document.addEventListener("DOMContentLoaded", function() {
  function toggleNav(doToggle) {
    var nav = document.querySelector('#nav-main');
    if (getComputedStyle(document.querySelector('#hamburger'))['display'] == 'none'
      || (doToggle && getComputedStyle(nav)['display'] == 'none')) {
      nav.style.display = 'block';
    } else {
      nav.style.display = 'none';
    }
  }
  var toggleLink = document.querySelector('#hamburger');
  toggleLink.addEventListener('click', function(event) {
    event.preventDefault();
    toggleNav(true);
  });
  window.addEventListener('resize', function() {
    toggleNav(false);
  });
});