permutation

permutate.js

const permutate = (n, choices = ['A', 'B', 'C', 'D']) => {
  const result = []

  const recursion = path => {
    if (path.length === n) {
      result.push(path.join(''))
      return
    }
    choices.forEach(c => { recursion([...path, c]) })
  }

  recursion([])
  return result
}