js+折叠菜单图标

<nav class="navbar">
  <div class="navbar-toggle" id="mobile-menu">
    <span class="bar"></span>
    <span class="bar"></span>
    <span class="bar"></span>
  </div>
  <ul class="navbar-menu">
    <li class="navbar-item"><a href="#">Home</a></li>
    <li class="navbar-item"><a href="#">About</a></li>
    <li class="navbar-item"><a href="#">Services</a></li>
    <li class="navbar-item"><a href="#">Contact</a></li>
  </ul>
</nav>

.navbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.navbar-menu {
  display: flex;
  list-style: none;
}

.navbar-menu li {
  margin-left: 20px;
}

.navbar-toggle {
  display: none;
  flex-direction: column;
  cursor: pointer;
}

.bar {
  height: 3px;
  width: 25px;
  background-color: black;
  margin: 4px 0;
}

@media (max-width: 768px) {
  .navbar-menu {
    display: none;
    flex-direction: column;
    width: 100%;
  }

  .navbar-menu.active {
    display: flex;
  }

  .navbar-toggle {
    display: flex;
  }
}

document.getElementById('mobile-menu').addEventListener('click', function() {
  var menu = document.querySelector('.navbar-menu');
  menu.classList.toggle('active');
});