@hs/transmute

kind of like lodash but works with Immutable

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@hs/transmute

transmute on npm Travis branch

@hs/transmute provides convenient, composable functions for transforming Arrays, Immutable.js data structures, and Objects.

Getting started

Transmute can be installed with npm or yarn.

npm install @hs/transmute
import { Map } from 'immutable';
import pick from 'transmute/pick';

// returns Map { one => 1, three => 3 }
pick(['one', 'three'], Map({one: 1, two: 2, three: 3}));

Most of the function (with the execption of some of the composition functions like compose and pipe) are curried to facilitate partial application. You might also notice that the argument order is the oposite of you'll find in other utility libraries. Passing the options and then the subject makes currying much more useful.

import { Map } from 'immutable';
import pick from 'transmute/pick';

const pickTwo = pick(['two']);
// returns Map { two => 2 }
pickTwo(Map({one: 1, two: 2, three: 3}));

transmute also includes some helpful composition functions which are powerful when we combine them with curried transforms.

import { Map, Set } from 'immutable';
import * as t from 'transmute';

const setOfKeysWithEvenValues = t.pipe(
  t.filter((val) => val % 2 === 0),
  t.keySeq,
  Set
);

// returns Set { 'two', 'four' }
takeEvenValues(Map({one: 1, two: 2, three: 3, four: 4}));

API

always

src/always.js:13-15

Creates a function that always returns returnValue.

Parameters

  • returnValue T

Examples

const alwaysBlue = always('blue');
alwaysBlue() === 'blue';

Returns T

bind

src/bind.js:18-18

Sets a function's this context. Similar to Function.prototype.bind.

Parameters

Examples

bind(console.log, console);

Returns Function

both

src/both.js:29-29

Returns true if the results of arg applied to both condition1 and condition2 are truthy.

Parameters

Examples

const isOneToTen = both(
  n => n >= 1,
  n => n <= 10
);

isOneToTen(3) === true;
isOneToTen(11) === false;

Returns boolean

clear

src/clear.js:14-14

Returns an empty copy of subject.

Parameters

Examples

clear([1, 2, 3]) // returns []
clear(List.of(1, 2, 3)) // returns List []
clear({one: 1, two: 2, three: 3}) // returns {}

Returns (Array | Collection | Object)

compose

src/compose.js:28-31

Create a function that runs operations from right-to-left.

compose is not curried.

Parameters

Examples

const doubleAndTakeEvens = pipe(
  filter(n => n % 2 === 0),
  map(n => n * 2)
);

doubleAndTakeEvens(List.of(1, 2, 3))
// returns List [ 2, 4, 6 ]

Returns Function

concat

src/concat.js:18-18

Joins two Iterable.Indexed objects together.

Examples

// Arrays
concat(List([3]), List([1, 2])); // Returns List [ 1, 2, 3 ]
const addY = concat(List(['y']);
addY(List(['x'])); // Returns List [ 'x', 'y' ]

Returns Iterable with the concatenated value. Does not support keyed Iterable subjects.

count

src/count.js:12-12

Returns the number of values in subject.

Parameters

  • subject TYPE

Examples

count(List.of(1, 2, 3)) === 3;

Returns number

curry

src/curry.js:14-16

Creates a curried version of operation.

Parameters

Examples

const toArray = curry((a, b, c) => [a, b, c]);
const toArrayWith1 = toArray(1);
toArrayWith1(2, 3) === [1, 2, 3];

Returns Function

curryN

src/curryN.js:41-41

Create a curried version of operation that expects arity arguments. Inception-ally, curryN is also curried.

Parameters

  • arity number number of arguments the curried function accepts
  • operation Function to curry

Examples

const toArray = curryN(3)((...args) => [...args]);
toArray(1, 2, 3) === [1, 2, 3];

Returns Function

debounce

src/debounce.js:42-42

operation is called interval milliseconds after the most recent call.

Parameters

Returns any the most recent result of operation

debounceImmediate

src/debounceImmediate.js:52-52

operation is called immediately and then interval milliseconds after the most recent call.

Parameters

Returns any the most recent result of operation

difference

src/difference.js:24-24

Take the difference between one iterable and another iterable. Only the elements present in just subject will remain.

Parameters

  • toRemove Iterable
  • subject Iterable

Examples

const removeOne = difference(Set.of(1));

removeOne(Set.of(1, 2, 3)) // returns Set { 2, 3 }

Returns Iterable

either

src/either.js:26-26

Returns true if the results of arg applied to either first or second are truthy.

