npm · #3958 most downloaded on npm

fp-ts

2.16.1119M downloads/mogcanti/fp-ts ↗New releases in your daily digest, changelog included.

Functional programming in TypeScript

Last release 1 years ago
18 Aug 2025
Release timing varies
gaps range from 2 weeks to 9 months
Nearly every release is documented
notes for 59 of the last 60 stable releases
Nothing withdrawn
no release was ever pulled
10 years old
233 releases · first in 2017

Release timeline

233 releases since 2017

2017201920212023

Releases

3.0.0-alpha.2625 Sept 2022pre-release
Nothing published for this version
3.0.0-alpha.2520 Sept 2022pre-release
Nothing published for this version
3.0.0-alpha.2420 Sept 2022pre-release
Nothing published for this version
3.0.0-alpha.2315 Sept 2022pre-release
Nothing published for this version

One column per quarter.

3.0.0-alpha.2228 Apr 2022pre-release

Nothing published for this version

3.0.0-alpha.2122 Apr 2022pre-release

Nothing published for this version

3.0.0-alpha.2023 Mar 2022pre-release

Nothing published for this version

3.0.0-alpha.1927 Sept 2021pre-release

Nothing published for this version

3.0.0-alpha.1815 Sept 2021pre-release

Nothing published for this version

3.0.0-alpha.1730 Apr 2021pre-release

Nothing published for this version

3.0.0-alpha.1626 Mar 2021pre-release

Nothing published for this version

3.0.0-alpha.151 Mar 2021pre-release

Nothing published for this version

3.0.0-alpha.148 Feb 2021pre-release

Nothing published for this version

3.0.0-alpha.137 Feb 2021pre-release

Nothing published for this version

3.0.0-alpha.127 Feb 2021pre-release

Nothing published for this version

3.0.0-alpha.113 Feb 2021pre-release

Nothing published for this version

3.0.0-alpha.101 Feb 2021pre-release

Nothing published for this version

3.0.0-alpha.925 Jan 2021pre-release

Nothing published for this version

3.0.0-alpha.821 Jan 2021pre-release

Nothing published for this version

3.0.0-alpha.720 Jan 2021pre-release

Nothing published for this version

3.0.0-alpha.68 Jan 2021pre-release

Nothing published for this version

3.0.0-alpha.52 Jan 2021pre-release

Nothing published for this version

3.0.0-alpha.430 Dec 2020pre-release

Nothing published for this version

3.0.0-alpha.329 Dec 2020pre-release

Nothing published for this version

3.0.0-alpha.229 Dec 2020pre-release

Nothing published for this version

3.0.0-alpha.129 Dec 2020pre-release

Nothing published for this version

2.16.1118 Aug 20252 sources agree

Fix Option.getOrd definition, #1963

Bug Fix

Fix Option.getOrd definition, #1963

Open source →

2.16.1018 Apr 20252 sources agree

Add apFirstW and apSecondW to ReaderTask, #1958

Polish

Add apFirstW and apSecondW to ReaderTask, #1958

Open source →

2.16.925 Jul 20243 sources agree

Support strictBuiltinIteratorReturn, #1949

Polish

Support strictBuiltinIteratorReturn, #1949

Open source →

2.16.87 Jul 20242 sources agree

Remove useless pure comment, closes #1937

Polish

Remove useless pure comment, closes #1937

Open source →

2.16.729 Jun 20242 sources agree

Polish Add tap for Identity #1943

Polish

Add tap for Identity #1943

Open source →

2.16.619 May 20242 sources agree

Allow dependencies to be widen when using orLeft #1938

Polish

Allow dependencies to be widen when using orLeft #1938

Open source →

2.16.525 Mar 20243 sources agree

Resolved a RangeError where the maximum call stack size was exceeded when invoking chainWithIndex, #1931

Polish

Resolved a RangeError where the maximum call stack size was exceeded when invoking chainWithIndex, #1931

Open source →

2.16.418 Mar 20242 sources agree

Fix __PURE__ annotation placement, closes #1926

Polish

Fix __PURE__ annotation placement, closes #1926

Open source →

2.16.311 Mar 20242 sources agree

Either.ts: toError: Don't fail when a value can't be converted to a primitive, #1924

Polish

Either.ts: toError: Don't fail when a value can't be converted to a primitive, #1924

