[WIP] V4

[zloirock]

• Drop ancient engines support:
  • The baseline is engines about IE11, ES5 with some additions:
    • Basic WeakMap support (no matter bugs, for internal usage only, in polyfills could be fixed)
    • Basic Map and Set support (no matter bugs, for internal usage only, in polyfills could be fixed or completely replaced)
    • Basic %TypedArray%, ArrayBuffer and DataView constructors support (no matter bugs, in polyfills could be fixed)
    • A way setting of a prototype - Object.setPrototypeOf or __proto__
  • Examples of supported engines:
    • IE11
    • Chrome 38
    • Safari 7.1
    • FF15
    • Node 0.11
  • Examples of no longer supported engines:
    • IE10-
    • Android 4.4.3-
    • PhantomJS (~ IIRC Safari 6.0)
    • Opera Presto (12-)
    • Duktape
  • Code changes coming from this:
    • Allow unquoted keyword properties
    • Allow trailing commas in multiline object literals
    • Drop descriptors check
    • Consider strict mode as supported
    • Use native Array.isArray without fallbacks
    • Use native Array.prototype.{ forEach, every, some } without fallbacks
    • Use native Date.now without fallbacks
    • Use native Date.prototype.toISOString without fallbacks
    • Use native Function.prototype.bind without fallbacks
    • Use native Object.create without fallbacks in simple cases
    • Use native Object.getPrototypeOf without fallbacks in simple cases
    • Use native Object.{ defineProperty, defineProperties, getOwnPropertyDescriptor } without fallbacks in simple cases
    • Use native Object.keys without fallbacks in simple cases
    • Use native Object.getOwnPropertyNames without fallbacks in simple cases
    • Use native Object.{ freeze, seal, preventExtensions } without fallbacks in simple cases
    • Use native Object.{ isFrozen, isSealed, isExtensible } without fallbacks in simple cases
    • Consider base JSON methods as existent
    • Drop arguments fallback from Object#toString
    • Drop ES3-related Babel transforms from tests processing
    • Drop workarounds of non-enumerable string chars (IE8-, also affects V8 ~ Node 0.10-)
    • Allow brackets notation on strings instead of .charAt
    • Etc.

    ---

    • Consider basic support of WeakMap
    • Consider basic support of Map and Set
    • Consider basic support of ArrayBuffer, DataView and %TypedArray%
    • Consider a way setting of a prototype - Object.setPrototypeOf or __proto__ - as existent

    ---

    • Use native Error.prototype.toString without fallbacks (IE8-, V8 ~ Chrome 32-, FF10- bugs)
    • Drop workarounds of V8 ~ Chrome 36- Object.{ defineProperty, defineProperties } bug with prototype
    • Drop workarounds of V8 ~ Chrome 27- non-redefinable__proto__ bug
    • Drop fallbacks to ancient FF iterators (with '@@iterator' string key)
    • Drop a workaround of an IE bug with non-enumerable integer keys on null proto objects
    • Drop a workaround of ancient Nashorn Object.prototype.propertyIsEnumerable bug
    • Drop a workaround for ancient engines whose RegExp.prototype.exec methods don't consistently return undefined for NPCG
    • Drop many and many other fallbacks / workarounds of ancient engines bugs that now make no sense
• Remove proposals:
  • Withdrawn:
    • Object iteration
    • Getting last item from Array
    • String.prototype.at with code points semantic
    • Math extensions
    • Math.signbit
    • Efficient 64 bit arithmetic
    • URL as a ES proposal, anyway it's left in web standards polyfills
  • Dead:
    • New collections methods - 6+ years without activity, there are no plans to advance it in its current form, I hope that it will be resurrected soon
