fjp

functional javascript playground

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Functional Javascript Playground
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Functional Programming was always a weird "why would you use this" way of coding as I've primarily been OOP. I set out to change my view on that and learn more about it and when to use it. These are some of the functions I collected/made along the way. They are all ES6/ESM, the parameter order for most lends itself to currying + composing. Still a little iffy on the Hindley-milner signatures so they may be slightly off.

This is very much a WIP

Functions

associate()

Sets the given property and value on the object. Returning a new object.

average()

Averages the given array values

A()

Calls the given function with the given value.

Fork()

Takes a joiner func, and two other funcs and a value. The value is given to both funcs and the results of each of these is given to the joiner func.

I()

Returns the given value.

K()

Takes two values and returns the given first.

OR()

Given two functions that take the same value, returns the first if the result is truthy, otherwise, the second.

T()

Calls the given function with the given value. (Reverse order of apply)

compact()

Removes falsey values from an array.

compose()

Performs right-to-left function composition.

concat()

Concatenates two String|Arrays together. Returns empty array if value arent of the same type or not String|Array.

concatN()

Concatenates N Arrays together.

curry()

Wraps the given function, if the number of provided args is sufficient, call the passed function fn. Otherwise, return a wrapped function fn that expects the rest of the arguments. If you want to curry a function that accepts a variable number of arguments (a variadic function), you can optionally pass the number of arguments to the second parameter arity.

difference()

Returns the difference between two arrays.

distinct()

Returns all of the distinct values of an array.

distinctN()

Returns all of the distinct values of the given arrays.

each()

Applies the given func to each element in the array.

every()

Determines if all element in an array satisfy the given test function

filter()

Filters the array using the given function.

find()

Finds the first element that satisfies the given test func.

flatten()

Flattens single nested array.

isArray()

Determines if the given value is an array.

isFunction()

Determines if the given value is a function.

isNumber()

Determines if the given value is a number.

isObject()

Determines if the given value is an object.

isString()

Determines if the given value is a string.

not()

Negates the given boolean-like value.

tap()

Calls the given function with the given value and returns the value.


associate()

Sets the given property and value on the object. Returning a new object.
Kind: global function
Signature: associate :: String k -> {} -> v -> {k: v}
Example
const obj = associate('c', { a: b }, d)  // { a: b, c: d }

average()

Averages the given array values
Kind: global function
Signature: average :: Number -> Number
Example
average([ 1, 2, 3 ]); // 2
average(1, 2, 3); // 2
average(); // 0

A()

Calls the given function with the given value.
Kind: global function
Signature: A :: (a -> b) -> a -> b
Aka: apply

Fork()

Takes a joiner func, and two other funcs and a value. The value is given to both funcs and the results of each of these is given to the joiner func.
Kind: global function
Signature: Fork :: (b -> c -> d) -> (a -> b) -> (a -> c) -> a -> d
Aka: join

I()

Returns the given value.
Kind: global function
Signature: I :: a -> a
Aka: identity

K()

Takes two values and returns the given first.
Kind: global function
Signature: K :: a -> b -> a
Aka: constant

OR()

Given two functions that take the same value, returns the first if the result is truthy, otherwise, the second.
Kind: global function
Signature: OR :: (a -> b) -> (a -> b) -> b
Aka: alternation

T()

Calls the given function with the given value. (Reverse order of apply)
Kind: global function
Signature: T :: a -> (a -> b) -> b
Aka: thrush, applyTo

compact()

Removes falsey values from an array.
Kind: global function
Signature: compact :: a -> a
Example
compact([ 0, 1, false, 2, '', 3, 'a', 'e' * 23, NaN, 's', 34 ]); // [ 1, 2, 3, 'a', 's', 34 ]
compact(null) // []

compose()

Performs right-to-left function composition.
Kind: global function
Signature: compose :: (m -> n), ..., (b -> c), (a -> b) -> a -> n
Example
const addOne = x => x + 1;
const timeTen = x => x * 10;
const addOneTimeTen = compose(timeTen, addOne);
const result = addOneTimeTen(9); // 100

concat()

Concatenates two String|Arrays together. Returns empty array if value arent of the same type or not String|Array.
Kind: global function
Signature: concat :: a -> b -> c
Example
concat('foo', 'bar') // foobar
concat([1, 2], [3, 4]) // [1, 2, 3, 4]

concatN()