Open source →

2.16.23 Jan 20242 sources agree

Fix "__PURE__" annotation placement #1919, closes #1916

Polish

Fix "__PURE__" annotation placement #1919, closes #1916

Open source →

2.16.127 Jul 20232 sources agree

fix type signature of ReaderTaskEither.tapReaderIO, #1895

Bug Fix

fix type signature of ReaderTaskEither.tapReaderIO, #1895

Open source →

2.16.025 May 20233 sources agree

tapEither (dual) (aka chainFirstEitherK / chainFirstEitherKW) https://github.com/gcanti/fp-ts/pull/1864

tapEither (dual) (aka chainFirstEitherK / chainFirstEitherKW) https://github.com/gcanti/fp-ts/pull/1864
tapIO (dual) (aka chainFirstIOK) https://github.com/gcanti/fp-ts/pull/1865
as / asUnit https://github.com/gcanti/fp-ts/pull/1867
tapTask (dual) (aka chainFirstTaskK) https://github.com/gcanti/fp-ts/pull/1869
mapError (dual) (aka mapLeft) https://github.com/gcanti/fp-ts/pull/1870
mapBoth (dual) (aka bimap) https://github.com/gcanti/fp-ts/pull/1872
tapReader (dual) (aka chainFirstReaderK / chainFirstIReaderKW) https://github.com/gcanti/fp-ts/pull/1871
tapReaderEither (dual) (aka chainFirstReaderEitherK / chainFirstEitherKW) https://github.com/gcanti/fp-ts/pull/1873
tapReaderIO (dual) (aka chainFirstReaderIOK) https://github.com/gcanti/fp-ts/pull/1873
tapReaderTask (dual) (aka chainFirstReaderTaskK) https://github.com/gcanti/fp-ts/pull/1873
tapTaskEither (dual) (aka chainFirstTaskEitherK / chainFirstTaskEitherKW) https://github.com/gcanti/fp-ts/pull/1873
flatMapReaderTask (dual) (aka chainReaderTaskK / chainReaderTaskKW) https://github.com/gcanti/fp-ts/pull/1874
flatMapTaskEither (dual) (aka chainTaskEitherK / chainTaskEitherKW) https://github.com/gcanti/fp-ts/pull/1874
flatMapIO (dual) (aka chainIOK) https://github.com/gcanti/fp-ts/pull/1874
Option.orElse (dual) (aka alt / altW) https://github.com/gcanti/fp-ts/pull/1868
flatMapTask (dual) (aka chainTaskK) https://github.com/gcanti/fp-ts/pull/1876
flatMapReader (dual) (aka chainReaderK / chainReaderKW) https://github.com/gcanti/fp-ts/pull/1876
flatMapReaderIO (dual) (aka chainReaderIOK / chainReaderIOKW) https://github.com/gcanti/fp-ts/pull/1879
flatMap* (aka chain*K / chain*KW) https://github.com/gcanti/fp-ts/pull/1880

Open source →

2.15.08 May 20233 sources agree

add tap (dual) (aka chainFirst / chainFirstW) to:

New Feature

function
- add LazyArg
add tap (dual) (aka chainFirst / chainFirstW) to:
- Either
- IO
- IOEither
- IOOption
- Option
- Reader
- ReaderEither
- ReaderIO
- ReaderTask
- ReaderTaskEither
- State
- StateReaderTaskEither
- Task
- TaskEither
- TaskOption
add tapError (dual) (aka orElseFirst / orElseFirstW) to:
- IOEither
- ReaderEither
- ReaderTaskEither
- TaskEither
add flatMapNullable (dual) to:
- Either
- IOEither
- ReaderEither
- ReaderTaskEither
- StateReaderTaskEither
- TaskEither
add flatMapOption (dual) to:
- Either
- IOEither
- ReaderEither
- ReaderTaskEither
- StateReaderTaskEither
- TaskEither
add liftNullable to:
- Either
- IOEither
- ReaderEither
- ReaderTaskEither
- StateReaderTaskEither
- TaskEither
add liftOption to:
- Either
- IOEither
- ReaderEither
- ReaderTaskEither
- StateReaderTaskEither
- TaskEither
add flatMapEither (dual) to:
- IOEither
- ReaderEither
- ReaderTaskEither
- TaskEither
Array
- add index to flatMap
NonEmptyArray
- add index to flatMap
ReadonlyArray
- add index to flatMap
ReadonlyNonEmptyArray
- add index to flatMap

Open source →

2.14.020 Apr 20233 sources agree

you can replace chain / chainW with flatMap

New Feature

add flatMap to
- Either
- IOEither
- Reader
- ReaderEither
- ReaderIO
- ReaderTask
- ReaderTaskEither
- StateReaderTaskEither
- TaskEither
- NonEmptyArray
- ReadonlyNonEmptyArray
- Tree
- Array
- Identity
- IO
- IOOption
- Option
- ReadonlyArray
- State
- Task
- TaskOption

the gist is:

you can replace chain / chainW with flatMap
you can call flatMap in 2 ways: pipe(ma, flatMap(f)) (data-last, aka pipeable) or flatMap(ma, f) (data-first)

