- **asapScheduler:** No longer stops after scheduling twice during flush ([#7198](https://github.com/reactivex/rxjs/issues/7198)) ([1b52405](https://github.com/reactivex/rxjs/commit/1b524057b4db157814bfd04ad7d10c999afdccfa)), closes [ReactiveX#7196](https://github.com/ReactiveX/issues/7196)
- **buffer:** `closingNotifier` now supports any `ObservableInput` ([#7073](https://github.com/reactivex/rxjs/issues/7073)) ([61b877a](https://github.com/reactivex/rxjs/commit/61b877a50c2557196a45e12622305c5a84fc3f0a))
- **delayWhen:** `delayWhen`'s `delayDurationSelector` now supports any `ObservableInput` ([#7049](https://github.com/reactivex/rxjs/issues/7049)) ([dfd95db](https://github.com/reactivex/rxjs/commit/dfd95db952a6772d35d11bdd1974f2c4b4d68b25))
- **sequenceEqual:** `compareTo` now supports any `ObservableInput` ([#7102](https://github.com/reactivex/rxjs/issues/7102)) ([d501961](https://github.com/reactivex/rxjs/commit/d50196187710c7a0cad50703b2071fc3f2cabd3c))
- **share:** `ShareConfig` factory properties now supports any `ObservableInput` ([#7093](https://github.com/reactivex/rxjs/issues/7093)) ([cc3995a](https://github.com/reactivex/rxjs/commit/cc3995a6f6baf9456ec11f749fe89bf61b9e2d62))
- **skipUntil:** `notifier` now supports any `ObservableInput` ([#7091](https://github.com/reactivex/rxjs/issues/7091)) ([60d6c40](https://github.com/reactivex/rxjs/commit/60d6c40fb484903286feca2bbfa9fcb2cde720e2))
- **window:** `windowBoundaries` now supports any `ObservableInput` ([#7088](https://github.com/reactivex/rxjs/issues/7088)) ([8c4347c](https://github.com/reactivex/rxjs/commit/8c4347c48f2432d7399c911d329fa74e0d6c6e8d))
- **distinct:** `flush` argument now supports any `ObservableInput` ([#7081](https://github.com/reactivex/rxjs/issues/7081)) ([74c9ebd](https://github.com/reactivex/rxjs/commit/74c9ebd818113f9f25f1fb2b9fee4a0eac121ae0))
- **retryWhen:** `notifier` now supports any `ObservableInput` ([#7105](https://github.com/reactivex/rxjs/issues/7105)) ([794f806](https://github.com/reactivex/rxjs/commit/794f8064cf8fe754e9dfebeee0ffef0ac1562252))
- **sample:** `notifier` now supports any `ObservableInput` ([#7104](https://github.com/reactivex/rxjs/issues/7104)) ([b18c2eb](https://github.com/reactivex/rxjs/commit/b18c2eb2bc8dc1a717c927f998028316eec83937))
- **schedulers:** no longer cause TypeScript build failures when Node types aren't included ([c1a07b7](https://github.com/reactivex/rxjs/commit/c1a07b71ac050ab36b371ff7f18dc9a924fffc9f))
- **types:** Improved subscribe and tap type overloads ([#6718](https://github.com/reactivex/rxjs/issues/6718)) ([af1a9f4](https://github.com/reactivex/rxjs/commit/af1a9f446a860883abaa36ace21345dc923e7e53)), closes [#6717](https://github.com/reactivex/rxjs/issues/6717)
### Features
- **onErrorResumeNextWith:** renamed `onErrorResumeNext` and exported from the top level. (`onErrorResumeNext` operator is stil available, but deprecated) ([#6755](https://github.com/reactivex/rxjs/issues/6755)) ([51e3b2c](https://github.com/reactivex/rxjs/commit/51e3b2c8ec28b5d30bca4c63ad69ce6942c2cdcc))
- **schedulers:** improve performance of animationFrameScheduler and asapScheduler ([#7059](https://github.com/reactivex/rxjs/issues/7059)) ([c93aa60](https://github.com/reactivex/rxjs/commit/c93aa60e9f073297d959fa1fff9323e48872d47e)), closes [#7017](https://github.com/reactivex/rxjs/issues/7017), related to [#7018](https://github.com/reactivex/rxjs/issues/7018) and [#6674](https://github.com/reactivex/rxjs/issues/6674)
- **share:** No longer results in a bad-state observable in an edge case where a synchronous source was shared and refCounted, and the result is subscribed to twice in a row synchronously. ([#7005](https://github.com/reactivex/rxjs/issues/7005)) ([5d4c1d9](https://github.com/reactivex/rxjs/commit/5d4c1d9a37b1347217223adb0d9e166fd85f67a9))
- **share & connect:** `share` and `connect` no longer bundle scheduling code by default ([#6873](https://github.com/reactivex/rxjs/issues/6873)) ([9948dc2](https://github.com/reactivex/rxjs/commit/9948dc2f5577eaa4013de234f3552508918518c7)), closes [#6872](https://github.com/reactivex/rxjs/issues/6872)
- **exhaustAll:** Result will now complete properly when flattening all synchronous observables. ([#6911](https://github.com/reactivex/rxjs/issues/6911)) ([3c1c6b8](https://github.com/reactivex/rxjs/commit/3c1c6b8303028eebc7af31cfc5e5bad42a5b2da4)), closes [#6910](https://github.com/reactivex/rxjs/issues/6910)
- **TypeScript:** Now compatible with TypeScript 4.6 type checks ([#6895](https://github.com/reactivex/rxjs/issues/6895)) ([fce9aa1](https://github.com/reactivex/rxjs/commit/fce9aa12931796892673581761bba1f7ceafabff))
- **timeout:** no longer will timeout when receiving the first value synchronously ([#6865](https://github.com/reactivex/rxjs/issues/6865)) ([2330c96](https://github.com/reactivex/rxjs/commit/2330c9660b20f2e0cda0c4eeb36bb582b4a85186)), closes [#6862](https://github.com/reactivex/rxjs/issues/6862)
### Performance Improvements
- Don't clone observers unless you have to ([#6842](https://github.com/reactivex/rxjs/issues/6842)) ([3289d20](https://github.com/reactivex/rxjs/commit/3289d20ddc3a84d2aede8e3ab9962a8ef5d43c83))
- removed code that would `bind` functions passed with observers to `subscribe`. ([#6815](https://github.com/reactivex/rxjs/issues/6815)) ([fb375a0](https://github.com/reactivex/rxjs/commit/fb375a0c5befd6852cd63d3c310448e42fa9580e)), closes [#6783](https://github.com/reactivex/rxjs/issues/6783)
- **subscribe:** allow interop with Monio and other libraries that patch function bind ([0ab91eb](https://github.com/reactivex/rxjs/commit/0ab91eb4c1da914efbf03a2732629914cd3398dc)), closes [#6783](https://github.com/reactivex/rxjs/issues/6783)
- operators that ignore input values now use `unknown` rather than `any`, which should resolve issues with eslint no-unsafe-argument ([#6738](https://github.com/reactivex/rxjs/issues/6738)) ([67cb317](https://github.com/reactivex/rxjs/commit/67cb317a7a6b9fdbd3d2e8fdbc2ac9ac7e57179c)), closes [#6536](https://github.com/reactivex/rxjs/issues/6536)
- **ajax:** crossDomain flag deprecated and properly reported to consumers ([#6710](https://github.com/reactivex/rxjs/issues/6710)) ([7fd0575](https://github.com/reactivex/rxjs/commit/7fd05756c595dddb288b732b00a90fcfb2a9080a)), closes [#6663](https://github.com/reactivex/rxjs/issues/6663)
- **takeWhile:** Now returns proper types when passed a `Boolean` constructor. ([#6633](https://github.com/reactivex/rxjs/issues/6633)) ([081ca2b](https://github.com/reactivex/rxjs/commit/081ca2ba7290aa3084c1477a6d4bcc573bf478f6))
- **forEach:** properly unsubs after error in next handler ([#6677](https://github.com/reactivex/rxjs/issues/6677)) ([b9ab67d](https://github.com/reactivex/rxjs/commit/b9ab67d21ca9d227fcd1123bf80ab87ca9296af9)), closes [#6676](https://github.com/reactivex/rxjs/issues/6676)
- RxJS now supports tslib 2.x, rather than just 2.1.x ([#6692](https://github.com/reactivex/rxjs/issues/6692)) ([0b2495f](https://github.com/reactivex/rxjs/commit/0b2495f72e76627fdd19dd7a670dd74847d6449c)), closes [#6689](https://github.com/reactivex/rxjs/issues/6689)
- schedulers will no longer error while rescheduling and unsubscribing during flushes ([e35f589](https://github.com/reactivex/rxjs/commit/e35f589e2ca10ab2d2d69f7e9fe60727edc4c53d)), closes [#6672](https://github.com/reactivex/rxjs/issues/6672)
### Features
- **repeat:** now has configurable delay ([#6640](https://github.com/reactivex/rxjs/issues/6640)) ([6b7a534](https://github.com/reactivex/rxjs/commit/6b7a534f579f95f97f47eff74bdea9991ee85712))
- Add es2015 entries to the exports declaration to support Angular ([#6614](https://github.com/reactivex/rxjs/issues/6614)) ([268777b](https://github.com/reactivex/rxjs/commit/268777bc3a4fd0cf76882683b51809771741ddc3)), closes [/github.com/ReactiveX/rxjs/pull/6613#discussion_r716958551](https://github.com//github.com/ReactiveX/rxjs/pull/6613/issues/discussion_r716958551)
- **Schedulers:** Throwing a falsy error in a scheduled function no longer results in strange error objects. ([#6594](https://github.com/reactivex/rxjs/issues/6594)) ([c70fcc0](https://github.com/reactivex/rxjs/commit/c70fcc02b4b737709aba559bf36b030a47902ee4))
- scheduling with Rx-provided schedulers will no longer leak action references ([#6562](https://github.com/reactivex/rxjs/issues/6562)) ([ff5a748](https://github.com/reactivex/rxjs/commit/ff5a748b31ee73a6517e2f4220c920c73fbdd1fc)), closes [#6561](https://github.com/reactivex/rxjs/issues/6561)
- **forkJoin:** now finalizes sources before emitting ([#6546](https://github.com/reactivex/rxjs/issues/6546)) ([c52ff2e](https://github.com/reactivex/rxjs/commit/c52ff2e3aae19cd0877adb63182c03b79427de96)), closes [#4914](https://github.com/reactivex/rxjs/issues/4914)
- **observeOn:** release action references on teardown ([321d205](https://github.com/reactivex/rxjs/commit/321d2052696a7c366786c1ef3be7ad2a98a55f62))
- Expose `Connectable`, the return type of `connectable` ([#6531](https://github.com/reactivex/rxjs/issues/6531)) ([69f5bfa](https://github.com/reactivex/rxjs/commit/69f5bfae0eb2880a3d5cfb34db3a182182b325de)), closes [#6529](https://github.com/reactivex/rxjs/issues/6529)
- **retry:** Now supports configurable delay as a named argument ([#6421](https://github.com/reactivex/rxjs/issues/6421)) ([5f69795](https://github.com/reactivex/rxjs/commit/5f69795f4be035499cf223bf9a3d7352c4975291))
- **tap:** Now supports subscribe, unsubscribe, and finalize handlers ([#6527](https://github.com/reactivex/rxjs/issues/6527)) ([eb26cbc](https://github.com/reactivex/rxjs/commit/eb26cbc4488c9953cdde565b598b1dbdeeeee9ea))
- **debounceTime:** unschedule dangling task on unsubscribe before complete ([#6464](https://github.com/reactivex/rxjs/issues/6464)) ([7ab0a4c](https://github.com/reactivex/rxjs/commit/7ab0a4c649b1b54e763a726c4ffdc183b0b45b23))
- **fromEvent:** Types now properly infer when resultSelector is provided ([#6447](https://github.com/reactivex/rxjs/issues/6447)) ([39b9d81](https://github.com/reactivex/rxjs/commit/39b9d818ef6ea033dc8e53800e3a220d56c76b4a))
### Features
- Operators are all exported at the top level, from "rxjs". From here on out, we encourage top-level imports with RxJS. Importing from `rxjs/operators` will be deprecated soon. ([#6488](https://github.com/reactivex/rxjs/issues/6488)) ([512adc2](https://github.com/reactivex/rxjs/commit/512adc25f350660113275d8277d16b7f3eec1d49)), closes [#6242](https://github.com/reactivex/rxjs/issues/6242)
- returned operator functions from multicast operators `share`, `publish`, `publishReplay` are now referentially transparent. Meaning if you take the result of calling `publishReplay(3)` and pass it to more than one observable's `pipe` method, it will behave the same in each case, rather than having a cumulative effect, which was a regression introduced sometime in version 6. If you required this broken behavior, there is a workaround posted [here](https://github.com/ReactiveX/rxjs/pull/6410#issuecomment-846087374) ([#6410](https://github.com/reactivex/rxjs/issues/6410)) ([e2f2e51](https://github.com/reactivex/rxjs/commit/e2f2e516514bdeb76229e69c639f10f21bccafad)), closes [/github.com/ReactiveX/rxjs/pull/6410#issuecomment-846087374](https://github.com//github.com/ReactiveX/rxjs/pull/6410/issues/issuecomment-846087374) [#5411](https://github.com/reactivex/rxjs/issues/5411)
### Features
- All subjects now have an `observed` property. This will allow users to check whether a subject has current subscribers without us allowing access to the `observers` array, which is going to be made private in future versions. ([#6405](https://github.com/reactivex/rxjs/issues/6405)) ([f47425d](https://github.com/reactivex/rxjs/commit/f47425d349475231c0f3542bb6ecef16a63e933a))
- **groupBy:** Support named arguments, support ObservableInputs for duration selector ([#5679](https://github.com/reactivex/rxjs/issues/5679)) ([7a99397](https://github.com/reactivex/rxjs/commit/7a9939773802c4f7948c6d868a8f75facdea9f37))
- **share:** use another observable to control resets ([#6169](https://github.com/reactivex/rxjs/issues/6169)) ([12c3716](https://github.com/reactivex/rxjs/commit/12c3716cecbf01f353c980488bf18845177b37b6))
- **bindCallback:** resulting function now recreated underlying Subject and is reusable once again. ([#6369](https://github.com/reactivex/rxjs/issues/6369)) ([abf2bc1](https://github.com/reactivex/rxjs/commit/abf2bc13e38406717127159c8c373b910223b562))
- Observable teardowns now properly called if `useDeprecatedSynchronousErrorHandling` is `true`. ([#6365](https://github.com/reactivex/rxjs/issues/6365)) ([e19e104](https://github.com/reactivex/rxjs/commit/e19e104d011233d83bc10c37f1ee0b3ac6e15612)), closes [#6364](https://github.com/reactivex/rxjs/issues/6364)
- **node**: do not reference DOM-related imports to assist in node usage. ([#6305](https://github.com/reactivex/rxjs/issues/6305)) ([b24818e](https://github.com/reactivex/rxjs/commit/b24818e96775045c7485932bf33349471e8f1363)), closes [#6297](https://github.com/reactivex/rxjs/issues/6297)
- VS code will now properly auto-import operators, et al ([#6276](https://github.com/reactivex/rxjs/issues/6276)) ([f43c728](https://github.com/reactivex/rxjs/commit/f43c72815f9ebe5ee3a8ed11513be0f541c9517d)), closes [#6067](https://github.com/reactivex/rxjs/issues/6067)
- finalize behaves well with useDeprecatedSynchronousErrorHandling ([#6251](https://github.com/reactivex/rxjs/issues/6251)) ([e4bed2a](https://github.com/reactivex/rxjs/commit/e4bed2a2bad994f05a39246707d4f203412cebbd)), closes [#6250](https://github.com/reactivex/rxjs/issues/6250)
- resolve run-time errors when using deprecated sync error handling ([#6272](https://github.com/reactivex/rxjs/issues/6272)) ([35daaf7](https://github.com/reactivex/rxjs/commit/35daaf77d3a9a909a7ec22c362c97ac42a597f79)), closes [#6271](https://github.com/reactivex/rxjs/issues/6271)
- resolve issue that made users unable to assert `instanceof AjaxError`. ([#6275](https://github.com/reactivex/rxjs/issues/6275)) ([a7c2d29](https://github.com/reactivex/rxjs/commit/a7c2d297ad6b2f405ac312b38f6360e9a645d890))
### Features
- add config object to connectable ([#6267](https://github.com/reactivex/rxjs/issues/6267)) ([4d98b40](https://github.com/reactivex/rxjs/commit/4d98b40f969d5f55381f9a178ef3c18e6850cf47))
### BREAKING CHANGES
- Our very new creation function, `connectable`, now takes a configuration object instead of just the `Subject` instance. This was necessary to make sure it covered all use cases for what we were trying to replace in the deprecated multicasting operators. Apologies for the late-in-the-game change, but we know it's not widely used yet (it's new in v7), and we want to get it right.
- **webSocket:** return the correct type for `WebSocketSubject``multiplex` method([#6232](https://github.com/reactivex/rxjs/issues/6232)) ([33383b8](https://github.com/reactivex/rxjs/commit/33383b884d895fa77866362b8b00fd2e2c3597e6))
- **TypeScript:** Add typesVersions definition to package.json in order to help VS Code find automatic imports. ([#6067](https://github.com/reactivex/rxjs/issues/6067)) ([659a623](https://github.com/reactivex/rxjs/commit/659a623c94bd6b210e9beb6bb6061be540b05538))
- **symbol:** revert unique symbol in [#5874](https://github.com/reactivex/rxjs/issues/5874) ([#6224](https://github.com/reactivex/rxjs/issues/6224)) ([3c49429](https://github.com/reactivex/rxjs/commit/3c49429fadc31ebaddd143d4412907edc50e32be)), closes [#5919](https://github.com/reactivex/rxjs/issues/5919) [#6178](https://github.com/reactivex/rxjs/issues/6178) [#6175](https://github.com/reactivex/rxjs/issues/6175)
- forkJoin/combineLatest return Observable<unknown> if passed any ([#6227](https://github.com/reactivex/rxjs/issues/6227)) ([ce0a2fa](https://github.com/reactivex/rxjs/commit/ce0a2fa975e7c08de2bbf893010f2c25c090b1ca)), closes [#6226](https://github.com/reactivex/rxjs/issues/6226)
- **fromEvent:** match targets properly; fix result selector type ([#6208](https://github.com/reactivex/rxjs/issues/6208)) ([8412c73](https://github.com/reactivex/rxjs/commit/8412c739bb47cc45ec3f38327115301b4fcc0118))
- **merge:** single array is not an array of sources ([#6211](https://github.com/reactivex/rxjs/issues/6211)) ([4e900dc](https://github.com/reactivex/rxjs/commit/4e900dc745b5fbd7659b104c49fb0fce4ae84707))
- **pipe:** Ensure that `unknown` is inferred for 9+ arguments. ([#6212](https://github.com/reactivex/rxjs/issues/6212)) ([6fa819b](https://github.com/reactivex/rxjs/commit/6fa819beb91ba99dadd6262d6c13f7ddfd9470c5))
- **share:** No longer throws errors for reentrant observables ([#6151](https://github.com/reactivex/rxjs/issues/6151)) ([fc728cd](https://github.com/reactivex/rxjs/commit/fc728cdf2f395620cca347602e66f3d173c057b5)), closes [#6144](https://github.com/reactivex/rxjs/issues/6144)
### Features
- **ajax:** Now allows configuration of query string parameters, via a `params` option in the request configuration ([#6174](https://github.com/reactivex/rxjs/issues/6174)) ([980f4d4](https://github.com/reactivex/rxjs/commit/980f4d4bb6a3bc1513a4335ed124f4d11b93d251))
- **esm:** Added exports within package.json to enable scoped package loading. ([#6192](https://github.com/reactivex/rxjs/issues/6192)) ([33a9f06](https://github.com/reactivex/rxjs/commit/33a9f06f2c59c8aef3bb583bdb7d61d08ab597a0)), closes [sveltejs/kit#612](https://github.com/sveltejs/kit/issues/612) [nodejs/node#27408](https://github.com/nodejs/node/issues/27408)
- **ReadableStreams:** RxJS now supports conversions for ReadableStreams e.g. `from(readableStream)`. ([#6163](https://github.com/reactivex/rxjs/issues/6163)) ([19d6502](https://github.com/reactivex/rxjs/commit/19d650223cf0e1964e893baca19f264154422a7d))
- **combineLatest:** POJO signature should match only ObservableInput values ([#6103](https://github.com/reactivex/rxjs/issues/6103)) ([d633494](https://github.com/reactivex/rxjs/commit/d633494dcdcabecda2c64ee84b8b6ceeaa2cb3d8))
- **forkJoin:** POJO signature should match only ObservableInput values ([#6095](https://github.com/reactivex/rxjs/issues/6095)) ([566427e](https://github.com/reactivex/rxjs/commit/566427e88e597589f21b8cfb057dd13d5c61e0f2))
- predicates that return `any` will now behave property with findIndex ([#6097](https://github.com/reactivex/rxjs/issues/6097)) ([c6f73d6](https://github.com/reactivex/rxjs/commit/c6f73d687e6b2142da4cab2a66047cc6dd123bf9))
- remove misused type parameter from isObservable ([#6083](https://github.com/reactivex/rxjs/issues/6083)) ([f16b634](https://github.com/reactivex/rxjs/commit/f16b6341eef85009fc16de13623dc860d8d87778))
- unhandled errors in observers correctly scheduled ([#6118](https://github.com/reactivex/rxjs/issues/6118)) ([c02ceb7](https://github.com/reactivex/rxjs/commit/c02ceb75e3de12fedbe270d5d323f508171f9cfd))
- **defaultIfEmpty:** Allow `undefined` as an argument, require an argument ([4983760](https://github.com/reactivex/rxjs/commit/4983760b9179da27ddfcbf419ac5975cff9447c9)), closes [#6064](https://github.com/reactivex/rxjs/issues/6064)
- **elementAt:** Allow `defaultValue` of `undefined`. ([5bc1b3e](https://github.com/reactivex/rxjs/commit/5bc1b3e22deceb5ea5f1882c0f92f061c1c4792d))
- **first:** Allow `defaultValue` of `undefined`. ([62a6bbe](https://github.com/reactivex/rxjs/commit/62a6bbe1c3c51468c57e4e8f754c1c09da2db51b))
- **last:** Allow `defaultValue` of `undefined`. ([ef3e721](https://github.com/reactivex/rxjs/commit/ef3e721f440132cf199f662b6a987349a0a70418))
### Features
- rename and alias `combineLatest` as `combineLatestAll` for consistency ([#6079](https://github.com/reactivex/rxjs/issues/6079)) ([42cee80](https://github.com/reactivex/rxjs/commit/42cee8045594779e8802b370c7244e6bbeeccaa3)), closes [#4590](https://github.com/reactivex/rxjs/issues/4590)
### BREAKING CHANGES
- **defaultIfEmpty:** `defaultIfEmpty` requires a value be passed. Will no longer convert `undefined` to `null` for no good reason.