Parameters

Examples

const oneOrTwo = either(
  n => n === 1,
  n => n === 2
);

oneOrTwo(1) === true;
oneOrTwo(2) === true;
oneOrTwo(3) === false;

Returns boolean

entrySeq

src/entrySeq.js:13-13

Get a Seq of the entries (i.e. [key, value] tuples) in subject.

Parameters

Examples

entrySeq(Map({one: 1, two: 2}))
// returns Seq [ ['one', 1], ['two', 2] ]

Returns Seq

every

src/every.js:17-17

Returns true if all items in subject match predicate.

Parameters

  • predicate Function returns true if item is a match.
  • subject Iterable

Examples

const alwaysBlue = every(v => v === 'blue');

alwaysBlue(List.of('blue', 'blue')) === true;
alwaysBlue(List.of('red', 'blue')) === false;

Returns bool

filter

src/filter.js:25-25

Remove values for which predicate returns false.

Parameters

  • predicate Function returns true if a value should be included.
  • subject Iterable to filter.

Examples

// returns List [ 2 ]
filter(
  (n) => n % 2 === 0,
  List.of(1, 2, 3)
);

Records have a fixed set of keys, so filter returns a Map instead.

// returns Map { 'one' => 1, 'three' => 3 }
filter(
  (n) => n % 2 === 0,
  ThreeRecord({one: 1, two: 2, three: 3})
);

Returns Iterable without values that didn't match predicate.

filterNot

src/filterNot.js:22-22

Remove values for which predicate returns true.

Parameters

  • predicate Function returns true if a value should be excluded.
  • subject Iterable to filter.

Examples

// returns List [ 1, 3 ]
filterNot(
  (n) => n % 2 === 0,
  List.of(1, 2, 3)
);

Returns Iterable without values that matched predicate.

flatten

src/flatten.js:13-15

Flattens an iterable as deeply as possible.

Parameters

  • subject Iterable

Examples

// return List [ 1, 2, 3, 4, 5, 6 ]
flatten(List.of(List.of(1, List.of(2, 3)), List.of(4, 5, 6)));

Returns Iterable

flattenN

src/flattenN.js:16-16

Flattens an iterable depth levels.

Parameters

  • depth number
  • subject Iterable

Examples

// return List [ 1, List [ 2, 3 ], 4, 5, 6 ]
flattenN(1, List.of(List.of(1, List.of(2, 3)), List.of(4, 5, 6)));

Returns Iterable

forEach

src/forEach.js:22-22

Executes effect for each value in subject, then returns subject.

Parameters

Examples

forEach(
  v => console.log(v),
  Map({ one: 1, two: 2, three: 3 })
);

// prints...
// 1
// 2
// 3

Returns TYPE

fromJS

src/fromJS.js:15-17

A version of Immutable.fromJS that drops all but the first argument for compatibility with other transmute functions like map.

Parameters

  • json any

Examples

fromJS({items: [1, 2, 3]})
// returns Map { items: List [ 1, 2, 3 ] }

Returns Iterable?

get

src/get.js:15-15

Retrieve the value at key from subject.

Parameters

  • key any to lookup in subject.
  • subject (Iterable | Object) in which to look up key.

Examples

// returns 1
get('one', Map({one: 1, two: 2, three: 3}))

Returns any the value at key.

getIn

src/getIn.js:23-23

Retrieve a keyPath from a nested Immutable or JS structure.

getIn short circuts when it encounters a null or undefined value.

Parameters

Examples

const getFirstName = getIn(['name', 'first']);
const user = UserRecord({
  name: Map({
    first: 'Test',
    last: 'Testerson',
  }),
});
getFirstName(user) === 'Test'

Returns any

has

src/has.js:17-17

Returns true if key exists in subject.

Parameters

Examples

const hasOne = has('one');

hasOne({one: 1}) === true;
hasOne(Map({two: 2})) === false;

Returns boolean

hasIn

src/hasIn.js:41-41

Returns true if keyPath is defined in a nested data structure.

hasIn short circuts and returns false when it encounters a null or undefined value.

Parameters

Examples

const hasFirstName = hasIn(['name', 'first']);
const user = UserRecord({
  name: Map({
    first: 'Test',
    last: 'Testerson',
  }),
});
hasFirstName(user) === true

Returns boolean

identity

src/identity.js:12-14

Returns it's first argument.