Open source →

2.13.219 Apr 20233 sources agree

add chainOptionKW, #1846 (@DenisFrezzato)

add chainOptionKW, #1846 (@DenisFrezzato)

Open source →

2.13.117 Oct 2022Deprecated3 sources agree

deprecate uncurried flip function, #1748 (@thewilkybarkid)

New Feature
- new modules:
  - ReaderIO, #1738 (@sukovanej)
- do notation:
  - add let helpers, #1725 (@Punie)
- Alternative
  - add getAlternativeMonoid, #1717 (@willheslam)
- function
  - flip is now curried, #1748 (@thewilkybarkid)
- pipeable
  - add pipeable helpers, #1764 (@gcanti)
    - alt
    - ap
    - bimap
    - chain
    - compose
    - contramap
    - extend
    - filter
    - filterMap
    - filterMapWithIndex
    - filterWithIndex
    - foldMap
    - foldMapWithIndex
    - map
    - mapLeft
    - mapWithIndex
    - partition
    - partitionMap
    - partitionMapWithIndex
    - partitionWithIndex
    - promap
    - reduce
    - reduceRight
    - reduceRightWithIndex
    - reduceWithIndex
- ReaderTask
  - add ReaderIO constructors/combinators, #1773 (@thewilkybarkid)
- ReaderTaskEither
  - add ReaderIO constructors/combinators, #1774 (@thewilkybarkid)
- TaskEither
  - add chainTaskOptionKW, #1744 (@AmirabbasJ)
Polish
- backport from v3 some handy defaults defined in natural transformations/combinators/constructors (@gcanti)
- fix wrong type parameter order:
  - FromIO
    - chainIOK
  - FromTask
    - chainTaskK
    - chainFirstTaskK
  - Whiterable
    - FilterE1
  - TheseT
    - both
  - Either
    - apFirstW
    - apSecondW
  - IOEither
    - apFirstW
    - apSecondW
  - Reader
    - apFirstW
    - apSecondW
  - ReaderEither
    - apFirstW
    - apSecondW
  - ReaderTaskEither
    - apFirstW
    - apSecondW
  - StateReaderTaskEither
    - apFirstW
    - apSecondW
  - TaskEither
    - apFirstW
    - apSecondW
- Apply
  - add ap overloadings, #1721 (@waynevanson)
- Either
  - remove useless type parameter in exists (@gcanti)
- ReadonlyRecord
  - fix fromEntries return type, closes #1745 (@gcanti)
- TaskEither
  - fix fromPredicate signature (@gcanti)
- These
  - add missing fromPredicate (@gcanti)
  - remove useless type parameter in exists (@gcanti)
- Traversable
  - add more overloadings to traverse / sequence helpers, #1758 (@gcanti)
- Writer
  - getChain requires a Semigroup instead of a Monoid (@gcanti)
Deprecation
- function
  - deprecate uncurried flip function, #1748 (@thewilkybarkid)

Open source →

2.13.017 Oct 2022

add exports field to package.json in order to support moduleResolution node12/nodenext, #1765 (@gcanti)

BROKEN RELEASE

Experimental
- add exports field to package.json in order to support moduleResolution node12/nodenext, #1765 (@gcanti)

Open source →

2.13.0-rc.620 Sept 2022pre-release

package.json exports field: move ./* to the end, closes #1786 (@gcanti)

How to install:

npm install fp-ts@rc

Bug Fix
- package.json exports field: move ./* to the end, closes #1786 (@gcanti)
- revert PR 1584 because is causing a regression (@gcanti)

Open source →

2.13.0-rc.520 Sept 2022pre-release

Nothing published for this version

2.13.0-rc.419 Sept 2022pre-release

backport from v3 some handy defaults defined in natural transformations, kleisli arrows helpers, of functions (@gcanti)

How to install:

npm install fp-ts@rc

Polish
- backport from v3 some handy defaults defined in natural transformations, kleisli arrows helpers, of functions (@gcanti)
- Either
  - remove useless type parameter in exists (@gcanti)
- TaskEither
  - fix fromPredicate signature (@gcanti)
- These
  - add missing fromPredicate (@gcanti)
  - remove useless type parameter in exists (@gcanti)

