Supported features

Last update: 2020-01-09

See also https://github.com/google/closure-compiler/issues/2899

Feature	Language Version	Support
ES3 keywords as identifiers	ES5	yes
getters & setters	ES5	Yes, but cannot be transpiled down to ES3. Negatively impact optimizations.
reserved words as properties	ES5	yes
string continuation	ES5	yes
trailing comma	ES5	yes
array destructuring	ES6	yes
Array.from	ES6	polyfill
Array.of	ES6	polyfill
array pattern rest	ES6	yes
Array.prototype.copyWithin	ES6	polyfill
Array.prototype.entries	ES6	polyfill
Array.prototype.fill	ES6	polyfill
Array.prototype.find	ES6	polyfill
Array.prototype.findIndex	ES6	polyfill
Array.prototype.keys	ES6	polyfill
arrow function	ES6	yes
binary literal	ES6	yes
block-scoped function declaration	ES6	yes
class	ES6	yes
class extends	ES6	yes
class getters / setters	ES6	Yes, but cannot be transpiled down to ES3. Negatively impact optimizations.
computed properties	ES6	yes
const declaration	ES6	yes
default parameter	ES6	yes
ES modules	ES6	yes in input, but output is one large script, possibly broken into chunks
extended object literal	ES6	yes
for-of loop	ES6	yes
generators	ES6	yes
let declaration	ES6	yes
Map	ES6	polyfill
Math.acosh	ES6	polyfill
Math.asinh	ES6	polyfill
Math.atanh	ES6	polyfill
math.cbrt	ES6	polyfill
Math.clz32	ES6	polyfill
Math.cosh	ES6	polyfill
Math.expm1	ES6	polyfill
Math.fround	ES6	polyfill
Math.hypot	ES6	polyfill
Math.imul	ES6	polyfill
Math.log10	ES6	polyfill
Math.log1p	ES6	polyfill
Math.log2	ES6	polyfill
Math.sign	ES6	polyfill
Math.sinh	ES6	polyfill
Math.tanh	ES6	polyfill
Math.trunc	ES6	polyfill
member declaration	ES6	yes
new.target	ES6	yes
Number.EPSILON	ES6	polyfill
Number.isFinite	ES6	polyfill
Number.isInteger	ES6	polyfill
Number.isNaN	ES6	polyfill
Number.isSafeInteger	ES6	polyfill
Number.MAX_SAFE_INTEGER	ES6	polyfill
Number.MIN_SAFE_INTEGER	ES6	polyfill
Number.parseFloat	ES6	polyfill
Number.parseInt	ES6	polyfill
Object.assign	ES6	polyfill
object destructuring	ES6	yes
Object.is	ES6	polyfill
Object.setPrototypeOf	ES6	polyfill
octal literal	ES6	yes
Promise	ES6	polyfill
Reflect.apply	ES6	polyfill
Reflect.construct	ES6	polyfill
Reflect.defineProperty	ES6	polyfill
Reflect.deleteProperty	ES6	polyfill
Reflect.get	ES6	polyfill
Reflect.getOwnPropertyDescriptor	ES6	polyfill
Reflect.getPrototypeOf	ES6	polyfill
Reflect.has	ES6	polyfill
Reflect.isExtensible	ES6	polyfill
Reflect.ownKeys	ES6	polyfill
Reflect.preventExtensions	ES6	polyfill
Reflect.set	ES6	polyfill
Reflect.setPrototypeOf	ES6	polyfill
RegExp flag 'u'	ES6	recognized in input, but cannot be transpiled
RegExp flag 'y'	ES6	recognized in input, but cannot be transpiled
rest parameter	ES6	yes
Set	ES6	polyfill
String.fromCodePoint	ES6	polyfill
String.prototype.codePointAt	ES6	polyfill
String.prototype.endsWith	ES6	polyfill
String.prototype.includes	ES6	polyfill
String.prototype.repeat	ES6	polyfill
String.prototype.startsWith	ES6	polyfill
string template literals	ES6	yes
WeakMap	ES6	polyfill
WeakSet	ES6	polyfill
exponent operators	ES_2016	yes
Array.prototype.includes	ES_2016	polyfill
Array.prototype.values	ES_2017	polyfill
async functions	ES_2017	yes
Object.entries	ES_2017	polyfill
Object.getOwnPropertyDescriptors	ES_2017	polyfill
Object.values	ES_2017	polyfill
String.prototype.padEnd	ES_2017	polyfill
String.prototype.padStart	ES_2017	polyfill
Array.prototype.flat	ES_2018	polyfill
Array.prototype.flatmap	ES_2018	polyfill
async generator functions	ES_2018	yes
for-await-of loop	ES_2018	yes
object pattern rest	ES_2018	yes
Promise.prototype.finally	ES_2018	polyfill
RegExp flag 's'	ES_2018	recognized in input, but cannot be transpiled
RegExp lookbehind	ES_2018	recognized in input, but cannot be transpiled
RegExp named groups	ES_2018	recognized in input, but cannot be transpiled
RegExp unicode property escape	ES_2018	yes
spread into object literal	ES_2018	yes
trailing comma in param list	ES_2018	yes
Object.fromEntries	ES_2019	polyfill
Optional catch binding	ES_2019	yes
String.prototype.trimEnd	ES_2019	polyfill
String.prototype.trimLeft	ES_2019	polyfill
String.prototype.trimRight	ES_2019	polyfill
String.prototype.trimStart	ES_2019	polyfill
Unescaped Unicode line or paragraph separator	ES_2019	yes
globalThis	ES_2020	polyfill
import.meta	ES_2020	recognized in input, but cannot be output or transpiled
Promise.allSettled	ES_2020	polyfill
String.prototype.matchAll	ES_2020	polyfill
Dynamic module import	ES_2020	recognized in input, but cannot be output or transpiled
Nullish coalescing operator ??	ES_2020	yes
Optional chaining operator ?.	ES_2020	yes
BigInt	ES_2020	see BigInt Support
Numeric separators	ES_2021	yes
String.prototype.replaceAll	ES_2021	yes
Promise.any	ES_2021	yes
Logical assignment operators	ES_2021	yes
WeakRefs	ES_2021	yes (externs only, no polyfill)
RegExp Match indices	ES_2022	recognized in input, but cannot be transpiled
.at()	ES_2022	polyfill
Error Cause	ES_2022	externs only, no polyfill
Object.hasOwn	ES_2022	polyfill
class public instance fields	ES_2022	no (implementation started, but stalled)
class public static fields	ES_2022	no (implementation started, but stalled)
class private instance fields	ES_2022	no
class private static fields	ES_2022	no
class private instance methods	ES_2022	no
class private static methods	ES_2022	no
Top-level await	ES_2022	no
#something in object	ES_2022	no
class static blocks	ES_2022	no
Array find from last	ES_2022	no
Hashbang grammar	ES_2022	no