    • compositeKey and compositeSymbol - 5+ years without activity, anyway the form will be changed, I hope that it will be resurrected soon
    • Number.fromString - 6 years w/o activity, semantics is not clear
    • String.prototype.codePoints - 6 years w/o activity
    • Function.{ isCallable, isConstructor } - 9 years w/o any progress on stage 0, there are no plans to advance it
  • Observable (will be replaced with this proposal in the future)
  • Seeded pseudo-random numbers because of changing of the API, waiting for the spec text
  • Reflect metadata didn't become an official proposal, should be replaced by @@metadata-based logic, see this issue
  • If any of those proposals will be resurrected, polyfills can be restored without any problems
• Remove built-ins:
  • Array.prototype.filterOut (obsolete, replaced with Array.prototype.filterReject)
  • Array.prototype.group (obsolete, replaced with Object.groupBy)
  • Array.prototype.groupBy (obsolete, replaced with Object.groupBy)
  • Array.prototype.groupByToMap (obsolete, replaced with Map.groupBy)
  • Array.prototype.groupToMap (obsolete, replaced with Map.groupBy)
  • Array.prototype.lastIndex (withdrawn)
  • Array.prototype.lastItem (withdrawn in favor of Array.prototype.at)
  • AsyncIterator.prototype.asIndexedPairs (obsolete in favor of the usage counter argument methods callbacks)
  • AsyncIterator.prototype.indexed (obsolete in favor of the usage counter argument methods callbacks)
  • BigInt.range (obsolete, replaced with Iterator.range)
  • Function.isCallable (proposal is dead)
  • Function.isConstructor (proposal is dead)
  • Function.prototype.unThis (obsolete, replaced with Function.prototype.demethodize)
  • Iterator.prototype.asIndexedPairs (obsolete in favor of the usage counter argument methods callbacks)
  • Iterator.prototype.indexed (obsolete in favor of the usage counter argument methods callbacks)
  • Map.keyBy (proposal is dead)
  • Map.prototype.deleteAll (proposal is dead)
  • Map.prototype.every (proposal is dead)
  • Map.prototype.filter (proposal is dead)
  • Map.prototype.find (proposal is dead)
  • Map.prototype.findKey (proposal is dead)
  • Map.prototype.includes (proposal is dead)
  • Map.prototype.keyOf (proposal is dead)
  • Map.prototype.mapKeys (proposal is dead)
  • Map.prototype.mapValues (proposal is dead)
  • Map.prototype.merge (proposal is dead)
  • Map.prototype.reduce (proposal is dead)
  • Map.prototype.some (proposal is dead)
  • Map.prototype.update (proposal is dead)
  • Map.prototype.updateOrInsert (obsolete, replaced with Map.prototype.emplace)
  • Map.prototype.upsert (obsolete, replaced with Map.prototype.emplace)
  • Math.DEG_PER_RAD (withdrawn)
  • Math.RAD_PER_DEG (withdrawn)
  • Math.clamp (withdrawn)
  • Math.degrees (withdrawn)
  • Math.fscale (withdrawn)
  • Math.iaddh (withdrawn in favor of BigInts)
  • Math.imulh (withdrawn in favor of BigInts)
  • Math.isubh (withdrawn in favor of BigInts)
  • Math.radians (withdrawn)
  • Math.scale (withdrawn)
  • Math.seededPRNG (changing of the API, waiting for the spec text)
  • Math.signbit (withdrawn)
  • Math.umulh (withdrawn in favor of BigInts)
  • Number.fromString (proposal is dead)
  • Number.range (obsolete, replaced with Iterator.range)
  • Object.iterateEntries (withdrawn)
  • Object.iterateKeys (withdrawn)
  • Object.iterateValues (withdrawn)
  • Observable (will be replaced with this proposal in the future)
  • Reflect.defineMetadata (obsolete)
  • Reflect.getMetadata (obsolete)
  • Reflect.getOwnMetadata (obsolete)
  • Reflect.hasMetadata (obsolete)
  • Reflect.hasOwnMetadata(obsolete)
  • Reflect.deleteMetadata (obsolete)
  • Reflect.getMetadataKeys (obsolete)
  • Reflect.getOwnMetadataKeys (obsolete)