Open source →

2.13.0-rc.317 Sept 2022pre-release

add ReaderIO constructors/combinators, #1773 (@thewilkybarkid)

How to install:

npm install fp-ts@rc

New Feature
- ReaderTask
  - add ReaderIO constructors/combinators, #1773 (@thewilkybarkid)
- ReaderTaskEither
  - add ReaderIO constructors/combinators, #1774 (@thewilkybarkid)
Polish
- backport from v3 some handy defaults defined in natural transformations/combinators/constructors (@gcanti)

Open source →

2.13.0-rc.215 Sept 2022pre-releaseDeprecated

deprecate uncurried flip function, #1748 (@thewilkybarkid)

2.13.0-rc.2

How to install:

npm install fp-ts@rc

Experimental
- add exports field to package.json in order to support moduleResolution node12/nodenext, #1765 (@gcanti)
New Feature
- new modules:
  - ReaderIO, #1738 (@sukovanej)
- do notation:
  - add let helpers, #1725 (@Punie)
- Alternative
  - add getAlternativeMonoid, #1717 (@willheslam)
- function
  - flip is now curried, #1748 (@thewilkybarkid)
- pipeable
  - add pipeable helpers, #1764 (@gcanti)
    - alt
    - ap
    - bimap
    - chain
    - compose
    - contramap
    - extend
    - filter
    - filterMap
    - filterMapWithIndex
    - filterWithIndex
    - foldMap
    - foldMapWithIndex
    - map
    - mapLeft
    - mapWithIndex
    - partition
    - partitionMap
    - partitionMapWithIndex
    - partitionWithIndex
    - promap
    - reduce
    - reduceRight
    - reduceRightWithIndex
    - reduceWithIndex
Bug Fix
- do notation
  - Ensuring that bind and bindW pass the correct params through rather than get rewritten by the function passed in, #1584 (@feydan)
Polish
- Traversable
  - add more overloadings to traverse / sequence helpers, #1758 (@gcanti)
- Writer
  - getChain requires a Semigroup instead of a Monoid (@gcanti)
Deprecation
- function
  - deprecate uncurried flip function, #1748 (@thewilkybarkid)

Open source →

2.13.0-rc.115 Sept 2022pre-release

Nothing published for this version

2.12.331 Aug 2022

add ap overloadings, #1721 (@waynevanson)

Polish
- Apply
  - add ap overloadings, #1721 (@waynevanson)
- ReadonlyRecord
  - fix fromEntries return type, closes #1745 (@gcanti)
- TaskEither
  - add chainTaskOptionKW, #1744 (@AmirabbasJ)
- fix wrong type parameter order:
  - FromIO
    - chainIOK
  - FromTask
    - chainTaskK
    - chainFirstTaskK
  - Whiterable
    - FilterE1
  - TheseT
    - both
  - Either
    - apFirstW
    - apSecondW
  - IOEither
    - apFirstW
    - apSecondW
  - Reader
    - apFirstW
    - apSecondW
  - ReaderEither
    - apFirstW
    - apSecondW
  - ReaderTaskEither
    - apFirstW
    - apSecondW
  - StateReaderTaskEither
    - apFirstW
    - apSecondW
  - TaskEither
    - apFirstW
    - apSecondW

Open source →

2.12.225 Jul 20223 sources agree

add Applicative4 overloadings to traverse / traverseWithIndex, #1733 (@mlegenhausen)

Polish
- ReadonlyRecord / Record
  - add Applicative4 overloadings to traverse / traverseWithIndex, #1733 (@mlegenhausen)

Open source →

2.12.128 Apr 20223 sources agree

fix traverseWithIndex implementation, #1704 (@waynevanson)

Bug Fix
- ReadonlyRecord
  - fix traverseWithIndex implementation, #1704 (@waynevanson)

Open source →

2.12.022 Apr 20223 sources agree

add intercalate, #1678 (@thewilkybarkid)

