Quick Sort with Javascript

quick_sort.js

/*
Best Case:n*logn
Average Case:n*logn
Worst Case:n^2

*/
(function(){
    let comparison=0;
    let arr2=[28, 31, 43, 97, 49, 11, 33, 71, 41, 80, 86, 38, 53, 54, 7, 67, 96, 52, 29, 25, 56, 77, 73, 42, 62, 84, 21, 68, 2, 44, 9, 94, 66, 78, 6, 57, 20, 89, 1, 55, 65, 85, 51, 23, 70, 32, 12, 27, 18, 90, 4, 82, 5, 35, 58, 69, 22, 83, 37, 61, 79, 34, 81, 30, 72, 95, 91, 48, 88, 46, 3, 26, 60, 39, 17, 24, 74, 99, 10, 16, 87, 98, 76, 13, 36, 45, 59, 100, 50, 93, 19, 75, 92, 40, 8, 47, 14, 15, 63, 64];
    let arr=[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100];

  function swap(items, firstIndex, secondIndex){
    let temp = items[firstIndex];
    items[firstIndex] = items[secondIndex];
    items[secondIndex] = temp;
}

function partition(items, left, right) {
    let pivot   = items[Math.floor((right + left) / 2)],
        i       = left,
        j       = right;

    while (i <= j) {
        while (items[i] < pivot) {
            comparison++;
            i++;
        }
        while (items[j] > pivot) {
            comparison++;
            j--;
        }
        if (i <= j) {
            comparison++;
            swap(items, i, j);
            i++;
            j--;
        }
    }
    return i;
}

function sort(items, left, right) {
    comparison++;
    let index;
    if (items.length > 1) {
        left = typeof left != "number" ? 0 : left;
        right = typeof right != "number" ? items.length - 1 : right;
        index = partition(items, left, right);
        if (left < index - 1) {
            sort(items, left, index - 1);
        }
        if (index < right) {
            sort(items, index, right);
        }
    }
    return items;
}
function quick_sort(array){
        var start = Date.now();
       array= sort(array);
    var end = Date.now();
   var elapsed = end - start; 
   console.log("Elapsed Time:"+elapsed);
  
    console.log("Total comparison:"+comparison);
    comparison=0;
    return array
}

  quick_sort(arr2);//Total comparison:894
  console.log(quick_sort(arr));
  
})();