  • Reflect.metadata (obsolete)
  • Set.prototype.addAll (proposal is dead)
  • Set.prototype.deleteAll (proposal is dead)
  • Set.prototype.every (proposal is dead)
  • Set.prototype.filter (proposal is dead)
  • Set.prototype.find (proposal is dead)
  • Set.prototype.join (proposal is dead)
  • Set.prototype.map (proposal is dead)
  • Set.prototype.reduce (proposal is dead)
  • Set.prototype.some (proposal is dead)
  • String.prototype.codePoints (proposal is dead)
  • Symbol.isRegistered (obsolete, replaced with Symbol.isRegisteredSymbol)
  • Symbol.isWellKnown (obsolete, replaced with Symbol.isWellKnownSymbol)
  • Symbol.matcher (obsolete, replaced with Symbol.customMatcher)
  • Symbol.metadataKey (obsolete, replaced with Symbol.metadata)
  • Symbol.patternMatch (obsolete, replaced with Symbol.customMatcher)
  • Symbol.replaceAll (obsolete)
  • %TypedArray%.fromAsync (obsolete)
  • %TypedArray%.prototype.filterOut (obsolete, replaced with %TypedArray%.prototype.filterReject)
  • %TypedArray%.prototype.groupBy (obsolete, replaced with Object.groupBy)
  • %TypedArray%.prototype.toSpliced (obsolete)
  • WeakSet.prototype.addAll (proposal is dead)
  • WeakSet.prototype.deleteAll (proposal is dead)
  • WeakMap.prototype.deleteAll (proposal is dead)
  • WeakMap.prototype.upsert (obsolete, replaced with WeakMap.prototype.emplace)
  • compositeKey (proposal is dead)
  • compositeSymbol (proposal is dead)
• Drop non-standard Symbol.{ useSetter, useSimple, withoutSetter } methods control of Symbol polyfill
• Drop fallbacks to ancient FF iterators (with '@@iterator' string key)
• Remove modules:
  • es.array.every (required for ES3 only)
  • es.array.for-each (required for ES3 only)
  • es.array.is-array (required for ES3 only)
  • es.array.some (required for ES3 only)
  • es.date.get-year (supported in all popular modern engines, required for IE8- only)
  • es.date.now (required for ES3 only)
  • es.date.set-year (supported in all popular modern engines)
  • es.date.to-iso-string (required for IE8- and other ancient engines)
  • es.date.to-gmt-string (supported in all popular modern engines)
  • es.date.to-string (required for IE8- only)
  • es.error.to-string (required for IE8-, V8 ~ Chrome 32-, FF10-)
  • es.escape (supported in all popular modern engines)
  • es.function.bind (required for ES3 only)
  • es.number.to-precision (required for ancient engines like IE8- or Android 4.3- only)
  • es.object.define-property (required for ES3 engines and V8 ~ Chrome 36- only)
  • es.object.define-properties (required for ES3 engines and V8 ~ Chrme 36- only)
  • es.object.create (required for ES3 only)
  • es.string.substr (supported in all popular modern engines)
  • es.unescape (supported in all popular modern engines)
  • esnext.aggregate-error (moved to stable ES)
  • esnext.array.at (moved to stable ES)
  • esnext.array.filter-out (obsolete)
  • esnext.array.find-last (moved to stable ES)
  • esnext.array.find-last-index (moved to stable ES)
  • esnext.array.group (obsolete)
  • esnext.array.group-by (obsolete)
  • esnext.array.group-by-to-map (obsolete)
  • esnext.array.group-to-map (obsolete)
  • esnext.array.last-index (withdrawn)
  • esnext.array.last-item (withdrawn in favor of Array.prototype.at)
  • esnext.array.to-reversed (moved to stable ES)
  • esnext.array.to-sorted (moved to stable ES)
  • esnext.array.to-spliced (moved to stable ES)
  • esnext.array.with (moved to stable ES)
  • esnext.async-iterator.as-indexed-pairs (obsolete)
  • esnext.async-iterator.indexed (obsolete)
  • esnext.bigint.range (obsolete)
  • esnext.composite-key (proposal is dead)
  • esnext.composite-symbol (proposal is dead)
  • esnext.function.is-callable (proposal is dead)
