document.addEventListener('DOMContentLoaded', function () {
  const navbarBurgerElements = document.querySelectorAll('.navbar-burger');
  const $navbarBurgers = Array.prototype.slice.call(navbarBurgerElements, 0);

  if ($navbarBurgers.length) {
    $navbarBurgers.forEach(function (element) {
      element.addEventListener('click', function () {
        const target = element.dataset.target;
        const $target = document.getElementById(target);

        element.classList.toggle('is-active');
        $target.classList.toggle('is-active');
      });
    });
  }
});

window.addEventListener('scroll', function () {
  if (window.scrollY > 50) {
    this.document.querySelector('.back-to-top').style.display = 'block';
  } else {
    this.document.querySelector('.back-to-top').style.display = 'none';
  }
});