Simple Hidden Nav

nav

function toggleGetNav(id)
  {
    var e = document.getElementsByTagName(id)[0];
    e.style.display = getComputedStyle(e, null).display === 'none' ? 'block' : 'none';
  }

nav-style

@-webkit-keyframes slide-left {
    100% {
        left: 0;
    }
}

@keyframes slide-left {
    100% {
        left: 0;
    }
}

nav {
  left: -999px;
  width: 100%;
  height: 100%;
  -webkit-animation: slide-left 0.5s forwards;
  -webkit-animation-delay: 0.05s;
  animation: slide-left 0.5s forwards;
  animation-delay: 0.05s;
}