  • esnext.function.is-constructor (proposal is dead)
  • esnext.function.un-this (obsolete)
  • esnext.global-this (moved to stable ES)
  • esnext.iterator.as-indexed-pairs (obsolete)
  • esnext.iterator.indexed (obsolete)
  • esnext.map.delete-all (proposal is dead)
  • esnext.map.every (proposal is dead)
  • esnext.map.filter (proposal is dead)
  • esnext.map.find (proposal is dead)
  • esnext.map.find-key (proposal is dead)
  • esnext.map.group-by (moved to stable ES)
  • esnext.map.includes (proposal is dead)
  • esnext.map.key-by (proposal is dead)
  • esnext.map.key-of (proposal is dead)
  • esnext.map.map-keys (proposal is dead)
  • esnext.map.map-values (proposal is dead)
  • esnext.map.merge (proposal is dead)
  • esnext.map.reduce (proposal is dead)
  • esnext.map.some (proposal is dead)
  • esnext.map.update (proposal is dead)
  • esnext.map.update-or-insert (obsolete)
  • esnext.map.upsert (obsolete)
  • esnext.math.clamp (withdrawn)
  • esnext.math.deg-per-rad (withdrawn)
  • esnext.math.degrees (withdrawn)
  • esnext.math.fscale (withdrawn)
  • esnext.math.iaddh (withdrawn)
  • esnext.math.imulh (withdrawn)
  • esnext.math.isubh (withdrawn)
  • esnext.math.rad-per-deg (withdrawn)
  • esnext.math.radians (withdrawn)
  • esnext.math.scale (withdrawn)
  • esnext.math.seeded-prng (obsolete)
  • esnext.math.signbit (withdrawn)
  • esnext.math.umulh (withdrawn)
  • esnext.number.from-string (proposal is dead)
  • esnext.number.range (obsolete)
  • esnext.object.has-own (moved to stable ES)
  • esnext.object.iterate-entries (withdrawn)
  • esnext.object.iterate-keys (withdrawn)
  • esnext.object.iterate-values (withdrawn)
  • esnext.object.group-by (moved to stable ES)
  • esnext.observable (will be replaced with this proposal in the future)
  • esnext.promise.all-settled (moved to stable ES)
  • esnext.promise.any (moved to stable ES)
  • esnext.promise.with-resolvers (moved to stable ES)
  • esnext.reflect.define-metadata (obsolete)
  • esnext.reflect.delete-metadata (obsolete)
  • esnext.reflect.get-metadata (obsolete)
  • esnext.reflect.get-metadata-keys (obsolete)
  • esnext.reflect.get-own-metadata (obsolete)
  • esnext.reflect.get-own-metadata-keys (obsolete)
  • esnext.reflect.has-metadata (obsolete)
  • esnext.reflect.has-own-metadata (obsolete)
  • esnext.reflect.metadata (obsolete)
  • esnext.set.add-all (proposal is dead)
  • esnext.set.delete-all (proposal is dead)
  • esnext.set.difference (old version of proposal, updated and moved to stable ES)
  • esnext.set.difference.v2 (moved to stable ES)
  • esnext.set.every (proposal is dead)
  • esnext.set.filter (proposal is dead)
  • esnext.set.find (proposal is dead)
  • esnext.set.intersection (old version of proposal, updated and moved to stable ES)
  • esnext.set.intersection.v2 (moved to stable ES)
  • esnext.set.is-disjoint-from (old version of proposal, updated and moved to stable ES)
  • esnext.set.is-disjoint-from.v2 (moved to stable ES)
  • esnext.set.is-subset-of (old version of proposal, updated and moved to stable ES)
  • esnext.set.is-subset-of.v2 (moved to stable ES)
  • esnext.set.is-superset-of (old version of proposal, updated and moved to stable ES)
  • esnext.set.is-superset-of.v2 (moved to stable ES)
  • esnext.set.join (proposal is dead)
  • esnext.set.map (proposal is dead)
  • esnext.set.reduce (proposal is dead)
  • esnext.set.symmetric-difference (old version of proposal, updated and moved to stable ES)
  • esnext.set.symmetric-difference.v2 (moved to stable ES)
  • esnext.set.union (old version of proposal, updated and moved to stable ES)
  • esnext.set.union.v2 (moved to stable ES)
  • esnext.set.some (proposal is dead)
