quickSort.js

var quickSort = function (arr, left, right) {
  var len = arr.length, pivot, partitionIndex, left = left || 0, right = right || arr.length - 1;
  if (left < right) {
      pivot = right;
      partitionIndex = partition(arr, pivot, left, right);
      quickSort(arr, left, partitionIndex - 1);
      quickSort(arr, partitionIndex+1, right)
  }
  return arr;
};

function partition(arr, pivot, left, right){
    var pivotValue = arr[pivot],
        partitionIndex = left;

    for(var i = left; i < right; i++){
        if(arr[i] < pivotValue){
            swap(arr, i, partitionIndex);
            partitionIndex++;
        }
    }
    swap(arr, right, partitionIndex);
    return partitionIndex;
}

var swap = function (arr, i, j) {
  var temp = arr[i];
  arr[i] = arr[j];
  arr[j] = temp;
};