New Feature
- add IOOption module (@gcanti)
- Array
  - add intercalate, #1678 (@thewilkybarkid)
- Bounded
  - add clamp (@gcanti)
  - add reverse (@gcanti)
- Either
  - add apFirstW, #1564 (@DenisFrezzato)
  - add apSecondW, #1564 (@DenisFrezzato)
- EitherT
  - add chainNullableK, #1619 (@cwstra)
  - add fromNullable, #1619 (@cwstra)
  - add fromNullableK, #1619 (@cwstra)
- FromEither
  - add chainFirstEitherK (@gcanti)
- IOEither
  - add apFirstW, #1564 (@DenisFrezzato)
  - add apSecondW, #1564 (@DenisFrezzato)
  - add chainFirstEitherK (@gcanti)
  - add chainFirstEitherKW (@gcanti)
  - add orElseFirstIOK, #1655 (@thewilkybarkid)
  - add bracketW, #1627 (@thomasvargiu)
- NonEmptyArray
  - add intercalate, #1678 (@thewilkybarkid)
- Option
  - add chainFirstEitherK (@gcanti)
- Ordering
  - add matchW, #1535 (@mlegenhausen)
- Reader
  - add apFirstW, #1564 (@DenisFrezzato)
  - add apSecondW, #1564 (@DenisFrezzato)
- ReaderEither
  - add apFirstW, #1564 (@DenisFrezzato)
  - add apSecondW, #1564 (@DenisFrezzato)
  - add chainFirstEitherK (@gcanti)
  - add chainFirstEitherKW (@gcanti)
- ReaderTaskEither
  - add apFirstW, #1564 (@DenisFrezzato)
  - add apSecondW, #1564 (@DenisFrezzato)
  - add chainFirstEitherK, #1562 (@DenisFrezzato)
  - add chainFirstEitherKW, #1562 (@DenisFrezzato)
  - add bracketW, #1627 (@thomasvargiu)
  - add chainNullableK (@gcanti)
  - add fromNullable (@gcanti)
  - add fromNullableK (@gcanti)
- ReadonlyArray
  - add intercalate, #1678 (@thewilkybarkid)
- ReadonlyNonEmptyArray
  - add intercalate, #1678 (@thewilkybarkid)
- ReadonlyRecord
  - add toEntries, #1552 (@bravely)
  - add fromEntries, #1552 (@bravely)
- Record
  - add toEntries, #1552 (@bravely)
  - add fromEntries, #1552 (@bravely)
- StateReaderTaskEither
  - add apFirstW, #1564 (@DenisFrezzato)
  - add apSecondW, #1564 (@DenisFrezzato)
  - add chainFirstEitherK (@gcanti)
  - add chainFirstEitherKW (@gcanti)
- TaskEither
  - add apFirstW, #1564 (@DenisFrezzato)
  - add apSecondW, #1564 (@DenisFrezzato)
  - add chainFirstEitherK, #1659 (@vinassefranche)
  - add chainFirstEitherKW, #1659 (@vinassefranche)
  - add orElseFirstIOK, #1655 (@thewilkybarkid)
  - add orElseFirstTaskK, #1655 (@thewilkybarkid)
  - add bracketW, #1627 (@thomasvargiu)
  - add chainNullableK, #1619 (@cwstra)
  - add fromNullable, #1619 (@cwstra)
  - add fromNullableK, #1619 (@cwstra)
- TaskOption
  - add fromEitherK (@gcanti)
  - add chainEitherK (@gcanti)
  - add chainFirstEitherK (@gcanti)

Open source →

2.11.1014 Apr 20223 sources agree

now tryCatch / tryCatchK will catch synchronous errors too, #1676 (@thewilkybarkid)

Polish
- TaskEither / TaskOption
  - now tryCatch / tryCatchK will catch synchronous errors too, #1676 (@thewilkybarkid)

Open source →

2.11.914 Mar 20223 sources agree

add Refinement overload to 'every' functions, #1681 (@mlegenhausen)

Polish
- add Refinement overload to 'every' functions, #1681 (@mlegenhausen)

Open source →

2.11.817 Jan 20223 sources agree

Add missing pure annotations, #1658 (@OliverJAsh)

Polish
- Add missing pure annotations, #1658 (@OliverJAsh)

Open source →

2.11.710 Jan 20223 sources agree

more Functor.map overloadings, closes #1623 (@gcanti)

Polish
- more Functor.map overloadings, closes #1623 (@gcanti)

Open source →

2.11.65 Jan 20223 sources agree

orElseFirstW: intersect dependencies like orElseW (@gcanti)

Polish
- ReaderEither
  - orElseFirstW: intersect dependencies like orElseW (@gcanti)
- ReaderTaskEither
  - orElseFirstW: intersect dependencies like orElseW, #1635 (@OliverJAsh)

Open source →

2.11.514 Oct 20213 sources agree

more curried elem overloads, #1602 (@ammut)

Polish
- more curried elem overloads, #1602 (@ammut)

Open source →

2.11.427 Sept 20213 sources agree

fix chainNullableK signature, #1589 (@bwlt)

Polish
- fix chainNullableK signature, #1589 (@bwlt)
- stack safety for Task via microtasks suspension, #1591 (@mikearnaldi)

Open source →

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