The Javascript behind this navigation menu is only to select the corresponding items in main and sub menu ("where am I?"). This "selection" is based on the url.

Javascript for select the corresponding menu items

let ref = location.href.split("/").pop()

// wait until DOM loaded
window.addEventListener("DOMContentLoaded", init())
function init() {
    if (ref === "") {
        location.href = "home"

//select menu item
function select() {
    let main = document.querySelectorAll('#mainlist li');
    let sub = document.querySelectorAll('#sublist li');

    // Remove the 'selected' class from all main and sub menu items
    main.forEach(item => item.classList.remove('selected'));
    sub.forEach(item => item.classList.remove('selected'));

    // Get the last part of the current URL
    let sub_id = "sub_" + location.href.split("/").pop(); //unique id so they don't interfere with main menu id

    if (sub_id) {
        let item = document.querySelector(`#${sub_id}`);
        if (sub_id) {

    //get correspondent main menu from page body dataset
    let main_id = document.body.dataset.main

    // Add the 'selected' class to the corresponding main menu item
    if (main_id) {
        let item = document.querySelector(`#${main_id}`);
        if (item) {