  • esnext.string.at (old version, replaced by module with the same name with actual behavior)
  • esnext.string.at-alternative (moved to stable ES)
  • esnext.string.code-points (proposal is dead)
  • esnext.string.is-well-formed (moved to stable ES)
  • esnext.string.match-all (moved to stable ES)
  • esnext.string.replace-all (moved to stable ES)
  • esnext.string.to-well-formed (moved to stable ES)
  • esnext.symbol.is-registered (obsolete)
  • esnext.symbol.is-well-known (obsolete)
  • esnext.symbol.matcher (obsolete)
  • esnext.symbol.metadata-key (obsolete)
  • esnext.symbol.pattern-match (obsolete)
  • esnext.symbol.replace-all (obsolete)
  • esnext.typed-array.from-async (obsolete)
  • esnext.typed-array.at (moved to stable ES)
  • esnext.typed-array.filter-out (obsolete)
  • esnext.typed-array.find-last (moved to stable ES)
  • esnext.typed-array.find-last-index (moved to stable ES)
  • esnext.typed-array.group-by (obsolete)
  • esnext.typed-array.to-reversed (moved to stable ES)
  • esnext.typed-array.to-sorted (moved to stable ES)
  • esnext.typed-array.to-spliced (obsolete)
  • esnext.typed-array.with (moved to stable ES)
  • esnext.weak-set.add-all (proposal is dead)
  • esnext.weak-set.delete-all (proposal is dead)
  • esnext.weak-map.delete-all (proposal is dead)
  • esnext.weak-map.upsert (obsolete)
  • web.timers (required for IE9- only)
• Split and / or rename:
  • es.array.iterator to:
    • es.array.iterator
    • es.array.keys
    • es.array.values
    • es.array.entries
  • es.array-buffer.constructor to:
    • es.array-buffer.constructor
    • es.array-buffer.species
    • es.array-buffer.to-string-tag
  • Extracted from Typed Array constructor entries:
    • es.typed-array.species
    • es.typed-array.to-string-tag
  • es.typed-array.iterator to:
    • es.typed-array.iterator
    • es.typed-array.keys
    • es.typed-array.values
    • es.typed-array.entries
  • es.data-view to:
    • es.data-view.constructor
    • es.data-view.set-int8
    • es.data-view.set-uint8
    • es.data-view.to-string-tag
  • es.map to:
    • es.map.constructor
    • es.map.species
  • es.promise to:
    • es.promise.constructor
    • es.promise.all
    • es.promise.catch
    • es.promise.race
    • es.promise.reject
    • es.promise.resolve
  • es.set to:
    • es.set.constructor
    • es.set.species
  • es.string.at-alternative to:
    • es.string.at
  • es.string.trim-end and es.string.trim-start to:
    • es.string.trim-end
    • es.string.trim-left
    • es.string.trim-right
    • es.string.trim-start
  • es.symbol to:
    • es.symbol.constructor
    • es.symbol.for
    • es.symbol.key-for
    • es.symbol.to-primitive
    • es.object.get-own-property-symbols
  • Set methods:
    • es.set.difference.v2 -> es.set.difference
    • es.set.intersection.v2 -> es.set.intersection
    • es.set.is-disjoint-from.v2 -> es.set.is-disjoint-from
    • es.set.is-subset-of.v2 -> es.set.is-subset-of
    • es.set.is-superset-of.v2 -> es.set.is-superset-of
    • es.set.symmetric-difference.v2 -> es.set.symmetric-difference
    • es.set.union.v2 -> es.set.union
  • web.dom-collections.iterator to:
    • web.dom-collections.iterator
    • web.dom-collections.keys
    • web.dom-collections.values
    • web.dom-collections.entries
  • web.immediate to:
    • web.clear-immediate
    • web.set-immediate
  • Constructors:
    • es.aggregate-error -> es.aggregate-error.constructor
    • es.weak-map -> es.weak-map.constructor
    • es.weak-set -> es.weak-set.constructor
    • web.url -> es.url.constructor
    • web.url-search-params -> es.url-search-params.constructor
• Complete refactoring of main library code. The modules that I saw in my nightmares have been completely rewritten.
