Functional Programming Fundamentals Code

01-composition-pipeline.js

'use strict'

const assert = require('assert')

function words (text) {
  return text.split(/\s+/)
}

function reverse (list) {
  return list.reverse()
}

function join (list) {
  return list.join(' ')
}

function pipeline (text) {
  return join(reverse(words(text)))
}

assert.strictEqual(
  pipeline('dog lazy the over jumps fox brown quick The'),
  'The quick brown fox jumps over the lazy dog'
)

02-composition-pipeline.js

'use strict'

const assert = require('assert')
const _ = require('lodash')

function words (text) {
  return text.split(/\s+/)
}

function reverse (list) {
  return list.reverse()
}

function join (list) {
  return list.join(' ')
}

// pipeline is a composition of other functions without mention of the arguments they will be applied to.
const pipeline = _.flow([words, reverse, join])

assert.strictEqual(
  pipeline('dog lazy the over jumps fox brown quick The'),
  'The quick brown fox jumps over the lazy dog'
)

03-currying.js

'use strict'

const assert = require('assert')
const map = require('lodash/fp/map')

function add (n1, n2) {
  return n1 + n2
}

assert.deepStrictEqual(
  map(n => add(10, n), [3, 4, 5]),
  [13, 14, 15]
)

04-currying-extract-fun.js

'use strict'

const assert = require('assert')
const map = require('lodash/fp/map')

function add (n1, n2) {
  return n1 + n2
}

function add10 (n) {
  return add(10, n)
}

assert.deepStrictEqual(
  map(add10, [3, 4, 5]),
  [13, 14, 15]
)

05-currying-add.js

'use strict'

const assert = require('assert')
const map = require('lodash/fp/map')
const curry = require('lodash').curry

const add = curry(function add (n1, n2) {
  return n1 + n2
})

assert.deepStrictEqual(
  map(add(10), [3, 4, 5]),
  [13, 14, 15]
)