@mobily/tifi NPM

Installation

yarn add @mobily/tifi

or with npm

npm install @mobily/tifi --save

Example

TODO

// TODO

Api Reference

Option

type Option<T> = None | Some<T>

fromNullable

If value is null or undefined, returns None, otherwise returns a value wrapped in Some.

fromNullable<T>(value: T | null | undefined): Option<T>

fromNullable(null) // None
fromNullable('string') // Some('string')

fromFalsy

If value is falsy, returns None, otherwise returns the value wrapped in Some.

fromFalsy<T>(value: T): Option<T>

fromFalsy(null) // None
fromFalsy('') // None
fromFalsy(0) // None
fromFalsy('string') // Some('string')
fromFalsy(1) // Some(1)

fromPredicate

If predicate returns false, returns None, otherwise returns a value wrapped in Some.

fromPredicate<T>(predicate: (value: T) => boolean, value: T): Option<T>

fromPredicate(str => str.length > 10, 'string') // None
fromPredicate(obj => obj.prop === 'string', { prop: 'string' }) // Some({ props: 'string' })

const takeEvenNumber = fromPredicate<number>(x => x % 2 === 0)

takeEvenNumber(4) // Some(4)
takeEvenNumber(1) // None

isSome

If option is Some, returns true.

isSome<T>(option: Option<T>): boolean

const option = fromNullable('string') // Some('string')
isSome(option) // true

isNone

If option is None, returns true.

isNone<T>(option: Option<T>): boolean

const option = fromNullable(null) // None
isNone(option) // true

flatMap

If option is Some, returns a result of fn, otherwise returns None. Function fn must have a return type of Option.

flatMap<T, R>(fn: (value: T) => Option<R>, option: Option<T>): Option<R>

pipe(
  fromNullable('string'), // Some('string')
  flatMap(_ => Some(1)), // Some(1)
  getWithDefault(0), // 1
)

pipe(
  fromNullable(null), // None
  flatMap(_ => Some(1)), // None
  getWithDefault(0), // 0
)

mapNullable

If a result of fn is null or undefined returns None.

mapNullable<T, R>(fn: (value: T) => R, option: Option<T>): Option<R>

pipe(
  fromNullable(null), // None
  mapNullable(_ => 1), // Some(1)
  getWithDefault(0), // 1
)

map

If option is Some, returns Some, otherwise returns None.

map<T, R>(fn: (value: T) => R, option: Option<T>): Option<R>

pipe(
  fromNullable(1), // Some(1)
  map(n => n * 3), // Some(3)
  getWithDefault(0), // 3
)

pipe(
  fromNullable(null), // None
  map(_ => 1), // None
  getWithDefault(0), // 0
)

mapWithDefault

If option is Some, returns a result of fn, otherwise returns defaultValue wrapped in Some.

mapWithDefault<T, R>(defaultValue: R, fn: (value: T) => R, option: Option<T>): Option<R>

pipe(
  fromNullable(null), // None
  mapWithDefault(0, _ => 1), // Some(0)
  getExn, // 0
)

const mapWithDefaultZero = mapWithDefault(0)

pipe(
  fromNullable(null), // None
  mapWithDefaultZero(_ => 1), // Some(0)
  getExn, // 0
)

getExn

If option is Some, returns value wrapped in Some, otherwise raises an error.

getExn<T>(option: Option<T>): T | never

pipe(
  fromNullable('string'), // Some('string')
  flatMap(_ => None), // None
  getExn, // raises an error
)

getWithDefault

If option is Some, returns value wrapped in Some, otherwise returns defaultValue.

getWithDefault<T>(defaultValue: T, option: Option<T>): T

pipe(
  fromNullable(null), // None
  getWithDefault(1), // 1
)

match

If option is Some, returns a result of someFn, otherwise returns a result of noneFn.

match<T, R>(someFn: (value: T) => R, noneFn: () => R, option: Option<T>): R

pipe(
  fromNullable(2), // Some(2)
  match(n => n * 10, () => 0), // 20
)

const multiplyByTenIfSome = match<number, number>(n => n * 2)

pipe(
  fromNullable(2), // Some(2)
  multiplyByTenIfSome(() => 0), // 20
)

const returnZeroIfNone = <T>(fn: (str: T) => number) =>
  match<T, number>(fn, () => 0)

pipe(
  fromNullable(null), // None
  returnZeroIfNone(n => n * 10), // 0
)

toNullable

If option is Some, returns value, otherwise returns null.

toNullable<T>(option: Option<T>): T | null

pipe(
  fromNullable('string'), // Some('string')
  flatMap(_ => None), // None
  toNullable, // null
)

toUndefined

If option is Some, returns value, otherwise returns undefined.