Parameters

  • thing any

Examples

identity('something') === 'something'

Returns any

ifElse

src/ifElse.js:31-31

Applies affirmative to subject if predicate(subject) is truthy. Otherwise applies negative to subject.

Parameters

Examples

const incrementAwayFromZero = ifElse(
  n => n >= 0,
  n => n + 1,
  n => n - 1
);

incrementAwayFromZero(1) === 2
incrementAwayFromZero(-1) === -2

Returns any

ifThen

src/ifThen.js:32-32

Applies affirmative to subject if predicate(subject) is truthy. Otherwise returns subject.

Parameters

Examples

import ifThen from 'transmute/ifThen';

const toJS = ifThen(
  subject => typeof subject.toJS === 'function',
  subject => subject.toJS
);

toJS(List.of(1, 2, 3)) //=> [1, 2, 3]
toJS([1, 2, 3]) //=> [1, 2, 3]

Returns any

indexBy

src/indexBy.js:27-27

Create a Map, or OrderedMap from subject with a key for each item returned by keyMapper.

Parameters

  • keyMapper Function generates keys for each item
  • subject Iterable to index

Examples

indexBy(get('id'), List.of({id: 123}, {id: 456}))
// returns Map { 123: {id: 123}, 456: {id: 456} }

Returns KeyedIterable

keySeq

src/keySeq.js:13-13

Get a Seq of the keys in subject.

Parameters

Examples

keySeq({one: 1, two: 2, three: 3})
// returns Seq [ 'one', 'two', 'three' ]

Returns Seq

map

src/map.js:18-18

Create a new Iterable by applying mapper to each item in subject.

Parameters

  • mapper Function applied to each item in subject.
  • subject Iterable the Iterable to map.

Examples

// returns List [ 2, 3, 4 ]
map(
  (val) => val + 1,
  List.of(1, 2, 3)
);

Returns Iterable with each value of subject updated with mapper.

reduce

src/reduce.js:21-21

Transform the contents of subject to into by applying operation to each item.

Parameters

  • into any
  • operation Function
  • subject Iterable [description]

Examples

reduce(
  List(),
  (acc, val) => acc.push(val),
  Map({ one: 1, two: 2, three: 3 })
);
// returns List [ 1, 2, 3 ]

Returns Iterable

set

src/set.js:16-16

Returns a copy of subject with key set to value.

Parameters

  • key any
  • value any
  • subject (Array | Iterable | Object)

Examples

set('one', 2, {one: 1});
// returns {one: 2}

Returns (Array | Iterable | Object)

some

src/some.js:17-17

Returns true if any items in subject match predicate.

Parameters

  • predicate Function returns true if item is a match.
  • subject Iterable

Examples

const anyBlue = some(v => v === 'blue');

anyBlue(List.of('blue', 'red')) === true;
anyBlue(List.of('red', 'red')) === true;

Returns bool

sortBy

src/sortBy.js:25-25

Sort subject according to the value returned by getSortValue.

Parameters

  • getSortValue Function returns a value to sort on for each item in subject.
  • subject (Array | Iterable | Object) the thing to sort.

Examples

// returns List [ 2, 1, 3 ]
sortBy(
  (n) => n % 2,
  List.of(1, 2, 3)
);
// returns OrderedMap { "one" => 1, "two" => 2, "three" => 3 }
sortBy(
  (n) => n % 2,
  Map({three: 3, one: 1, two: 2})
);

Returns Iterable an ordered version of subject (e.g. sorting a Map returns an OrderedMap).

valueSeq

src/valueSeq.js:13-13

Get a Seq of the values in subject.

Parameters

Examples

valueSeq(Map({ one: 1, two: 2, three: 3 }))
// returns Seq [ 1, 2, 3 ]

Returns Seq

isArray

src/isArray.js:9-11

Returns true if value is an Array.

Parameters

  • value any

Returns boolean

isEmpty

src/isEmpty.js:11-16

Returns true if value is "empty". If given null, undefined, isEmpty will return true.

Parameters

  • value any

Returns boolean

isFunction

src/isFunction.js:9-11

Returns true if value is a Function.

Parameters

  • value any

Returns boolean

isInstanceOf

src/isInstanceOf.js:14-14

Returns true if value is an instance of Constructor.

Parameters

Returns boolean

isNull

src/isNull.js:9-11

Returns true if subject is null.

