data-structures-and-algorithms/heapq

/**
 * Sifts up a node.
 *
 * @param {function} compare the comparison function
 * @param {array} a the array where the heap is stored
 * @param {number} i is the root element
 * @param {number} j - 1 is the last leaf
 * @param {number} k is the target node
 */

export default function siftup(compare, a, i, j, k) {
    let current = k - i;

    // While we are not the root

    while (current !== 0) {
        // Address of the parent in a zero-based
        // d-ary heap

        // eslint-disable-next-line no-bitwise
        const parent = i + ((current - 1) >>> 1);

        // If current value is greater than its parent
        // then we are done

        if (compare(a[i + current], a[parent]) >= 0) return i + current;

        // Otherwise
        // swap with parent

        const tmp = a[i + current];
        a[i + current] = a[parent];
        a[parent] = tmp;

        current = parent - i;
    }

    return i + current;
}