#Quick sort in javascript

QuickSort.js

function Array(arr){
  this.arr = arr;
};
Array.prototype.doQuickSort = function(low, high) {
  if(low < high) {
    var pi = this.partition(low, high);
    this.doQuickSort(low, pi-1);
    this.doQuickSort(pi+1, high);
  }
  return this.arr;
}

Array.prototype.partition = function(low, high) {
  var pivot = this.arr[high];
  var i = low-1;
  for(var j = low; j<high-1; j++) {
    if(this.arr[j] < pivot) {
      i++;
      [this.arr[i],this.arr[j]] = [this.arr[j],this.arr[i]];
    }
  }
  [this.arr[i+1], this.arr[high]] = [this.arr[high], this.arr[i+1]];
  return i+1;
}
//test QuickSort
var arr = [7,5,3,8,6];
var testArray = new Array(arr);
console.log(testArray.doQuickSort(0, arr.length-1));

Another implementation with O(n) extra space

function quickSort(arr) {
  if(arr.length == 0) {
    return [];
  }
  var left = [];
  var right = [];
  var pivot = arr[arr.length-1];
  for(var i = 0; i < arr.length-1; i++) {
    if(arr[i]<pivot) {
      left.push(arr[i]);
    } else {
      right.push(arr[i]);
    }
  }
  return quickSort(left).concat(pivot, quickSort(right));
}
//test quickSort
var arr = [7,6,9,11,3];
console.log(quickSort(arr));