Parameters

  • subject any

Returns boolean

isNumber

src/isNumber.js:9-11

Returns true if subject is a JavaScript Number and not NaN.

Parameters

  • value any

Returns boolean

isObject

src/isObject.js:9-11

Returns true if value is an Object.

Parameters

  • value any

Returns boolean

isRecord

src/isRecord.js:10-14

Returns true if subject is an instance of a Record.

Parameters

  • subject any

Returns boolean

isString

src/isString.js:9-11

Returns true if value is a String.

Parameters

  • value any

Returns boolean

isUndefined

src/isUndefined.js:9-11

Returns true if subject is undefined.

Parameters

  • subject any

Returns boolean

mapKeys

src/mapKeys.js:37-37

Like map but transforms an Iterable's keys rather than its values.

Parameters

  • keyMapper Function returns a new key
  • subject KeyedIterable

Examples

Can be useful for converting keys of API results to a common type.

import { mapKeys, toString } from 'transmute';
const stringifyKeys = mapKeys(toString);
const m = Map.of(123, Map(), 456, Map(), 789, Map());
stringifyKeys(m).equals(Map.of('123', Map(), '456', Map(), '789', Map()));

Returns KeyedIterable

match

src/match.js:25-25

Returns true if the key => value pairs in pattern match the correspoding key => value pairs in subject.

Parameters

Examples

const hasOneAndThree = match({one: 1, three: 3});
hasOneAndThree(Map({one: 1, two: 2, three: 3})) === true;

Returns boolean

memoize

src/memoize.js:54-61

Memoizer that uses a Map to allow for arbitrarily many/complex keys.

Parameters

  • operation Function to memoize.
  • hashFunction Function that generates the cache key. (optional, default defaultHashFunction)

Examples

const sum = memoize((list) => {
  return list.reduce((total, n) => total + n, 0);
});
// does work and returns 15
sum(List.of(1, 2, 3, 4, 5))
// returns 15 but does no work
sum(List.of(1, 2, 3, 4, 5))

We can use the hashFunction param to customize the key used in the cache.

const sum = memoize(
  (list) => list.reduce((total, n) => total + n, 0),
  (list) => return list.join('-')
);

It's also possible to inspect the state of an instance by reading the .cache property.

const sum = memoize(...);
Map.isMap(sum.cache) === true;

Returns Function memoized version of operation.

memoizeLast

src/memoizeLast.js:21-44

Like memoize, but only caches the most recent value. It's often useful for caching expensive calculations in react components.

Parameters

Examples

const sum = memoizeLast((...nums) => nums.reduce((acc, n) => acc + n));
sum(List.of(1, 2, 3))
//> does work, returns 6
sum(List.of(1, 2, 3))
//> takes cached value, returns 6
sum(List.of(4, 5, 6))
//> does work, returns 15
sum(List.of(1, 2, 3))
//> does work again, returns 6

Returns Function

merge

src/merge.js:23-23

Takes each entry of updates and sets it on subject.

Parameters

  • updates Iterable key-value pairs to merge in subject.
  • subject Iterable the thing to update.

Examples

// returns Map { "one" => 3, "two" => 2, "three" => 1}
merge(
  Map({one: 1, two: 2, three: 3}),
  Map({one: 3, three: 1})
);

Returns Iterable with each key-value of updates merged into subject.

omit

src/omit.js:24-24

Drop specified keys from a KeyedIterable (e.g. a Map or OrderedMap).

Parameters

  • keys Array<any> to remove.
  • subject KeyedIterable from which to remove keys.

Examples

// returns Map { "two" => 2 }
omit(
  ['one', 'three'],
  Map({one: 1, two: 2, three: 3})
);

Returns KeyedIterable without keys.

once

src/once.js:7-17

fn is only run one time.

Parameters

Returns any the result of the first time fn was called

partial

src/partial.js:17-20

Like fn.bind(), but without the option to pass context.

partial is not curried.

const add = (a, b, c) => a + b + c; const add11 = partial(add, 5, 6); add11(7); // returns 18

Parameters

  • operation Function the function to bind.
  • first any the first argument to pass to operation
  • args ...any

Returns Function

partialApply

src/partialApply.js:34-34

Like transmute/partial, but takes an Array or Iterable of arguments to pass to operation rather than a dynamic number of args. Unlike partial it is curried.

partial : partialApply :: Function.prototype.call : Function.prototype.apply

Parameters

  • operation Function the function to bind.
  • args (Array | Iterable) ordered collection of arguments to bind to fn.

