wagtail_bakerydemo/bakerydemo/static/js/main.js

const navigation = document.querySelector('[data-navigation]');
const mobileNavigation = navigation.querySelector('[data-mobile-navigation]');
const body = document.querySelector('body');
const mobileNavigationToggle = navigation.querySelector('[data-mobile-navigation-toggle]');

function toggleMobileNavigation() {
    if (mobileNavigation.hidden) {
      body.classList.add('no-scroll');
      mobileNavigation.hidden = false;
      mobileNavigationToggle.setAttribute('aria-expanded', 'true');
    } else {
      body.classList.remove('no-scroll');
      mobileNavigation.hidden = true;
      mobileNavigationToggle.setAttribute('aria-expanded', 'false');
    }
}

document.addEventListener('DOMContentLoaded', () => {
  mobileNavigationToggle.addEventListener('click', () => {
    toggleMobileNavigation();
  });
})