toUndefined<T>(option: Option<T>): T | undefined

pipe(
  fromNullable('string'), // Some('string')
  flatMap(_ => None), // None
  toUndefined, // undefined
)

List

head

If list is empty or the first value is undefined or null, returns None, otherwise returns the first element wrapped in Some.

head<T>(list: T[]): Option<T>

pipe(
  head([1, 2, 3]), // Some(1)
  getWithDefault(0), // 1
)

tail

If list is empty, returns None, otherwise returns everything except the first element of the list.

tail<T>(list: T[]): Option<T[]>

pipe(
  tail([1, 2, 3]), // Some([2, 3])
  flatMap(list => get(2, list)), // None
  // or flatMap(get(2)), all functions are curried
  getWithDefault(0), // 0
)

get

If index is larger than a list length, returns None, otherwise returns the nth element in the list wrapped in Some.

get<T>(index: number, list: T[]): Option<T>

pipe(
  get(1, [1, 2, 3]), // Some(2)
  map(value => value * 2), // Some(4)
  getExn, // 4
)

const getThirdElement = get(2)

pipe(
  getThirdElement([1, 3, 6]), // Some(6)
  map(value => value * 2), // Some(12)
  getExn, // 12
)

getBy

If no element satisfies predicate, returns None, otherwise returns the first value wrapped in Some that satisfies the predicate function.

getBy<T>(predicate: (value: T, index: number) => boolean, list: T[]): Option<T>

pipe(
  getBy(str => str.length === 2, ['a', 'ab', 'bc']), // Some('ab')
  map(str => `${str}cde`), // Some('abcde')
  getWithDefault('xyz'), // abcde
)

const equalsTwo = getBy(value => value === 2)

pipe(
  equalsTwo([0, 2, 4]), // Some(2)
  map(n => n * 10), // Some(20)
  getWithDefault(0), // 20
)

pipe(
  equalsTwo([0, 4, 8]), // None
  map(n => n * 10), // None
  getWithDefault(0), // 0
)

take

If list has fewer than n elements, returns None, otherwise returns a new array with the first n elements from list.

take<T>(n: number, list: T[]): Option<T[]>

pipe(
  take(2, [1, 2, 3]), // Some([1, 2])
  flatMap(list => getBy(value => value % 2 === 0, list)), // Some(2)
  // or flatMap(getBy(value => value % 2 === 0)), all functions are curried
  getWithDefault(0), // 2
)

const takeThreeElements = take(3)

pipe(
  takeThreeElements([0, 2, 4, 6]), // Some([0, 2, 4])
  getWithDefault([]), // [0, 2, 4]
)

pipe(
  takeThreeElements([0, 2]), // None
  getWithDefault([]), // []
)

drop

If list has fewer than n elements, returns None, otherwise returns a list obtained by dropping the first n elements.

drop<T>(n: number, list: T[]): Option<T[]>

pipe(
  drop(1, [1, 2, 3]), // Some([2, 3])
  flatMap(head), // Some(2)
  getWithDefault(0), // 2
)

const dropThreeElements = drop(3)

pipe(
  dropThreeElements([]), // None
  flatMap(head), // None
  getWithDefault(0), // 0
)

pipe(
  dropThreeElements([1, 2, 3, 4, 5, 6]), // Some([4, 5, 6])
  flatMap(tail), // Some([5, 6])
  flatMap(head), // Some(5)
  getWithDefault(0), // 5
)

splitAt

If index is larger than a list length, returns None, otherwise split a list at position index.

splitAt<T>(index: number, list: T[]): Option<[T[], T[]]>

pipe(
  splitAt(2, [1, 2, 3, 4]), // Some([[1, 2], [3, 4]])
  flatMap(head), // Some([1, 2])
  flatMap(list => getBy(value => value % 2 === 0, list)), // Some(2)
  // or flatMap(getBy(value => value % 2 === 0)), all functions are curried
  getExn, // 2
)

Result

type Result<A, B> = Ok<A> | Error<B>

fromNullable

If value is null or undefined, returns a value wrapped in Error, otherwise returns a value wrapped in Ok.

fromNullable<A, B>(error: B, value: A | null | undefined): Result<A, B>

fromNullable('error', null) // Error('error')
fromNullable('error', 'string') // Ok('string')

const fromNullableWithError = fromNullable('error')

fromNullableWithError(null) // Error('error')
fromNullableWithError('string') // Ok('string')

fromFalsy

If value is falsy, returns a value wrapped in Error, otherwise returns a value wrapped in Ok.