5bc8e3361 Fix/6052 ajax responseType should default to "json" (#6056)
### Bug Fixes
- **ajax**: `responseType` is now properly defaulted to `"json"` again. ([#6056](https://github.com/reactivex/rxjs/issues/6056)) ([5bc8e3361](https://github.com/reactivex/rxjs/commit/5bc8e3361))
- Corner case resolved where an error thrown in a completion handler might delay teardown if it happened to be after a completing operator like `take`. ([#6062](https://github.com/reactivex/rxjs/issues/6062)) ([a2b9563](https://github.com/reactivex/rxjs/commit/a2b95631be882d2cf0fd87f43804d1ed699591d7))
- **AsyncGenerator support**: consumed async generators are now properly finalized. ([#6062](https://github.com/reactivex/rxjs/issues/6062)) ([a2b9563](https://github.com/reactivex/rxjs/commit/a2b95631be882d2cf0fd87f43804d1ed699591d7)), closes [#5998](https://github.com/reactivex/rxjs/issues/5998)
- **throttle:** no longer emits more than necessary in sync/sync trailing case ([#6059](https://github.com/reactivex/rxjs/issues/6059)) ([9da638a](https://github.com/reactivex/rxjs/commit/9da638a70d5abb862439ab4ee6a55368228811b0)), closes [#6058](https://github.com/reactivex/rxjs/issues/6058)
- **ajax:** now errors on forced abort ([#6041](https://github.com/reactivex/rxjs/issues/6041)) ([d950921](https://github.com/reactivex/rxjs/commit/d95092143c1860eef054d27f2a1e50cb98b0ef58)), closes [#4251](https://github.com/reactivex/rxjs/issues/4251)
- **buffer:** closingNotifier completion does not complete resulting observable ([358ae84](https://github.com/reactivex/rxjs/commit/358ae84cb9d59170216e7e0845c192eb3e1dcb51))
- **buffer:** Remaining buffer will correctly be emitted on source close. ([0c667d5](https://github.com/reactivex/rxjs/commit/0c667d596d4a14002ffe9d4db319ed7cd7442ada)), closes [#3990](https://github.com/reactivex/rxjs/issues/3990) [#6035](https://github.com/reactivex/rxjs/issues/6035)
- **debounceTime:** improves performance on quick succession of emits ([#6049](https://github.com/reactivex/rxjs/issues/6049)) ([9b70861](https://github.com/reactivex/rxjs/commit/9b708613cb7687647dc43c5e15b821e17ccc23ef))
- **distinctUntilChanged:** Ensure reentrant code is compared properly ([#6014](https://github.com/reactivex/rxjs/issues/6014)) ([0ebcf17](https://github.com/reactivex/rxjs/commit/0ebcf1751a5359072b137ff197789570be4d7ead))
- **share:** Ensure proper memory clean up ([1aa400a](https://github.com/reactivex/rxjs/commit/1aa400a5214325bc843a74602022a7912da20166))
- **window:** final window stays open until source complete ([e8b05ef](https://github.com/reactivex/rxjs/commit/e8b05ef090d33af5b883e8020b8b7a3c4c8fa30e))
- **concat/merge:** operators will finalize inners before moving to the next ([#6010](https://github.com/reactivex/rxjs/issues/6010)) ([5249a23](https://github.com/reactivex/rxjs/commit/5249a23b38bdda4639e9d669afd62a624172f89c)), closes [#3338](https://github.com/reactivex/rxjs/issues/3338)
- predicates that return `any` will now behave property in TS ([#5987](https://github.com/reactivex/rxjs/issues/5987)) ([f5ae97d](https://github.com/reactivex/rxjs/commit/f5ae97d49a35b9f99ac59f79dd244a6d8d6c8a7b)), closes [#5986](https://github.com/reactivex/rxjs/issues/5986)
-`publish` variants returning `ConnectableObservable` not properly utilizing lift ([#6003](https://github.com/reactivex/rxjs/issues/6003)) ([9acb950](https://github.com/reactivex/rxjs/commit/9acb950aec9efda95eb7492bfc47a33b71ef2e55))
- Resolve issues with deprecated synchronous error handling and chained operators ([#5980](https://github.com/reactivex/rxjs/issues/5980)) ([0ad2802](https://github.com/reactivex/rxjs/commit/0ad2802a5aa9cd19875dc05c1cfb33f0b2f2c153)), closes [#5979](https://github.com/reactivex/rxjs/issues/5979)
-`useDeprecatedSynchronousErrorThrowing` honored for flattened sync sources ([#5984](https://github.com/reactivex/rxjs/issues/5984)) ([abd95ce](https://github.com/reactivex/rxjs/commit/abd95ce1aa81a64de81c074a72570a8f0949cd0d)), closes [#5983](https://github.com/reactivex/rxjs/issues/5983)
### Features
- **ajax:** Add option for streaming progress ([#6001](https://github.com/reactivex/rxjs/issues/6001)) ([873e52d](https://github.com/reactivex/rxjs/commit/873e52d0d67b0f8470e6290c6fbc35c571464aaf))
- **exhaustAll:** renamed `exhaust` to `exhaustAll` ([#5639](https://github.com/reactivex/rxjs/issues/5639)) ([701c7d4](https://github.com/reactivex/rxjs/commit/701c7d48cf1c3e60941692010254d6a27fc70980))
### BREAKING CHANGES
- **window:** The `windowBoundaries` observable no longer completes the result. It was only ever meant to notify of the window boundary. To get the same behavior as the old behavior, you would need to add an `endWith` and a `skipLast(1)` like so: `source$.pipe(window(notifier$.pipe(endWith(true))), skipLast(1))`.
- **buffer:** Final buffered values will now always be emitted. To get the same behavior as the previous release, you can use `endWith` and `skipLast(1)`, like so: `source$.pipe(buffer(notifier$.pipe(endWith(true))), skipLast(1))`
- **buffer:** `closingNotifier` completion no longer completes the result of `buffer`. If that is truly a desired behavior, then you should use `takeUntil`. Something like: `source$.pipe(buffer(notifier$), takeUntil(notifier$.pipe(ignoreElements(), endWith(true))))`, where `notifier$` is multicast, although there are many ways to compose this behavior.
- **combineLatest:** Ensure `EMPTY` is returned if no observables are passed. ([#5963](https://github.com/reactivex/rxjs/issues/5963)) ([157c7e8](https://github.com/reactivex/rxjs/commit/157c7e8068befdfb26a9ba6ca770d38a66966ab5)), closes [#5962](https://github.com/reactivex/rxjs/issues/5962)
- **fromEvent:** fixed HasEventTargetAddRemove to support EventTarget types ([#5945](https://github.com/reactivex/rxjs/issues/5945)) ([5f022d7](https://github.com/reactivex/rxjs/commit/5f022d784570684632e6fd5ae247fc259ee34c4b))
### Features
- **connect:** Adds new `connect` operator. ([9d53af0](https://github.com/reactivex/rxjs/commit/9d53af04103dbbb3bae40a4c511e2eebf117be09))
- **share:** Make `share` completely configurable. Also adds `SubjectLike`. ([2d600c7](https://github.com/reactivex/rxjs/commit/2d600c75c1065d862a2089dc1cd26007996b1c9d))
- ensure same hidden class for OperatorSubscriber ([#5878](https://github.com/reactivex/rxjs/issues/5878)) ([246b449](https://github.com/reactivex/rxjs/commit/246b44902acde3a80e659f362969e6e2f8b19ef2))
### BREAKING CHANGES
- **share:** The TypeScript type `Subscribable` now only supports what is a valid return for `[Symbol.observable]()`.
- **share:** The TypeScript type `Observer` no longer incorrectly has an optional `closed` property.
- **audit:** don't signal on complete ([54cb428](https://github.com/reactivex/rxjs/commit/54cb42823ceec4db469f6155de67993b67ec85be))
- **bufferToggle:** don't signal on complete ([65686ff](https://github.com/reactivex/rxjs/commit/65686ffd23f2d5a5145f2b7c33ea739e9bb808cd))
- **bufferWhen:** don't signal on complete ([a2ba364](https://github.com/reactivex/rxjs/commit/a2ba364ede3c69c7703795a744f57122b49eac40))
- **debounce:** don't signal on complete ([c919c68](https://github.com/reactivex/rxjs/commit/c919c684ad63724f0b55ccc4561f847773d945c8))
- **delayWhen:** no longer emits if duration selector is empty ([#5769](https://github.com/reactivex/rxjs/issues/5769)) ([0872341](https://github.com/reactivex/rxjs/commit/087234146760ab2c67a04f9f0b5494a93affadb7)), closes [#3665](https://github.com/reactivex/rxjs/issues/3665)
- **forkJoin:** ensure readonly array argument `forkJoin([a$, b$, c$] as const)` result is correct ([6baec53](https://github.com/reactivex/rxjs/commit/6baec536015253ac96827f2136ede17a324c634e))
- **iif:** No longer allow accidental undefined arguments ([#5829](https://github.com/reactivex/rxjs/issues/5829)) ([23b98b4](https://github.com/reactivex/rxjs/commit/23b98b4e61c3284c81c07a8d810e8c3ec99ddfec))
- **sample:** don't signal on complete ([95e0b70](https://github.com/reactivex/rxjs/commit/95e0b703caaf288657c7d722b9823458280be88b))
- **Symbol.observable:** properly defined as a `unique symbol`. ([#5874](https://github.com/reactivex/rxjs/issues/5874)) ([374138e](https://github.com/reactivex/rxjs/commit/374138e09eb7ceb6f8da556c6c11dea1ba8cdbee)), closes [#5861](https://github.com/reactivex/rxjs/issues/5861) [#4415](https://github.com/reactivex/rxjs/issues/4415)
- **throttle:** don't signal on complete ([4af0227](https://github.com/reactivex/rxjs/commit/4af022753d6dd4e94bcfcf0cc6082bb2312a3f02))
- **windowToggle:** don't signal on complete ([9cb56c4](https://github.com/reactivex/rxjs/commit/9cb56c45de289ef5b062f33971996bdb8414cf99)), closes [#5838](https://github.com/reactivex/rxjs/issues/5838)
- use empty object type in combineLatest/forkJoin sigs ([#5832](https://github.com/reactivex/rxjs/issues/5832)) ([22aaaa2](https://github.com/reactivex/rxjs/commit/22aaaa2f03dc721f850d9836243773c5310e85e8))
- support emoji in marble diagrams ([#5907](https://github.com/reactivex/rxjs/issues/5907)) ([1b4608c](https://github.com/reactivex/rxjs/commit/1b4608cea3a9db96d7a629ad5de0e100145c180e))
- **filter:** improve type inference for filter(Boolean) ([#5831](https://github.com/reactivex/rxjs/issues/5831)) ([d2658fa](https://github.com/reactivex/rxjs/commit/d2658fa32d7a86ac1e0796c452df258fc5470f67))
### BREAKING CHANGES
- **windowToggle:** the observable returned by the windowToggle operator's
closing selector must emit a next notification to close the window.
Complete notifications no longer close the window.
- **bufferToggle:** the observable returned by the bufferToggle operator's
closing selector must emit a next notification to close the buffer.
Complete notifications no longer close the buffer.
- **bufferWhen:** the observable returned by the bufferWhen operator's
closing selector must emit a next notification to close the buffer.
Complete notifications no longer close the buffer.
- **debounce:** the observable returned by the debounce operator's
duration selector must emit a next notification to end the duration.
Complete notifications no longer end the duration.
- **throttle:** the observable returned by the throttle operator's
duration selector must emit a next notification to end the duration.
Complete notifications no longer end the duration.
- **sample:** the sample operator's notifier observable must emit a next notification to effect a sample. Complete notifications no longer effect a sample.
- **audit:** the observable returned by the audit operator's duration selector must emit a next notification to end the duration. Complete notifications no longer end the duration.
- **Symbol.observable:** `rxjs@7` is only compatible with `@types/node@14.14.3` or higher and `symbol-observable@3.0.0` and higher. Older versions of `@types/node` incorrectly defined `Symbol.observable` and will be in conflict with `rxjs` and `symbol-observable@3.0.0`.
- **delayWhen:** `delayWhen` will no longer emit if the duration selector simply completes without a value. Notifiers must notify with a value, not a completion.
- **iif:** `iif` will no longer allow result arguments that are `undefined`. This was a bad call pattern that was likely an error in most cases. If for some reason you are relying on this behavior, simply substitute `EMPTY` in place of the `undefined` argument. This ensures that the behavior was intentional and desired, rather than the result of an accidental `undefined` argument.
- **audit, auditTime:** audit and auditTime emit last value after source completes ([#5799](https://github.com/reactivex/rxjs/issues/5799)) ([643bc85](https://github.com/reactivex/rxjs/commit/643bc85ab17a15a5d96f8bef8f08c3987d16eb40)), closes [#5730](https://github.com/reactivex/rxjs/issues/5730)
- No longer allow invalid "Subscribable" type as valid observable source in `from` and others. ([258dddd](https://github.com/reactivex/rxjs/commit/258dddd8a392456e7d0b5ed9a7e294044f7c2518)), closes [#4532](https://github.com/reactivex/rxjs/issues/4532)
- **bindNodeCallback:** ensure underlying function is not called twice during subscription ([#5780](https://github.com/reactivex/rxjs/issues/5780)) ([74aa4b2](https://github.com/reactivex/rxjs/commit/74aa4b2ea6685f475329a8b8ecbcebed9adae547))
- **delay:** Now properly handles Date and negative numbers ([#5719](https://github.com/reactivex/rxjs/issues/5719)) ([868c02b](https://github.com/reactivex/rxjs/commit/868c02b47bb6f4ec4cd1d68b5b474731c470f27e)), closes [#5232](https://github.com/reactivex/rxjs/issues/5232)
- **delayWhen:** only deprecates when subscriptionDelay presents ([#5797](https://github.com/reactivex/rxjs/issues/5797)) ([43d1731](https://github.com/reactivex/rxjs/commit/43d17311a521234375146029aa5c4709cb221344))
- **every:** index properly increments in predicate ([5686f83](https://github.com/reactivex/rxjs/commit/5686f838fdc3da710d3f1eed1a6381791e3cc644))
- **firstValueFrom:** now unsubscribes from source after first value is received ([#5813](https://github.com/reactivex/rxjs/issues/5813)) ([a321516](https://github.com/reactivex/rxjs/commit/a321516908aa036fb658395a372668a986af2504)), closes [#5811](https://github.com/reactivex/rxjs/issues/5811)
- **from:** objects that are thennable that happen to have a subscribe method will no longer error. ([789d6e3](https://github.com/reactivex/rxjs/commit/789d6e3d851d57ab3b4488381f702120fd079737))
- **fromEvent:** now properly types JQuery event targets ([b5aa15a](https://github.com/reactivex/rxjs/commit/b5aa15a7f58377310438aa5957e1516749d36219))
- **mergeScan:** no longer emits state again upon completion. ([#5805](https://github.com/reactivex/rxjs/issues/5805)) ([68c2894](https://github.com/reactivex/rxjs/commit/68c28943b4d2c51068fecbc359a68ca6982307bf)), closes [#5372](https://github.com/reactivex/rxjs/issues/5372)
- **throttle:** now supports synchronous duration selectors ([55e953e](https://github.com/reactivex/rxjs/commit/55e953e1f7b915e6c9072bf14a2febd5b8431393)), closes [#5658](https://github.com/reactivex/rxjs/issues/5658)
- **throttle:** trailing values will now emit after source completes ([d5fd69c](https://github.com/reactivex/rxjs/commit/d5fd69c123d2232335563eea95c69c07576d079d))
- **timeout:** allows synchronous observable as a source ([84c5c0b](https://github.com/reactivex/rxjs/commit/84c5c0b9d9e0d1791ac2f066c26e462e822d73e1)), closes [#5746](https://github.com/reactivex/rxjs/issues/5746)
- **zip:** zip now accepts an array of arguments like its counterparts ([3123b67](https://github.com/reactivex/rxjs/commit/3123b670cca9b77919845333952ef70275ed6e90))
### Code Refactoring
- **count:** Base off of `reduce`. ([98a6d09](https://github.com/reactivex/rxjs/commit/98a6d0991df2a28366ab8f34098109a67257c235))
- **pairs:** Based off of `from` and `Object.entries` ([#5775](https://github.com/reactivex/rxjs/issues/5775)) ([d39f830](https://github.com/reactivex/rxjs/commit/d39f8309c33917cb7070c7432fcd382395e4211e))
### Features
- **ajax:** now supports passing custom XSRF cookies in a custom header ([#5702](https://github.com/reactivex/rxjs/issues/5702)) ([1a2c2e4](https://github.com/reactivex/rxjs/commit/1a2c2e49482a460778ea92c7f6a92e58cc3e87bb)), closes [#4003](https://github.com/reactivex/rxjs/issues/4003)
- **mergeScan:** `mergeScan` will no longer emit its inner state again upon completion.
- **pairs:** `pairs` will no longer function in IE without a polyfill for `Object.entries`. `pairs` itself is also deprecated in favor of users just using `from(Object.entries(obj))`.
- **zip:** Zipping a single array will now have a different result. This is an extreme corner-case, because it is very unlikely that anyone would want to zip an array with nothing at all. The workaround would be to wrap the array in another array `zip([[1,2,3]])`. But again, that's pretty weird.
- **count:** No longer passes `source` observable as a third argument to the predicate. That feature was rarely used, and of limited value. The workaround is to simply close over the source inside of the function if you need to access it in there.
- **multicast:** and other publish variants will handle errors thrown in a selector appropriately ([bde8eda](https://github.com/reactivex/rxjs/commit/bde8eda09310463b05c5ec7d8a1dd1bafe9dba6f))
### Code Refactoring
- **tap:** reduce the size of the implementation ([1222d5a](https://github.com/reactivex/rxjs/commit/1222d5a68faa9d3f3c9ad8f8d5db1440971502bd))
- **Subscriber:** Massively untangle Subscriber and SafeSubscriber ([07902ca](https://github.com/reactivex/rxjs/commit/07902ca99ee828521ce238826f10b55e25fbf554))
### BREAKING CHANGES
- **Subscriber:** `new Subscriber` no longer takes 0-3 arguments. To create a `Subscriber` with 0-3 arguments, use `Subscriber.create`. However, please note that there is little to no reason that you should be creating `Subscriber` references directly, and `Subscriber.create` and `new Subscriber` are both deprecated.
