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 Jint 3 Traceur Babel 6 +
core-js 2		 Babel 7 +
core-js 2		 Babel 7 +
core-js 3		 Closure 2020.06 Closure 2020.09 Closure 2021.08 Closure 2021.09 Closure 2021.10 Closure 2021.11 Closure 2022.05 Closure 2022.07 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		 es7-shim IE 11 FF 78 ESR FF 91 ESR FF 93 FF 94 FF 95 FF 96 FF 97 FF 98 FF 99 FF 100 FF 101 FF 102 ESR FF 103 FF 104 FF 105 FF 106 FF 107 FF 108 OP 12.10 CH 96 CH 97 CH 98 CH 99 CH 100 CH 101 CH 102 CH 103 CH 104 CH 105 CH 106 CH 107 CH 108 Edge 18 Edge 95 Edge 96 Edge 97 Edge 98 Edge 99 Edge 100 Edge 101 Edge 102 Edge 103 Edge 104 Edge 105 Edge 106 Edge 107 SF 14 SF 14.1 SF 15 SF 15.2 SF 15.4 SF 16 SF TP WK OP 82 OP 83 OP 84 OP 85 OP 86 OP 87 OP 88 OP 89 OP 90 OP 91 OP 92 OP 93 Rhino 1.7.13 Rhino 1.7.14 PJS Node 0.4[1] Node 0.6[1] Node 0.8[1] Node 0.10[1] Node 0.12[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 13.0-13.1[2] Node >=13.2 <14[2] Node >=14.0 <14.5[2] Node >=14.5 <14.6[2] Node >=14.6 <15[2] Node >=15.0 <16[2] Node >=16.0 <16.8[2] Node >=16.9 <16.11 Node >=16.11 <17 Node >=17.0 <17.2 Node >=17.2 <18 Node >=18.0 <18.3 Node >=18.3 <19 Node >=19 DUK 2.6 DUK 2.7 JrS 2.3.0 JrS 2.4.0 GraalVM 19.3.1[3] GraalVM 19.3.6[3] GraalVM 20.0.0[3] GraalVM 20.1.0[3] GraalVM 20.3.0[3] GraalVM 20.3.1[3] GraalVM 21.0.0[3] GraalVM 21.3.3[4] GraalVM 22.2.0[4] Hermes 0.7.0 Hermes 0.12.0 Deno 1.19 Deno 1.20 Deno 1.21 Deno 1.22 Deno 1.23 Deno 1.24 AN 4.4 AN 4.4.3 iOS 12 iOS 12.2 iOS 13 iOS 13.4 iOS 14 iOS 15 iOS 15.2 iOS 15.4 iOS 16 Samsung 12 Samsung 13 Samsung 14 Samsung 15 Opera Mobile 65 Opera Mobile 66 Opera Mobile 67 Opera Mobile 68 Opera Mobile 69 Opera Mobile 70 Opera Mobile 71 React Native 0.70.3 (Hermes + Babel)
2016 features
§exponentiation (**) operator MDN (Mozilla Development Network) logo  3/3 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 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 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 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 3/3 3/3 3/3 3/3 3/3 3/3 3/3 3/3 3/3 3/3 3/3 0/3 3/3 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 3/3 3/3 3/3 3/3 3/3 3/3 3/3 2/3 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 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 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
§basic support 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes ? ? ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 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 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 Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§early syntax error for unary negation without parens 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes ? ? ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Array.prototype.includes MDN (Mozilla Development Network) logo  4/4 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 3/4 0/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 3/4 3/4 3/4 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 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 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 2/4 3/4 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 4/4 4/4 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 4/4 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 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4
§Array.prototype.includes MDN (Mozilla Development Network) logo  Yes ? 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 No 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 Yes Yes Yes Yes Yes Yes Yes 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Array.prototype.includes handles sparse arrays MDN (Mozilla Development Network) logo  Yes ? 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 No Yes Yes Yes Yes Yes Yes Yes Yes No No No 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 Yes Yes Yes Yes Yes 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Array.prototype.includes is generic Yes ? 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 No 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 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§%TypedArray%.prototype.includes MDN (Mozilla Development Network) logo  Yes ? Yes[5] Yes[5] Yes[5] ? ? ? ? ? ? ? ? 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
2016 misc
§generator functions can't be used with "new" MDN (Mozilla Development Network) logo [7] Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§generator throw() caught by inner generator MDN (Mozilla Development Network) logo [8] No ? ? ? 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] ? No 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? Flag 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§strict fn w/ non-strict non-simple params is error[10] Yes ? ? ? Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§nested rest destructuring, declarations MDN (Mozilla Development Network) logo [11] 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 ? ? ? ? ? ? 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§nested rest destructuring, parameters[12] 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 ? ? ? ? ? ? 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Proxy, "enumerate" handler removed MDN (Mozilla Development Network) logo [13] Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Proxy internal calls, Array.prototype.includes Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
2017 features
§Object static methods 4/4 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 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 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 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 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 0/4 2/4 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 4/4 4/4 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 4/4 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 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  Yes ? 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 No 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 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Object.entries MDN (Mozilla Development Network) logo  Yes ? 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 No 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 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Object.getOwnPropertyDescriptors MDN (Mozilla Development Network) logo  Yes ? 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 No 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 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Object.getOwnPropertyDescriptors doesn't provide undefined descriptors Yes ? Yes[5] Yes[5] Yes[5] ? ? ? ? ? ? ? ? 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§String padding 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 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 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 2/2 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 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 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 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 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
§String.prototype.padStart MDN (Mozilla Development Network) logo  Yes ? 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 No 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 Yes Yes Yes Yes Yes Yes Yes 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§String.prototype.padEnd MDN (Mozilla Development Network) logo  Yes ? 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 No 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 Yes Yes Yes Yes Yes Yes Yes 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§trailing commas in function syntax MDN (Mozilla Development Network) logo  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 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 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 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 2/2 2/2 2/2 2/2 2/2 2/2 2/2 1/2 1/2 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 2/2 2/2 2/2 2/2 2/2 0/2 0/2 1/2 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 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
§in parameter lists MDN (Mozilla Development Network) logo  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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 ? ? ? ? ? ? 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 Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§in argument lists MDN (Mozilla Development Network) logo  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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§async functions MDN (Mozilla Development Network) logo  12/16 4/16 4/16 9/16 12/16 12/16 12/16 12/16 12/16 12/16 12/16 12/16 12/16 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 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 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 16/16 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 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 16/16 16/16 0/16 0/16 9/16 13/16 16/16 16/16 16/16 16/16 16/16 16/16 16/16 16/16 16/16 0/16 12/16 16/16 16/16 16/16 16/16 16/16 16/16 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 16/16 16/16 16/16 16/16 11/16
§return Yes 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] ? No 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 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 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
§throw Yes ? ? 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] ? No 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 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 No 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
§no line break between async and function 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 ? ? ? ? ? ? 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 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
§no "prototype" property Yes ? ? ? ? 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 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 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 No No 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 No
§await MDN (Mozilla Development Network) logo  No 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] ? No 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 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 No No 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
§await, rejection No ? ? 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] ? No 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 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 No No 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
§must await a value 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 ? ? ? ? ? ? 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 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
