lowdash

lowdash is a functional JavaScript library including compose, pipe, curry, transduce, identity, trace, Functor, Monad, Applicative

Examples

1const {compose, curry, pipe, identity, trace, transduce, Functor, Monad, Applicative} = require('lowdash')
2
3// curry
4
5const match = curry(function(what, str) {
6  return str.match(what)
7})
8
9const replace = curry(function(what, replacement, str) {
10  return str.replace(what, replacement)
11})
12
13const filter = curry(function(f, ary) {
14  return ary.filter(f)
15})
16
17const map = curry(function(f, ary) {
18  return ary.map(f)
19})
20
21match(/\s+/g)('hello world')
22//=> [ ' ' ]
23
24const hasSpaces = match(/\s+/g)
25// function(x) { return x.match(/\s+/g) }
26
27hasSpaces('hello world')
28//=> [ ' ' ]
29
30hasSpaces('spaceless')
31//=> null
32
33filter(hasSpaces, ['the_spelling', 'te amo'])
34//=> ['te amo']
35
36const findSpaces = filter(hasSpaces)
37// function(xs) { return xs.filter(function(x) { return x.match(/\s+/g) }) }
38
39findSpaces(['the_spelling', 'te amo'])
40//=> ['te amo']
41
42const noVowels = replace(/[aeiou]/ig)
43// function(replacement, x) { return x.replace(/[aeiou]/ig, replacement) }
44
45const censored = noVowels('*')
46// function(x) { return x.replace(/[aeiou]/ig, '*') }
47
48censored('Chocolate Cake')
49//=> 'Ch*c*l*t* C*k*'
50
51// compose
52
53const toUpperCase = function(x) { return x.toUpperCase() }
54const exclaim = function(x) { return x + '!' }
55const shout = compose(exclaim, toUpperCase)
56
57shout('angry or hungry')
58//=> 'ANGRY OR HUNGRY!'
59
60const reduce = curry(function(f, ary) {
61  return ary.reduce(f)
62})
63
64const head = function(x) { return x[0] }
65const reverse = reduce(function(acc, x) { return [x].concat(acc) })
66const last = compose(head, reverse)
67
68last(['jump', 'house', 'upper'])
69//=> 'upper'
70
71const lastUpper = compose(toUpperCase, head, reverse)
72
73lastUpper(['jump', 'house', 'upper'])
74//=> 'UPPER'
75
76// pipe
77
78const shoutPipe = pipe(exclaim, toUpperCase)
79
80console.log( shoutPipe('angry or hungry') )
81//=> 'ANGRY OR HUNGRY!'
82
83// pointfree
84
85const toLowerCase = function(x) { return x.toLowerCase() }
86const snakeCase = compose(replace(/\s+/ig, '_'), toLowerCase)
87
88snakeCase('Snake Case')
89//=> 'snake_case'
90
91const split = curry(function(separator, str) {
92  return str.split(separator)
93})
94const join = curry(function(separator, ary) {
95  return ary.join(separator)
96})
97const initials = compose(join('. '), map(compose(toUpperCase, head)), split(' '))
98
99initials('json jackson jason')
100//=> 'J. J. J'
101
102// transduce =  transform + reduce
103
104const t = curry(transduce)(
105  compose(map(x => x +1), filter(x => x > 2)),
106  (result, x) => result.concat(x),
107  []
108)
109console.log(t([1,2,3,4]))
110//=> [4, 5]
111
112// debug
113
114const dasherize = compose(join('-'), map(toLowerCase), trace('after split'),
115  split(' '), replace(/\s{2,}/ig, ' '))
116
117dasherize('The world is a  vampire')
118//=> after split [ 'The', 'world', 'is', 'a', 'vampire' ]
119//=> 'the-world-is-a-vampire'
120
121// Functor, Monad, Applicative
122
123const increment = x => x + 1
124const add2 = compose(increment, increment)
125const add4 = compose(add2, add2)
126
127console.log(
128  Functor.of(1)
129    .map(increment)
130    .map(add4)
131)
132
133const incrementMonad = compose(Monad.of, increment)
134const add2Monad = x => Monad.of(x).bind(incrementMonad).bind(incrementMonad)
135const add4Monad = x => Monad.of(x).bind(add2Monad).bind(add2Monad)
136
137console.log(
138  Monad.of(1)
139    .bind(incrementMonad)
140    .bind(add4Monad)
141    .join()
142)
143
144const add = a => b => a + b
145const add2 = add(2)
146
147let left = Applicative.of(add2).ap(Applicative.of(3))
148let right = Applicative.of(3).map(add2)
149
150console.log(
151  left.val === right.val // 5
152)
153

Installation

npm install --save lowdash

Usage

You can import from lowdash:

1import {compose, curry, pipe, identity, trace, transduce, Functor, Monad, Applicative} from 'lowdash';
2// or
3const {compose, curry, pipe, identity, trace, transduce, Functor, Monad, Applicative} = require('lowdash');