- **AsyncSubject:** fixed reentrancy issue in complete ([9e00f11](https://github.com/reactivex/rxjs/commit/9e00f11e992d223edf1013d0a44c7cad41b72470)), closes [/github.com/ReactiveX/rxjs/pull/5729/files/30d429cf1b791db15c04a61f6a683e189b53fb3e#r492314703](https://github.com//github.com/ReactiveX/rxjs/pull/5729/files/30d429cf1b791db15c04a61f6a683e189b53fb3e/issues/r492314703)
- **delay:** proper handling of absolute time (`Date`) passed as an argument ([8ae89b1](https://github.com/reactivex/rxjs/commit/8ae89b19a095541eb3dfe6e6d9f26367486c435e))
- **fromEvent:** properly teardown for ArrayLike targets ([066de74](https://github.com/reactivex/rxjs/commit/066de7408810864891b9fd16e05c6c8b4ca88087))
- **ReplaySubject:** no longer buffers additional values after it's already stopped ([#5696](https://github.com/reactivex/rxjs/issues/5696)) ([a08232b](https://github.com/reactivex/rxjs/commit/a08232be6dcab74e94cfbb17cc5138050bcd6ddb))
- **scan:** proper indexes when seed is not supplied ([f93fb9c](https://github.com/reactivex/rxjs/commit/f93fb9c1fb7434c97e1d156370756159c5f2b077)), closes [#4348](https://github.com/reactivex/rxjs/issues/4348) [#3879](https://github.com/reactivex/rxjs/issues/3879)
- **windowTime:** Passing no creation interval will now properly open new window when old one closes ([cbd0ac0](https://github.com/reactivex/rxjs/commit/cbd0ac0478730ec10172b57210e7d269d1ce62a2))
### Code Refactoring
- **Massive Size Reduction:** reduced the size of all operator implementations as well as other utilities and types ([#5729](https://github.com/reactivex/rxjs/issues/5729)) ([4d3fc23](https://github.com/reactivex/rxjs/commit/fc41e13a1b9a05fc242c1369b4f597c931bd28b5))
### Features
- **onUnhandledError:** configuration point added for unhandled errors ([#5681](https://github.com/reactivex/rxjs/issues/5681)) ([3485dd5](https://github.com/reactivex/rxjs/commit/3485dd5149b731e1103d2d070e3892735cbacef1))
- **skipLast:** counts zero or less will mirror the source ([02e113b](https://github.com/reactivex/rxjs/commit/02e113b3345a9efe8f7c29f8b9c1c0d088aaf726))
### BREAKING CHANGES
- **skipLast:** `skipLast` will no longer error when passed a negative number, rather it will simply return the source, as though `0` was passed.
- **map:** `thisArg` will now default to `undefined`. The previous default of `MapSubscriber` never made any sense. This will only affect code that calls map with a `function` and references `this` like so: `source.pipe(map(function () { console.log(this); }))`. There wasn't anything useful about doing this, so the breakage is expected to be very minimal. If anything we're no longer leaking an implementation detail.
- **onUnhandledError:** Errors that occur during setup of an observable subscription after the subscription has emitted an error or completed will now throw in their own call stack. Before it would call `console.warn`. This is potentially breaking in edge cases for node applications, which may be configured to terminate for unhandled exceptions. In the unlikely event this affects you, you can configure the behavior to `console.warn` in the new configuration setting like so: `import { config } from 'rxjs'; config.onUnhandledError = (err) => console.warn(err);`
- **ajax:** Allow XHR to perform body serialization and set content-type where possible ([d8657ed](https://github.com/reactivex/rxjs/commit/d8657ede8d9620ac2a7d61557e1f1d0e89b0b52a)), closes [#2837](https://github.com/reactivex/rxjs/issues/2837)
- **ajax:** Do not mutate headers passed as arguments ([0d66ba4](https://github.com/reactivex/rxjs/commit/0d66ba458f07fba51cfc73440d01ef453c24cda7)), closes [#2801](https://github.com/reactivex/rxjs/issues/2801)
- **bindCallback:** now emits errors that happen after callback ([2bddd31](https://github.com/reactivex/rxjs/commit/2bddd317fad962ad375de4a04dd528b02479ec5b))
- **bindNodeCallback:** now emits errors that happen after callback ([edc28cf](https://github.com/reactivex/rxjs/commit/edc28cfd13ba3d7fadc24ea3c20ec8ca5a19064d))
- **buffer:** Ensure notifier is subscribed after source ([#5654](https://github.com/reactivex/rxjs/issues/5654)) ([c088b0e](https://github.com/reactivex/rxjs/commit/c088b0eca904ab835b23df629d472003d6a82561)), closes [#2195](https://github.com/reactivex/rxjs/issues/2195) [#1754](https://github.com/reactivex/rxjs/issues/1754)
- **catchError:** ensure proper handling of async return for synchronous source error handling ([#5627](https://github.com/reactivex/rxjs/issues/5627)) ([1b29d4b](https://github.com/reactivex/rxjs/commit/1b29d4b6d42e3d6b649f9f2c4bb718f343233d83)), closes [#5115](https://github.com/reactivex/rxjs/issues/5115)
- **catchError:** inner synchronous observables will properly terminate ([#5655](https://github.com/reactivex/rxjs/issues/5655)) ([d3fd2fb](https://github.com/reactivex/rxjs/commit/d3fd2fb2bd619b79d0c4afebc3c10299afbca262))
- **errors:** Custom RxJS errors now all have a call stack ([#5686](https://github.com/reactivex/rxjs/issues/5686)) ([9bb046c](https://github.com/reactivex/rxjs/commit/9bb046c744cc1f9438a805849b655946e5793936)), closes [#4250](https://github.com/reactivex/rxjs/issues/4250)
- **onErrorResumeNext:** observables always finalized before moving to next source ([#5650](https://github.com/reactivex/rxjs/issues/5650)) ([ff68ad2](https://github.com/reactivex/rxjs/commit/ff68ad2caa3d275a23416984fab5570d3fed9458))
- **package.json:** change homepage setting to official docs site. ([#5669](https://github.com/reactivex/rxjs/issues/5669)) ([e57c402](https://github.com/reactivex/rxjs/commit/e57c402b29288f61fe886b00e51817730bcb320b))
- **repeatWhen:** Ensure teardown happens between repeat subscriptions ([#5625](https://github.com/reactivex/rxjs/issues/5625)) ([98356f4](https://github.com/reactivex/rxjs/commit/98356f4ebefdba1f5a14edbd96de1592694a01a8))
- **retry:** Ensure teardown happens before resubscription with synchronous observables ([6f90597](https://github.com/reactivex/rxjs/commit/6f90597e51e038dabd8397b9f066ab4e3d344a5b)), closes [#5620](https://github.com/reactivex/rxjs/issues/5620)
- **retryWhen:** Ensure subscription tears down between retries ([#5623](https://github.com/reactivex/rxjs/issues/5623)) ([6752af7](https://github.com/reactivex/rxjs/commit/6752af7c1839baf3cd7ed9d024499de61a2477e9))
- **throttleTime:** ensure the spacing between throttles is always at least the throttled amount ([#5687](https://github.com/reactivex/rxjs/issues/5687)) ([ea84fc4](https://github.com/reactivex/rxjs/commit/ea84fc4dce84e32598701f79d9449be00a05352c)), closes [#3712](https://github.com/reactivex/rxjs/issues/3712) [#4864](https://github.com/reactivex/rxjs/issues/4864) [#2727](https://github.com/reactivex/rxjs/issues/2727) [#4727](https://github.com/reactivex/rxjs/issues/4727) [#4429](https://github.com/reactivex/rxjs/issues/4429)
- **zip:** zip operators and functions are now able to zip all iterable sources ([#5688](https://github.com/reactivex/rxjs/issues/5688)) ([02c3a1b](https://github.com/reactivex/rxjs/commit/02c3a1b70c0e96b784a3c5c214c0f89c5ebdd696)), closes [#4304](https://github.com/reactivex/rxjs/issues/4304)
-`switchMap` and `exhaustMap` behave correctly with re-entrant code. ([c289688](https://github.com/reactivex/rxjs/commit/c289688f5e1f33ec21306b4d2f5539dd19f963f2))
- **webSocket:** close websocket connection attempt on unsubscribe ([e1a671c](https://github.com/reactivex/rxjs/commit/e1a671cbd7f5a6ce547ed9ee6ce98c22264500f4)), closes [#4446](https://github.com/reactivex/rxjs/issues/4446)
### Code Refactoring
- **ajax:** Use simple Observable ([17b9add](https://github.com/reactivex/rxjs/commit/17b9add03a90aec6e708a87c0fc387745f0b9df6))
- **VirtualTimeScheduler:** remove sortActions from public API ([#5657](https://github.com/reactivex/rxjs/issues/5657)) ([a468f88](https://github.com/reactivex/rxjs/commit/a468f881c8c02195b089889486d1a94fab2771e0))
### Features
- **combineLatest:** add N-args signature for observable inputs ([#5488](https://github.com/reactivex/rxjs/issues/5488)) ([fcc47e7](https://github.com/reactivex/rxjs/commit/fcc47e75a4c811199c5071144172f4d06ffc7c70))
- **Subscription:** `remove` will now remove any teardown by reference ([#5659](https://github.com/reactivex/rxjs/issues/5659)) ([1531152](https://github.com/reactivex/rxjs/commit/15311529fa1b880ed469b6c253cd0be7ff2f98a1))
- **throwError:** now accepts a factory to create the error ([#5647](https://github.com/reactivex/rxjs/issues/5647)) ([dad270a](https://github.com/reactivex/rxjs/commit/dad270afcf496de74b4392024191715d7dbef4f5)), closes [#5617](https://github.com/reactivex/rxjs/issues/5617)
- **useDeprecatedNextContext:** Puts deprecated next context behavior behind a flag ([dfdef5d](https://github.com/reactivex/rxjs/commit/dfdef5dcaf52363be59359786aef8bc733197b43))
- support schedulers within run ([#5619](https://github.com/reactivex/rxjs/issues/5619)) ([c63de0d](https://github.com/reactivex/rxjs/commit/c63de0d380a923987aab587720473fad1d205d71))
### Performance Improvements
- **SafeSubscriber:** avoid using `Object.create` ([40a9e77](https://github.com/reactivex/rxjs/commit/40a9e77fe3d75df9161ad0093f54750b70f57245))
### BREAKING CHANGES
- **ajax:**
-`ajax` body serialization will now use default XHR behavior in all cases. If the body is a `Blob`, `ArrayBuffer`, any array buffer view (like a byte sequence, e.g. `Uint8Array`, etc), `FormData`, `URLSearchParams`, `string`, or `ReadableStream`, default handling is use. If the `body` is otherwise `typeof``"object"`, then it will be converted to JSON via `JSON.stringify`, and the `Content-Type` header will be set to `application/json;charset=utf-8`. All other types will emit an error.
- The `Content-Type` header passed to `ajax` configuration no longer has any effect on the serialization behavior of the AJAX request.
- For TypeScript users, `AjaxRequest` is no longer the type that should be explicitly used to create an `ajax`. It is now `AjaxConfig`, although the two types are compatible, only `AjaxConfig` has `progressSubscriber` and `createXHR`.
* **zip:** `zip` operators will no longer iterate provided iterables "as needed", instead the iterables will be treated as push-streams just like they would be everywhere else in RxJS. This means that passing an endless iterable will result in the thread locking up, as it will endlessly try to read from that iterable. This puts us in-line with all other Rx implementations. To work around this, it is probably best to use `map` or some combination of `map` and `zip`. For example, `zip(source$, iterator)` could be `source$.pipe(map(value => [value, iterator.next().value]))`.
* **Subscription:** `add` no longer returns an unnecessary Subscription reference. This was done to prevent confusion caused by a legacy behavior. You can now add and remove functions and Subscriptions as teardowns to and from a `Subscription` using `add` and `remove` directly. Before this, `remove` only accepted subscriptions.
* **RxJS Error types** Tests that are written with naive expectations against errors may fail now that errors have a proper `stack` property. In some testing frameworks, a deep equality check on two error instances will check the values in `stack`, which could be different.
* **Undocumented Behaviors/APIs Removed**:
-`unsubscribe` no longer available via the `this` context of observer functions. To reenable, set `config.useDeprecatedNextContext = true` on the rxjs `config` found at `import { config } from 'rxjs';`. Note that enabling this will result in a performance penalty for all consumer subscriptions.
- Leaked implementation detail `_unsubscribeAndRecycle` of `Subscriber` has been removed. Just use new `Subscription` objects
- Removed an undocumented behavior where passing a negative count argument to `retry` would result in an observable that repeats forever.
- An undocumented behavior where passing a negative count argument to `repeat` would result in an observable that repeats forever.
- The static `sortActions` method on `VirtualTimeScheduler` is no longer publicly exposed by our TS types.
* **throwError:** In an extreme corner case for usage, `throwError` is no longer able to emit a function as an error directly. If you need to push a function as an error, you will have to use the factory function to return the function like so: `throwError(() => functionToEmit)`, in other words `throwError(() => () => console.log('called later'))`.
- **ajax:** Partial observers passed to `progressSubscriber` will no longer error ([25d279f](https://github.com/reactivex/rxjs/commit/25d279f0b45d07f39bfb87b19bc7e2279df8b542))
- **ajax:** Unparsable responses will no longer prevent full AjaxError from being thrown ([605ee55](https://github.com/reactivex/rxjs/commit/605ee550e5efc266b5dc5d3a9756c7c3b3968a61))
- **animationFrames:** emit the timestamp from the rAF's callback ([#5438](https://github.com/reactivex/rxjs/issues/5438)) ([c980ae6](https://github.com/reactivex/rxjs/commit/c980ae65ee1b585e8ed66a366eb534ac3e50c205))
- Ensure unsubscriptions/teardowns on internal subscribers are idempotent ([#5465](https://github.com/reactivex/rxjs/issues/5465)) ([3e39749](https://github.com/reactivex/rxjs/commit/3e39749a58ca663c17f5f0354b0f27532fb6d319)), closes [#5464](https://github.com/reactivex/rxjs/issues/5464)
- **ajax:** Drop support for IE10 and lower ([0eaadd6](https://github.com/reactivex/rxjs/commit/0eaadd60c716050f5e3701d513a028a9cd49085a))
- **Observable:** Update property and method types ([#5572](https://github.com/reactivex/rxjs/issues/5572)) ([144b626](https://github.com/reactivex/rxjs/commit/144b626c3905640b4adeb2b97e722912eff1b264))
### Features
- **combineLatest:** support for observable dictionaries ([#5022](https://github.com/reactivex/rxjs/issues/5022)) ([#5363](https://github.com/reactivex/rxjs/issues/5363)) ([f5278aa](https://github.com/reactivex/rxjs/commit/f5278aa89ea164caf5cf10e77d7bd00eff26fc0f))
- **TestScheduler:** add an animate "run mode" helper ([#5607](https://github.com/reactivex/rxjs/issues/5607)) ([edd6731](https://github.com/reactivex/rxjs/commit/edd67313814bfc32e8a5129d8049e4d4678cd35d))
- **timeout:** One timeout to rule them all ([def1d34](https://github.com/reactivex/rxjs/commit/def1d346b43008bc413a3ac985e1611bbbf62003))
### BREAKING CHANGES
- **ajax:** In an extreme corner-case... If an error occurs, the responseType is `"json"`, we're in IE, and the `responseType` is not valid JSON, the `ajax` observable will no longer emit a syntax error, rather it will emit a full `AjaxError` with more details.
- **ajax:** Ajax implementation drops support for IE10 and lower. This puts us in-line with other implementations and helps clean up code in this area
- **Observable:** `lift` no longer exposed. It was _NEVER_ documented that end users of the library should be creating operators using `lift`. Lift has a [variety of issues](https://github.com/ReactiveX/rxjs/issues/5431) and was always an internal implementation detail of rxjs that might have been used by a few power users in the early days when it had the most value. The value of `lift`, originally, was that subclassed `Observable`s would compose through all operators that implemented lift. The reality is that feature is not widely known, used, or supported, and it was never documented as it was very experimental when it was first added. Until the end of v7, `lift` will remain on Observable. Standard JavaScript users will notice no difference. However, TypeScript users might see complaints about `lift` not being a member of observable. To workaround this issue there are two things you can do: 1. Rewrite your operators as [outlined in the documentation](https://rxjs.dev/guide/operators), such that they return `new Observable`. or 2. cast your observable as `any` and access `lift` that way. Method 1 is recommended if you do not want things to break when we move to version 8.
- **perf:** Reduce memory pressure by no longer retaining outer values across the majority of operators. ([#5610](https://github.com/reactivex/rxjs/pull/5610)) ([bff1827](https://github.com/ReactiveX/rxjs/commit/bff18272dca23938a5f5b57cec6eb8d8be5bfddf))
- **Observable:** Update property and method types ([#5572](https://github.com/reactivex/rxjs/issues/5572)) ([144b626](https://github.com/reactivex/rxjs/commit/144b626c3905640b4adeb2b97e722912eff1b264))
### Features
- **combineLatest:** support for observable dictionaries ([#5022](https://github.com/reactivex/rxjs/issues/5022)) ([#5363](https://github.com/reactivex/rxjs/issues/5363)) ([f5278aa](https://github.com/reactivex/rxjs/commit/f5278aa89ea164caf5cf10e77d7bd00eff26fc0f))
- **Observable:** `lift` no longer exposed. It was _never_ documented that end users of the library should be creating operators using `lift`. Lift has a [variety of issues](https://github.com/ReactiveX/rxjs/issues/5431) and was always an internal implementation detail of rxjs that might have been used by a few power users in the early days when it had the most value. The value of `lift`, originally, was that subclassed `Observable`s would compose through all operators that implemented lift. The reality is that feature is not widely known, used, or supported, and it was never documented as it was very experimental when it was first added. Until the end of v7, `lift` will remain on Observable. Standard JavaScript users will notice no difference. However, TypeScript users might see complaints about `lift` not being a member of observable. To workaround this issue there are two things you can do: 1. Rewrite your operators as [outlined in the documentation](https://rxjs.dev/guide/operators), such that they return `new Observable`. or 2. cast your observable as `any` and access `lift` that way. It is recommended that operators be implemented in terms of functions that return `(source: Observable<T>) => new Observable<R>(...)`, per the documentation/guide.
- **pluck:** operator breaks with null/undefined inputs. ([#5524](https://github.com/reactivex/rxjs/issues/5524)) ([c5f6550](https://github.com/reactivex/rxjs/commit/c5f65508505cf1f90560e6be76425e09c455bec3))
- **shareReplay:** no longer misses synchronous values from source ([92452cc](https://github.com/reactivex/rxjs/commit/92452cc20021141aa0f047c7e5af569a413143e5))
- **finalize:** chain subscriptions for interop with finalize ([#5239](https://github.com/reactivex/rxjs/issues/5239)) ([04ba662](https://github.com/reactivex/rxjs/commit/04ba6621fe9e09238e1796217d04107e52dd36d5)), closes [#5237](https://github.com/reactivex/rxjs/issues/5237) [#5237](https://github.com/reactivex/rxjs/issues/5237)
- **animationFrameScheduler:** don't execute rescheduled animation frame and asap actions in flush ([#5399](https://github.com/reactivex/rxjs/issues/5399)) ([33c9c8c](https://github.com/reactivex/rxjs/commit/33c9c8cf7e247d4ad4d7318bfd02e8e5bedb0f40)), closes [#4972](https://github.com/reactivex/rxjs/issues/4972) [#5397](https://github.com/reactivex/rxjs/issues/5397)
- **iterables:** errors thrown from iterables now properly propagated ([#5444](https://github.com/reactivex/rxjs/issues/5444)) ([75d4c2f](https://github.com/reactivex/rxjs/commit/75d4c2f33d2e2121b2a316849044ad17ab28dbaf))
- **finalize:** callback will be called after the source observable is torn down. ([0d7b7c1](https://github.com/reactivex/rxjs/commit/0d7b7c14e34eed43fb2ad1386281800fa3ae8aec)), closes [#5357](https://github.com/reactivex/rxjs/issues/5357)
- **TestScheduler:** support empty subscription marbles ([#5502](https://github.com/reactivex/rxjs/issues/5502)) ([e65696e](https://github.com/reactivex/rxjs/commit/e65696e2f7f7338659a873f6653026b33b9011a9)), closes [#5499](https://github.com/reactivex/rxjs/issues/5499)
- **expand:** now works properly with asynchronous schedulers ([294b27e](https://github.com/reactivex/rxjs/commit/294b27eb6a96e8edee3af35e6aaaef50628376e4))
- **subscribeOn:** allow Infinity as valid delay ([#5500](https://github.com/reactivex/rxjs/issues/5500)) ([cd7d649](https://github.com/reactivex/rxjs/commit/cd7d64901e82fd7fb5e8407f1f30828906fac420))
- **Subject:** resolve issue where Subject constructor errantly allowed an argument ([#5476](https://github.com/reactivex/rxjs/issues/5476)) ([e1d35dc](https://github.com/reactivex/rxjs/commit/e1d35dc258edea0237ef49a31f7b34c058755969))
- **Subject:** no default generic ([e678e81](https://github.com/reactivex/rxjs/commit/e678e81ba80f5bcc27b0e956295ce2fc8dfe4576))
- **defer:** No longer allows `() => undefined` to observableFactory (#5449) ([1ae937a](https://github.com/reactivex/rxjs/commit/1ae937a8e594aef96b93313bb3c68ea910e6f528)), closes [#5449](https://github.com/reactivex/rxjs/issues/5449)
- **single:** Corrected behavior for `single(() => false)` on empty observables. (#5325) ([27931bc](https://github.com/reactivex/rxjs/commit/27931bcfd2aa864e277d3e72128c57e807b28bb0)), closes [#5325](https://github.com/reactivex/rxjs/issues/5325)
- **take/takeLast**: Properly assert number types at runtime (#5326) ([5efc474](https://github.com/reactivex/rxjs/commit/5efc474161c9196dbdf4803a9cc444a547067549)), closes [#5326](https://github.com/reactivex/rxjs/issues/5326)
- **groupBy:** Add typeguards support for groupBy ([#5441](https://github.com/reactivex/rxjs/issues/5441)) ([da382da](https://github.com/reactivex/rxjs/commit/da382da4cdcc6e7ab1ffc6a499f4f7f5ea7de130))
- **raceWith:** add raceWith, the renamed `race` operator ([#5303](https://github.com/reactivex/rxjs/issues/5303)) ([ca7f370](https://github.com/reactivex/rxjs/commit/ca7f370d8379f22526cfb17d40deff53e1358742))
- **TimestampProvider:** Reduced scheduler footprint for default usage of shareReplay, timeInterval, and timestamp ([#4973](https://github.com/reactivex/rxjs/issues/4973)) ([b2e67e3](https://github.com/reactivex/rxjs/commit/b2e67e3139f0be1fb000ba42bb42c5ba60cc803a))
- Type signatures tightened up around `Notification` and `dematerialize`, may uncover issues with invalid types passed to those operators.