• Reduce minimalistic bundles size
  • Optimize export logic
    • Global version
    • Pure version
  • Optimize internal dependencies
• Move dependencies of many modules to entry points for better optimization by tools like @core-js/builder, babel, swc
• Automatically generate core-js entry points, get dependencies from entries definitions and direct declarations from modules - simplification of maintenance, reducing of potential errors and code size
• Changes in entry points:
  • Make core-js entry an equal of core-js/actual
  • Actualize /proposals/ namespace - some proposals were renamed, some entries had some versions
  • Drop /features/ namespace in favor of /full/
  • Drop /web/ namespace as almost useless in favor of /stable/, /actual/, /full/
  • Drop /stage/4, /stage and /proposals entries without specifying a stage / a proposal as almost useless
  • Drop */virtual/index.js entries as useless
  • Drop some other entries that make no practical sense as separate, like /math/to-string-tag
  • /proposals/* entries now contain required modules with dependencies
  • /stage/* entries now include not only modules from the higher stages than the specified stage but also all stable ES modules
• Add exports fields with all entries to package.json of packages
• Drop configurable level of aggressiveness from core-js/configurator in favor of future / alternative approaches since the current way is too dangerous, inapplicable in most cases and almost no one uses it
• No longer publish on deno.land/x since core-js is almost not used from this
• Move to scoped packages:
  • core-js-compat -> @core-js/compat
  • core-js-builder -> @core-js/builder
  • core-js-bundle -> @core-js/bundle
  • core-js-pure -> @core-js/pure
• Drop NodeJS < 18.12 support in @core-js/builder and @core-js/compat
• Drop @core-js/compat modules-by-versions history for core-js@3
• Make @core-js/compat / @core-js/builder default modules list an equal of core-js/actual for consistency with import 'core-js'
• core-js version in @core-js/compat
  • Should be specified as a SemVer string with minor component, similarly to this
  • Allowed node_modules and package.json magic options as core-js, similarly to this
• Changes in @core-js/compat / @core-js/builder targets keys:
  • { chrome, firefox, opera }-android repaced with { chrome, firefox, opera }_mobile because of allowing 3rd party browsers on iOS in EU
  • react-native also replaced with react_native for consistency
  • _ is beter replacement for space than -, keys with _ could be used in object literals without quotes and those keys are consistent with related keys in other tools
  • Removed phantom since this engine is no longer supported by polyfill
  • Removed oculus in favor of quest
  • Removed other data by legacy keys from compat data
• Drop @core-js/compat filter deprecated option in favor of modules
• Drop @core-js/builder blacklist deprecated option in favor of exclude
• Make @core-js/builder return an object (for future extensions)
• Update @core-js/builder dependencies (Node 8 support no longer block that)
• Add minify option to @core-js/builder, bundles minified by default
• Add built-in definitions to compat data

That's part of the planned changes, many of the already-done moments are not documented, the rest will be added later.