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No Yes Yes Yes Yes Flag[4] Yes Yes Yes Yes
§Promise.prototype.finally MDN (Mozilla Development Network) logo  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 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 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 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 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 3/3 0/3 3/3 3/3 3/3 3/3
§basic support No Yes[5] Yes[5] Yes[5] No 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 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 No No[24] No[24] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No Yes Yes Yes Yes No Yes Yes Yes Yes
§don't change resolution value No Yes[5] Yes[5] Yes[5] No 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 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 No No[24] No[24] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No Yes Yes Yes Yes No Yes Yes Yes Yes
§change rejection value No Yes[5] Yes[5] Yes[5] No 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 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 No No[24] No[24] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No Yes Yes Yes Yes No Yes Yes Yes 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes No ? ? ? ? ? ? ? Flag[22] Flag[22] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? No No Yes ? ? No No Yes Yes Yes Yes ? 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 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] Flag[22] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No Yes Yes Yes Yes No Flag[22] Yes Yes Yes
§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 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 Yes Yes Yes Yes Yes No No No No Yes No No No No No No No No Flag[22] Yes Yes Yes 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 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] Flag[22] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No Yes Yes Yes Yes Flag[22] Flag[22] Yes Yes Yes
§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 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 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 0/2 0/2 0/2 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 2/2 0/2 0/2 0/2 0/2 0/2 2/2 2/2 2/2 0/2 2/2 2/2 2/2 2/2
§async generators No Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes 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 Flag[22] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No No Yes Yes Yes No Yes Yes Yes Yes
§for-await-of loops MDN (Mozilla Development Network) logo  No Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes 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 Flag[22] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No No Yes Yes Yes No Yes Yes Yes Yes
2018 misc
§template literal revision No No No No No 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 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 Flag[22] Flag[22] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No Yes Yes Yes Yes Yes Flag[22] Yes Yes Yes Yes
2019 features
§Object.fromEntries MDN (Mozilla Development Network) logo  No No No Yes[5] No No No No No Yes Yes Yes No[25] No[25] No[25] 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 No No No No 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 No Yes Yes Yes Yes Yes No No No No Yes No No No No No No Yes Yes No No 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 4/4 4/4 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 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 2/4 2/4 4/4 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 4/4 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 4/4 2/4 2/4 4/4 4/4 4/4
§String.prototype.trimLeft MDN (Mozilla Development Network) logo  No Yes[5] Yes[5] Yes[5] 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] Yes 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 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 Yes Yes Yes
§String.prototype.trimRight MDN (Mozilla Development Network) logo  No Yes[5] Yes[5] Yes[5] 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] Yes 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 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 Yes Yes Yes
§String.prototype.trimStart MDN (Mozilla Development Network) logo  No Yes[5] Yes[5] Yes[5] No No No No No No[26] 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 Flag[27] 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 Yes Yes Yes Yes Yes No No No No Yes No No No No No Yes Yes Yes No No Yes Yes Yes
§String.prototype.trimEnd MDN (Mozilla Development Network) logo  No Yes[5] Yes[5] Yes[5] No No No No No No[28] 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 Flag[27] 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 Yes Yes Yes Yes Yes No No No No Yes No No No No No Yes Yes Yes No No Yes Yes Yes
§Array.prototype.{flat, flatMap}[29] 0/3 1/3 1/3 3/3 0/3 0/3 0/3 0/3 2/3 2/3 2/3 2/3 1/3 1/3 1/3 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 2/3 2/3 2/3 2/3 3/3 3/3 3/3 3/3 3/3 3/3 0/3 2/3 2/3 2/3 3/3 3/3 3/3 3/3 3/3 3/3 3/3 3/3 0/3 0/3 2/3 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 2/3 3/3 3/3 3/3 3/3 3/3 0/3 0/3 0/3 0/3 3/3 0/3 0/3 0/3 0/3 0/3 2/3 2/3 3/3 0/3 0/3 0/3 0/3 2/3
§Array.prototype.flat MDN (Mozilla Development Network) logo  No No No Yes[5] No No No No Yes Yes Yes Yes No[25] No[25] No[25] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] No No No No No No No[30] 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 No No No Yes Yes Yes Yes Yes Yes No No No No Yes No No No No No Yes Yes Yes No No No No Yes
§Array.prototype.flatMap MDN (Mozilla Development Network) logo  No Yes[5] Yes[5] Yes[5] No No No No 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 No Flag[27] 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 No No No Yes Yes Yes Yes Yes Yes No No No No Yes No No No No No Yes Yes Yes No No No No Yes
§flat and flatMap in Array.prototype[@@unscopables] No No No Yes[5] No No No No No No No No No[25] No[25] No[25] Yes[6] Yes[6] 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 No No No No 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 No Yes Yes Yes Yes Yes No No No No Yes No No No No No No No Yes No No No No No
2019 misc
§optional catch binding 0/3 0/3 3/3 3/3 0/3 0/3 0/3 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 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 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 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 0/3 0/3 0/3 0/3 3/3 0/3 0/3 0/3 0/3 3/3 3/3 3/3 3/3 0/3 0/3 3/3 3/3 3/3
§basic No No Yes Yes No No No Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes 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 No No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No Yes Yes Yes Yes No No Yes Yes Yes
§await No No Yes Yes No No No Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes 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 No No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No Yes Yes Yes Yes No No Yes Yes Yes
§yield No No Yes Yes No No No Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes 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 No No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No Yes Yes Yes Yes No No Yes Yes Yes
§Symbol.prototype.description MDN (Mozilla Development Network) logo  0/3 0/3 0/3 3/3 0/3 0/3 0/3 0/3 2/3 2/3 2/3 2/3 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 0/3 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 2/3 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 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 3/3 0/3 0/3 0/3 0/3 0/3 2/3 3/3 3/3 0/3 0/3 0/3 0/3 3/3
§basic No No No Yes[5] No No No No Yes Yes Yes Yes No[25] No[25] No[25] 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 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 No No No Yes Yes Yes Yes Yes Yes No No No No Yes No No No No No Yes Yes Yes No No No No Yes