- Experimental support for `for await` as been removed. Use https://github.com/benlesh/rxjs-for-await instead.
-`defer` no longer allows factories to return `void` or `undefined`. All factories passed to defer must return a proper `ObservableInput`, such as `Observable`, `Promise`, et al. To get the same behavior as you may have relied on previously, `return EMPTY` or `return of()` from the factory.
-`single` operator will now throw for scenarios where values coming in are either not present, or do not match the provided predicate. Error types have thrown have also been updated, please check documentation for changes.
-`take` and will now throw runtime error for arguments that are negative or NaN, this includes non-TS calls like `take()`.
-`takeLast` now has runtime assertions that throw `TypeError`s for invalid arguments. Calling takeLast without arguments or with an argument that is `NaN` will throw a `TypeError`
-`ReplaySubject` no longer schedules emissions when a scheduler is provided. If you need that behavior,
please compose in `observeOn` using `pipe`, for example: `new ReplaySubject(2, 3000).pipe(observeOn(asap))`
-`timestamp` operator accepts a `TimestampProvider`, which is any object with a `now` method
that returns a number. This means pulling in less code for the use of the `timestamp` operator. This may cause
issues with `TestScheduler` run mode. (Issue here: https://github.com/ReactiveX/rxjs/issues/5553)
- **delay:** emit complete notification as soon as possible ([63b8797](https://github.com/reactivex/rxjs/commit/63b8797fbeed09eb675ea64b0b83607cef1367a9)), closes [#4249](https://github.com/reactivex/rxjs/issues/4249)
- **endWith:** will properly type N arguments ([#5246](https://github.com/reactivex/rxjs/issues/5246)) ([81ee1f7](https://github.com/reactivex/rxjs/commit/81ee1f72408854f4017615fe7949edf5dd50533b))
- **pipe:** Special handling for 0-arg case. ([#4936](https://github.com/reactivex/rxjs/issues/4936)) ([290fa51](https://github.com/reactivex/rxjs/commit/290fa51c44881f25f2fe4cf9885028396c7fd74c))
- **pluck:** fix pluck's catch-all signature for better type safety ([#5192](https://github.com/reactivex/rxjs/issues/5192)) ([e0c5b7c](https://github.com/reactivex/rxjs/commit/e0c5b7c790bb9d99fa8bee26c805b5e70c1e456b))
- **pluck:** param type now accepts number and symbol ([9697b69](https://github.com/reactivex/rxjs/commit/9697b695c23c3dcb614e6a70be63a94ffcd86ed9))
- **startWith:** accepts N arguments and returns correct type ([#5247](https://github.com/reactivex/rxjs/issues/5247)) ([150ed8b](https://github.com/reactivex/rxjs/commit/150ed8b75909b0e0bb9dc8928287ebdc47e19c51))
- **combineLatestWith:** and zipWith infer types from n-arguments ([#5257](https://github.com/reactivex/rxjs/issues/5257)) ([3e282a5](https://github.com/reactivex/rxjs/commit/3e282a58b1baf7aa03b17142f858bca09a542adf))
- **race:** support N args in static race and ensure observable returned ([#5286](https://github.com/reactivex/rxjs/issues/5286)) ([6d901cb](https://github.com/reactivex/rxjs/commit/6d901cbb0c0f2aa3fc5a02ef895cc9e9a7a09243))
- **toPromise:** correct toPromise return type ([#5072](https://github.com/reactivex/rxjs/issues/5072)) ([b1c3573](https://github.com/reactivex/rxjs/commit/b1c35738204b5b1a5d325a16e70cdbf25b523976))
- add `lastValueFrom` and `firstValueFrom` methods ([#5295](https://github.com/reactivex/rxjs/issues/5295)) ([e69b765](https://github.com/reactivex/rxjs/commit/e69b76584d6872b3c55aa1bdf39c8984e9d9b00e))
- RxJS now supports first-class interop with AsyncIterables ([4fa9d01](https://github.com/reactivex/rxjs/commit/4fa9d016a83049d014d77b89c56301e42db16b4d))
- **retry:** add config to reset error count on successful emission ([#5280](https://github.com/reactivex/rxjs/issues/5280)) ([ab6e9fc](https://github.com/reactivex/rxjs/commit/ab6e9fc32c19c1f14f8f59459db75312e75b9351))
- **zipWith:** add `zipWith` which is just a rename of legacy `zip` operator ([#5249](https://github.com/reactivex/rxjs/issues/5249)) ([86b6a27](https://github.com/reactivex/rxjs/commit/86b6a272fd48c4712adba78963e05bb759ecf4f9))
### BREAKING CHANGES
- **startWith:** `startWith` will return incorrect types when called with more than 7 arguments and a scheduler. Passing scheduler to startWith is deprecated
- **toPromise:** toPromise return type now returns `T | undefined` in TypeScript, which is correct, but may break builds.
- chain subscriptions from observables that belong to other instances of RxJS (e.g. in node_modules) ([#5059](https://github.com/reactivex/rxjs/issues/5059)) ([d7f7078](https://github.com/reactivex/rxjs/commit/d7f7078))
- clear subscription on `shareReplay` completion ([#5044](https://github.com/reactivex/rxjs/issues/5044)) ([35e600f](https://github.com/reactivex/rxjs/commit/35e600f)), closes [#5034](https://github.com/reactivex/rxjs/issues/5034)
- **closure:** Annotate next() for ReplaySubject ([#5088](https://github.com/reactivex/rxjs/issues/5088)) ([8687fbd](https://github.com/reactivex/rxjs/commit/8687fbd))
- **closure:** static prop frameTimeFactor being collapsed when compiled with closure. ([39872c9](https://github.com/reactivex/rxjs/commit/39872c9))
- **docs:** remove repetitive op3() in example ([#5043](https://github.com/reactivex/rxjs/issues/5043)) ([e17df33](https://github.com/reactivex/rxjs/commit/e17df33))
- **filter:** Fix overload order for filter to support inferring the generic type ([#5024](https://github.com/reactivex/rxjs/issues/5024)) ([8255365](https://github.com/reactivex/rxjs/commit/8255365))
- **fromFetch:** passing already aborted signal to init aborts fetch ([0e4849a](https://github.com/reactivex/rxjs/commit/0e4849a))
- missing package.json in rxjs/fetch ([#5001](https://github.com/reactivex/rxjs/issues/5001)) ([f4bee07](https://github.com/reactivex/rxjs/commit/f4bee07))
- **filter:** Resolve TS build failures for certain situations where Boolean is the predicate ([77c7dfd](https://github.com/reactivex/rxjs/commit/77c7dfd))
- **pluck:** key union type strictness ([#4585](https://github.com/reactivex/rxjs/issues/4585)) ([bd5ec2d](https://github.com/reactivex/rxjs/commit/bd5ec2d))
- **race:** ignore latter sources after first complete or error ([#4809](https://github.com/reactivex/rxjs/issues/4809)) ([f31c3df](https://github.com/reactivex/rxjs/commit/f31c3df)), closes [#4808](https://github.com/reactivex/rxjs/issues/4808)
- **scan/reduce:** Typings correct for mixed seed/value types ([#4858](https://github.com/reactivex/rxjs/issues/4858)) ([b89ebe5](https://github.com/reactivex/rxjs/commit/b89ebe5))
- **scheduled:** import from relative paths ([#4832](https://github.com/reactivex/rxjs/issues/4832)) ([1d37a87](https://github.com/reactivex/rxjs/commit/1d37a87))
- **TS:** Error impls now properly type `this` ([#4978](https://github.com/reactivex/rxjs/issues/4978)) ([7606dc7](https://github.com/reactivex/rxjs/commit/7606dc7))
- **TS:** fix type inference for defaultIfEmpty. ([#4833](https://github.com/reactivex/rxjs/issues/4833)) ([9b5ce2f](https://github.com/reactivex/rxjs/commit/9b5ce2f))
- **animationFrames:** Adds an observable of animationFrames ([#5021](https://github.com/reactivex/rxjs/issues/5021)) ([6a4cd68](https://github.com/reactivex/rxjs/commit/6a4cd68))
- **concat:** can infer N types ([6c0cbc4](https://github.com/reactivex/rxjs/commit/6c0cbc4))
- **of:** Update of typings ([e8adbb5](https://github.com/reactivex/rxjs/commit/e8adbb5))
- **rxjs-compat:** removed for v7 ([#4839](https://github.com/reactivex/rxjs/issues/4839)) ([79b1b95](https://github.com/reactivex/rxjs/commit/79b1b95))
- **TS:** Update to TypeScript 3.5.3 ([741a136](https://github.com/reactivex/rxjs/commit/741a136))
### BREAKING CHANGES
- **concat:** Generic signature changed. Recommend not explicitly passing generics, just let inference do its job. If you must, cast with `as`.
- **of:** Generic signature changed, do not specify generics, allow them to be inferred or use `as`
- **of:** Use with more than 9 arguments, where the last argument is a `SchedulerLike` may result in the wrong type which includes the `SchedulerLike`, even though the run time implementation does not support that. Developers should be using `scheduled` instead
- **TS:** RxJS requires TS 3.5
- **rxjs-compat:** `rxjs/Rx` is no longer a valid import site.
- **rxjs-compat:** `rxjs-compat` is not published for v7 (yet)
- **race:** `race()` will no longer subscribe to subsequent observables if a provided source synchronously errors or completes. This means side effects that might have occurred during subscription in those rare cases will no longer occur.
- **general:** Refactor modules so they don't show side effects in some tools ([#4769](https://github.com/reactivex/rxjs/issues/4769)) ([9829c5e0](https://github.com/reactivex/rxjs/commit/9829c5e0))
- **endWith:** wrap args - they are not observables - in of before concatenating ([#4735](https://github.com/reactivex/rxjs/issues/4735)) ([986be2f](https://github.com/reactivex/rxjs/commit/986be2f))
- **forkJoin:** test for object literal ([#4741](https://github.com/reactivex/rxjs/issues/4741)) ([c11e1b3](https://github.com/reactivex/rxjs/commit/c11e1b3)), closes [#4737](https://github.com/reactivex/rxjs/issues/4737) [#4737](https://github.com/reactivex/rxjs/issues/4737)
- **pairwise:** make it recursion-proof ([#4743](https://github.com/reactivex/rxjs/issues/4743)) ([21ab261](https://github.com/reactivex/rxjs/commit/21ab261))
- **scan:** fixed declarations to properly support different return types ([#4598](https://github.com/reactivex/rxjs/issues/4598)) ([126d2b6](https://github.com/reactivex/rxjs/commit/126d2b6))
- **Subscription:** Return Empty when teardown === null ([#4575](https://github.com/reactivex/rxjs/issues/4575)) ([ffc4e68](https://github.com/reactivex/rxjs/commit/ffc4e68))
- **throttleTime:** emit single value with trailing enabled ([#4564](https://github.com/reactivex/rxjs/issues/4564)) ([fd690a6](https://github.com/reactivex/rxjs/commit/fd690a6)), closes [#2859](https://github.com/reactivex/rxjs/issues/2859) [#4491](https://github.com/reactivex/rxjs/issues/4491)
- **throttleTime:** emit single value with trailing enabled ([#4564](https://github.com/reactivex/rxjs/issues/4564)) ([fd690a6](https://github.com/reactivex/rxjs/commit/fd690a6)), closes [#2859](https://github.com/reactivex/rxjs/issues/2859) [#4491](https://github.com/reactivex/rxjs/issues/4491)
- **docs-app:** remove stopWordFilter from lunr pipeline ([#4536](https://github.com/reactivex/rxjs/issues/4536)) ([9eaebd4](https://github.com/reactivex/rxjs/commit/9eaebd4))
- **dtslint:** disable tests that break in TS@next ([#4705](https://github.com/reactivex/rxjs/issues/4705)) ([ecc73d2](https://github.com/reactivex/rxjs/commit/ecc73d2))
- **fromFetch:** We now export a `fromFetch` static observable creation method from `rxjs/fetch`. Mirrors native `fetch` only it's lazy and cancellable via `Observable` interface. ([#4702](https://github.com/reactivex/rxjs/issues/4702)) ([5a1ef86](https://github.com/reactivex/rxjs/commit/5a1ef86))
- **forkJoin:** accepts a dictionary of sources ([#4640](https://github.com/reactivex/rxjs/issues/4640)) ([b5a2ac9](https://github.com/reactivex/rxjs/commit/b5a2ac9))
- **partition:** new `partition` observable creation function. Old `partition` operator is deprecated ([#4419](https://github.com/reactivex/rxjs/issues/4419)) ([#4685](https://github.com/reactivex/rxjs/issues/4685)) ([d5d6980](https://github.com/reactivex/rxjs/commit/d5d6980))
- **scheduled:** Add `scheduled` creation function to use to create scheduled observable of values. Deprecate scheduled versions of `from`, `range`, et al. ([#4595](https://github.com/reactivex/rxjs/issues/4595)) ([f57e1fc](https://github.com/reactivex/rxjs/commit/f57e1fc))
- **ajax:** Fix case-insensitive headers in HTTP request ([#4453](https://github.com/reactivex/rxjs/issues/4453)) ([673bf47](https://github.com/reactivex/rxjs/commit/673bf47))
- **bundle:** closure to not rewrite polyfills for minification ([#4487](https://github.com/reactivex/rxjs/issues/4487)) ([a1fedb9](https://github.com/reactivex/rxjs/commit/a1fedb9))
- **endWith:** ability to endWith different types ([#4183](https://github.com/reactivex/rxjs/issues/4183)) ([#4185](https://github.com/reactivex/rxjs/issues/4185)) ([83533d1](https://github.com/reactivex/rxjs/commit/83533d1))
- **fromEventPattern:** improve typings for fromEventPattern ([#4496](https://github.com/reactivex/rxjs/issues/4496)) ([037f53d](https://github.com/reactivex/rxjs/commit/037f53d))
- **Observable:** Fix Observable.subscribe to add operator TeardownLogic to returned Subscription. ([#4434](https://github.com/reactivex/rxjs/issues/4434)) ([f28955f](https://github.com/reactivex/rxjs/commit/f28955f))
- **combineLatest:** support passing union types ([ffda319](https://github.com/reactivex/rxjs/commit/ffda319))
- **from:** support passing union types ([eb1d596](https://github.com/reactivex/rxjs/commit/eb1d596))
- **withLatestFrom:** support passing union types ([1e19a24](https://github.com/reactivex/rxjs/commit/1e19a24))
- **zip:** support passing union types ([0d87f52](https://github.com/reactivex/rxjs/commit/0d87f52))
- **multicast:** support returning union types from projection ([e9e9041](https://github.com/reactivex/rxjs/commit/e9e9041))
- **exhaustMap:** support returning union types from projection ([ff1f5dc](https://github.com/reactivex/rxjs/commit/ff1f5dc))
- **merge:** support union type inference for merge operators ([c2ac39c](https://github.com/reactivex/rxjs/commit/c2ac39c))
- **catchError:** support union type returns ([8350622](https://github.com/reactivex/rxjs/commit/8350622))
- **switchMap:** support union type returns ([32d35fd](https://github.com/reactivex/rxjs/commit/32d35fd))
- **defer:** support union types passed ([5aea50e](https://github.com/reactivex/rxjs/commit/5aea50e))
- **race:** Update typings to support proper return types ([#4465](https://github.com/reactivex/rxjs/issues/4465)) ([0042846](https://github.com/reactivex/rxjs/commit/0042846))
- **VirtualTimeScheduler:** rework flush so it won't lose actions ([#4433](https://github.com/reactivex/rxjs/issues/4433)) ([d068bc9](https://github.com/reactivex/rxjs/commit/d068bc9))
- **WebSocketSubject:** fix subject failing to close socket ([#4446](https://github.com/reactivex/rxjs/issues/4446)) ([dcfa52b](https://github.com/reactivex/rxjs/commit/dcfa52b))
### Features
- **shareReplay:** Add configuration object for named arguments, and add argument to support unsubscribing from source observable by `refCount` when all resulting subscriptions have unsubscribed. The default behavior is to leave the source subscription running.