§can await non-Promise values Yes ? ? 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] ? No 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 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 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
§cannot await in parameters No ? ? ? 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 ? ? ? ? ? ? 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 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 No
§async methods, object literals Yes ? ? 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] ? No 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 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 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
§async methods, classes Yes ? ? 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] ? No 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 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 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 Yes Yes Yes Yes Yes
§async arrow functions in methods, classes Yes 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] ? No 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 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 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 Yes Yes Yes Yes Yes
§async arrow functions No 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] ? No 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 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 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 Yes Yes Yes Yes Yes
§correct prototype chain Yes ? ? ? ? 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 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 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 No 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 No
§async function prototype, Symbol.toStringTag Yes ? ? ? ? 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 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 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 No 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 No
§async function constructor Yes ? ? ? ? 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 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 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 No 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 No
§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 12/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 0/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 0/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 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 17/17 17/17 17/17 17/17 17/17 17/17 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 17/17 17/17 17/17 17/17 17/17 17/17 17/17 0/17 0/17 0/17 0/17 16/17 16/17 17/17 17/17 17/17 17/17 17/17 17/17 17/17 0/17 0/17 17/17 17/17 17/17 17/17 17/17 17/17 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 17/17 17/17 17/17 0/17
§SharedArrayBuffer MDN (Mozilla Development Network) logo  No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No No[15] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[17] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] 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 No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? No[18] No[18] No[18] No[18] No[18] No[18] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§SharedArrayBuffer[Symbol.species] No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No No[15] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[17] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] 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 No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? No[18] No[18] No[18] No[18] No[18] No[18] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§SharedArrayBuffer.prototype.byteLength MDN (Mozilla Development Network) logo  No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No No[15] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[17] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] 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 No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? No[18] No[18] No[18] No[18] No[18] No[18] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§SharedArrayBuffer.prototype.slice MDN (Mozilla Development Network) logo  No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No No[15] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[17] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] 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 No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? No[18] No[18] No[18] No[18] No[18] No[18] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§SharedArrayBuffer.prototype[Symbol.toStringTag] No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No No[15] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] Yes[16] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[17] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] 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 No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? No[18] No[18] No[18] No[18] No[18] No[18] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§Atomics.add MDN (Mozilla Development Network) logo  No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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[17] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] 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 No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? No[18] No[18] No[18] No[18] No[18] No[18] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§Atomics.and MDN (Mozilla Development Network) logo  No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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[17] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] 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 No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? No[18] No[18] No[18] No[18] No[18] No[18] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§Atomics.compareExchange MDN (Mozilla Development Network) logo  No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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[17] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] 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 No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? No[18] No[18] No[18] No[18] No[18] No[18] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§Atomics.exchange MDN (Mozilla Development Network) logo  No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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[17] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] 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 No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? No[18] No[18] No[18] No[18] No[18] No[18] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§Atomics.wait MDN (Mozilla Development Network) logo  No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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[17] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] 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 No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? No[18] No[18] No[18] No[18] No[18] No[18] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§Atomics.notify MDN (Mozilla Development Network) logo  No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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[17] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] 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 No No No No Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? No[18] No[18] No[18] No[18] No[18] No[18] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§Atomics.isLockFree MDN (Mozilla Development Network) logo  No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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[17] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] 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 No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? No[18] No[18] No[18] No[18] No[18] No[18] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§Atomics.load MDN (Mozilla Development Network) logo  No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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[17] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] 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 No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? No[18] No[18] No[18] No[18] No[18] No[18] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§Atomics.or MDN (Mozilla Development Network) logo  No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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[17] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] 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 No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? No[18] No[18] No[18] No[18] No[18] No[18] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§Atomics.store MDN (Mozilla Development Network) logo  No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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[17] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] 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 No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? No[18] No[18] No[18] No[18] No[18] No[18] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§Atomics.sub MDN (Mozilla Development Network) logo  No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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[17] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] 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 No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? No[18] No[18] No[18] No[18] No[18] No[18] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§Atomics.xor MDN (Mozilla Development Network) logo  No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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[17] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No[18] No[18] No[18] 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 No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? No[18] No[18] No[18] No[18] No[18] No[18] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
2017 misc
§RegExp "u" flag, case folding No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 ? ? ? ? ? ? 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 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 No
§arguments.caller removed MDN (Mozilla Development Network) logo  Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 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 No 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 Yes Yes Yes Yes No
2017 annex b
