Which of these functions are pure? https://medium.com/@robinpokorny/do-pure-functions-exist-in-javascript-b128ed5f0ed2

pure-functions.js

// A: Simple multiplication
function doubleA(n) {
  return n * 2
}

// B: With a variable
var two = 2
function doubleB(n) {
  return n * two
}

// C: With a helper function
function getTwo() {
  return 2
}
function doubleC(n) {
  return n * getTwo()
}

// D: Mapping an array
function doubleD(arr) {
  return arr.map(n => n * 2)
}