quickSort.js

function pivotHelper(array, start = 0, end = array.length) {
    let pivotValue = array[start]
    let pivotIndex = start
    for (let i = start + 1; i < end; i++) {
        if (pivotValue >= array[i]) {
            pivotIndex++
            [array[pivotIndex], array[i]] = [array[i], array[pivotIndex]]
        }
    }

    [array[pivotIndex], array[start]] = [array[start], array[pivotIndex]]

    return pivotIndex
}

function quickSort(array, left = 0, right = array.length) {
    if (left === right) {
        return array
    }

    let pivotIndex = pivotHelper(array, left, right)

    quickSort(array, left, pivotIndex)
    quickSort(array, pivotIndex + 1, right)

    return array
}