All permutations for an array

permutate.js

// http://stackoverflow.com/a/22063440/2684055
function allPermutations (arr) {
  function permutate (res, value, key, arr) {
    if (arr.length <= 1) return [value]
    // Eliminate current value
    let result = arr.slice(0, key).concat(arr.slice(key + 1))
      .reduce(permutate, [])
      .map(perm => [value].concat(perm))
    return res.concat(result)
  }
  return arr.reduce(permutate, [])
}