§empty description No No No Yes[5] No No No No Yes Yes Yes Yes No[25] No[25] No[25] 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 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 No No No Yes Yes Yes Yes Yes Yes No No No No Yes No No No No No Yes Yes Yes No No No No Yes
§undefined description No No No Yes[5] No No No No No No No No No[25] No[25] No[25] 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 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 No No No Yes Yes Yes Yes Yes Yes No No No No Yes No No No No No No Yes Yes No No No No Yes
§Function.prototype.toString revision MDN (Mozilla Development Network) logo  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 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 7/7 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 7/7 7/7 7/7
§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 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 Yes Yes Yes Yes Yes No No No No Yes No No No No No No No No Flag[22] Flag[22] Yes Yes Yes
§arrows 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 Yes Yes Yes Yes Yes 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 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 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 Yes Yes Yes Yes Yes No No Yes Yes Yes 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 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 Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes 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 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 Yes Yes Yes Yes Yes No No No No Yes No No Yes Yes Yes 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 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 Yes Yes Yes Yes Yes No No No No Yes No No No No No No No No Flag[22] Flag[22] Yes Yes Yes
§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 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 Yes Yes Yes Yes Yes No No No No Yes No No No No No No No No Flag[22] Flag[22] Yes Yes Yes
§JSON superset 0/2 0/2 0/2 0/2 0/2 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 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 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 0/2 0/2 0/2 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 2/2 0/2 0/2 0/2 0/2 0/2 2/2 2/2 2/2 0/2 0/2 2/2 2/2 2/2
§LINE SEPARATOR can appear in string literals 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 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 Yes Yes Yes Yes Yes No No No No Yes No No No No No Yes Yes Yes No No Yes Yes Yes
§PARAGRAPH SEPARATOR can appear in string literals 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 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 Yes Yes Yes Yes Yes No No No No Yes No No No No No Yes Yes Yes No No Yes Yes Yes
§Well-formed JSON.stringify MDN (Mozilla Development Network) logo  No No No Yes[5] No No No No No No No No No[25] No[25] No[25] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] No No No No No No No No Yes 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 No Yes Yes Yes Yes Yes No No No No Yes No No No No No No Yes Yes No No No No No
2020 features
§String.prototype.matchAll MDN (Mozilla Development Network) logo  0/2 1/2 1/2 2/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 1/2 1/2 1/2 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 1/2 1/2 1/2 1/2 1/2 1/2 0/2 0/2 0/2 0/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 2/2 0/2 0/2 0/2 0/2 1/2 1/2 1/2 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 1/2 1/2 1/2 1/2 1/2 0/2 0/2 0/2 0/2 1/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 1/2 0/2 0/2 0/2 0/2 0/2
§basic functionality No Yes[5] Yes[5] Yes[5] 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 Flag[27] Yes Yes Yes Yes Yes Yes No Flag[22] Flag[22] 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 Flag[22] Flag[22] Yes Yes Yes Yes Yes No No No No Yes No No No No No No No Yes No No No No Flag[22]
§throws on non-global regex No No No Yes[5] No No No No No No No No No[25] No[25] No[25] 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 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 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
§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 8/8 8/8 8/8 8/8 8/8 0/8 8/8 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 8/8 8/8 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 8/8 8/8 8/8
§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 Flag[31] 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 No No No No Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No No No No No No No Yes Yes Yes
§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 Flag[31] 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 No No No No Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No No No No No No No Yes Yes Yes
§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 Flag[31] 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 No No No No Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No No No No No No No Yes Yes Yes
§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 Flag[31] 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 No No No No Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No No No No No No No Yes Yes Yes
§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 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 No No No No Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No No No No No No No Yes Yes Yes
§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 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 No No No No Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No No No No No No No Yes Yes Yes
§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 Flag[31] 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 No No No No Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No No No No No No No Yes Yes Yes
§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 Flag[31] 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 No No No No Yes Yes Yes Yes Yes Yes Yes Yes No No No No Yes No No No No No No No No No No Yes Yes Yes
§Promise.allSettled No No No Yes[5] No No No No No No No Yes No[25] No[25] No[25] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] No No No No No No No No No No No No Flag[27] Flag[27] Flag[27] 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 Yes Yes Yes No No No No No No No No No No No No Yes No No No No No
§globalThis MDN (Mozilla Development Network) logo  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 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 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 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 0/2 0/2 0/2 0/2 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 0/2 0/2 2/2 2/2 0/2 0/2 0/2 0/2 2/2
§"globalThis" global property is global object No No No Yes[5] No No No No No No No No No[25] No[25] No[25] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes Yes No Flag[4] 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 No No No Flag[4] Yes Yes Yes Yes Yes No No No No Yes No No No No No No Yes Yes No No No No Yes
§"globalThis" global property has correct property descriptor No No No Yes[5] No No No No No No No No No[25] No[25] No[25] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes Yes No Flag[4] 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 No No No Flag[4] Yes Yes Yes Yes Yes No No No No Yes No No No No No No Yes Yes No No No No Yes

[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 have to be enabled via "Experimental enabled SharedArrayBuffer support in JavaScript." setting under about:flags

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

[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.