§Object.prototype getter/setter methods 16/16 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 0/16 8/16 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 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 14/16 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 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 10/16 10/16 12/16 0/16 0/16 0/16 0/16 10/16 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 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 6/16 6/16 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 16/16 16/16 16/16
§__defineGetter__ MDN (Mozilla Development Network) logo  Yes ? Yes[5] Yes[5] Yes[5] ? ? ? ? ? ? ? ? Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§__defineGetter__, symbols Yes ? Yes[5] Yes[5] Yes[5] ? ? ? ? ? ? ? ? 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Flag[19] Flag[19] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§__defineGetter__, ToObject(this) Yes ? Yes[5] Yes[5] Yes[5] ? ? ? ? ? ? ? ? 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§__defineSetter__ MDN (Mozilla Development Network) logo  Yes ? Yes[5] Yes[5] Yes[5] ? ? ? ? ? ? ? ? Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§__defineSetter__, symbols Yes ? Yes[5] Yes[5] Yes[5] ? ? ? ? ? ? ? ? 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Flag[19] Flag[19] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§__defineSetter__, ToObject(this) Yes ? Yes[5] Yes[5] Yes[5] ? ? ? ? ? ? ? ? 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§__lookupGetter__ MDN (Mozilla Development Network) logo  Yes ? Yes[5] Yes[5] Yes[5] ? ? ? ? ? ? ? ? Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§__lookupGetter__, prototype chain Yes ? Yes[5] Yes[5] Yes[5] ? ? ? ? ? ? ? ? Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§__lookupGetter__, symbols Yes ? Yes[5] Yes[5] Yes[5] ? ? ? ? ? ? ? ? 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Flag[19] Flag[19] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§__lookupGetter__, ToObject(this) Yes ? Yes[5] Yes[5] Yes[5] ? ? ? ? ? ? ? ? Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 Yes ? ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§__lookupGetter__, data properties can shadow accessors Yes ? Yes[5] Yes[5] Yes[5] ? ? ? ? ? ? ? ? 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? Yes Yes Yes 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 Yes Yes Yes
§__lookupSetter__ MDN (Mozilla Development Network) logo  Yes ? Yes[5] Yes[5] Yes[5] ? ? ? ? ? ? ? ? Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§__lookupSetter__, prototype chain Yes ? Yes[5] Yes[5] Yes[5] ? ? ? ? ? ? ? ? Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§__lookupSetter__, symbols Yes ? Yes[5] Yes[5] Yes[5] ? ? ? ? ? ? ? ? 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Flag[19] Flag[19] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§__lookupSetter__, ToObject(this) Yes ? Yes[5] Yes[5] Yes[5] ? ? ? ? ? ? ? ? Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 Yes ? ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§__lookupSetter__, data properties can shadow accessors Yes ? Yes[5] Yes[5] Yes[5] ? ? ? ? ? ? ? ? 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? Yes Yes Yes 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 Yes Yes Yes
§Proxy internal calls, getter/setter methods 4/4 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 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 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 4/4 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 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 4/4 4/4 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 4/4 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 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4
§__defineGetter__ Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§__defineSetter__ Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§__lookupGetter__ Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§__lookupSetter__ Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§assignments allowed in for-in head in non-strict mode MDN (Mozilla Development Network) logo  No Yes ? ? Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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
2018 features
§object rest/spread properties 2/2 0/2 2/2 2/2 2/2 0/2 0/2 0/2 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 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 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 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 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 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 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 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
§object rest properties Yes ? Yes Yes Yes No[20] No[20] No[20] 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 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 ? ? ? ? ? ? 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 Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§object spread properties Yes ? Yes Yes Yes No[20] No[20] No[20] 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 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 ? ? ? ? ? ? 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 Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Promise.prototype.finally MDN (Mozilla Development Network) logo  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 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 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 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 3/3 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 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 3/3 3/3 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 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 3/3 3/3 3/3 3/3 3/3
§basic support Yes ? 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] ? No 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 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 No 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
§don't change resolution value Yes ? 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] ? No 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 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 No 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
§change rejection value Yes ? 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] ? No 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 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 No 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
§s (dotAll) flag for regular expressions MDN (Mozilla Development Network) logo  Yes ? Yes Yes Yes No No No No No No No No ? ? ? ? ? ? ? ? ? No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No 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 ? ? ? ? ? ? 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 Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§RegExp named capture groups MDN (Mozilla Development Network) logo  Yes ? Yes Yes Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 ? ? ? ? ? ? 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 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 No
§RegExp Lookbehind Assertions MDN (Mozilla Development Network) logo  Yes ? ? ? No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 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 ? ? ? ? ? ? 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 ? ? ? ? ? No No No No No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§RegExp Unicode Property Escapes MDN (Mozilla Development Network) logo  No ? Yes Yes Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 ? ? ? ? ? ? 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 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
§Asynchronous Iterators 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 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 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 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 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 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 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 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 2/2 2/2 2/2 2/2 0/2
§async generators No ? 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 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 ? ? ? ? ? ? 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 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 No
§for-await-of loops MDN (Mozilla Development Network) logo  No ? 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 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 ? ? ? ? ? ? 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 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 No
2018 misc
§Proxy "ownKeys" handler, duplicate keys for non-extensible targets MDN (Mozilla Development Network) logo  Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 No 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§template literal revision No ? ? ? 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 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 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 Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
2019 features
§Symbol.prototype.description MDN (Mozilla Development Network) logo  3/3 0/3 0/3 0/3 3/3 2/3 2/3 2/3 2/3 2/3 2/3 2/3 2/3 0/3 0/3 0/3 3/3 3/3 3/3 3/3 3/3 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 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 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 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 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 3/3 3/3 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 2/3 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 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
§basic Yes ? No No Yes[5] Yes Yes Yes Yes Yes Yes Yes Yes ?[21] ?[21] ?[21] 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 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 ? ? ? ? ? ? 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 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
§empty description Yes ? No No Yes[5] Yes Yes Yes Yes Yes Yes Yes Yes ?[21] ?[21] ?[21] 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 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 ? ? ? ? ? ? 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 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
§undefined description Yes ? No No Yes[5] ? ? ? ? ? ? ? ? ?[21] ?[21] ?[21] 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 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 ? ? ? ? ? ? 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 No No 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
