postcardmojo/public/js/nav.js

(function () {
  document.documentElement.classList.add('has-js');

  var toggle = document.querySelector('.nav-toggle');
  var nav = document.getElementById('site-nav');
  if (!toggle || !nav) return;

  function setMenu(open) {
    nav.classList.toggle('is-open', open);
    toggle.setAttribute('aria-expanded', String(open));
  }

  toggle.addEventListener('click', function () {
    setMenu(toggle.getAttribute('aria-expanded') !== 'true');
  });

  nav.addEventListener('click', function (event) {
    if (event.target.closest('a')) setMenu(false);
  });

  document.addEventListener('keydown', function (event) {
    if (event.key === 'Escape' && nav.classList.contains('is-open')) {
      setMenu(false);
      toggle.focus();
    }
  });
})();