クイックソートです

quicksort.js

function quicksort(arr){
  if(arr.length < 2) return arr
  var pivot = arr[Math.random() * arr.length >> 0]
  var low = [], high = []
  for(var i = 0; i < arr.length; i += 1){
    if(arr[i] <= pivot) low.push(arr[i])
    else high.push(arr[i])
  }
  if([low.length, high.length].indexOf(0) !== -1){
    var ret = low.concat(high)
    for(var i = 1; i < ret.length; i += 1) if(ret[i] !== ret[0]) return quicksort(ret)
    return ret
  }
  return quicksort(low).concat(quicksort(high))
};