- **mergeScan:** Add index to the accumulator function ([#4458](https://github.com/reactivex/rxjs/issues/4458)) ([f5e143d](https://github.com/reactivex/rxjs/commit/f5e143d)), closes [#4441](https://github.com/reactivex/rxjs/issues/4441)
- **range:** accept one argument ([#4360](https://github.com/reactivex/rxjs/issues/4360)) ([a388578](https://github.com/reactivex/rxjs/commit/a388578))
- **takeWhile:** add an `inclusive` option to the operator which causes to emit final value ([#4115](https://github.com/reactivex/rxjs/issues/4115)) ([6e7f407](https://github.com/reactivex/rxjs/commit/6e7f407))
### Performance Improvements
- **internal:** optimize Subscription#add() for the common case ([#4489](https://github.com/reactivex/rxjs/issues/4489)) ([bdd201c](https://github.com/reactivex/rxjs/commit/bdd201c))
- **internal:** use strict equality for isObject() ([#4493](https://github.com/reactivex/rxjs/issues/4493)) ([fc84a00](https://github.com/reactivex/rxjs/commit/fc84a00))
- **Subscription:** use `instanceof` to avoid megamorphic LoadIC ([#4499](https://github.com/reactivex/rxjs/issues/4499)) ([065b4e3](https://github.com/reactivex/rxjs/commit/065b4e3))
- **RxJS:** each instance of RxJS now has a unique Subscriber symbol ([0972c56](https://github.com/reactivex/rxjs/commit/0972c56))
- **subscribe:** report errors that occur in subscribe after the initial error ([#4089](https://github.com/reactivex/rxjs/issues/4089)) ([9b4b2bc](https://github.com/reactivex/rxjs/commit/9b4b2bc)), closes [#3803](https://github.com/reactivex/rxjs/issues/3803)
- **Subscriber:** Can no longer subscribe to itself in a circular manner ([#4106](https://github.com/reactivex/rxjs/issues/4106)) ([e623ec6](https://github.com/reactivex/rxjs/commit/e623ec6)), closes [#4095](https://github.com/reactivex/rxjs/issues/4095)
- **Subscriber:** use only local Subscriber instances ([50ee0a7](https://github.com/reactivex/rxjs/commit/50ee0a7))
- **TypeScript:** ensure RxJS builds with TS@next as well ([f03e790](https://github.com/reactivex/rxjs/commit/f03e790))
- **node:** will no longer error mixing RxJS 6.3 and 6.2 ([#4078](https://github.com/reactivex/rxjs/issues/4078)) ([69d9ccf](https://github.com/reactivex/rxjs/commit/69d9ccf)), closes [#4077](https://github.com/reactivex/rxjs/issues/4077)
- **find:** unsubscribe from source when found ([#3968](https://github.com/reactivex/rxjs/issues/3968)) ([fd01f7b](https://github.com/reactivex/rxjs/commit/fd01f7b))
- convert [@internal](https://github.com/internal) comment to JSDoc ([#3932](https://github.com/reactivex/rxjs/issues/3932)) ([f8a9d6e](https://github.com/reactivex/rxjs/commit/f8a9d6e))
- **AjaxObservable:** notify with error if fails to parse json response ([#3139](https://github.com/reactivex/rxjs/issues/3139)) ([d8231e2](https://github.com/reactivex/rxjs/commit/d8231e2)), closes [#3138](https://github.com/reactivex/rxjs/issues/3138)
- **distinctUntilKeyChanged:** improved key typing with keyof T ([#3988](https://github.com/reactivex/rxjs/issues/3988)) ([4ec4ff1](https://github.com/reactivex/rxjs/commit/4ec4ff1))
- **Observable:** forEach will no longer next values after an error ([b4bad1f](https://github.com/reactivex/rxjs/commit/b4bad1f))
- **Observable:** use more granular Observable exports in compat mode ([#3974](https://github.com/reactivex/rxjs/issues/3974)) ([3f75564](https://github.com/reactivex/rxjs/commit/3f75564))
- **onErrorResumeNext:** stop listening to a synchronous inner-observable when unsubscribed ([1d14277](https://github.com/reactivex/rxjs/commit/1d14277))
- **takeUntil:** takeUntil should subscribe to the source if notifier sync completes without emitting ([#4039](https://github.com/reactivex/rxjs/issues/4039)) ([21fd0b4](https://github.com/reactivex/rxjs/commit/21fd0b4)), closes [#3504](https://github.com/reactivex/rxjs/issues/3504)
- **testscheduler:** type arguments to Observable creation functions ([#3928](https://github.com/reactivex/rxjs/issues/3928)) ([0e30ef1](https://github.com/reactivex/rxjs/commit/0e30ef1))
### Features
- **delayWhen:** add index to the selector function ([#2473](https://github.com/reactivex/rxjs/issues/2473)) ([0979d31](https://github.com/reactivex/rxjs/commit/0979d31))
- **from:** Objects implementing Symbol.observable take precedence over other types ([80ceea0](https://github.com/reactivex/rxjs/commit/80ceea0))
- **fromEvent:** Support React Native and node-compatible event sources. ([#3821](https://github.com/reactivex/rxjs/issues/3821)) ([1969f18](https://github.com/reactivex/rxjs/commit/1969f18))
- **Observable.prototype.pipe:** TS typings now more correct for >8 parameters ([#3789](https://github.com/reactivex/rxjs/issues/3789)) ([ad010ea](https://github.com/reactivex/rxjs/commit/ad010ea))
- **subscribe:** ignore syncError when deprecated ([#3749](https://github.com/reactivex/rxjs/issues/3749)) ([f94560c](https://github.com/reactivex/rxjs/commit/f94560c))
- **Symbol.observable:** make observable declaration readonly ([#3697](https://github.com/reactivex/rxjs/issues/3697)) ([#3773](https://github.com/reactivex/rxjs/issues/3773)) ([e1c203f](https://github.com/reactivex/rxjs/commit/e1c203f))
- **TypeScript:** resolved typings issue for TS 3.0 ([bf2cdeb](https://github.com/reactivex/rxjs/commit/bf2cdeb))
- **ajax:** Handle timeouts as errors ([#3653](https://github.com/ReactiveX/RxJS/issues/3653)) ([e4128ea](https://github.com/ReactiveX/RxJS/commit/e4128ea))
- **ajax:** RxJS v6 TimeoutError is missing name property ([576d943](https://github.com/ReactiveX/RxJS/commit/576d943))
- **isObservable:** Fix throwing error when testing isObservable(null) ([#3688](https://github.com/ReactiveX/RxJS/issues/3688)) ([c9acc61](https://github.com/ReactiveX/RxJS/commit/c9acc61))
- **range:** Range should be same for every subscriber ([#3707](https://github.com/ReactiveX/RxJS/issues/3707)) ([9642133](https://github.com/ReactiveX/RxJS/commit/9642133))
- **skipUntil:** fix skipUntil when innerSubscription is null ([#3686](https://github.com/ReactiveX/RxJS/issues/3686)) ([4226432](https://github.com/ReactiveX/RxJS/commit/4226432))
- **TestScheduler:** restore run changes upon error ([27cb9b6](https://github.com/ReactiveX/RxJS/commit/27cb9b6))
- **TimeoutError:** Add name to TimeoutError ([44042d0](https://github.com/ReactiveX/RxJS/commit/44042d0))
- **WebSocketSubject:** Check to see if WebSocket exists in global scope ([#3694](https://github.com/ReactiveX/RxJS/issues/3694)) ([2db0788](https://github.com/ReactiveX/RxJS/commit/2db0788))
### Features
- **endWith:** add new operator endWith ([#3679](https://github.com/ReactiveX/RxJS/issues/3679)) ([537fe7d](https://github.com/ReactiveX/RxJS/commit/537fe7d))
- **audit:** will not crash if duration is synchronous ([#3608](https://github.com/ReactiveX/RxJS/issues/3608)) ([76b7e27](https://github.com/ReactiveX/RxJS/commit/76b7e27)), closes [#2743](https://github.com/ReactiveX/RxJS/issues/2743)
- **websocket:** no longer throws errors in operators applied to it ([#3577](https://github.com/ReactiveX/RxJS/issues/3577)) ([cb38ddf](https://github.com/ReactiveX/RxJS/commit/cb38ddf))
### Code Refactoring
- **webSocket:** rename back to webSocket ala 5.0 ([#3590](https://github.com/ReactiveX/RxJS/issues/3590)) ([d5658fe](https://github.com/ReactiveX/RxJS/commit/d5658fe))
- **interop:** functions with `[Symbol.observable]` on them will now be accepted in operators like `mergeMap`, `from`, etc ([#3562](https://github.com/ReactiveX/RxJS/issues/3562)) ([c9570df](https://github.com/ReactiveX/RxJS/commit/c9570df))
- **migrations:** change the version the migration applies to ([#3564](https://github.com/ReactiveX/RxJS/issues/3564)) ([9217a03](https://github.com/ReactiveX/RxJS/commit/9217a03))
- **rxjs:** no longer requires `dom` lib ([#3566](https://github.com/ReactiveX/RxJS/issues/3566)) ([8b33ee2](https://github.com/ReactiveX/RxJS/commit/8b33ee2))
- **throttleTime:** emit throttled values when complete if trailing=true ([#3559](https://github.com/ReactiveX/RxJS/issues/3559)) ([3e846f2](https://github.com/ReactiveX/RxJS/commit/3e846f2)), closes [#3351](https://github.com/ReactiveX/RxJS/issues/3351)
- **websocket:** export WebSocketSubject, WebSocketSubjectConfig from rxjs/websocket ([#3557](https://github.com/ReactiveX/RxJS/issues/3557)) ([c365405](https://github.com/ReactiveX/RxJS/commit/c365405))
- **groupBy:** reexporting the GroupedObservable type ([#3556](https://github.com/ReactiveX/RxJS/issues/3556)) ([12d4933](https://github.com/ReactiveX/RxJS/commit/12d4933)), closes [#3551](https://github.com/ReactiveX/RxJS/issues/3551)
- **migrations:** build now properly copies migration into package ([#3555](https://github.com/ReactiveX/RxJS/issues/3555)) ([329a145](https://github.com/ReactiveX/RxJS/commit/329a145))
Why "tactical"? Because I _TOTALLY MEANT_ to ruin the release names by publishing an amazingly funny April Fool's joke about smooshMap. So this was "tactical". Super tactical. So very tactical.
### Bug Fixes
- **closure-compiler:** adds nocollapse to static members ([#3519](https://github.com/ReactiveX/RxJS/issues/3519)) ([8758a5d](https://github.com/ReactiveX/RxJS/commit/8758a5d))
- **closure-compiler:** remove internal flag from \_isScalar ([#3520](https://github.com/ReactiveX/RxJS/issues/3520)) ([b3a657d](https://github.com/ReactiveX/RxJS/commit/b3a657d))
- **closure-compiler:** remove top level throws ([#3518](https://github.com/ReactiveX/RxJS/issues/3518)) ([b069473](https://github.com/ReactiveX/RxJS/commit/b069473))
- **closure-compiler:** removes bad \[@params](https://github.com/params) comments that caused issues ([#3521](https://github.com/ReactiveX/RxJS/issues/3521)) ([09c874c](https://github.com/ReactiveX/RxJS/commit/09c874c))
- fix type mismatch in NodeStyleEventEmitter ([#3530](https://github.com/ReactiveX/RxJS/issues/3530)) ([3f51ddd](https://github.com/ReactiveX/RxJS/commit/3f51ddd))
- **sourcemaps:** fix mappings for source maps so they will work ([#3523](https://github.com/ReactiveX/RxJS/issues/3523)) ([32e7f75](https://github.com/ReactiveX/RxJS/commit/32e7f75)), closes [#3479](https://github.com/ReactiveX/RxJS/issues/3479)
### Features
- **compat:** add Observable extension classes with static create() ([ecd7f68](https://github.com/ReactiveX/RxJS/commit/ecd7f68))
- **ajax:** properly encode body with form data that includes URLs ([#3502](https://github.com/ReactiveX/RxJS/issues/3502)) ([4455d21](https://github.com/ReactiveX/RxJS/commit/4455d21)), closes [#2399](https://github.com/ReactiveX/RxJS/issues/2399)
- **bindNodeCallback:** better type inference ([932bb7a](https://github.com/ReactiveX/RxJS/commit/932bb7a))
- **elementAt:** now allows falsy defaultValues ([13706e7](https://github.com/ReactiveX/RxJS/commit/13706e7))
- **lint_perf:** fix lint issues with newer perf tests ([1013754](https://github.com/ReactiveX/RxJS/commit/1013754))
- **throttle:** now properly trailing throttles for individual values ([#3505](https://github.com/ReactiveX/RxJS/issues/3505)) ([3db18d1](https://github.com/ReactiveX/RxJS/commit/3db18d1)), closes [#2864](https://github.com/ReactiveX/RxJS/issues/2864)
### Features
- **takeUntil:** no longer subscribes to source if notifier synchronously emits ([#3504](https://github.com/ReactiveX/RxJS/issues/3504)) ([7b8a3e3](https://github.com/ReactiveX/RxJS/commit/7b8a3e3)), closes [#2189](https://github.com/ReactiveX/RxJS/issues/2189)
### Performance Improvements
- **pluck,bufferTime,asObservable:** add performance tests for pluck(), bufferTime() and asObservable() operators ([#2491](https://github.com/ReactiveX/RxJS/issues/2491)) ([24506b3](https://github.com/ReactiveX/RxJS/commit/24506b3))
- **websocket:** WebSocketSubject will now JSON serialize all messages sent over it by default, to return to the old behavior, pass a config setting of `serializer: x => x` like so: `websocket({ url, serializer: x => x })`
- **AjaxObservable:** 1xx,2xx,3xx requests shouldn't error, only 4xx,5xx ([#3438](https://github.com/ReactiveX/RxJS/issues/3438)) ([2128932](https://github.com/ReactiveX/RxJS/commit/2128932))
- **compat:** adjustments to get rxjs-compat to build correctly ([dea6964](https://github.com/ReactiveX/RxJS/commit/dea6964))
- **config:** expose configuration via rxjs exports ([#3441](https://github.com/ReactiveX/RxJS/issues/3441)) ([4287424](https://github.com/ReactiveX/RxJS/commit/4287424))
- **config:** make sure that Promise config is undefined initially ([#3440](https://github.com/ReactiveX/RxJS/issues/3440)) ([469afe8](https://github.com/ReactiveX/RxJS/commit/469afe8))
- **forkJoin:** fix forkJoin typings for forkJoin(Observable<any>[]) ([#3436](https://github.com/ReactiveX/RxJS/issues/3436)) ([17c7f8f](https://github.com/ReactiveX/RxJS/commit/17c7f8f))
- **fromEvent:** Defines toString to fix Closure compilations ([#3417](https://github.com/ReactiveX/RxJS/issues/3417)) ([1558b43](https://github.com/ReactiveX/RxJS/commit/1558b43))
- **fromEvent:** pass options in unsubscribe ([f1872b0](https://github.com/ReactiveX/RxJS/commit/f1872b0)), closes [#3349](https://github.com/ReactiveX/RxJS/issues/3349)
- **publishReplay:** type inference improved ([#3437](https://github.com/ReactiveX/RxJS/issues/3437)) ([dd7c9f1](https://github.com/ReactiveX/RxJS/commit/dd7c9f1)), closes [#3260](https://github.com/ReactiveX/RxJS/issues/3260)
- **rxjs:** add exports for symbols/interfaces that were missing ([#3380](https://github.com/ReactiveX/RxJS/issues/3380)) ([1622ee0](https://github.com/ReactiveX/RxJS/commit/1622ee0))
- **rxjs:** make sure esm imports from index.js by default, not Rx.js ([#3316](https://github.com/ReactiveX/RxJS/issues/3316)) ([c2b00f4](https://github.com/ReactiveX/RxJS/commit/c2b00f4)), closes [#3315](https://github.com/ReactiveX/RxJS/issues/3315)
- **rxjs:** once again exports custom error types ([#3371](https://github.com/ReactiveX/RxJS/issues/3371)) ([4465a9f](https://github.com/ReactiveX/RxJS/commit/4465a9f))
- **rxjs:** remove types.ts importing from itself. ([#3383](https://github.com/ReactiveX/RxJS/issues/3383)) ([8fd50ad](https://github.com/ReactiveX/RxJS/commit/8fd50ad))
- **spec:** get tests running using compatibility package ([916e968](https://github.com/ReactiveX/RxJS/commit/916e968))
- correct internal module paths to be systemjs compatible ([#3412](https://github.com/ReactiveX/RxJS/issues/3412)) ([35abc9d](https://github.com/ReactiveX/RxJS/commit/35abc9d))
- **Symbol.iterator:** correctly handle case where Symbol constructor itself is not defined ([#3394](https://github.com/ReactiveX/RxJS/issues/3394)) ([6725be1](https://github.com/ReactiveX/RxJS/commit/6725be1))
- **typings:** fixed some cases where multicast and publish would not return a ConnectableObservable ([#3320](https://github.com/ReactiveX/RxJS/issues/3320)) ([ddffecc](https://github.com/ReactiveX/RxJS/commit/ddffecc))
- remove the root operators.ts because it overshadows operators/package.json ([184b6d4](https://github.com/ReactiveX/RxJS/commit/184b6d4))
### Code Refactoring
- **Observable.if:** remove ts hacks from Observable ([f46f261](https://github.com/ReactiveX/RxJS/commit/f46f261))
- **Rx.ts:** move Rx.ts to internal ([#3400](https://github.com/ReactiveX/RxJS/issues/3400)) ([7ad2119](https://github.com/ReactiveX/RxJS/commit/7ad2119))
### Features
- **ajax:** default to opting into CORS ([#3442](https://github.com/ReactiveX/RxJS/issues/3442)) ([aa3bf57](https://github.com/ReactiveX/RxJS/commit/aa3bf57)), closes [#3273](https://github.com/ReactiveX/RxJS/issues/3273)
- **bindCallback:** remove result selector ([2535641](https://github.com/ReactiveX/RxJS/commit/2535641))
- **compat:** add concat operator to compatibility layer ([6e84e78](https://github.com/ReactiveX/RxJS/commit/6e84e78))
- **compat:** add legacy reexport compat layer for 'rxjs/Observable' and other top-level symbols ([70e562b](https://github.com/ReactiveX/RxJS/commit/70e562b))
- **compat:** add Rx.ts to rxjs-compat ([df25de1](https://github.com/ReactiveX/RxJS/commit/df25de1))
- **compat:** compatibility mode for merge operator ([ffce980](https://github.com/ReactiveX/RxJS/commit/ffce980))
- **compat:** compatibility mode for zip operator ([9f131d0](https://github.com/ReactiveX/RxJS/commit/9f131d0))
- **compat:** make Rx.ts for compatability layer work as the default for rxjs-compat ([d43a4c2](https://github.com/ReactiveX/RxJS/commit/d43a4c2))
- **compat:** set up correct imports & get build working for rxjs-comapt ([1a0dc97](https://github.com/ReactiveX/RxJS/commit/1a0dc97))
- **deprecated-error-handling-warning:** add console warning when code sets the flag to bad mode ([49be56a](https://github.com/ReactiveX/RxJS/commit/49be56a))
- **error-handling:** add deprecated sync error handling behind a flag ([583cd1d](https://github.com/ReactiveX/RxJS/commit/583cd1d))
- **never:** no longer export `never` function ([#3386](https://github.com/ReactiveX/RxJS/issues/3386)) ([53debc8](https://github.com/ReactiveX/RxJS/commit/53debc8))
- **Symbol.iterator:** no longer polyfilled ([#3389](https://github.com/ReactiveX/RxJS/issues/3389)) ([6319f3c](https://github.com/ReactiveX/RxJS/commit/6319f3c))
- **Symbol.observable:** is no longer polyfilled ([#3387](https://github.com/ReactiveX/RxJS/issues/3387)) ([4a5aaaf](https://github.com/ReactiveX/RxJS/commit/4a5aaaf))
- **umd:** UMD now mirrors export schema for ESM and CJS ([#3426](https://github.com/ReactiveX/RxJS/issues/3426)) ([556c904](https://github.com/ReactiveX/RxJS/commit/556c904))
### BREAKING CHANGES
- **ajax:** will no longer execute a CORS request by default, you must opt-in with the `crossDomain` flag in the config.
- **mergeMap|concatMap|concatMapTo:** mergeMap, concatMap and concatMapTo no longer support a result selector, if you need to use a result selector, use the following pattern: `source.mergeMap(x => of(x + x).pipe(map(y => y + x))` (the pattern would be the same for `concatMap`).
- **never:** no longer exported. Use the `NEVER` constant instead.
- **bindCallback:** removes result selector, use `map` instead: `bindCallback(fn1, fn2)()` becomes `bindCallback(fn1)().pipe(map(fn2))`
- **Rx.ts:** importing from `rxjs/Rx` is no longer available. Upcoming backwards compat solution will allow that
- **Symbol.iterator:** We are no longer polyfilling `Symbol.iterator`. That would be done by a proper polyfilling library
- **Observable.if:** TypeScript users using `Observable.if` will have to cast `Observable` as any to get to `if`. It is a better idea to just use `iif` directly via `import { iif } from 'rxjs';`
- **Symbol.observable:** RxJS will no longer be polyfilling Symbol.observable. That should be done by an actual polyfill library. This is to prevent duplication of code, and also to prevent having modules with side-effects in rxjs.
- **fromEvent:** result selector removed, use `map` instead: `fromEvent(target, 'click', fn)` becomes `fromEvent(target, 'click').pipe(map(fn))`
- **last:** no longer accepts `resultSelector` argument. To get this same functionality, use `map`.
- **first:** no longer supports `resultSelector` argument. The same functionality can be achieved by simply mapping either before or after `first` depending on your use case.
- **exhaustMap:** `resultSelector` no longer supported, to get this functionality use: `source.pipe(exhaustMap(x => of(x + x).pipe(map(y => x + y))))`
- **switchMap|switchMapTo:** `switchMap` and `switchMapTo` no longer take `resultSelector` arguments, to get the same functionality use `switchMap` and `map` in combination: `source.pipe(switchMap(x => of(x + x).pipe(y => x + y)))`.
- **mergeMapTo:** `mergeMapTo` no longer accepts a resultSelector, to get this functionality, you'll want to use `mergeMap` and `map` together: `source.pipe(mergeMap(() => inner).pipe(map(y => x + y)))`
- **fromEventPattern:** no longer supports a result selector, use `map` instead: `fromEventPattern(fn1, fn2, fn3)` becomes `fromEventPattern(fn1, fn2).pipe(map(fn3))`
- **fromEvent:** Defines toString to fix Closure compilations ([#3417](https://github.com/ReactiveX/RxJS/issues/3417)) ([1558b43](https://github.com/ReactiveX/RxJS/commit/1558b43))
- **fromEvent:** pass options in unsubscribe ([f1872b0](https://github.com/ReactiveX/RxJS/commit/f1872b0)), closes [#3349](https://github.com/ReactiveX/RxJS/issues/3349)
- **rxjs:** add exports for symbols/interfaces that were missing ([#3380](https://github.com/ReactiveX/RxJS/issues/3380)) ([1622ee0](https://github.com/ReactiveX/RxJS/commit/1622ee0))
- **rxjs:** make sure esm imports from index.js by default, not Rx.js ([#3316](https://github.com/ReactiveX/RxJS/issues/3316)) ([c2b00f4](https://github.com/ReactiveX/RxJS/commit/c2b00f4)), closes [#3315](https://github.com/ReactiveX/RxJS/issues/3315)
- **rxjs:** once again exports custom error types ([#3371](https://github.com/ReactiveX/RxJS/issues/3371)) ([4465a9f](https://github.com/ReactiveX/RxJS/commit/4465a9f))
- **rxjs:** remove types.ts importing from itself. ([#3383](https://github.com/ReactiveX/RxJS/issues/3383)) ([8fd50ad](https://github.com/ReactiveX/RxJS/commit/8fd50ad))
- correct internal module paths to be systemjs compatible ([#3412](https://github.com/ReactiveX/RxJS/issues/3412)) ([35abc9d](https://github.com/ReactiveX/RxJS/commit/35abc9d))
- **Symbol.iterator:** correctly handle case where Symbol constructor itself is not defined ([#3394](https://github.com/ReactiveX/RxJS/issues/3394)) ([6725be1](https://github.com/ReactiveX/RxJS/commit/6725be1))
- **typings:** fixed some cases where multicast and publish would not return a ConnectableObservable ([#3320](https://github.com/ReactiveX/RxJS/issues/3320)) ([ddffecc](https://github.com/ReactiveX/RxJS/commit/ddffecc))
- **never:** no longer export `never` function ([#3386](https://github.com/ReactiveX/RxJS/issues/3386)) ([53debc8](https://github.com/ReactiveX/RxJS/commit/53debc8))
- **Symbol.iterator:** no longer polyfilled ([#3389](https://github.com/ReactiveX/RxJS/issues/3389)) ([6319f3c](https://github.com/ReactiveX/RxJS/commit/6319f3c))
- **Symbol.observable:** is no longer polyfilled ([#3387](https://github.com/ReactiveX/RxJS/issues/3387)) ([4a5aaaf](https://github.com/ReactiveX/RxJS/commit/4a5aaaf))
- **umd:** UMD now mirrors export schema for ESM and CJS ([#3426](https://github.com/ReactiveX/RxJS/issues/3426)) ([556c904](https://github.com/ReactiveX/RxJS/commit/556c904))
### BREAKING CHANGES
- **Symbol.observable:** RxJS will no longer be polyfilling Symbol.observable. That should be done by an actual polyfill library. This is to prevent duplication of code, and also to prevent having modules with side-effects in rxjs.
