lowdash
lowdash is a functional JavaScript library including compose, pipe, curry, transduce, identity, trace, Functor, Monad, Applicative
Examples
const {compose, curry, pipe, identity, trace, transduce, Functor, Monad, Applicative} = require('lowdash')
// curry
const match = curry(function(what, str) {
return str.match(what)
})
const replace = curry(function(what, replacement, str) {
return str.replace(what, replacement)
})
const filter = curry(function(f, ary) {
return ary.filter(f)
})
const map = curry(function(f, ary) {
return ary.map(f)
})
match(/\s+/g)('hello world')
//=> [ ' ' ]
const hasSpaces = match(/\s+/g)
// function(x) { return x.match(/\s+/g) }
hasSpaces('hello world')
//=> [ ' ' ]
hasSpaces('spaceless')
//=> null
filter(hasSpaces, ['the_spelling', 'te amo'])
//=> ['te amo']
const findSpaces = filter(hasSpaces)
// function(xs) { return xs.filter(function(x) { return x.match(/\s+/g) }) }
findSpaces(['the_spelling', 'te amo'])
//=> ['te amo']
const noVowels = replace(/[aeiou]/ig)
// function(replacement, x) { return x.replace(/[aeiou]/ig, replacement) }
const censored = noVowels('*')
// function(x) { return x.replace(/[aeiou]/ig, '*') }
censored('Chocolate Cake')
//=> 'Ch*c*l*t* C*k*'
// compose
const toUpperCase = function(x) { return x.toUpperCase() }
const exclaim = function(x) { return x + '!' }
const shout = compose(exclaim, toUpperCase)
shout('angry or hungry')
//=> 'ANGRY OR HUNGRY!'
const reduce = curry(function(f, ary) {
return ary.reduce(f)
})
const head = function(x) { return x[0] }
const reverse = reduce(function(acc, x) { return [x].concat(acc) })
const last = compose(head, reverse)
last(['jump', 'house', 'upper'])
//=> 'upper'
const lastUpper = compose(toUpperCase, head, reverse)
lastUpper(['jump', 'house', 'upper'])
//=> 'UPPER'
// pipe
const shoutPipe = pipe(exclaim, toUpperCase)
console.log( shoutPipe('angry or hungry') )
//=> 'ANGRY OR HUNGRY!'
// pointfree
const toLowerCase = function(x) { return x.toLowerCase() }
const snakeCase = compose(replace(/\s+/ig, '_'), toLowerCase)
snakeCase('Snake Case')
//=> 'snake_case'
const split = curry(function(separator, str) {
return str.split(separator)
})
const join = curry(function(separator, ary) {
return ary.join(separator)
})
const initials = compose(join('. '), map(compose(toUpperCase, head)), split(' '))
initials('json jackson jason')
//=> 'J. J. J'
// transduce = transform + reduce
const t = curry(transduce)(
compose(map(x => x +1), filter(x => x > 2)),
(result, x) => result.concat(x),
[]
)
console.log(t([1,2,3,4]))
//=> [4, 5]
// debug
const dasherize = compose(join('-'), map(toLowerCase), trace('after split'),
split(' '), replace(/\s{2,}/ig, ' '))
dasherize('The world is a vampire')
//=> after split [ 'The', 'world', 'is', 'a', 'vampire' ]
//=> 'the-world-is-a-vampire'
// Functor, Monad, Applicative
const increment = x => x + 1
const add2 = compose(increment, increment)
const add4 = compose(add2, add2)
console.log(
Functor.of(1)
.map(increment)
.map(add4)
)
const incrementMonad = compose(Monad.of, increment)
const add2Monad = x => Monad.of(x).bind(incrementMonad).bind(incrementMonad)
const add4Monad = x => Monad.of(x).bind(add2Monad).bind(add2Monad)
console.log(
Monad.of(1)
.bind(incrementMonad)
.bind(add4Monad)
.join()
)
const add = a => b => a + b
const add2 = add(2)
let left = Applicative.of(add2).ap(Applicative.of(3))
let right = Applicative.of(3).map(add2)
console.log(
left.val === right.val // 5
)
Installation
npm install --save lowdash
Usage
You can import from lowdash:
import {compose, curry, pipe, identity, trace, transduce, Functor, Monad, Applicative} from 'lowdash';
// or
const {compose, curry, pipe, identity, trace, transduce, Functor, Monad, Applicative} = require('lowdash');
