ecmascript-proposals.md

ECMAScript Proposals

ECMAScript, the standard for JavaScript, is an evolving language specification, ECMA-262, and maintained by Ecma Technical Committee 39 - ECMAScript (TC39). Proposed changes go through four stages to archive approval for the next version of the standard that is currently released yearly. Status for proposals are tracked by the tc39/proposals repository README.

Axel Rauschmayer provides a useful guide to the coming features in the next version of the standard in his post Feature watch: ECMAScript 2018.

Typescript support for proposals is tracked here. Babel support for proposals is tracked here. NodeJs support for proposals is tracked here.

Table Of Proposals

Table of ECMAScript proposals and their usage in Jail.

Proposal	Status	Information	Jali	Polyfill	TypeScript	Babel Plugin	NodeJs	Comment
modules	ES2015	mdn01 mdn02	Yes		Yes	transform-es2015-modules-commonjs	9	Babel transform not used as modules are supported by Webpack 2. Used by AVA based unit testing
function.name property	ES2015	mdn03	Yes		Yes	transform-es2015-function-name	6 LTS	Transform used for browser.
Array#includes	ES2016	mdn05	Yes	core.js	Yes	NA	6 LTS
exponentiation operator	ES2016	mdn04	Yes		Yes	transform-exponentiation-operator	8 LTS
Object.{values,entries}	ES2017	mdn06 mdn07	Yes	core.js	Yes	NA	8 LTS
String#{padStart,padEnd}	ES2017	mdn08 mdn09	Yes	core.js	Yes	NA	8 LTS
Object.getOwnPropertyDescriptors	ES2017	mdn10	Yes	core.js	Yes	NA	8 LTS
trailing commas from function calls	ES2017	2ality00	Yes		Yes	syntax-trailing-function-commas	8 LTS
Async Functions	ES2017	mdn11	Yes		Yes	transform-async-to-generator	8 LTS
Shared memory and atomics	ES2017	mdn13	See notes		2.6 #15753		9	Typescript supports the syntax. Implementation support javascript runtime and version
Lifting Template Literal Restriction	ES2018	mdn14 2ality02			#12700	V7 Core See PR #274	9
s (dotAll) flag for regular expressions	ES2018	2ality10	Yes			transform-modern-regexp	9
RegExp named capture groups	ES2018	2ality09	Yes			transform-modern-regexp	10	Babel may also support through regexpu See babel proposals #35
RegExp Lookbehind Assertions	ES2018	2ality07				No. See transform-modern-regexp #5	9
RegExp Unicode Property Escapes	ES2018	2ality08	Yes			transform-unicode-property-regex	10
Rest/Spread Properties	ES2018	2ality04	Yes		2.1]	transform-object-rest-spread	8 LTS
Promise#finally	ES2018	2ality11	Yes	core.js			10	promise.prototype.finally
Asynchronous Iteration	ES2018	2ality05	Yes		2.3 #11326	transform-async-generator-functions	10
Optional catch binding	ES2019	2ality14	Yes		2.5 #17467	transform-optional-catch-binding		Added to chrome codebase 2018-01-19
JSON superset	ES2019					PR #[#7985]
Function#toString revision	Stage 3	2ality01					10. 6 LTS (Partial)
global	Stage 3	2ality03	Yes	core.js	#12902			core.js v2.5.0
import()	Stage 3	2ality06	Yes		2.4 #14495	syntax-dynamic-import		Babel syntax/transform not used as dynamic modules are supported by Webpack 2. Used by AVA based unit testing
Legacy RegExp features in JavaScript	Stage 3
BigInt	Stage 3	2ality12			#15096	PR #6015
import.meta	Stage 3	2ality15
Private instance methods and accessors	Stage 3	2ality13			#9950	V7 transform-class-properties		See #7842 Merged 2018-05-18 for 7.0.0-beta.48
Array#{flat,flatMap}	Stage 3		Yes	core.js
Instance class fields and methods	Stage 3	2ality13	Yes		Yes. See comment	transform-class-properties		Bug in TypeScript #12212 does not pass through to Babel
Static class fields and methods	Stage 3	2ality13	Yes		Yes. See comment	transform-class-properties		Bug in TypeScript #12212 does not pass through to Babel
String#{trimStart,trimEnd}	Stage 3		Yes	core.js
String#matchAll	Stage 3		Yes	core.js
Symbol#description	Stage 3		Yes	core.js
Numeric separators	Stage 2				2.7 #20582	transform-numeric-separator
function.sent metaproperty	Stage 2		Yes			transform-function-sent
Decorators	Stage 2		Yes		Yes	transform-decorators-legacy		Needs write in Babel
Throw expressions	Stage 2
Atomics.waitAsync	Stage 2
Hashbang Grammar	Stage 2
WeakRefs	Stage 2
Object.fromEntries	Stage 2
Top-level await	Stage 2
New Set methods	Stage 2
Well-formed JSON.stringify	Stage 2
Function#toString() censorship	Stage 2
Realms	Stage 2
Date.parse fallback semantics	Stage 1
export v from "mod"; statements	Stage 1
Observable	Stage 1		Yes	core.js
Frozen Realms	Stage 1
Math Extensions	Stage 1		Yes	core.js
of and from on collection constructors	Stage 1		Yes	core.js
Generator arrow functions	Stage 1
Promise.try	Stage 1		Yes	core.js
Optional Chaining	Stage 1
Math.signbit: IEEE-754 sign bit	Stage 1		Yes	core.js
Error stacks	Stage 1
do expressions	Stage 1
Temporal	Stage 1
Float16 on TypedArrays, DataView, Math.hfround	Stage 1
[Number.{parseInt,parseFloat} changes	Stage 1
Binary AST	Stage 1
Pipeline Operator	Stage 1
Extensible numeric literals	Stage 1
First-Class Protocols	Stage 1
Nullary coalescing operator	Stage 1
Partial application	Stage 1
Cancellation API	Stage 1
InterpreterDirective	Stage 1
String#replaceAll	Stage 1
String#codePoints	Stage 1
Distinguishing literal strings	Stage 1
Object.freeze + Object.seal syntax	Stage 1
Block Params	Stage 1
{BigInt,Number}.fromString	Stage 1
Math.seededRandoms	Stage 1
Maximally minimal mixins	Stage 1
Getting last item from Array	Stage 1
Collection methods	Stage 1
Richer Keys	Stage 1
Slice notation	Stage 1
Logical Assignment Operators	Stage 1
Sequence properties in Unicode property escapes	Stage 1
Module Keys	Stage 1
Class Static Block	Stage 1
class Access Expressions	Stage 1
Pattern Matching	Stage 1
RegExp Match array offsets	Stage 1
String.prototype.at	Stage 0		Yes	core.js

Document Workflow

Next update to process for meeting TC39 2018-05 from TC39 Proposals README document is 83f2325 on 2018-05-22.

Process Status

• Looking at TC39 2018-05
• Add transform-optional-catch-binding