- **mergeMap|concatMap|concatMapTo:** mergeMap, concatMap and concatMapTo no longer support a result selector, if you need to use a result selector, use the following pattern: `source.mergeMap(x => of(x + x).pipe(map(y => y + x))` (the pattern would be the same for `concatMap`).
- **bindCallback:** removes result selector, use `map` instead: `bindCallback(fn1, fn2)()` becomes `bindCallback(fn1)().pipe(map(fn2))`
- **Rx.ts:** importing from `rxjs/Rx` is no longer available. Upcoming backwards compat solution will allow that
- **Symbol.iterator:** We are no longer polyfilling `Symbol.iterator`. That would be done by a proper polyfilling library
- **Observable.if:** TypeScript users using `Observable.if` will have to cast `Observable` as any to get to `if`. It is a better idea to just use `iif` directly via `import { iif } from 'rxjs';`
- **never:** no longer exported. Use the `NEVER` constant instead.
- **fromEvent:** result selector removed, use `map` instead: `fromEvent(target, 'click', fn)` becomes `fromEvent(target, 'click').pipe(map(fn))`
- **last:** no longer accepts `resultSelector` argument. To get this same functionality, use `map`.
- **first:** no longer supports `resultSelector` argument. The same functionality can be achieved by simply mapping either before or after `first` depending on your use case.
- **exhaustMap:** `resultSelector` no longer supported, to get this functionality use: `source.pipe(exhaustMap(x => of(x + x).pipe(map(y => x + y))))`
- **switchMap|switchMapTo:** `switchMap` and `switchMapTo` no longer take `resultSelector` arguments, to get the same functionality use `switchMap` and `map` in combination: `source.pipe(switchMap(x => of(x + x).pipe(y => x + y)))`.
- **mergeMapTo:** `mergeMapTo` no longer accepts a resultSelector, to get this functionality, you'll want to use `mergeMap` and `map` together: `source.pipe(mergeMap(() => inner).pipe(map(y => x + y)))`
- **fromEventPattern:** no longer supports a result selector, use `map` instead: `fromEventPattern(fn1, fn2, fn3)` becomes `fromEventPattern(fn1, fn2).pipe(map(fn3))`
- **onErrorResumeNext:** no longer holds onto subscriptions too long ([abbbdad](https://github.com/ReactiveX/RxJS/commit/abbbdad)), closes [#3178](https://github.com/ReactiveX/RxJS/issues/3178)
- **typings:** correct compilation warnings from missing types in tests ([3aad6bc](https://github.com/ReactiveX/RxJS/commit/3aad6bc))
- **typings:** relax debounce selector type ([c419ab4](https://github.com/ReactiveX/RxJS/commit/c419ab4)), closes [#3164](https://github.com/ReactiveX/RxJS/issues/3164)
- **typings:** relax throttle selector type ([#3205](https://github.com/ReactiveX/RxJS/issues/3205)) ([e83fda7](https://github.com/ReactiveX/RxJS/commit/e83fda7)), closes [#3204](https://github.com/ReactiveX/RxJS/issues/3204)
- **typings:** the return type of factory of defer should be ObservableInput<T> ([#3211](https://github.com/ReactiveX/RxJS/issues/3211)) ([dc41a5e](https://github.com/ReactiveX/RxJS/commit/dc41a5e))
### Features
- **empty:** empty() returns the same instance ([5c7c749](https://github.com/ReactiveX/RxJS/commit/5c7c749))
- **EMPTY:** observable constant EMPTY now exported ([08fb074](https://github.com/ReactiveX/RxJS/commit/08fb074))
- **never:** always return the same instance ([#3249](https://github.com/ReactiveX/RxJS/issues/3249)) ([d57fa52](https://github.com/ReactiveX/RxJS/commit/d57fa52))
- **rxjs:** move rxjs/create into rxjs ([#3299](https://github.com/ReactiveX/RxJS/issues/3299)) ([6711fe2](https://github.com/ReactiveX/RxJS/commit/6711fe2))
- **throwError:** functional version of throwError ([639236e](https://github.com/ReactiveX/RxJS/commit/639236e))
### BREAKING CHANGES
- **rxjs:** `rxjs/create` items are now exported from `rxjs`
- **throwError:** Observable.throw no longer available in TypeScript without a cast
- **empty:** `empty()` without a scheduler will return the same
instance every time.
- **empty:** In TypeScript, `empty()` no longer accepts a generic
argument, as it returns `Observable<never>`
- **never:** `never()` always returns the same instance
- **never:** TypeScript typing for `never()` is now `Observable<never>` and the function no longer requires a generic type.
- **debounceTime:** synchronous reentrancy of debounceTime no longer swallows the second value ([#3218](https://github.com/ReactiveX/RxJS/issues/3218)) ([598e9ce](https://github.com/ReactiveX/RxJS/commit/598e9ce)), closes [#2748](https://github.com/ReactiveX/RxJS/issues/2748)
- **dependency:** move symbol-observable into devdependency ([4400628](https://github.com/ReactiveX/RxJS/commit/4400628))
- **IteratorObservable:** get new iterator for each subscription ([#2497](https://github.com/ReactiveX/RxJS/issues/2497)) ([1bd0a58](https://github.com/ReactiveX/RxJS/commit/1bd0a58)), closes [#2496](https://github.com/ReactiveX/RxJS/issues/2496)
- **Observable.toArray:** Fix toArray with multiple subscriptions. ([#3134](https://github.com/ReactiveX/RxJS/issues/3134)) ([3390926](https://github.com/ReactiveX/RxJS/commit/3390926))
- **tap:** make next optional ([#3073](https://github.com/ReactiveX/RxJS/issues/3073)) ([e659f0c](https://github.com/ReactiveX/RxJS/commit/e659f0c)), closes [#2534](https://github.com/ReactiveX/RxJS/issues/2534)
- **typings:** the return type of project of mergeScan should be ObservableInput<R> ([23fe17d](https://github.com/ReactiveX/RxJS/commit/23fe17d))
### Chores
- **TypeScript:** Bump up typescript to latest ([#3009](https://github.com/ReactiveX/RxJS/issues/3009)) ([2f395da](https://github.com/ReactiveX/RxJS/commit/2f395da))
- **Observable:** unhandled errors are now reported to HostReportErrors ([#3062](https://github.com/ReactiveX/RxJS/issues/3062)) ([cd9626a](https://github.com/ReactiveX/RxJS/commit/cd9626a))
- **reorganize:** move ./interfaces.ts to internal/types.ts ([cfbfaac](https://github.com/ReactiveX/RxJS/commit/cfbfaac))
- **reorganize:** move observable implementations under internal directory ([2d5c3f8](https://github.com/ReactiveX/RxJS/commit/2d5c3f8))
- **reorganize:** move operator impls under internal directory ([207976f](https://github.com/ReactiveX/RxJS/commit/207976f))
- **reorganize:** move top-level impls under internal directory ([c3bb705](https://github.com/ReactiveX/RxJS/commit/c3bb705))
- **reorganize:** moved symbols to be internal ([80783ab](https://github.com/ReactiveX/RxJS/commit/80783ab))
- **reorganize:** operators all exported from `rxjs/operators` ([b1f8bfe](https://github.com/ReactiveX/RxJS/commit/b1f8bfe))
- **reorganize:** websocket subject creator now exported from `rxjs/websocket` ([5ac62c0](https://github.com/ReactiveX/RxJS/commit/5ac62c0))
### BREAKING CHANGES
- **webSocket:** `webSocket` creator function now exported from `rxjs/websocket` as `websocket`.
- **IteratorObservable:** IteratorObservable no longer share iterator between
subscription
- **utils:** Many internal use utilities like `isArray` are now hidden under `rxjs/internal`, they are implementation details and should not be used.
- **testing observables:** `HotObservable` and `ColdObservable`, and other testing support types are no longer exported directly.
- **creation functions:** All create functions such as `of`, `from`, `combineLatest` and `fromEvent` should now be imported from `rxjs/create`.
- **types and interfaces:** Can no longer explicitly import types from `rxjs/interfaces`, import them from `rxjs` instead
- **symbols:** Symbols are no longer exported directly from modules such as `rxjs/symbol/observable` please use `Symbol.observable` and `Symbol.iterator` (polyfills may be required)
- **deep imports:** Can no longer deep import top-level types such as `rxjs/Observable`, `rxjs/Subject`, `rxjs/ReplaySubject`, et al. All imports should be done directly from `rxjs`, for example: `import \{ Observable, Subject \} from 'rxjs';`
- **schedulers:** Scheduler instances have changed names to be suffixed with `Scheduler`, (e.g. `asap` -> `asapScheduler`)
- **operators:** Pipeable operators must now be imported from `rxjs`
like so: `import { map, filter, switchMap } from 'rxjs/operators';`. No deep imports.
- **ajax:** Ajax observable should be imported from `rxjs/ajax`.
- **Observable:** You should no longer deep import custom Observable
implementations such as `ArrayObservable` or `ForkJoinObservable`.
- **\_throw:** `_throw` is now exported as `throwError`
- **if:** `if` is now exported as `iif`
- **operators:** Deep imports to `rxjs/operator/*` will no longer work. Again, pipe operators are still where they were.
- **error handling:** Unhandled errors are no longer caught and rethrown, rather they are caught and scheduled to be thrown, which causes them to be reported to window.onerror or process.on('error'), depending on the environment. Consequently, teardown after a synchronous, unhandled, error will no longer occur, as the teardown would not exist, and producer interference cannot occur
- **distinct:** Using `distinct` requires a `Set` implementation and must be polyfilled in older runtimes
- **asap:** Old runtimes must polyfill Promise in order to use ASAP scheduling.
- **groupBy:** Older runtimes will require Map to be polyfilled to use
`groupBy`
- **TypeScript:** IE10 and lower will need to polyfill `Object.setPrototypeOf`
- **operators removed:** Operator versions of static observable creators such as
`merge`, `concat`, `zip`, `onErrorResumeNext`, and `race` have been
removed. Please use the static versions of those operations. e.g.
- **Observable:** rethrow errors when syncErrorThrowable and inherit it from destination. Fixes [#2813](https://github.com/ReactiveX/RxJS/issues/2813) ([541b49d](https://github.com/ReactiveX/RxJS/commit/541b49d))
- **scheduler:** resolve regression on angular router with zones ([#3158](https://github.com/ReactiveX/RxJS/issues/3158)) ([520b06a](https://github.com/ReactiveX/RxJS/commit/520b06a))
- **publish:** re-publish after having built with proper version of TypeScript. ([f0ff5bc](https://github.com/ReactiveX/RxJS/commit/f0ff5bc), closes[#3155](https://github.com/ReactiveX/rxjs/issues/3155))
- **concatStatic:** missing exports for mergeStatic and concatStatic ([#2999](https://github.com/ReactiveX/RxJS/issues/2999)) ([cae5f9b](https://github.com/ReactiveX/RxJS/commit/cae5f9b))
- **package:** fixed import failures in Webpack ([#2987](https://github.com/ReactiveX/RxJS/issues/2987)) ([e16202d](https://github.com/ReactiveX/RxJS/commit/e16202d))
- **typings:** improved type inference for arguments to publishReplay ([#2992](https://github.com/ReactiveX/RxJS/issues/2992)) ([0753ff7](https://github.com/ReactiveX/RxJS/commit/0753ff7)), closes [#2991](https://github.com/ReactiveX/RxJS/issues/2991)
- **typings:** ensure TS types for `zip` and `combineLatest` are properly inferred. ([b8e6cf8](https://github.com/ReactiveX/RxJS/commit/b8e6cf8))
- **typings:** publish variants will properly return ConnectableObservable([#2983](https://github.com/ReactiveX/RxJS/issues/2983)) ([d563bfa](https://github.com/ReactiveX/RxJS/commit/d563bfa))
- **build:** CJS sourceMaps now inlined into sourcesContent ([39b4af5](https://github.com/ReactiveX/RxJS/commit/39b4af5)), closes [#2934](https://github.com/ReactiveX/RxJS/issues/2934)
### Features
- **publishReplay:** add selector function to publishReplay ([#2885](https://github.com/ReactiveX/RxJS/issues/2885)) ([e0efd13](https://github.com/ReactiveX/RxJS/commit/e0efd13))
(Due to a publish snafu, there is no 5.5.0-beta.6) (womp womp 👎)
### Bug Fixes
- **build:** sourceMaps updated to support CJS properly again ([75f7f11](https://github.com/ReactiveX/RxJS/commit/75f7f11)), closes [#2934](https://github.com/ReactiveX/RxJS/issues/2934)
- **flatMap:** reexport flatMap as alias of mergeMap ([#2920](https://github.com/ReactiveX/RxJS/issues/2920)) ([9922c02](https://github.com/ReactiveX/RxJS/commit/9922c02))
- **publish:** correct the name and republish to sync packages ([464b115](https://github.com/ReactiveX/RxJS/commit/464b115))
- **shareReplay:** no longer exporting function unnecessarily ([#2928](https://github.com/ReactiveX/RxJS/issues/2928)) ([e159578](https://github.com/ReactiveX/RxJS/commit/e159578))
- **toPromise:** remove lettable version of toPromise ([031edca](https://github.com/ReactiveX/RxJS/commit/031edca)), closes [#2868](https://github.com/ReactiveX/RxJS/issues/2868)
### Features
- **toPromise:** now exists as a permanent method on Observable ([2e49a5c](https://github.com/ReactiveX/RxJS/commit/2e49a5c))
- **shareReplay:** properly retains history on subscribe ([#2910](https://github.com/ReactiveX/RxJS/issues/2910)) ([accbcd0](https://github.com/ReactiveX/RxJS/commit/accbcd0)), closes [#2908](https://github.com/ReactiveX/RxJS/issues/2908)
- **subscribeOn:** remove subscribeOn from reexport to support treesha… ([#2899](https://github.com/ReactiveX/RxJS/issues/2899)) ([fb51a02](https://github.com/ReactiveX/RxJS/commit/fb51a02))
- **build:** revert to 5.4.x build output for CJS & add configurable support for ESM ([#2878](https://github.com/ReactiveX/RxJS/issues/2878)) ([167456a](https://github.com/ReactiveX/RxJS/commit/167456a))
- **concatAll:** use higher-order lettable version of concatAll ([60c96ab](https://github.com/ReactiveX/RxJS/commit/60c96ab))
- **mergeAll:** use higher-order lettable version of mergeAll ([f0b703b](https://github.com/ReactiveX/RxJS/commit/f0b703b))
- **build:** make CJS references to import X from '../operators' work correctly with SystemJS ([#2874](https://github.com/ReactiveX/RxJS/issues/2874)) ([3dd4cc4](https://github.com/ReactiveX/RxJS/commit/3dd4cc4))
- **package:** published from a Linux machine to prevent a strange issue where
the Observable directory was not showing up when installed on some Linux
environments.
