explain heapsort code example

Example 1: heap sort

// @see https://www.youtube.com/watch?v=H5kAcmGOn4Q

function heapify(list, size, index) {
    let largest = index;
    let left = index * 2 + 1;
    let right = left + 1;
    if (left < size && list[left] > list[largest]) {
        largest = left;
    }
    if (right < size && list[right] > list[largest]) {
        largest = right;
    }
    if (largest !== index) {
        [list[index], list[largest]] = [list[largest], list[index]];
        heapify(list, size, largest);
    }
    return list;
}

function heapsort(list) {
    const size = list.length;
    let index = ~~(size / 2 - 1);
    let last = size - 1;
    while (index >= 0) {
        heapify(list, size, --index);
    }
    while (last >= 0) {
        [list[0], list[last]] = [list[last], list[0]];
        heapify(list, --last, 0);
    }
    return list;
}

heapsort([4, 7, 2, 6, 4, 1, 8, 3]);

Example 2: heap sort name meaning

A sorting algorithm that works by first organizing the data to be sorted into a special type of binary tree called a heap. The heap itself has, by definition, the largest value at the top of the tree.