Técnicas com curry e composição

curry.js

const map = transform => arr => {
  let transformed = []
  
  for(let i=0; i<=arr.length; i++) {
    transformed = [...transformed, transform(arr[i], i)]
  }
  
  return transformed
}

//------------------------

const double = map(n => n * 2)
const triple = map(n => n * 3)

double([1 2, 3, 4])
triple([1, 2, 3, 4])

//------------------------


const filter = predicate => arr => {
  let filtered = []
  
  for(let i=0; i<=arr.length; i++) {
    if(predicate(arr[i], i))
      filtered = [...filtered, arr[i]]
  }
  
  return filtered
}


//------------------------


let servers = [
  { name: 'server1', status: 'online' },
  { name: 'server2', status: 'offline' },
  { name: 'server3', status: 'online' },
  { name: 'server4', status: 'online' }
]

const getName = server => server.name

const getStatus = server => server.status

const isOnline = server => getStatus(server) === 'online'

const allOnline = filter(isOnline)

const pluckNames = map(getName)

const namesOfAllOnline = pluckNames(allOnline(servers))


// without curry using common map/filter

const allOnline2 = arr =>
  arr.filter(isOnline)

const pluckNames2 = arr =>
  arr.map(getName)

// extract common map/filter to curried versions

const map2 = transform => arr =>
  arr.map(transform)

const filter2 = predicate => arr =>
  arr.filter(predicate)