如何仅使用HTML、CSS和Javascript突出显示导航栏

<nav>
  <ul>
    <li><a href="#" class="active">首页</a></li>
    <li><a href="#">产品</a></li>
    <li><a href="#">服务</a></li>
    <li><a href="#">关于我们</a></li>
    <li><a href="#">联系我们</a></li>
  </ul>
</nav>

nav ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
  overflow: hidden;
  background-color: #f9f9f9;
}

nav li {
  float: left;
}

nav li a {
  display: block;
  color: #333;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
}

nav li a:hover {
  background-color: #ddd;
}

nav li a.active {
  background-color: #4CAF50;
  color: white;
}

var navItems = document.querySelectorAll('nav li a');

for (var i = 0; i < navItems.length; i++) {
  navItems[i].addEventListener('click', function() {
    var current = document.getElementsByClassName('active');
    current[0].className = current[0].className.replace(' active', '');
    this.className += ' active';
  });
}