§Object.fromEntries MDN (Mozilla Development Network) logo  Yes ? No No Yes[5] Yes Yes Yes Yes Yes Yes Yes Yes ?[21] ?[21] ?[21] 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 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 Yes ? ? ? ? ? ? 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 Yes ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§string trimming 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 4/4 2/4 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 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 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 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 4/4 4/4 4/4 4/4 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 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 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 4/4 4/4 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 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4
§String.prototype.trimLeft MDN (Mozilla Development Network) logo  Yes ? 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§String.prototype.trimRight MDN (Mozilla Development Network) logo  Yes ? 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§String.prototype.trimStart MDN (Mozilla Development Network) logo  Yes ? 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] ? No 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§String.prototype.trimEnd MDN (Mozilla Development Network) logo  Yes ? 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] ? No 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Array.prototype.{flat, flatMap}[22] 3/3 0/3 1/3 1/3 3/3 2/3 2/3 2/3 2/3 2/3 2/3 2/3 2/3 1/3 1/3 1/3 3/3 3/3 3/3 3/3 3/3 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 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 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 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 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 3/3 3/3 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 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 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
§Array.prototype.flat MDN (Mozilla Development Network) logo  Yes ? No No Yes[5] Yes Yes Yes Yes Yes Yes Yes Yes ?[21] ?[21] ?[21] 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 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 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 Yes Yes No No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Array.prototype.flatMap MDN (Mozilla Development Network) logo  Yes ? 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] ? No 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 ? ? ? ? ? ? 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 Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§flat and flatMap in Array.prototype[@@unscopables] Yes ? No No Yes[5] ? ? ? ? ? ? ? ? ?[21] ?[21] ?[21] 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 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 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 Yes Yes No No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No 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
2019 misc
§optional catch binding 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 0/3 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 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 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 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 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 3/3 3/3 0/3 0/3 0/3 3/3 2/3 2/3 3/3 3/3 3/3 3/3 3/3 3/3 3/3 2/3 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 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
§basic 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 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 ? ? ? ? ? ? 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 Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§await 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 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 ? ? ? ? ? ? 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 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
§yield 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 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 ? ? ? ? ? ? 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Function.prototype.toString revision MDN (Mozilla Development Network) logo  1/7 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 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 1/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 4/7 7/7 7/7 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 4/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 1/7 1/7 1/7 0/7 0/7 0/7 0/7 0/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 1/7 1/7 0/7 0/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 7/7 1/7 1/7 7/7 7/7 7/7 7/7 7/7 7/7 0/7 0/7 4/7 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 7/7 7/7 1/7
§functions created with the Function constructor No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 Yes 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 ? ? ? ? ? ? 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 No No Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§arrows No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 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 No No 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 Yes Yes Yes Yes No
§[native code] Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§class expression with implicit constructor No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 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 No No 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 Yes Yes Yes Yes No
§class expression with explicit constructor No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 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 No No 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 Yes Yes Yes Yes No
§unicode escape sequences in identifiers No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 Yes 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 ? ? ? ? ? ? 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 No No Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§methods and computed property names No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 Yes 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 ? ? ? ? ? ? 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 No No Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§JSON superset 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 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 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 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 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 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 2/2 2/2 2/2 2/2 2/2 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 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 2/2 2/2 2/2 2/2 2/2
§LINE SEPARATOR can appear in string literals No ? ? 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 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 Yes ? ? ? ? ? ? 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 Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§PARAGRAPH SEPARATOR can appear in string literals No ? ? 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 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 Yes ? ? ? ? ? ? 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 Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Well-formed JSON.stringify MDN (Mozilla Development Network) logo  Yes ? No No Yes[5] ? ? ? ? ? ? ? ? ?[21] ?[21] ?[21] 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 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 ? ? ? ? ? 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 No No 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
2020 features
§String.prototype.matchAll MDN (Mozilla Development Network) logo  2/2 0/2 1/2 1/2 2/2 2/2 2/2 2/2 2/2 2/2 2/2 2/2 2/2 1/2 1/2 1/2 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 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 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 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 0/2 1/2 1/2 1/2 1/2 1/2 1/2 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 2/2 1/2 1/2 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 0/2 0/2 0/2 0/2 1/2 2/2 2/2 2/2 2/2 2/2 2/2 1/2 2/2 2/2 2/2 2/2 2/2 2/2 2/2 2/2 2/2 2/2 2/2
§basic functionality Yes ? 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] ? No 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 ? ? ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No Yes Yes Yes Flag[23] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§throws on non-global regex Yes ? No No Yes[5] Yes Yes Yes Yes Yes Yes Yes Yes ?[21] ?[21] ?[21] 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 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 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 No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No Yes No No Flag[23] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? No Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§BigInt MDN (Mozilla Development Network) logo  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 0/8 0/8 0/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 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 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 8/8 8/8 4/8 4/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 0/8 4/8 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 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 6/8 8/8 8/8 8/8 8/8 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 0/8 0/8 0/8 0/8 0/8 0/8 4/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8 8/8
§basic functionality 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 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 Yes ? ? ? ? ? ? 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 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
§constructor 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 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 Yes ? ? ? ? ? ? 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 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
§BigInt.asUintN 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 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 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 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
§BigInt.asIntN 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 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 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 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
