Solution to CodeFights `secretArchivesLock` challenge

secretArchivesLock.js

const secretArchivesLock = (lock, actions) =>
  optimizeActions([...actions]).reduce((lock, direction) => move(lock, direction), lock)

const move = (lock, direction) => {
    return {
      'L': moveLeft(lock),
      'R': moveRight(lock),
      'U': moveUp(lock),
      'D': moveDown(lock)
    }[direction] || lock
}

const optimizeActions = actions => removeConsecutiveDuplicates(actions)

const moveLeft = lock =>
  lock.map(row => row.replace(/\./g, '').padEnd(lock[0].length, '.'))

const moveRight = lock =>
  lock.map(row => row.replace(/\./g, '').padStart(lock[0].length, '.'))

const moveUp = lock => transpose(moveLeft(transpose(lock)))

const moveDown = lock => transpose(moveRight(transpose(lock)))

const transpose = lock => {
  const columnRange = Array(lock[0].length).fill()
  return columnRange.map((_, col) => lock.map(row => row.charAt(col)).join(''))
}

const removeConsecutiveDuplicates = actions => {
  return actions
    .map((action, i) => (action === actions[i-1]) ? NULL : action)
    .filter(action => !NULL)
}