fromFalsy<A, B>(error: B, value: A | null | undefined): Result<A, B>

fromFalsy('error', null) // Error('error')
fromFalsy('error', '') // Error('error')
fromFalsy('error', 0) // Error('error')
fromFalsy('error', 'string') // Ok('string')
fromFalsy('error', 1) // Ok(1)

const fromFalsyWithError = fromFalsy('error')

fromFalsyWithError(0) // Error('error')
fromFalsyWithError(1) // Ok(1)

fromPredicate

If predicate returns false, returns a value wrapped in Error, otherwise returns a value wrapped in Ok.

fromPredicate<A, B>(predicate: (value: A) => boolean, error: B, value: A): Result<A, B>

fromPredicate(str => str.length > 10, 'error', 'string') // Error('error')
fromPredicate(obj => obj.prop === 'string', 'error', { prop: 'string' }) // Ok({ props: 'string' })

const takeEvenNumber = fromPredicate<number, string>(
  x => x % 2 === 0,
  'error',
)

takeEvenNumber(4) // Ok(4)
takeEvenNumber(1) // Error('error')

isOk

If result is Ok, returns true.

isOk<A, B>(result: Result<A, B>): boolean

const result = fromNullable('error', 'string') // Ok('string')
isOk(result) // true

isError

If result is Error, returns true.

isError<A, B>(result: Result<A, B>): boolean

const result = fromNullable('error', null) // Error('error')
isError(result) // true

flatMap

If result is Ok, returns the result of fn, otherwise returns result unchanged. Function fn must have a return type of Result.

flatMap<A, B, R>(fn: (value: A) => Result<R, B>, result: Result<A, B>): Result<R, B>

pipe(
  fromNullable('error', null), // Error('error')
  flatMap(_ => Ok(1)), // Error('error')
  getWithDefault(0), // 0
)

pipe(
  fromNullable('error', 'string'), // Ok('string')
  flatMap(_ => Ok(1)), // Ok(1)
  getWithDefault(0), // 1
)

map

If result is Ok, returns the result of fn, otherwise returns result unchanged. Function fn takes a value of the same type as value.

map<A, B, R>(fn: (value: A) => R, result: Result<A, B>): Result<R, B>

pipe(
  fromNullable('error', 1), // Ok(1)
  map(n => n * 3), // Ok(3)
  getWithDefault(0), // 3
)

pipe(
  fromNullable('error', null), // Error('error')
  map(n => n * 3), // Error('error')
  getWithDefault(0), // 0
)

mapWithDefault

If result is Ok, returns a result of fn, otherwise returns defaultValue wrapped in Ok.

mapWithDefault<A, B, R>(defaultValue: R, fn: (value: A) => R, result: Result<A, B>): Result<R, B>

pipe(
  fromNullable('error', null), // Error('error')
  mapWithDefault(0, _ => 1), // Ok(0)
  getExn, // 0
)

const fromNullableWithError = fromNullable('error')
const mapWithDefaultZero = mapWithDefault(0)

pipe(
  fromNullableWithError(null), // Error('error')
  mapWithDefaultZero(_ => 1), // Ok(0)
  getExn, // 0
)

pipe(
  fromNullableWithError(1), // Ok(1)
  mapWithDefaultZero(n => n * 10), // Ok(10)
  getExn, // 10
)

getExn

If result is Ok, returns value wrapped in Ok, otherwise raises an error.

getExn<A, B>(option: Result<A, B>): A | never

pipe(
  fromNullable('error', null), // Error('error')
  getExn, // raises an error
)

getWithDefault

If result is Ok, returns value wrapped in Ok, otherwise returns defaultValue.

getWithDefault<A, B>(defaultValue: A, result: Result<A, B>): A

pipe(
  fromNullable('error', null), // Error('error')
  getWithDefault(1), // 1
)

match

If result is Ok, returns a result of okFn, otherwise returns a result of errorFn.

match<A, B, R>(okFn: (okValue: A) => R, errorFn: (errorValue: B) => R, result: Result<A, B>): R

pipe(
  fromNullable('error', 2), // Ok(2)
  match(n => n * 10, () => 0), // 20
)

const fromNullableWithError = fromNullable('error')
const matchWithDefaultOk = match<string, string>(str => `${str}!`)
const matchWithDefaultError = <T>(fn: (str: T) => string) =>
  match<T, string, string>(fn, str => `${str} x2`)

pipe(
  fromNullableWithError('string'), // Ok('string')
  matchWithDefaultError(str => `${str}!`), // string!
)

 pipe(
  fromNullableWithError(null), // Error('error')
  matchWithDefaultError(str => `${str}!`), // error x2
)