Electro - Department menu vertical scroll

functions.php

add_action( 'wp_head', 'ec_child_department_menu_vertical_scroll', 10 );

function ec_child_department_menu_vertical_scroll() { ?>
    <script>
        document.addEventListener("DOMContentLoaded", function () {

            const ul = document.getElementById("menu-all-departments-menu-1");
            if (!ul) return;

            const visibleCount = 10;
            const lis = Array.from(ul.querySelectorAll(":scope > li"));

            let startIndex = 0;

            function renderMenu() {
                lis.forEach((li, index) => {
                    if (index >= startIndex && index < startIndex + visibleCount) {
                        li.style.display = "block";
                    } else {
                        li.style.display = "none";
                    }
                });
            }

            renderMenu();

            ul.addEventListener("wheel", function (e) {
                e.preventDefault();

                if (e.deltaY > 0) {
                    if (startIndex + visibleCount < lis.length) {
                        startIndex++;
                        renderMenu();
                    }
                } else {
                    if (startIndex > 0) {
                        startIndex--;
                        renderMenu();
                    }
                }

            }, { passive: false });

        });
    </script>
<?php }