Nodejs Utililty Methods Array Quick Sort

var arr = [2, 4, 6, 1, 3, 5, 8, 7];
Array.prototype.swap=function(a, b)
  var tmp=this[a];
  this[a]=this[b];
  this[b]=tmp;
function qsort(array, begin, end)
  if(end-1>begin) {
    var pivot=begin+Math.floor(Math.random()*(end-begin));
    pivot=partition(array, begin, end, pivot);
    qsort(array, begin, pivot);
    qsort(array, pivot+1, end);
    return  array;
function partition(array, begin, end, pivot)
  var piv=array[pivot];
  array.swap(pivot, end-1);
  var store=begin;
  var ix;
  for(ix=begin; ix<end-1; ++ix) {
    if(array[ix]<=piv) {
      array.swap(store, ix);
      ++store;
  array.swap(end-1, store);
  return store;
console.log(qsort(arr, 0, arr.length));

Array.prototype.qsort = function()
    if (this.length < 2)
        return this;
    var head = this.shift();
    return unpack(function(low, high) {
        return [].concat(low.qsort(), head, high.qsort());
    }, this.partition(function(_) { return _ < head; }));
};
...

Array.prototype.qsort = function(begin,end){
  function swap(array,a,b){
    var c = array[a];
    array[a] = array[b];
    array[b] = c;
  if(begin < end){
    var array = this;
    var index = begin;
...