- **build:** fix source maps by adding back sources and fixing path ([#2872](https://github.com/ReactiveX/RxJS/issues/2872)) ([daaf424](https://github.com/ReactiveX/RxJS/commit/daaf424))
**Important! Checkout the explanation of the new [lettable operators features here](doc/lettable-operators.md)**
### Bug Fixes
- **package:** correct errors generated during rollup for UMD generation ([#2839](https://github.com/ReactiveX/RxJS/issues/2839)) ([124cc93](https://github.com/ReactiveX/RxJS/commit/124cc93))
- **partition:** update TypeScript signature to match docs and filter operator ([#2819](https://github.com/ReactiveX/RxJS/issues/2819)) ([755df9b](https://github.com/ReactiveX/RxJS/commit/755df9b))
- **subscribeToResult:** throw error in subscriber with inner observable ([d7bffa9](https://github.com/ReactiveX/RxJS/commit/d7bffa9)), closes [#2618](https://github.com/ReactiveX/RxJS/issues/2618)
### Features
- **ajax:** Include the response on instances of AjaxError ([3f6553c](https://github.com/ReactiveX/RxJS/commit/3f6553c))
- **audit:** add higher-order lettable version of audit ([e2daefe](https://github.com/ReactiveX/RxJS/commit/e2daefe))
- **auditTime:** add higher-order lettable version of auditTime ([9e963aa](https://github.com/ReactiveX/RxJS/commit/9e963aa))
- **buffer:** add higher-order lettable version of buffer ([d8ca9de](https://github.com/ReactiveX/RxJS/commit/d8ca9de))
- **bufferCount:** add higher-order lettable version of bufferCount ([0ae2ed5](https://github.com/ReactiveX/RxJS/commit/0ae2ed5))
- **bufferTime:** add higher-order lettable version of bufferTime operator ([0377ca6](https://github.com/ReactiveX/RxJS/commit/0377ca6))
- **bufferToggle:** add higher-order lettable version of bufferToggle ([ea1c3ee](https://github.com/ReactiveX/RxJS/commit/ea1c3ee))
- **bufferWhen:** add higher-order lettable version of bufferWhen ([ec3eceb](https://github.com/ReactiveX/RxJS/commit/ec3eceb))
- **catchError:** add higher-order lettable version of `catch` ([408a2af](https://github.com/ReactiveX/RxJS/commit/408a2af))
- **combineAll:** add higher-order lettable version of combineAll ([97704b3](https://github.com/ReactiveX/RxJS/commit/97704b3))
- **combineLatest:** add higher-order lettable version of combineLatest ([b7154f2](https://github.com/ReactiveX/RxJS/commit/b7154f2))
- **concatMap:** add higher-order lettable version of concatMap ([c4125ff](https://github.com/ReactiveX/RxJS/commit/c4125ff))
- **concatMapTo:** add higher-order lettable version of concatMapTo ([0a6672e](https://github.com/ReactiveX/RxJS/commit/0a6672e))
- **count:** add higher-order lettable version of count ([caf713e](https://github.com/ReactiveX/RxJS/commit/caf713e))
- **debounce:** add higher-order lettable version of debounce ([cb8ce46](https://github.com/ReactiveX/RxJS/commit/cb8ce46))
- **debounceTime:** add higher-order lettable version of debounceTime ([df0d439](https://github.com/ReactiveX/RxJS/commit/df0d439))
- **delay:** add higher-order lettable version of delay ([7efb803](https://github.com/ReactiveX/RxJS/commit/7efb803))
- **delayWhen:** add higher-order lettable version of delayWhen ([cb91c3f](https://github.com/ReactiveX/RxJS/commit/cb91c3f))
- **distinct:** add higher-order lettable version of distinct ([0429a69](https://github.com/ReactiveX/RxJS/commit/0429a69))
- **distinctUntilChanged:** add higher-order lettable version of distinctUntilChanged ([b2725e7](https://github.com/ReactiveX/RxJS/commit/b2725e7))
- **distinctUntilKeyChanged:** add higher-order lettable version of distinctUntilKeyChanged ([9db141c](https://github.com/ReactiveX/RxJS/commit/9db141c))
- **elementAt:** add higher-order lettable version of elementAt ([b8e956b](https://github.com/ReactiveX/RxJS/commit/b8e956b))
- **every:** add higher-order lettable version of every ([13f3503](https://github.com/ReactiveX/RxJS/commit/13f3503))
- **exhaust:** add higher-order lettable version of exhaust ([b145dca](https://github.com/ReactiveX/RxJS/commit/b145dca))
- **merge:** add higher-order lettable version of merge ([#2809](https://github.com/ReactiveX/RxJS/issues/2809)) ([3136403](https://github.com/ReactiveX/RxJS/commit/3136403))
- **mergeMap:** add higher-order lettable version of mergeMap ([417efde](https://github.com/ReactiveX/RxJS/commit/417efde))
- **mergeMapTo:** add higher-order lettable version of mergeMapTo ([653b47a](https://github.com/ReactiveX/RxJS/commit/653b47a))
- **mergeScan:** add higher-order lettable version of mergeScan ([fde7205](https://github.com/ReactiveX/RxJS/commit/fde7205))
- **multicast:** add higher-order lettable variant of multicast ([fb6014d](https://github.com/ReactiveX/RxJS/commit/fb6014d))
- **observeOn:** add higher-order lettable version of observeOn ([feb0f5a](https://github.com/ReactiveX/RxJS/commit/feb0f5a))
- **onErrorResumeNext:** add higher-order lettable version of onErrorResumeNext ([badec6a](https://github.com/ReactiveX/RxJS/commit/badec6a))
- **operators:** higher-order lettables of reduce, min, max and defaultIfEmpty added ([9974fc2](https://github.com/ReactiveX/RxJS/commit/9974fc2))
- **package:** rxjs distribution now supports main, module and es2015 keys in package.json ([988e1af](https://github.com/ReactiveX/RxJS/commit/988e1af))
- **pairwise:** add higher-order lettable version of pairwise ([bb21a44](https://github.com/ReactiveX/RxJS/commit/bb21a44))
- **partition:** add higher-order lettable version of partition ([595e588](https://github.com/ReactiveX/RxJS/commit/595e588))
- **pipe:** add pipe method ot Observable ([9f6312d](https://github.com/ReactiveX/RxJS/commit/9f6312d))
- **Notification:** Don't reference `this` from static methods. ([9f8e375](https://github.com/ReactiveX/RxJS/commit/9f8e375))
- **Subject:** lift signature is now appropriate for stricter TypeScript 2.4 checks ([#2722](https://github.com/ReactiveX/RxJS/issues/2722)) ([9804de7](https://github.com/ReactiveX/RxJS/commit/9804de7))
- **ajax:** Only set timeout & responseType if request is asynchronous ([#2486](https://github.com/ReactiveX/RxJS/issues/2486)) ([380fbcf](https://github.com/ReactiveX/RxJS/commit/380fbcf))
- **audit:** will now properly mirror source if durations are Observable.empty() ([#2595](https://github.com/ReactiveX/RxJS/issues/2595)) ([6ded82e](https://github.com/ReactiveX/RxJS/commit/6ded82e))
- **elementAt:** will now properly unsubscribe when it completes or errors ([#2501](https://github.com/ReactiveX/RxJS/issues/2501)) ([a400cab](https://github.com/ReactiveX/RxJS/commit/a400cab))
- **ErrorObservable:** will now propagate errors properly when used in a `catch` after `fromPromise`. ([#2552](https://github.com/ReactiveX/RxJS/issues/2552)) ([cf88a20](https://github.com/ReactiveX/RxJS/commit/cf88a20))
- **groupBy:** group duration notifiers will now properly unsubscribe and clean up ([#2662](https://github.com/ReactiveX/RxJS/issues/2662)) ([ab92083](https://github.com/ReactiveX/RxJS/commit/ab92083)), closes [#2660](https://github.com/ReactiveX/RxJS/issues/2660) [#2661](https://github.com/ReactiveX/RxJS/issues/2661)
- **Observable:** errors thrown in observer/handlers without an operator applied will no longer be swallowed ([#2626](https://github.com/ReactiveX/RxJS/issues/2626)) ([c250afc](https://github.com/ReactiveX/RxJS/commit/c250afc)), closes [#2565](https://github.com/ReactiveX/RxJS/issues/2565)
- **reduce:** type definitions overloads for TypeScript are now in proper order ([#2523](https://github.com/ReactiveX/RxJS/issues/2523)) ([ccc0647](https://github.com/ReactiveX/RxJS/commit/ccc0647))
- **Schedulers:** Fix issue where canceling an asap or animationFrame action early could throw ([#2638](https://github.com/ReactiveX/RxJS/issues/2638)) ([fc39043](https://github.com/ReactiveX/RxJS/commit/fc39043))
- **race:** allow TypeScript support for array of observables other than rest param ([#2548](https://github.com/ReactiveX/RxJS/issues/2548)) ([ace553c](https://github.com/ReactiveX/RxJS/commit/ace553c))
- **Subscriber:** do not call complete with undefined value param ([#2559](https://github.com/ReactiveX/RxJS/issues/2559)) ([3d63de2](https://github.com/ReactiveX/RxJS/commit/3d63de2))
**(NOTE: 5.3.2 was a broken release and was removed)**
- **AsyncAction:** rescheduling an action with the same delay before it has executed will now schedule appropriately. ([#2580](https://github.com/ReactiveX/RxJS/issues/2580)) ([281760e](https://github.com/ReactiveX/RxJS/commit/281760e))
- **closure:** make root.ts work with closure ([#2546](https://github.com/ReactiveX/RxJS/issues/2546)) ([0ecf55d](https://github.com/ReactiveX/RxJS/commit/0ecf55d))
- **tests:** add missing babel-polyfill to package.json ([b277ce9](https://github.com/ReactiveX/RxJS/commit/b277ce9)), closes [#2261](https://github.com/ReactiveX/RxJS/issues/2261)
- **withLatestFrom:** change from hot to cold observable in marble test ([0c65446](https://github.com/ReactiveX/RxJS/commit/0c65446)), closes [#2526](https://github.com/ReactiveX/RxJS/issues/2526)
- **catch:** return type is now the union of input types ([#2478](https://github.com/ReactiveX/RxJS/issues/2478)) ([840def0](https://github.com/ReactiveX/RxJS/commit/840def0))
- **forEach:** fix a temporal dead zone issue in forEach. ([#2474](https://github.com/ReactiveX/RxJS/issues/2474)) ([e9e9801](https://github.com/ReactiveX/RxJS/commit/e9e9801))
- **multicast:** Ensure ConnectableObservables returned by multicast are state-isolated. ([aaa9e6b](https://github.com/ReactiveX/RxJS/commit/aaa9e6b))
- **timeout:** Cancels scheduled timeout, if no longer needed ([3e9d529](https://github.com/ReactiveX/RxJS/commit/3e9d529)), closes [#2134](https://github.com/ReactiveX/RxJS/issues/2134) [#2244](https://github.com/ReactiveX/RxJS/issues/2244) [#2355](https://github.com/ReactiveX/RxJS/issues/2355) [#2347](https://github.com/ReactiveX/RxJS/issues/2347) [#2353](https://github.com/ReactiveX/RxJS/issues/2353) [#2254](https://github.com/ReactiveX/RxJS/issues/2254) [#2372](https://github.com/ReactiveX/RxJS/issues/2372) [#1301](https://github.com/ReactiveX/RxJS/issues/1301)
- **zipAll:** complete when the source is empty ([712fece](https://github.com/ReactiveX/RxJS/commit/712fece))
### Features
- **delayWhen:** add index to the selector function ([5d6291e](https://github.com/ReactiveX/RxJS/commit/5d6291e))
- **symbol exports:** symbols now also exported without `$$` prefix to work with Babel UMD exporting ([#2435](https://github.com/ReactiveX/RxJS/issues/2435)) ([747bef6](https://github.com/ReactiveX/RxJS/commit/747bef6)), closes [#2415](https://github.com/ReactiveX/RxJS/issues/2415)
- **ajax:** will set `withCredentials` after `open` on XHR for IE10 ([#2332](https://github.com/ReactiveX/RxJS/issues/2332)) ([0ab1d3b](https://github.com/ReactiveX/RxJS/commit/0ab1d3b))
- **bindCallback:** emit undefined when callback is without arguments ([915a2a8](https://github.com/ReactiveX/RxJS/commit/915a2a8))
- **bindNodeCallback:** emit undefined when callback has no success arguments ([8b81fc6](https://github.com/ReactiveX/RxJS/commit/8b81fc6)), closes [#2254](https://github.com/ReactiveX/RxJS/issues/2254)
- **bindNodeCallback:** errors thrown in callback will be scheduled if a scheduler is provided ([#2344](https://github.com/ReactiveX/RxJS/issues/2344)) ([82ec4f1](https://github.com/ReactiveX/RxJS/commit/82ec4f1))
- **concat:** will now return Observable when given a single object implementing Symbol.observable ([#2387](https://github.com/ReactiveX/RxJS/issues/2387)) ([f5d035a](https://github.com/ReactiveX/RxJS/commit/f5d035a))
- **ErrorObservable:** remove type constraint to error value ([2f951cd](https://github.com/ReactiveX/RxJS/commit/2f951cd)), closes [#2395](https://github.com/ReactiveX/RxJS/issues/2395)
- **forkJoin:** add type signature for single observable with selector ([7983b91](https://github.com/ReactiveX/RxJS/commit/7983b91)), closes [#2347](https://github.com/ReactiveX/RxJS/issues/2347)
- **merge:** return Observable when called with single lowerCaseO ([85752eb](https://github.com/ReactiveX/RxJS/commit/85752eb))
- **mergeAll:** introduce variant support <T,R> for mergeMap ([656f2b3](https://github.com/ReactiveX/RxJS/commit/656f2b3)), closes [#2372](https://github.com/ReactiveX/RxJS/issues/2372)
- **single:** predicate function receives indices starting at 0 ([#2396](https://github.com/ReactiveX/RxJS/issues/2396)) ([c81882f](https://github.com/ReactiveX/RxJS/commit/c81882f))
- **bindCallback:** input function context can now be properly set via output function ([#2319](https://github.com/ReactiveX/RxJS/issues/2319)) ([cb91c76](https://github.com/ReactiveX/RxJS/commit/cb91c76))
- **bindNodeCallback:** input function context can now be properly set via output function ([#2320](https://github.com/ReactiveX/RxJS/issues/2320)) ([3ec315d](https://github.com/ReactiveX/RxJS/commit/3ec315d))
- **Subscription:** fold ChildSubscription logic into Subscriber to prevent operators from leaking ChildSubscriptions. ([#2360](https://github.com/ReactiveX/RxJS/issues/2360)) ([22e4c17](https://github.com/ReactiveX/RxJS/commit/22e4c17)), closes [#2244](https://github.com/ReactiveX/RxJS/issues/2244) [#2355](https://github.com/ReactiveX/RxJS/issues/2355)
- **catch:** update the catch operator to dispose inner subscriptions if the catch subscription is di ([#2271](https://github.com/ReactiveX/RxJS/issues/2271)) ([8a1e089](https://github.com/ReactiveX/RxJS/commit/8a1e089))
- **combineLatest:** Don't mutate array of observables passed to ([#2276](https://github.com/ReactiveX/RxJS/issues/2276)) ([9b73c46](https://github.com/ReactiveX/RxJS/commit/9b73c46))
- **ISubscription:** update type definition of ISubscription::closed ([#2249](https://github.com/ReactiveX/RxJS/issues/2249)) ([0c304a2](https://github.com/ReactiveX/RxJS/commit/0c304a2))
- **Observable:** Ensure the generic type of the Observer passed to Observable's initializer function is the same. ([51a0bc1](https://github.com/ReactiveX/RxJS/commit/51a0bc1)), closes [#2166](https://github.com/ReactiveX/RxJS/issues/2166)
- **Observable:** errors thrown during subscription are now properly sent down error channel ([#2313](https://github.com/ReactiveX/RxJS/issues/2313)) ([d4a9aac](https://github.com/ReactiveX/RxJS/commit/d4a9aac)), closes [#1833](https://github.com/ReactiveX/RxJS/issues/1833)
- **reduce:** index will properly start at 1 if no seed is provided, to match native Array reduce behavior ([30a4ca4](https://github.com/ReactiveX/RxJS/commit/30a4ca4)), closes [#2290](https://github.com/ReactiveX/RxJS/issues/2290)
- **repeatWhen:** resulting observable will wait for the source to complete, even if a hot notifier completes first. ([#2209](https://github.com/ReactiveX/RxJS/issues/2209)) ([c65a098](https://github.com/ReactiveX/RxJS/commit/c65a098)), closes [#2054](https://github.com/ReactiveX/RxJS/issues/2054)
- **Subject:** ensure subject properly throws ObjectUnsubscribedError when unsubscribed then resubscribed to ([#2318](https://github.com/ReactiveX/RxJS/issues/2318)) ([41489eb](https://github.com/ReactiveX/RxJS/commit/41489eb))
- **TestScheduler:** helper methods return proper types, `HotObservable` and `ColdObservable` instead of Observable ([#2305](https://github.com/ReactiveX/RxJS/issues/2305)) ([758aae9](https://github.com/ReactiveX/RxJS/commit/758aae9))
- **windowTime:** ensure windows created when only a timespan is passed are closed and cleaned up properly. ([#2278](https://github.com/ReactiveX/RxJS/issues/2278)) ([d4533c4](https://github.com/ReactiveX/RxJS/commit/d4533c4))
### Features
- **fromEventPattern:** support optional removeHandler ([86960c2](https://github.com/ReactiveX/RxJS/commit/86960c2))
- **fromEventPattern:** support pass signal from addHandler to removeHandler ([01d0622](https://github.com/ReactiveX/RxJS/commit/01d0622))
- **observeOn:** seal memory leak involving old notifications ([9664a38](https://github.com/ReactiveX/RxJS/commit/9664a38)), closes [#2244](https://github.com/ReactiveX/RxJS/issues/2244)
- **Subscription:** `add` will return Subscription that `remove`s itself when unsubscribed ([375d4a5](https://github.com/ReactiveX/RxJS/commit/375d4a5))
- **TypeScript:** interfaces that accepted `Scheduler` now accept `IScheduler` interface ([a0d28a8](https://github.com/ReactiveX/RxJS/commit/a0d28a8))
- **ajax:** upload progress is now set correctly ([#2200](https://github.com/ReactiveX/RxJS/issues/2200)) ([1a83041](https://github.com/ReactiveX/RxJS/commit/1a83041))
- **groupBy:** Fix groupBy to dispose of outer subscription. ([#2201](https://github.com/ReactiveX/RxJS/issues/2201)) ([2269618](https://github.com/ReactiveX/RxJS/commit/2269618))
- **race:** unsubscribe raced observables with immediate scheduler ([#2158](https://github.com/ReactiveX/RxJS/issues/2158)) ([7dd533b](https://github.com/ReactiveX/RxJS/commit/7dd533b))
- **SubscribeOnObservable:** Add the source subscription to the action disposable so the source will ([64e3815](https://github.com/ReactiveX/RxJS/commit/64e3815))
- **AjaxObservable:** remove needless type param R from AjaxObservable.getJSON() ([#2069](https://github.com/ReactiveX/RxJS/issues/2069)) ([0c3d4a4](https://github.com/ReactiveX/RxJS/commit/0c3d4a4))
- **bufferCount:** will behave as expected when `startBufferEvery` is less than `bufferSize` ([#2076](https://github.com/ReactiveX/RxJS/issues/2076)) ([d13dbb4](https://github.com/ReactiveX/RxJS/commit/d13dbb4)), closes [#2062](https://github.com/ReactiveX/RxJS/issues/2062)
- **build_docs:** fix doc building ([#1974](https://github.com/ReactiveX/RxJS/issues/1974)) ([1bbbe8b](https://github.com/ReactiveX/RxJS/commit/1bbbe8b))
- **ErrorObservable:** Add generic error type for ErrorObservable. ([#2071](https://github.com/ReactiveX/RxJS/issues/2071)) ([9df86ba](https://github.com/ReactiveX/RxJS/commit/9df86ba))
- **first:** will now only emit one value in recursive cases ([#2100](https://github.com/ReactiveX/RxJS/issues/2100)) ([a047e7a](https://github.com/ReactiveX/RxJS/commit/a047e7a)), closes [#2098](https://github.com/ReactiveX/RxJS/issues/2098)
- **fromEvent:** Throw if event target is invalid ([#2107](https://github.com/ReactiveX/RxJS/issues/2107)) ([147ce3e](https://github.com/ReactiveX/RxJS/commit/147ce3e))
- **IteratorObservable:** clarify the return type of IteratorObservable.create() ([#2070](https://github.com/ReactiveX/RxJS/issues/2070)) ([4f0f865](https://github.com/ReactiveX/RxJS/commit/4f0f865))
- **IteratorObservable:** Observables `from` generators will now finalize when subscription ends ([22d286a](https://github.com/ReactiveX/RxJS/commit/22d286a)), closes [#1938](https://github.com/ReactiveX/RxJS/issues/1938)
- **multicast:** fix a bug that caused multicast to omit messages after termination ([#2021](https://github.com/ReactiveX/RxJS/issues/2021)) ([44fbc14](https://github.com/ReactiveX/RxJS/commit/44fbc14))
- **Notification:** `materialize` output will now match Rx4 ([#2106](https://github.com/ReactiveX/RxJS/issues/2106)) ([c83bab9](https://github.com/ReactiveX/RxJS/commit/c83bab9)), closes [#2105](https://github.com/ReactiveX/RxJS/issues/2105)
- **Observable/Ajax:** mount properties to origin readystatechange fn ([#2025](https://github.com/ReactiveX/RxJS/issues/2025)) ([76a9abb](https://github.com/ReactiveX/RxJS/commit/76a9abb))
- **reduce/scan:** both scan/reduce operators now accepts `undefined` itself as a valid seed ([#2050](https://github.com/ReactiveX/RxJS/issues/2050)) ([fee7585](https://github.com/ReactiveX/RxJS/commit/fee7585)), closes [#2047](https://github.com/ReactiveX/RxJS/issues/2047)
- **ReplaySubject:** observer now subscribed prior to running subscription function ([#2046](https://github.com/ReactiveX/RxJS/issues/2046)) ([fea08e9](https://github.com/ReactiveX/RxJS/commit/fea08e9)), closes [#2044](https://github.com/ReactiveX/RxJS/issues/2044)
- **sample:** source is now subscribed to before the notifier ([ffe99e8](https://github.com/ReactiveX/RxJS/commit/ffe99e8)), closes [#2075](https://github.com/ReactiveX/RxJS/issues/2075)
- **Symbol.iterator:** will not polyfill Symbol iterator unless Symbol exists ([#2082](https://github.com/ReactiveX/RxJS/issues/2082)) ([1138c99](https://github.com/ReactiveX/RxJS/commit/1138c99))
- **typings:** fixed Subject<T>.lift to have the same shape as Observable<T>.lift ([b07f597](https://github.com/ReactiveX/RxJS/commit/b07f597))
- **WebSocketSubject.prototype.multiplex:** no longer nulls out socket after first unsubscribe ([#2039](https://github.com/ReactiveX/RxJS/issues/2039)) ([a5e9cfe](https://github.com/ReactiveX/RxJS/commit/a5e9cfe)), closes [#2037](https://github.com/ReactiveX/RxJS/issues/2037)
- **groupBy:** Adds subjectSelector argument to groupBy ([#2023](https://github.com/ReactiveX/RxJS/issues/2023)) ([f94ceb9](https://github.com/ReactiveX/RxJS/commit/f94ceb9))
- **typescript:** remove dependency to 3rd party es2015 definition ([#2027](https://github.com/ReactiveX/RxJS/issues/2027)) ([4c31974](https://github.com/ReactiveX/RxJS/commit/4c31974)), closes [#2016](https://github.com/ReactiveX/RxJS/issues/2016)
### BREAKING CHANGES
- Notification: `Notification.prototype.exception` is now `Notification.prototype.error` to match Rx4 semantics
- Symbol.iterator: RxJS will no longer polyfill `Symbol.iterator` if `Symbol` does not exist. This may break code that inadvertently relies on this behavior
- Object.assign: RxJS will no longer polyfill `Object.assign`. It does
not require `Object.assign` to function, however, your code may be
inadvertently relying on this polyfill.
- AjaxObservable: Observable.ajax.getJSON() now only supports a single type parameter,
- **AnonymousSubject:** is now exposed on Rx namespace ([0a6f049](https://github.com/ReactiveX/RxJS/commit/0a6f049)), closes [#2002](https://github.com/ReactiveX/RxJS/issues/2002)
- **bufferTime:** no errors with take after bufferTime with maxBufferSize ([ecec640](https://github.com/ReactiveX/RxJS/commit/ecec640)), closes [#1944](https://github.com/ReactiveX/RxJS/issues/1944)
- **docs:** Fix esdoc for Observable.merge spread argument ([b794e9b](https://github.com/ReactiveX/RxJS/commit/b794e9b))
- **Observer:** fix Observable#subscribe() signature to suggest correct usable ([459d2a2](https://github.com/ReactiveX/RxJS/commit/459d2a2))
- **operator:** Fix take to complete when the source is re-entrant. ([86615cb](https://github.com/ReactiveX/RxJS/commit/86615cb))
- **root:** find global context (window/self/global) in a more safe way ([a098132](https://github.com/ReactiveX/RxJS/commit/a098132)), closes [#1930](https://github.com/ReactiveX/RxJS/issues/1930)
- **schedulers:** Queue, Asap, and AnimationFrame Schedulers should be Async if delay > 0 ([d5c682c](https://github.com/ReactiveX/RxJS/commit/d5c682c))
- **util/toSubscriber:** Supplies the Subscriber constructor with emptyObserver as destination if no ([8e7e4e3](https://github.com/ReactiveX/RxJS/commit/8e7e4e3))
- **WebSocketSubject:** ensure all internal state properly reset when socket is nulled out ([62d242e](https://github.com/ReactiveX/RxJS/commit/62d242e)), closes [#1863](https://github.com/ReactiveX/RxJS/issues/1863)
- **ES2015:** stop publishing `rxjs-es`, ES2015 output no longer included in `@reactivex/rxjs` package under `/dist/es6` ([6be9968](https://github.com/ReactiveX/RxJS/commit/6be9968)), closes [#1671](https://github.com/ReactiveX/RxJS/issues/1671)
- **filter:** Observable<T>.filter() can take type guard as the predicate function ([d62fbf0](https://github.com/ReactiveX/RxJS/commit/d62fbf0))
- **find:** Observable<T>.find() can take type guard as the predicate function ([b952718](https://github.com/ReactiveX/RxJS/commit/b952718))
- **first:** Observable<T>.first() can take type guard as the predicate function ([f99ca49](https://github.com/ReactiveX/RxJS/commit/f99ca49))
- **last:** Observable<T>.last() can take type guard as the predicate function ([76a8a57](https://github.com/ReactiveX/RxJS/commit/76a8a57))
- **operators:** Use lift in the operators that don't currently use lift. ([68af9ef](https://github.com/ReactiveX/RxJS/commit/68af9ef))
- **TypeScript:** update TypeScript to v2.0 ([3478b0b](https://github.com/ReactiveX/RxJS/commit/3478b0b))
### BREAKING CHANGES
- **cache:** The .cache() operator has been removed, pending further discussion ([1b23ace](https://github.com/ReactiveX/RxJS/commit/1b23ace))
- ES2015: `rxjs-es` is no longer being published
- ES2015: `@reactivex/rxjs` no longer has `/dist/es6` output
related #2016
related #1992
- package.json: TypeScript definitions are now for TS 2.0 and higher
Even if we use getter for class, they are marked with `readonly` properties
in d.ts.
