data-structures-and-algorithms/skip-list

import assert from 'assert';

const bottomMostPredecessor = (compare, node, key) => {
    // eslint-disable-next-line no-constant-condition
    while (true) {
        assert(node !== null);
        // Predecessor search on current level
        while (node.right !== null && compare(key, node.right.key) > 0)
            node = node.right;

        // Continue on bottom level or abandon
        if (node.down === null) return node;
        node = node.down;
    }
};

export default bottomMostPredecessor;