SOURCE

function quickSort(arr, start, end) {
    if (start > end) {
        return;
    }
    let i = start,
        j = end,
        pivot = arr[start];
    while (i !== j) {
        while (arr[j] >= pivot && i < j) {
            j--;
        }
        while (arr[i] <= pivot && i < j) {
            i++
        }
        if (i < j) {
            let tmp = arr[i];
            arr[i] = arr[j];
            arr[j] = tmp;
        }
    }
    arr[start] = arr[i];
    arr[i] = pivot;
    quickSort(arr, start, i - 1);
    quickSort(arr, i + 1, end);
}
let nums = [2, 4, 5, 9, 19, 1];
quickSort(nums, 0, nums.length - 1);
console.log(nums);