heapSort implementation in javascript

heapSort.js

function heapify(array, index, heapSize, cmp) {
    let left = 2 * index + 1;
    let right = 2 * index + 2;
    let largest = index;
    if (left < heapSize && cmp(array[left], array[index]) > 0) {
        largest = left;
    }
    if (right < heapSize && cmp(array[right], array[largest]) > 0) {
        largest = right;
    }
    if (largest !== index) {
        swapArrayItem(array, largest, index);
        heapify(array, largest, heapSize, cmp);
    }
}

const swapArrayItem = (arr, i, j) => {
    let tmp = arr[i];
    arr[i] = arr[j];
    arr[j] = tmp;
};

function buildMaxHeap(array, cmp) {
    for (let i = Math.floor(array.length / 2); i >= 0; i -= 1) {
      heapify(array, i, array.length, cmp);
    }
    return array;
}

function comparator(a, b) {
    return a - b;
}

function heapSort(array, cmp = comparator) {
    cmp = cmp;
    let size = array.length;
    buildMaxHeap(array, cmp);
    for (let i = array.length - 1; i > 0; i -= 1) {
        swapArrayItem(array, 0, i);
        size -= 1;
        heapify(array, 0, size, cmp);
    }
    return array;
}