§BigInt64Array 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 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 ? ? ? ? ? ? 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 No Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§BigUint64Array 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 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 ? ? ? ? ? ? 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 No Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§DataView.prototype.getBigInt64 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 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 ? ? ? ? ? ? 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 No Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§DataView.prototype.getBigUint64 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 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 ? ? ? ? ? ? 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 No Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Promise.allSettled MDN (Mozilla Development Network) logo  Yes ? No No Yes[5] Yes Yes Yes Yes Yes Yes Yes Yes ?[21] ?[21] ?[21] 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 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 ? ? ? ? ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No No No Flag[23] 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 Yes Yes No
§globalThis MDN (Mozilla Development Network) logo  2/2 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 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 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 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 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 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 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 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
§"globalThis" global property is global object Yes ? No No Yes[5] Yes Yes Yes Yes Yes Yes Yes Yes ?[21] ?[21] ?[21] 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 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes ? ? ? ? No No 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§"globalThis" global property has correct property descriptor Yes ? No No Yes[5] Yes Yes Yes Yes Yes Yes Yes Yes ?[21] ?[21] ?[21] 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 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes ? ? ? ? No No 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§optional chaining operator (?.) MDN (Mozilla Development Network) logo  5/5 0/5 0/5 4/5 5/5 0/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 0/5 0/5 0/5 4/5 4/5 4/5 4/5 4/5 0/5 0/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 0/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 0/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 0/5 0/5 0/5 0/5 0/5 0/5 0/5 0/5 0/5 0/5 0/5 0/5 0/5 0/5 4/5 4/5 4/5 4/5 4/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 0/5 0/5 0/5 0/5 0/5 0/5 0/5 4/5 4/5 4/5 4/5 5/5 5/5 4/5 4/5 5/5 5/5 5/5 5/5 5/5 5/5 0/5 0/5 0/5 0/5 0/5 5/5 5/5 5/5 5/5 5/5 5/5 0/5 4/5 4/5 4/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5
§optional property access Yes ? ? Yes Yes 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 Yes Yes Yes Yes Yes Yes Yes ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? No Flag[24] Flag[24] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No No No Flag[23] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? Yes Yes Yes Yes Yes Yes Flag[24] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§optional bracket access Yes ? ? Yes Yes 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 Yes Yes Yes Yes Yes Yes Yes ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? No Flag[24] Flag[24] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No No No Flag[23] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? Yes Yes Yes Yes Yes Yes Flag[24] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§optional method call Yes ? ? Yes Yes 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 Yes Yes Yes Yes Yes Yes Yes ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? No Flag[24] Flag[24] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No No No Flag[23] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? Yes Yes Yes Yes Yes Yes Flag[24] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§optional function call Yes ? ? Yes Yes 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 Yes Yes Yes Yes Yes Yes Yes ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? No Flag[24] Flag[24] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No No No Flag[23] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? Yes Yes Yes Yes Yes Yes Flag[24] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§spread parameters after optional chaining Yes ? ? ? Yes No 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 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 No No No No No No Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? 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
§nullish coalescing operator (??) MDN (Mozilla Development Network) logo  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 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 Flag[25] Flag[25] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No Yes No No Flag[23] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? Yes Yes Yes Yes Yes Yes Flag[25] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
2021 features
§String.prototype.replaceAll MDN (Mozilla Development Network) logo  Yes ? No No Yes[5] No No Yes Yes Yes Yes Yes Yes ?[21] ?[21] ?[21] 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 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 No Flag[26] Flag[26] Flag[26] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No Yes No No Flag[23] Flag[27] Flag[27] Flag[27] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? Yes Yes Yes Yes Yes Yes No Flag[26] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Promise.any MDN (Mozilla Development Network) logo  2/2 0/2 0/2 0/2 2/2 0/2 0/2 2/2 2/2 2/2 2/2 2/2 2/2 0/2 0/2 0/2 2/2 2/2 2/2 2/2 2/2 0/2 0/2 0/2 2/2 2/2 2/2 2/2 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 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 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 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 0/2 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 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 0/2 0/2 2/2 2/2 2/2 2/2 2/2 2/2 2/2 2/2 2/2 0/2
§fulfillment Yes ? No No Yes[5] No No Yes Yes Yes Yes Yes Yes ?[21] ?[21] ?[21] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] ? No Flag[28] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? No No No No No Flag[29] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No ? ? ? ? Flag[27] Flag[27] Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§AggregateError Yes ? No No Yes[5] No No Yes Yes Yes Yes Yes Yes ?[21] ?[21] ?[21] Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] ? No Flag[28] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? No No No No No Flag[29] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No ? ? ? ? Flag[27] Flag[27] Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§WeakReferences MDN (Mozilla Development Network) logo  2/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 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 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 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 2/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 2/2 2/2 2/2 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 2/2 2/2 2/2 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 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 0/2
§WeakRef minimal support Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No Flag[30] 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 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 ? ? ? ? ? ? Flag[31] Flag[31] Flag[31] Flag[31] Flag[31] Flag[31] Flag[31] Flag[31] Flag[31] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No No No Flag[27] Flag[27] Flag[27] Flag[27] Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? ? ? No No No Yes Yes Yes Yes Flag[31] Flag[31] Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§FinalizationRegistry minimal support Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No Flag[30] 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 Yes Yes Yes Yes Yes Yes Yes Yes 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 No No No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No No No No No Flag[27] Flag[27] Yes Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§Logical Assignment 9/9 0/9 0/9 9/9 9/9 0/9 0/9 9/9 9/9 9/9 9/9 9/9 9/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 0/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 0/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 0/9 0/9 0/9 0/9 0/9 0/9 9/9 9/9 9/9 9/9 9/9 0/9 0/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9 9/9
§||= basic support MDN (Mozilla Development Network) logo  Yes ? ? Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? No Flag[28] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? ? ? ? No No Flag[32] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No ? ? ? ? Flag[27] Flag[27] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? No No Yes Yes Yes Yes Yes ? No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§||= short-circuiting behaviour Yes ? ? Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? No Flag[28] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? ? ? ? No No Flag[32] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No ? ? ? ? Flag[27] Flag[27] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? No No Yes Yes Yes Yes Yes ? No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§||= setter not unecessarily invoked Yes ? ? Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? No Flag[28] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? ? ? ? No No Flag[32] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No ? ? ? ? Flag[27] Flag[27] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? No No Yes Yes Yes Yes Yes ? No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§&&= basic support MDN (Mozilla Development Network) logo  Yes ? ? Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? No Flag[28] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? ? ? ? No No Flag[32] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No ? ? ? ? Flag[27] Flag[27] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? No No Yes Yes Yes Yes Yes ? No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§&&= short-circuiting behaviour Yes ? ? Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? No Flag[28] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? ? ? ? No No Flag[32] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No ? ? ? ? Flag[27] Flag[27] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? No No Yes Yes Yes Yes Yes ? No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§&&= setter not unecessarily invoked Yes ? ? Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? No Flag[28] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? ? ? ? No No Flag[32] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No ? ? ? ? Flag[27] Flag[27] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? No No Yes Yes Yes Yes Yes ? No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§??= basic support MDN (Mozilla Development Network) logo  Yes ? ? Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? No Flag[28] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? ? ? ? No No Flag[32] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No ? ? ? ? Flag[27] Flag[27] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? No No Yes Yes Yes Yes Yes ? No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§??= short-circuiting behaviour Yes ? ? Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? No Flag[28] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? ? ? ? No No Flag[32] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No ? ? ? ? Flag[27] Flag[27] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? No No Yes Yes Yes Yes Yes ? No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§??= setter not unecessarily invoked Yes ? ? Yes Yes No No Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? No Flag[28] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? ? ? ? No No Flag[32] Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No ? ? ? ? Flag[27] Flag[27] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? No No Yes Yes Yes Yes Yes ? No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§numeric separators Yes ? ? Yes Yes No No Yes Yes Yes Yes Yes Yes No 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 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 Yes ? ? ? ? ? ? Flag[33] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No Yes No No Flag[23] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