- operators: Removes MulticastObservable subclass in favor of a MulticastOperator.
- **AjaxObservable:** return null value from JSON.Parse (#1904) ([6ba374e](https://github.com/ReactiveX/RxJS/commit/6ba374e))
- **catch:** removed unneeded overload for catch ([dd0e586](https://github.com/ReactiveX/RxJS/commit/dd0e586))
- **max:** do not return comparer values ([f454e93](https://github.com/ReactiveX/RxJS/commit/f454e93)), closes [#1892](https://github.com/ReactiveX/RxJS/issues/1892)
- **min:** do not return comparer values ([222fd17](https://github.com/ReactiveX/RxJS/commit/222fd17)), closes [#1892](https://github.com/ReactiveX/RxJS/issues/1892)
- **operators:** export reserved name operators on prototype ([34c39dd](https://github.com/ReactiveX/RxJS/commit/34c39dd)), closes [#1924](https://github.com/ReactiveX/RxJS/issues/1924)
- **ajaxObservable:** only set default Content-Type header when no body is sent (#1830) ([5a895e8](https://github.com/ReactiveX/RxJS/commit/5a895e8))
- **AjaxObservable:** drop resultSelector support in ajax method ([7a77437](https://github.com/ReactiveX/RxJS/commit/7a77437)), closes [#1783](https://github.com/ReactiveX/RxJS/issues/1783)
- **AsyncSubject:** do not allow change value after complete ([801f282](https://github.com/ReactiveX/RxJS/commit/801f282)), closes [#1800](https://github.com/ReactiveX/RxJS/issues/1800)
- **BoundNodeCallbackObservable:** cast to `any` to access to private field in `source` ([54f342f](https://github.com/ReactiveX/RxJS/commit/54f342f))
- **schedulers:** fix asap and animationFrame schedulers to execute across async boundaries. (#182 ([548ec2a](https://github.com/ReactiveX/RxJS/commit/548ec2a)), closes [(#1820](https://github.com/(/issues/1820) [#1814](https://github.com/ReactiveX/RxJS/issues/1814)
- **subscribeToResult:** update subscription to iterables ([5d6339a](https://github.com/ReactiveX/RxJS/commit/5d6339a))
- **WebSocketSubject:** prevent early close (#1831) ([848a527](https://github.com/ReactiveX/RxJS/commit/848a527)), closes [(#1831](https://github.com/(/issues/1831)
### Features
- **fromEvent:** Pass through event listener options (#1845) ([8f0dc01](https://github.com/ReactiveX/RxJS/commit/8f0dc01))
- **AjaxObservable:** ignore content-type for formdata (#1746) ([43d05e7](https://github.com/ReactiveX/RxJS/commit/43d05e7))
- **AjaxObservable:** support withCredentials for CORS request ([8084572](https://github.com/ReactiveX/RxJS/commit/8084572)), closes [#1732](https://github.com/ReactiveX/RxJS/issues/1732) [#1711](https://github.com/ReactiveX/RxJS/issues/1711)
- **babel:** fix an issue where babel could not compile `Scheduler.async` (#1807) ([12c5c74](https://github.com/ReactiveX/RxJS/commit/12c5c74)), closes [(#1807](https://github.com/(/issues/1807) [#1806](https://github.com/ReactiveX/RxJS/issues/1806)
- **multicast:** Fixes multicast with selector to create a new source connection per subscriber. ([c3ac852](https://github.com/ReactiveX/RxJS/commit/c3ac852)), closes [(#1774](https://github.com/(/issues/1774)
- **Subject:** allow optional next value in type definition ([3e0c6d9](https://github.com/ReactiveX/RxJS/commit/3e0c6d9)), closes [#1728](https://github.com/ReactiveX/RxJS/issues/1728)
- **AnonymousSubject:** allow anonymous observers as destination ([0e2c28b](https://github.com/ReactiveX/RxJS/commit/0e2c28b))
- **combineLatest:** rxjs/observable/combineLatest is now properly exported ([21fab73](https://github.com/ReactiveX/RxJS/commit/21fab73)), closes [#1722](https://github.com/ReactiveX/RxJS/issues/1722)
- **ConnectableObservable:** fix race conditions in ConnectableObservable and refCount. ([d1412bc](https://github.com/ReactiveX/RxJS/commit/d1412bc))
- **Rx:** remove kitchenSink and DOM, let Rx export all ([f5090b4](https://github.com/ReactiveX/RxJS/commit/f5090b4)), closes [#1650](https://github.com/ReactiveX/RxJS/issues/1650)
- **ScalarObservable:** set \_isScalar to false when initialized with a scheduler ([5037b3a](https://github.com/ReactiveX/RxJS/commit/5037b3a))
- **Subject:** correct Subject behaviors to be more like Rx4 ([ba9ef2b](https://github.com/ReactiveX/RxJS/commit/ba9ef2b))
- **subscriptions:** fixes bug that tracked subscriber subscriptions twice. ([29ff794](https://github.com/ReactiveX/RxJS/commit/29ff794))
- **scan:** accumulator passes current index ([a3ec896](https://github.com/ReactiveX/RxJS/commit/a3ec896)), closes [#1614](https://github.com/ReactiveX/RxJS/issues/1614)
- **AjaxObservable:** support json responseType on IE ([bba13d8](https://github.com/ReactiveX/RxJS/commit/bba13d8)), closes [#1381](https://github.com/ReactiveX/RxJS/issues/1381)
- **typings:** explicitly export typings for arguments to functions that destructure configuration objects ([ef305af](https://github.com/ReactiveX/RxJS/commit/ef305af))
- **Observable.if:** accept promise as source ([147166e](https://github.com/ReactiveX/RxJS/commit/147166e))
- **mergeMap:** allow concurrent to be set as the second argument for mergeMap and mergeMapTo ([c003468](https://github.com/ReactiveX/RxJS/commit/c003468))
- **observable:** ensure the subscriber chain is complete before calling this.\_subscribe ([1631224](https://github.com/ReactiveX/RxJS/commit/1631224))
- **Symbol:** fixed issue where \$\$observable is not defined ([e66b2d8](https://github.com/ReactiveX/RxJS/commit/e66b2d8))
- **ajax:** add FormData support in AjaxObservable and add percent encoding for parameters ([1f6119c](https://github.com/ReactiveX/RxJS/commit/1f6119c))
- **Subscription:** `add()` now returns a Subscription reference ([a3f4552](https://github.com/ReactiveX/RxJS/commit/a3f4552))
- **AjaxObservable:** update type definition for AjaxObservable ([3f5c269](https://github.com/ReactiveX/RxJS/commit/3f5c269)), closes [#1382](https://github.com/ReactiveX/RxJS/issues/1382)
- **do:** fix do operator to invoke observer message handlers in the right context. ([67a2f25](https://github.com/ReactiveX/RxJS/commit/67a2f25))
- **exhaustMap:** remove innersubscription when it completes ([7ca0859](https://github.com/ReactiveX/RxJS/commit/7ca0859))
- **forEach:** ensure that teardown logic is called when nextHandler throws ([c50f528](https://github.com/ReactiveX/RxJS/commit/c50f528)), closes [#1411](https://github.com/ReactiveX/RxJS/issues/1411)
- **forkJoin:** dispose the inner subscriptions when the outer subscription is disposed ([c7bf30c](https://github.com/ReactiveX/RxJS/commit/c7bf30c))
- **FutureAction:** add support for periodic scheduling with setInterval instead of setTimeout ([c4f5408](https://github.com/ReactiveX/RxJS/commit/c4f5408))
- **Observable:** introduce Subscribable interface that will be used instead of Observable in input ([2256e7b](https://github.com/ReactiveX/RxJS/commit/2256e7b))
- **forkJoin:** fix forkJoin to complete if sources Array is empty. ([412b13b](https://github.com/ReactiveX/RxJS/commit/412b13b))
- **groupBy:** does not emit on unsubscribed group ([6d08705](https://github.com/ReactiveX/RxJS/commit/6d08705))
- **groupBy:** fix groupBy to use lift(), supports composability ([815cfae](https://github.com/ReactiveX/RxJS/commit/815cfae)), closes [#1085](https://github.com/ReactiveX/RxJS/issues/1085)
- **merge/concat:** passed scalar observables will now complete properly ([c01b92f](https://github.com/ReactiveX/RxJS/commit/c01b92f)), closes [#1150](https://github.com/ReactiveX/RxJS/issues/1150)
- **MergeMapSubscriber:** clarify type definitions for MergeMapSubscriber's members ([4ee5f02](https://github.com/ReactiveX/RxJS/commit/4ee5f02))
- **Observable.forEach:** errors thrown in nextHandler reject returned promise ([c5ead88](https://github.com/ReactiveX/RxJS/commit/c5ead88)), closes [#1184](https://github.com/ReactiveX/RxJS/issues/1184)
- **Observer:** fix typing to allow observation via partial observables with PartialObservable<T([7b6da90](https://github.com/ReactiveX/RxJS/commit/7b6da90))
- **Subject:** align parameter order to match with RxJS4 ([44dfa07](https://github.com/ReactiveX/RxJS/commit/44dfa07)), closes [#1285](https://github.com/ReactiveX/RxJS/issues/1285)
- **Subject:** throw ObjectUnsubscribedError when unsubscribed ([29b630b](https://github.com/ReactiveX/RxJS/commit/29b630b)), closes [#859](https://github.com/ReactiveX/RxJS/issues/859)
- **Subscriber:** adds unsubscription when errors are thrown from user-land handlers. ([dc67d21](https://github.com/ReactiveX/RxJS/commit/dc67d21))
- **Subscription:** fix leaks caused by unsubscribe functions that throw ([9e88c2e](https://github.com/ReactiveX/RxJS/commit/9e88c2e))
- **subscriptions:** unsubscribe correctly when a Subscriber throws during synchronous dispatch. ([b1698fe](https://github.com/ReactiveX/RxJS/commit/b1698fe))
- **zip:** extra 1x-2x factor gains from custom tryCatch member function ([a1b0e52](https://github.com/ReactiveX/RxJS/commit/a1b0e52))
### BREAKING CHANGES
- Subject: Subject.create arguments have been swapped to match Rx 4 signature. `Subject.create(observable, observer)` is now `Subject.create(observer, observable)`
- Observable patching: Patch files for static observable methods such as `of` and `from` can now be found in `rxjs/add/observable/of`, `rxjs/add/observable/from`, etc.
- Observable modules: Observable modules for subclassed Observables like `PromiseObservable`, `ArrayObservable` are now in appropriately named files like `rxjs/observable/PromiseObservable` and `rxjs/observable/ArrayObservable`
as opposed to `rxjs/observable/fromPromise` and `rxjs/observable/fromArray`, since they're not patching, they simply house the Observable implementations.
- **ajax:** response properly based off responseType ([b2a27a2](https://github.com/ReactiveX/RxJS/commit/b2a27a2))
- **ajax:** should no longer succeed on 300 status ([4d4fa32](https://github.com/ReactiveX/RxJS/commit/4d4fa32))
- **animationFrame:** req/cancel animationFrame has to be called within the context of root. ([30a11ee](https://github.com/ReactiveX/RxJS/commit/30a11ee))
- **debounceTime:** align value emit behavior as same as RxJS4 ([5ee11e0](https://github.com/ReactiveX/RxJS/commit/5ee11e0)), closes [#1081](https://github.com/ReactiveX/RxJS/issues/1081)
- **scheduling:** Fixes bugs in scheduled actions. ([e050f01](https://github.com/ReactiveX/RxJS/commit/e050f01))
- **Subscriber:** errors in nextHandler no longer propagate to errorHandler ([f42eed2](https://github.com/ReactiveX/RxJS/commit/f42eed2)), closes [#1135](https://github.com/ReactiveX/RxJS/issues/1135)
- **WebSocketSubject:** ensure error codes passed to WebSocket close method ([3b1655e](https://github.com/ReactiveX/RxJS/commit/3b1655e))
- **WebSocketSubject:** ensure WebSocketSubject can be resubscribed ([861a0c1](https://github.com/ReactiveX/RxJS/commit/861a0c1))
- **WebSocketSubject:** resultSelector and protocols specifications work properly ([580f69a](https://github.com/ReactiveX/RxJS/commit/580f69a))
### Features
- **ajax:** add resultSelector and improve perf ([6df755f](https://github.com/ReactiveX/RxJS/commit/6df755f))
- **ajax:** adds ajax methods from rx-dom. ([2ca4236](https://github.com/ReactiveX/RxJS/commit/2ca4236))
- **every:** handle thisArg for scalar and array observables ([eae4b00](https://github.com/ReactiveX/RxJS/commit/eae4b00))
- **SymbolShim:** ensure for function even if Symbol already exists ([e942776](https://github.com/ReactiveX/RxJS/commit/e942776)), closes [#999](https://github.com/ReactiveX/RxJS/issues/999)
- **SymbolShim:** Symbol polyfill is a function ([1f57157](https://github.com/ReactiveX/RxJS/commit/1f57157)), closes [#988](https://github.com/ReactiveX/RxJS/issues/988)
- **timeoutWith:** fix to avoid unnecessary inner subscription ([6e63752](https://github.com/ReactiveX/RxJS/commit/6e63752))
- **AsyncSubject:** emit value when it's subscribed after complete ([ed0eaf6](https://github.com/ReactiveX/RxJS/commit/ed0eaf6))
- **bindCallback:** only call function once even while scheduled ([8637d47](https://github.com/ReactiveX/RxJS/commit/8637d47)), closes [#881](https://github.com/ReactiveX/RxJS/issues/881)
- **bufferToggle:** fix disposal of subscriptions when errors occur ([a20325c](https://github.com/ReactiveX/RxJS/commit/a20325c))
- **catch:** fix catch to dispose old subscriptions ([280f7ed](https://github.com/ReactiveX/RxJS/commit/280f7ed)), closes [#763](https://github.com/ReactiveX/RxJS/issues/763)
- **catch:** fix catch() to preserve Subscriber chain ([e1447ac](https://github.com/ReactiveX/RxJS/commit/e1447ac))
- **throttleTime:** fix and rename throttleTime operator ([3b0c1f3](https://github.com/ReactiveX/RxJS/commit/3b0c1f3))
- **TimerObservable:** accepts absolute date for dueTime ([e284fb8](https://github.com/ReactiveX/RxJS/commit/e284fb8)), closes [#648](https://github.com/ReactiveX/RxJS/issues/648)
- **combineLatest:** accept array of observable as parameter ([2edd92c](https://github.com/ReactiveX/RxJS/commit/2edd92c)), closes [#594](https://github.com/ReactiveX/RxJS/issues/594)
- **forkJoin:** accept array of observable as parameter ([d45f672](https://github.com/ReactiveX/RxJS/commit/d45f672))
- **mergeScan:** support concurrency parameter for mergeScan ([fe0eb37](https://github.com/ReactiveX/RxJS/commit/fe0eb37)), closes [#868](https://github.com/ReactiveX/RxJS/issues/868)
- **operators:** Remove shareReplay and shareBehavior ([536a6a6](https://github.com/ReactiveX/RxJS/commit/536a6a6)), closes [#710](https://github.com/ReactiveX/RxJS/issues/710)
- **test:** make explicit unsubscription for observable ([505f5b7](https://github.com/ReactiveX/RxJS/commit/505f5b7))
- **throttleTime:** fix and rename throttleTime operator ([3b0c1f3](https://github.com/ReactiveX/RxJS/commit/3b0c1f3))
- **TimerObservable:** accepts absolute date for dueTime ([e284fb8](https://github.com/ReactiveX/RxJS/commit/e284fb8)), closes [#648](https://github.com/ReactiveX/RxJS/issues/648)
- **Immediate:** set immediate should no longer throw in Chrome ([a3de7d9](https://github.com/ReactiveX/RxJS/commit/a3de7d9)), closes [#690](https://github.com/ReactiveX/RxJS/issues/690)
- **concat:** handle a given scheduler correctly ([8745216](https://github.com/ReactiveX/RxJS/commit/8745216))
- **package.json:** loosen the engines/npm semver range to prevent false warnings ([df791c6](https://github.com/ReactiveX/RxJS/commit/df791c6))
- **skipUntil:** unsubscribe source when it completes ([8a4162b](https://github.com/ReactiveX/RxJS/commit/8a4162b)), closes [#577](https://github.com/ReactiveX/RxJS/issues/577)
- **take:** deal with total <= 0 and add tests ([c5cc06f](https://github.com/ReactiveX/RxJS/commit/c5cc06f))
- **windowWhen:** fix windowWhen with regard to unsubscriptions ([8174947](https://github.com/ReactiveX/RxJS/commit/8174947))
### Features
- **mergeScan:** add new mergeScan operator. ([0ebb5bd](https://github.com/ReactiveX/RxJS/commit/0ebb5bd))
- **multicast:** support both Subject and subjectFactory arguments ([f779027](https://github.com/ReactiveX/RxJS/commit/f779027))
### BREAKING CHANGES
- **publish:** reverted to RxJS 4 behavior
- **publishBehavior:** reverted to RxJS 4 behavior
- **buffer:** cleanup notifier subscription when unsubscribed ([1b30aa9](https://github.com/ReactiveX/RxJS/commit/1b30aa9))
- **delay:** accepts absolute time delay ([b109100](https://github.com/ReactiveX/RxJS/commit/b109100))
- **mergeMapTo:** mergeMapTo result should complete ([6f9859e](https://github.com/ReactiveX/RxJS/commit/6f9859e))
- **operator:** update type definitions for union types ([9d90c75](https://github.com/ReactiveX/RxJS/commit/9d90c75)), closes [#581](https://github.com/ReactiveX/RxJS/issues/581)
- **TestScheduler:** support unsubscription marbles ([ffb0bb9](https://github.com/ReactiveX/RxJS/commit/ffb0bb9))
- **count:** add predicate support in count() ([42d1add](https://github.com/ReactiveX/RxJS/commit/42d1add)), closes [#425](https://github.com/ReactiveX/RxJS/issues/425)
- **do:** do will now handle an observer as an argument ([c1a4994](https://github.com/ReactiveX/RxJS/commit/c1a4994)), closes [#476](https://github.com/ReactiveX/RxJS/issues/476)
- **zip:** zip now supports never-ending iterables ([a5684ba](https://github.com/ReactiveX/RxJS/commit/a5684ba)), closes [#397](https://github.com/ReactiveX/RxJS/issues/397)
- **bufferCount:** set default value for skip argument, do not emit empty buffer at the end ([2c1a9dc](https://github.com/ReactiveX/RxJS/commit/2c1a9dc))
- **windowCount:** set default value for skip argument, do not emit empty buffer at the end ([a513dbb](https://github.com/ReactiveX/RxJS/commit/a513dbb))
- **combineLatest:** check for limits higher than total observable count ([81e5dfb](https://github.com/ReactiveX/RxJS/commit/81e5dfb))
- **rx:** add hack to export global until better global build exists ([1a543b0](https://github.com/ReactiveX/RxJS/commit/1a543b0))
- **subscription-ref:** add setter for isDisposed ([6fe5427](https://github.com/ReactiveX/RxJS/commit/6fe5427))
- **take:** complete on limit reached ([801a711](https://github.com/ReactiveX/RxJS/commit/801a711))
### Features
- **benchpress:** add benchpress config and flatmap spec ([0441dea](https://github.com/ReactiveX/RxJS/commit/0441dea))
- **catch:** add catch operator, related to #141, closes #130 ([94b4c01](https://github.com/ReactiveX/RxJS/commit/94b4c01)), closes [#130](https://github.com/ReactiveX/RxJS/issues/130)
- **from:** let from handle any "observablesque" ([526d4c3](https://github.com/ReactiveX/RxJS/commit/526d4c3)), closes [#156](https://github.com/ReactiveX/RxJS/issues/156) [#236](https://github.com/ReactiveX/RxJS/issues/236)
- **index:** add index module which requires commonjs build ([379d2d1](https://github.com/ReactiveX/RxJS/commit/379d2d1)), closes [#117](https://github.com/ReactiveX/RxJS/issues/117)
