Quick Sort in Javascript

Quick sort is faster than bubble sort.

It uses the idea of divide and conquers. Divides the array into two halves using a pivot in such a way that elements in the left half are smaller than the pivot and elements in the right are greater than the pivot — then recursive using quick sort on the left and right parts.

I would recommend below youtube to understand Quick Sort:
https://www.youtube.com/watch?v=eqo2LxRADhU

Here is my implementation in javascript:

function quickSort(arr, start, end) {
  // Stop the recursion when the start equal or smaller to the end
  if (start >= end) { 
    return ; 
  };
  
  // Here is the magic happen
  let pivotIndex = partition(arr, start, end);
  
  // Recursion - quick sort the left part
  quickSort(arr, start, pivotIndex - 1);
  
  // Recursion - quick sort the right part
  quickSort(arr, pivotIndex + 1, end);
}

function partition (arr, start, end) {
  let pivotIndex = start; // Pivot location
  let pivotValue = arr[end]; // Use the last number  
  
  for (let i=start; i<end; i++) {
    // Move number that smaller than pivot value to the front.
    // Update pivot index
    if (arr[i] < pivotValue) {
      // Move to front
      swap(arr, i, pivotIndex);
      pivotIndex++;
    }
  }
  
  // Swap the pivot value to correct location
  swap(arr, end, pivotIndex);
  return pivotIndex;
}

function swap(arr, a, b) {
  let temp = arr[a];
  arr[a] = arr[b];
  arr[b] = temp;
}

let arr = [2 ,1, 4, 5, 3, 6, 6, 8, 1, 3];
quickSort(arr, 0, arr.length - 1);