quick-sort.js

const quickSort = (arr, left, right) => {
  let len = arr.length, 
  pivot,
  partitionIndex;

  if (left < right){
    pivot = right;
    partitionIndex = partition(arr, pivot, left, right);
    
    //sort left and right
    quickSort(arr, left, partitionIndex - 1);
    quickSort(arr, partitionIndex + 1, right);
  }
  return arr;
}

const partition = (arr, pivot, left, right) => {
   let pivotValue = arr[pivot],
       partitionIndex = left;

   for (let i = left; i < right; i++){
    if (arr[i] < pivotValue){
      swap(arr, i, partitionIndex);
      partitionIndex++;
    }
  }
  swap(arr, right, partitionIndex);
  return partitionIndex;
}
  
const swap = (arr, i, j) => {
   let temp = arr[i];
   arr[i] = arr[j];
   arr[j] = temp;
}