array permutations

permutations.js

function ipslice(arr, l) {
  var arr = arr.slice()
  arr.splice(l, 1)
  return arr
}

var permutations = function(arr) {
  if(!arr.length) return [arr]
  var perm = []
  for(var i in arr) {
    perms = permutations(ipslice(arr, i))
    for(var j in perms)
      perm.push([arr[i]].concat(perms[j]))
  }
  return perm
}