text: var items = [5,3,7,6,2,9,4];
  function swap(items, leftIndex, rightIndex){
      var temp = items[leftIndex];
      items[leftIndex] = items[rightIndex];
      items[rightIndex] = temp;
  }
  function: partition(items, left, right) {
      var pivot   = items[Math.floor((right + left) / 2)], //middle element
          i       = left, //left pointer
          j       = right; //right pointer
      while (i <= j) {
          while (items[i] < pivot) {
              i++;
          }
          while (items[j] > pivot) {
              j--;
          }
          if (i <= j) {
              swap(items, i, j); //sawpping two elements
              i++;
              j--;
          }
      }
      return i;
  }
  
  function quickSort(items, left, right) {
      var index;
      if (items.length > 1) {
          index = partition(items, left, right); //index returned from partition
          if (left < index - 1) { //more elements on the left side of the pivot
              quickSort(items, left index - 1);
          }
          if (index < right) { //more elements on the right side of the pivot
              quickSort(items, index, right);
          }
      }
      return items;
  }
  // first call to quick sort
  var sortedArray = quickSort(items, 0, items.length - 1);
  console.log(sortedArray); //prints [2,3,5,6,7,9]
  