2022 features
§instance class fields 1/6 1/6 1/6 6/6 6/6 0/6 0/6 0/6 0/6 0/6 0/6 0/6 0/6 1/6 1/6 1/6 1/6 1/6 1/6 1/6 1/6 0/6 0/6 2/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 0/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 0/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 2/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 0/6 0/6 0/6 0/6 0/6 0/6 0/6 0/6 4/6 4/6 4/6 4/6 4/6 4/6 5/6 5/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 0/6 0/6 0/6 0/6 0/6 0/6 4/6 4/6 6/6 6/6 6/6 6/6 6/6 0/6 0/6 6/6 6/6 6/6 6/6 6/6 6/6 0/6 0/6 0/6 0/6 0/6 0/6 2/6 6/6 6/6 6/6 6/6 4/6 5/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6
§public instance class fields MDN (Mozilla Development Network) logo  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 Yes Yes Yes Yes Yes Yes Yes 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 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 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes
§private instance class fields basic support MDN (Mozilla Development Network) logo  Yes ? ? Yes Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No No[34] 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 Yes Yes Yes Yes Yes Yes Yes Yes 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 ? ? ? ? ? ? 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 Yes Yes Yes Yes Yes Yes Yes Yes
§private instance class fields initializers No ? ? Yes Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No No[34] 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 Yes Yes Yes Yes Yes Yes Yes Yes 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 ? ? ? ? ? ? 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 Yes Yes Yes Yes Yes Yes Yes Yes
§optional private instance class fields access No ? ? Yes Yes ? ? ? ? ? ? ? ? ? ? ? No No No No No ? No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 Yes Yes No 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 No No 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 Yes Yes Yes No No No No No No No Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§optional deep private instance class fields access No ? ? Yes Yes ? ? ? ? ? ? ? ? ? ? ? No No No No No ? No No[34] 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 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 No No No No No No No No No No Flag[24] Flag[24] 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 No No No Yes Yes Yes Yes Flag[24] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§computed instance class fields No ? ? Yes Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes 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 ? ? ? ? ? ? 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 Yes Yes Yes Yes Yes Yes Yes Yes Yes
§static class fields 0/4 1/4 1/4 3/4 3/4 0/4 0/4 0/4 0/4 0/4 0/4 0/4 0/4 1/4 1/4 1/4 1/4 1/4 1/4 1/4 1/4 0/4 0/4 2/4 3/4 3/4 3/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 0/4 4/4 3/4 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 3/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 0/4 3/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 3/4 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 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 4/4 4/4 0/4 0/4 0/4 0/4 0/4 0/4 3/4 3/4 3/4 3/4 3/4 3/4 4/4 0/4 0/4 4/4 4/4 4/4 4/4 4/4 4/4 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
§public static class fields MDN (Mozilla Development Network) logo  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 Yes Yes Yes Yes Yes Yes Yes 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 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 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 Yes Yes Yes Yes Yes Yes Yes Yes
§static class fields use [[Define]] 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 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 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 Yes Yes Yes Yes Yes Yes
§private static class fields MDN (Mozilla Development Network) logo  No ? ? Yes Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 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 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 No 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 Yes Yes Yes Yes Yes Yes Yes Yes
§computed static class fields No ? ? Yes Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No 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 Yes Yes Yes Yes Yes Yes Yes Yes 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 ? ? ? ? ? ? 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 Yes Yes Yes Yes Yes Yes Yes Yes
§private class methods 4/4 0/4 0/4 4/4 4/4 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 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 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 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 4/4 4/4 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 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 0/4 0/4 4/4 4/4 4/4 4/4 4/4 4/4 0/4 0/4 0/4 0/4 0/4 0/4 0/4 4/4 4/4 4/4 4/4 0/4 0/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 4/4 0/4
§private instance methods Yes ? ? Yes Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 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 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 Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? ? ? Flag[33] Flag[33] Flag[33] 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 Yes Yes Yes Yes Flag[33] Flag[33] Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§private static methods Yes ? ? Yes Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 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 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 Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? ? ? Flag[33] Flag[33] Flag[33] 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 Yes Yes Yes Yes Flag[33] Flag[33] Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§private accessor properties Yes ? ? Yes Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 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 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 Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? ? ? Flag[33] Flag[33] Flag[33] 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 Yes Yes Yes Yes Flag[33] Flag[33] Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§private static accessor properties Yes ? ? Yes Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 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 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 Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? ? ? Flag[33] Flag[33] Flag[33] 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 Yes Yes Yes Yes Flag[33] Flag[33] Yes Yes Yes Yes Yes Yes Yes Yes Yes No
§Ergonomic brand checks for private fields No ? No Yes Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 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 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 Yes Yes Yes Yes Yes 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 No No ? ? ? ? ? ? ? ? ? Flag[35] Yes ? ? Yes Yes Yes Yes Yes Yes No No No No No No No Yes Yes Yes Yes No No No No Yes Yes Yes Yes Yes Yes Yes Yes
§.at() method on the built-in indexables 3/3 0/3 0/3 0/3 3/3 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 3/3 3/3 3/3 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 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 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 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 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 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 0/3 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 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 3/3 3/3 0/3 0/3 0/3 0/3 3/3 3/3 3/3 3/3 3/3 3/3 3/3 0/3
§Array.prototype.at() Yes ? ? ? Yes[5] No No No No No No No[36] Yes ? ? ? ? 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 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 ? Flag[37] Flag[37] Flag[37] 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 No No ? ? ? ? ? ? ? ? Flag[38] Flag[35] Yes ? ? Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? Flag[37] Flag[37] Yes Yes ? ? No No Yes Yes Yes Yes Yes Yes Yes No
§String.prototype.at() Yes ? ? ? Yes[5] No No No No No No No[36] Yes ? ? ? ? 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 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 ? Flag[37] Flag[37] Flag[37] 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 No No ? ? ? ? ? ? ? ? Flag[38] Flag[35] Yes ? ? Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? Flag[37] Flag[37] Yes Yes ? ? No No Yes Yes Yes Yes Yes Yes Yes No
§%TypedArray%.prototype.at() Yes ? ? ? Yes[5] No No No No No No No[39] No[39] ? ? ? ? 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 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 ? Flag[37] Flag[37] Flag[37] 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 No No ? ? ? ? ? ? ? ? Flag[38] Flag[35] Yes ? ? Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? Flag[37] Flag[37] Yes Yes ? ? No No Yes Yes Yes Yes Yes Yes Yes No
§Object.hasOwn MDN (Mozilla Development Network) logo  2/2 0/2 0/2 0/2 2/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 2/2 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 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 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 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 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 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 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 0/2 0/2 0/2 0/2 0/2 2/2 2/2 2/2 2/2 2/2 2/2 2/2
