Deconstructing a recursive map from Reddit user tarley_apologizer, with an alternative

recursiveMap.js

function map (array, mapFunction) {
  if (array.length === 0) return []
  return [
    mapFunction(array[0]),
    ...map(array.slice(1), mapFunction)
  ]
}
map([1, 2, 3], x => x * 2) // [2, 4, 6]


function map (array, mapFunction) {
  const mappedValues = []
  for (value of array) {
    mappedValues.push(mapFunction(value))
  }
  return mappedValues
}
map([1, 2, 3], x => x * 2) // [2, 4, 6]