Examples

const add = (a, b, c) => a + b + c;
const add11 = partialApply(add, [5, 6]);
add11(7); // returns 18

Returns Function

pick

src/pick.js:24-24

Select specified keys from a KeyedIterable (e.g. a Map or OrderedMap).

Parameters

  • keys (Array | Iterable | Object) to select.
  • subject KeyedIterable from which to select keys.

Examples

// returns Map { "one" => 1, "three" => 3 }
pick(
  ['one', 'three'],
  Map({one: 1, two: 2, three: 3})
);

Returns KeyedIterable with just keys.

pipe

src/pipe.js:28-31

Create a function that runs operations from left-to-right.

pipe is not curried.

Parameters

Examples

const takeEvensAndDouble = pipe(
  filter(n => n % 2 === 0),
  map(n => n * 2)
);

takeEvensAndDouble(List.of(1, 2, 3))
// returns List [ 4 ]

Returns Function

pluck

src/pluck.js:20-20

Select key from each item in subject.

Parameters

  • key any
  • subject Iterable

Examples

const pluckName = pluck('name');
pluckName(userMap) === Map({123: 'Testing'});

Returns Iterable

setArity

src/setArity.js:18-18

Creates a function identical to operation but with length arity.

Parameters

Examples

const op = (...args) => args;
op.length === 0;

const twoArgOp = setArity(2, op);
twoArgOp.length === 2;

Returns Function

setIn

src/setIn.js:23-23

Set the value at keyPath in a nested structure.

Parameters

  • keyPath (Array<any> | Iterable<any>)
  • value any
  • subject (Array | Iterable | Object)

Examples

setIn(['one', 'two'], 3, {one: {two: 2}});
// returns {one: {two: 3}}

Unset keyPaths will be set based on the most recent type.

setIn(['one', 'two'], 3, {});
// returns {one: {two: 3}}

setIn(['one', 'two'], 3, Map());
// returns Map { one => Map { two => 3 } }

throttle

src/throttle.js:47-47

Ensures operation is only called once every interval milliseconds.

Parameters

Returns any the most recent result of operation

toJS

src/toJS.js:7-18

Converts an Iterable to a native JS structure.

Parameters

  • subject Iterable to convert.

Returns (Array | Object) native JS requivalent of subject.

toSeq

src/toSeq.js:11-15

Converts subject to a Seq if possible.

Parameters

Returns Seq

toString

src/toString.js:6-8

Returns the value converted to a string.

Parameters

  • value any

uniqueId

src/uniqueId.js:12-14

Returns a unique integer string appended to prefix.

Parameters

  • prefix string (optional, default '')

Examples

uniqueId('test-') === 'test-1';
uniqueId('other-') === 'other-2';
uniqueId('test-') === 'test-3';

update

src/update.js:23-23

Sets the value at key to the result of updater.

Parameters

Examples

const incrementCount = update('count', n => n + 1);
incrementCount({count: 1});
// returns {count: 2}

Returns (Array | Iterable | Object)

updateIn

src/updateIn.js:31-31

Apply updater to the value at keyPath.

Parameters

  • keyPath (Array<any> | Iterable<any>) the location where updater should be applied.
  • updater Function the tranformation to apply.
  • subject (Array | Iterable | Object) the thing to update.

Examples

const incrementUserCount = updateIn(['users', 'count'], n => n + 1);
incrementUserCount({users: {count: 1}});
// returns {users: {count: 2}}

Unset keyPaths will be set based on the most recent type.

const incrementUserCount = updateIn(['users', 'count'], (n = 0) => n + 1);
incrementUserCount({});
// returns {users: {count: 1}}

incrementUserCount(Map());
// returns Map { users => Map { count => 1 } }

Returns (Array | Iterable | Object)

where

src/where.js:25-25

Takes items in subject that match pattern.

Parameters

Examples

const users = Map({
  123: {id: '123', name: 'Jack'},
  456: {id: '456', name: 'Jill'},
});

where({name: 'Jack'}, users);
// returns Map { 123: {id: '123', name: 'Jack'} }

Returns Iterable

without

src/without.js:23-23

Removes values in unwanted from subject.

Parameters

  • unwanted Iterable
  • subject Iterable

Examples

const removeOne = without(Set.of(1));

removeOne(Set.of(1, 2, 3)) // returns Set { 2, 3 }

Returns Iterable

If you find any bugs or have a feature request, please open an issue on github!

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