§Basic functionality Yes ? ? ? Yes[5] ? ? ? ? ? ? ? Yes ? ? ? Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] ? No No Flag[28] 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 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 No No No No No No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? Flag[35] Yes ? ? Yes Yes Yes Yes Yes Yes No No No No No No No No No Yes Yes No No No No No Yes Yes Yes Yes Yes Yes Yes
§ToObject called before ToPropertyKey Yes ? ? ? Yes[5] ? ? ? ? ? ? ? Yes ? ? ? Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] ? No No Flag[28] 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 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 No No No No No No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? Flag[35] Yes ? ? Yes Yes Yes Yes Yes Yes No No No No No No No No No Yes Yes No No No No No Yes Yes Yes Yes Yes Yes Yes
§Class static initialization blocks No ? No Yes Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No No Flag[40] 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 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 No No No No No No No No No No No No No No Flag[41] Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? Flag[35] Yes ? ? Yes Yes Yes Yes Yes Yes No No No No No No No No No No No No No No No Flag[41] Yes Yes Yes Yes Yes Yes No
§Error.cause property 16/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 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 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 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 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 16/16 16/16 0/16 7/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 8/16 16/16 16/16 16/16 16/16 16/16 16/16 7/16 7/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 8/16 16/16 0/16 0/16 16/16 16/16 16/16 16/16 16/16 16/16 0/16 0/16 0/16 0/16 0/16 0/16 0/16 16/16 16/16 16/16 16/16 0/16 0/16 0/16 0/16 0/16 16/16 16/16 16/16 16/16 16/16 16/16 14/16
§Error has cause 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 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 Yes Yes Yes Yes Yes ? No ? No No No No No No No No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? No Yes ? ? Yes Yes Yes Yes Yes Yes No No ? ? ? ? No Yes Yes Yes Yes No No No No No Yes Yes Yes Yes Yes Yes Yes
§Error.prototype lacks cause 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 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 Yes Yes Yes Yes Yes ? Yes ? No No No No No No No No No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? Yes Yes ? ? Yes Yes Yes Yes Yes Yes No No ? ? ? ? No Yes Yes Yes Yes No No No No No Yes Yes Yes Yes Yes Yes Yes
§EvalError has cause 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 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 Yes Yes Yes Yes Yes ? No ? No No No No No No No No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? No Yes ? ? Yes Yes Yes Yes Yes Yes No No ? ? ? ? No Yes Yes Yes Yes No No No No No Yes Yes Yes Yes Yes Yes Yes
§EvalError.prototype lacks cause 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 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 Yes Yes Yes Yes Yes ? Yes ? No No No No No No No No No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? Yes Yes ? ? Yes Yes Yes Yes Yes Yes No No ? ? ? ? No Yes Yes Yes Yes No No No No No Yes Yes Yes Yes Yes Yes Yes
§RangeError has cause 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 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 Yes Yes Yes Yes Yes ? No ? No No No No No No No No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? No Yes ? ? Yes Yes Yes Yes Yes Yes No No ? ? ? ? No Yes Yes Yes Yes No No No No No Yes Yes Yes Yes Yes Yes Yes
§RangeError.prototype lacks cause 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 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 Yes Yes Yes Yes Yes ? Yes ? No No No No No No No No No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? Yes Yes ? ? Yes Yes Yes Yes Yes Yes No No ? ? ? ? No Yes Yes Yes Yes No No No No No Yes Yes Yes Yes Yes Yes Yes
§ReferenceError has cause 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 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 Yes Yes Yes Yes Yes ? No ? No No No No No No No No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? No Yes ? ? Yes Yes Yes Yes Yes Yes No No ? ? ? ? No Yes Yes Yes Yes No No No No No Yes Yes Yes Yes Yes Yes Yes
§ReferenceError.prototype lacks cause 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 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 Yes Yes Yes Yes Yes ? Yes ? No No No No No No No No No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? Yes Yes ? ? Yes Yes Yes Yes Yes Yes No No ? ? ? ? No Yes Yes Yes Yes No No No No No Yes Yes Yes Yes Yes Yes Yes
§SyntaxError has cause 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 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 Yes Yes Yes Yes Yes ? No ? No No No No No No No No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? No Yes ? ? Yes Yes Yes Yes Yes Yes No No ? ? ? ? No Yes Yes Yes Yes No No No No No Yes Yes Yes Yes Yes Yes Yes
§SyntaxError.prototype lacks cause 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 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 Yes Yes Yes Yes Yes ? Yes ? No No No No No No No No No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? Yes Yes ? ? Yes Yes Yes Yes Yes Yes No No ? ? ? ? No Yes Yes Yes Yes No No No No No Yes Yes Yes Yes Yes Yes Yes
§TypeError has cause 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 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 Yes Yes Yes Yes Yes ? No ? No No No No No No No No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? No Yes ? ? Yes Yes Yes Yes Yes Yes No No ? ? ? ? No Yes Yes Yes Yes No No No No No Yes Yes Yes Yes Yes Yes Yes
§TypeError.prototype lacks cause 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 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 Yes Yes Yes Yes Yes ? Yes ? No No No No No No No No No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? Yes Yes ? ? Yes Yes Yes Yes Yes Yes No No ? ? ? ? No Yes Yes Yes Yes No No No No No Yes Yes Yes Yes Yes Yes Yes
§URIError has cause 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 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 Yes Yes Yes Yes Yes ? No ? No No No No No No No No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? No Yes ? ? Yes Yes Yes Yes Yes Yes No No ? ? ? ? No Yes Yes Yes Yes No No No No No Yes Yes Yes Yes Yes Yes Yes
§URIError.prototype lacks cause 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 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 Yes Yes Yes Yes Yes ? Yes ? No No No No No No No No No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? Yes Yes ? ? Yes Yes Yes Yes Yes Yes No No ? ? ? ? No Yes Yes Yes Yes No No No No No Yes Yes Yes Yes Yes Yes Yes
§AggregateError has cause 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 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 Yes Yes Yes Yes Yes ? No ? No No No No No No No No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes No No ? ? ? ? ? ? ? ? ? No Yes ? ? Yes Yes Yes Yes Yes Yes No No ? ? ? ? No Yes Yes Yes Yes No No No No No Yes Yes Yes Yes Yes Yes No
§AggregateError.prototype lacks cause 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 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 Yes Yes Yes Yes Yes ? 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 ? ? ? ? ? ? ? ? ? Yes Yes ? ? Yes Yes Yes Yes Yes Yes No No ? ? ? ? No Yes Yes Yes Yes No No No No No Yes Yes Yes Yes Yes Yes No
§RegExp Match Indices (`hasIndices` / `d` flag) 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 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 2/2 2/2 2/2 2/2 2/2 0/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 0/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 0/2 0/2 2/2 2/2 2/2 2/2 2/2 2/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 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 0/2 0/2 0/2 1/2 1/2 1/2 1/2 1/2 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 2/2 0/2 0/2 1/2 1/2 1/2 1/2 1/2 1/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 2/2 2/2 2/2 2/2 0/2 0/2 0/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 0/2
§constructor supports it 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 Yes Yes Yes Yes Yes ? ? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? ? ? ? ? Flag[35] Yes ? ? Yes Yes Yes Yes Yes Yes ? ? ? ? ? ? ? Yes Yes Yes Yes ? ? ? Yes Yes Yes Yes Yes Yes Yes Yes No
§shows up in flags No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes ? No No No No No No No No No No No No No ? No No No No No No No No No No No No No ? ? Yes Yes Yes Yes Yes Yes No No No No No No No No No No No No ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? No No No No No No No No ? ? ? ? ? ? ? ? ? ? ? Flag[35] Yes ? ? No No No No No No ? ? ? ? ? ? ? Yes Yes Yes Yes ? ? ? No No No No No No No No No
2023 features
§Array find from last 2/2 0/2 0/2 0/2 2/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 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 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 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 0/2 0/2 0/2 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 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 2/2 2/2 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 2/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 2/2 2/2 0/2 0/2 0/2 0/2 0/2 0/2 0/2 2/2 2/2 2/2 2/2 2/2
§Array.prototype.findLast Yes ? ? ? Yes[5] ? ? ? ? ? ? ? ? ? ? ? Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] ? No No No No No No No No No No No No No Flag[42] Yes Yes Yes Yes Yes No No 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 No No No No 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 No No No Yes Yes Yes No No ? ? ? ? ? ? ? ? ? No Flag[35] ? ? Yes Yes Yes Yes Yes Yes No No No No No No No No No Yes Yes No No No No No No No Yes Yes Yes Yes Yes
§Array.prototype.findLastIndex Yes ? ? ? Yes[5] ? ? ? ? ? ? ? ? ? ? ? Yes[6] Yes[6] Yes[6] Yes[6] Yes[6] ? No No No No No No No No No No No No No Flag[42] Yes Yes Yes Yes Yes No No 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 No No No No 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 No No No Yes Yes Yes No No ? ? ? ? ? ? ? ? ? No Flag[35] ? ? Yes Yes Yes Yes Yes Yes No No No No No No No No No Yes Yes No No No No No No No Yes Yes Yes Yes Yes
§Hashbang Grammar MDN (Mozilla Development Network) logo  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 Yes Yes Yes Yes Yes Yes Yes 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 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 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 No No No No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 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] Executed using js --js.intl-402.