Concatenates N Arrays together.
Kind: global function
Signature: concat :: a -> b -> ...n -> m
Example
concatN([1, 2], [3, 4], [5, 6]) // [1, 2, 3, 4, 5, 6]

curry()

Wraps the given function, if the number of provided args is sufficient, call the passed function fn. Otherwise, return a wrapped function fn that expects the rest of the arguments. If you want to curry a function that accepts a variable number of arguments (a variadic function), you can optionally pass the number of arguments to the second parameter arity.
Kind: global function
Signature: curry :: ((a, b, ..., n) -> m) -> a -> b -> ...n -> m
Example
const add = curry((x, y) => x + y);
const addFiveTo = add(5);
addFiveTo(10); // 15

difference()

Returns the difference between two arrays.
Kind: global function
Signature: difference :: a -> b -> c
Example
difference([ 1, 2, 3 ], [ 1, 2, 4 ]) // [3]
difference([], [ 1, 2, 4 ]) // [ 1, 2, 4 ]
difference([ 1, 2, 3 ], []) // [ 1, 2, 3 ]
difference([ 1, 2, 3 ], null) // [ 1, 2, 3 ]

distinct()

Returns all of the distinct values of an array.
Kind: global function
Signature: distinct :: a -> b
Example
distinct([ 1, 2, 2, 3, 4, 4, 5 ]) // [ 1, 2, 3, 4, 5 ]

distinctN()

Returns all of the distinct values of the given arrays.
Kind: global function
Signature: distinctN :: a -> b -> ...n -> m
Example
distinctN([ 1, 2 ], [ 2, 3, 4 ], [ 4, 5 ]) // [ 1, 2, 3, 4, 5 ]

each()

Applies the given func to each element in the array.
Kind: global function
Signature: each :: (a -> b) -> c -> undefined
Example
difference(log, [1, 2, 3])

every()

Determines if all element in an array satisfy the given test function
Kind: global function
Signature: every :: (a -> Bool) -> a -> Bool
Aka: all
Example
every(Boolean, [1, 2, 3, 4]) // true
every(Boolean, [1, 2, null, 4]) // false

filter()

Filters the array using the given function.
Kind: global function
Signature: filter :: (a -> Boolean) -> a -> a
Example
filter(x => x > 5, [1, 2, 3, 5, 6, 7]) // [6, 7]

find()

Finds the first element that satisfies the given test func.
Kind: global function
Signature: find :: (a -> Boolean) -> a -> a
Example
find(x => x.score === 5, [{score: 1}, {score: 2}, {score: 5}, {score: 6}, {score: 7}]) // {score: 5}

flatten()

Flattens single nested array.
Kind: global function
Signature: flatten :: a -> a
Example
flatten([[ 1, 2 ], [ 3, 4 ]];); // [ 1, 2, 3, 4 ]
flatten(null) // []

isArray()

Determines if the given value is an array.
Kind: global function
Signature: isArray :: a -> Boolean
Example
isArray([1, 2, 3])  // true
isArray({ a: 'b' })  // false

isFunction()

Determines if the given value is a function.
Kind: global function
Signature: isFunction :: a -> Boolean
Example
isFunction(() => {})  // true
isFunction([1, 2, 3])  // false

isNumber()

Determines if the given value is a number.
Kind: global function
Signature: isNumber :: a -> Boolean
Example
isNumber(42)  // true
isNumber(8e5)  // true
isNumber(0x2F)  // true
isNumber('foo bar')  // false

isObject()

Determines if the given value is an object.
Kind: global function
Signature: isObject :: a -> Boolean
Example
isObject({ a: 'b' })  // true
isObject([1, 2, 3])  // false

isString()

Determines if the given value is a string.
Kind: global function
Signature: isString :: a -> Boolean
Example
isString('foo bar')  // true
isString({ a: 'b' })  // false

not()

Negates the given boolean-like value.
Kind: global function
Signature: not :: Boolean -> Boolean
Example
not(true); // false
not(false); // true
not(2); // false

tap()

Calls the given function with the given value and returns the value.
Kind: global function
Signature: tap :: (a -> b) -> a -> a
Example
tap(console.log, 'foobar') // foobar

License

FJP is licensed under the MIT license.
Copyright © 2018 Bryan Kizer