const quickSort = (arr, start, end) => {

if(start < end) {

// You can learn about how the pivot value is derived in the comments below

let pivot = partition(arr, start, end)

// Make sure to read the below comments to understand why pivot - 1 and pivot + 1 are used

// These are the recursive calls to quickSort

quickSort(arr, start, pivot - 1)

quickSort(arr, pivot + 1, end)

}

}

const partition = (arr, start, end) => {

let pivot = end

// Set i to start - 1 so that it can access the first index in the event that the value at arr[0] is greater than arr[pivot]

// Succeeding comments will expound upon the above comment

let i = start - 1

let j = start

// Increment j up to the index preceding the pivot

while (j < pivot) {

// If the value is greater than the pivot increment j

if (arr[j] > arr[pivot]) {

j++

}

// When the value at arr[j] is less than the pivot:

// increment i (arr[i] will be a value greater than arr[pivot]) and swap the value at arr[i] and arr[j]

else {

i++

swap(arr, j, i)

j++

}

}

//The value at arr[i + 1] will be greater than the value of arr[pivot]

swap(arr, i + 1, pivot)

//You return i + 1, as the values to the left of it are less than arr[i+1], and values to the right are greater than arr[i + 1]

// As such, when the recursive quicksorts are called, the new sub arrays will not include this the previously used pivot value

return i + 1

}

const swap = (arr, firstIndex, secondIndex) => {

let temp = arr[firstIndex]

arr[firstIndex] = arr[secondIndex]

arr[secondIndex] = temp

}

quickSort(arr, 0, arr.length - 1)