[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] The feature was intentionally disabled to prepare for Firefox 78 ESR

[16] The feature is available with properly set CORS isolation headers or via enabling dom.postMessage.sharedArrayBuffer.bypassCOOP_COEP.insecure.enabled setting under about:config

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

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

[19] The feature has to be enabled via "Experimental Javascript features" setting under about:flags

[20] Requires native support for Object.assign

[21] 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.

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

[23] Requires the --js.ecmascript-version=2020 flag.

[24] The feature has to be enabled via --js-flags="--harmony-optional-chaining" flag

[25] The feature has to be enabled via --js-flags="--harmony-nullish" flag

[26] The feature is considered unstable, but can be enabled via --js-flags="--harmony-string-replaceall" flag

[27] Requires the --js.ecmascript-version=2021 flag.

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

[29] Available behind the --js-flags="--harmony-promise-any" flag in V8.

[30] The feature has to be enabled via javascript.options.experimental.weakrefs setting under about:config.

[31] Available behind the --js-flags="--harmony-weak-refs --expose-gc" flag in V8.

[32] Available behind the --js-flags="--logical-assignment" flag in V8.

[33] The feature has to be enabled via --js-flags="--harmony" flag

[34] The feature has to be enabled via javascript.options.experimental.fields setting under about:config. Private fields are supported by parser, but behave as public fields.

[35] Requires the --js.ecmascript-version=staging flag.

[36] Requires native support for Math.trunc

[37] The feature has to be enabled via jscOptions=--useAtMethod=true flag.

[38] Requires the --js.ecmascript-version=2022 flag.

[39] Requires native support for typed arrays

[40] The feature has to be enabled via javascript.options.experimental.class_static_blocks=true flag.

[41] The feature has to be enabled via harmony_class_static_blocks flag.

[42] The feature has to be enabled via javascript.options.experimental.array_find_last setting under about:config.