ハンバーガーメニュー

html

<body>
 <div id="app">
  <header class="header">
    <div class="header_menu">
      <div class="header_menu_line" @click="naviOpen" :class="{'is-active': active}">
        <span></span>
        <span></span>
        <span></span>
      </div>
    </div>
  </header>
   <transition name="navi">
  <nav class="navi" v-show="navi">
    <ul class="navi_wrap">
      <li><a href="#">AAA</a></li>
      <li><a href="#">BBB</a></li>
      <li><a href="#">CCC</a></li>
      <li><a href="#">DDD</a></li>
      <li><a href="#">EEE</a></li>
    </ul>
  </nav>
 </transition>
 
 </div>
</body>

  <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
  <script>
    var app = new Vue({
  el: '#app',
  data: {
    active: false,
    navi: false,
  },
  methods: {
    naviOpen: function() {
      this.active = !this.active;
      this.navi = !this.navi;
    }
  }
    })
  </script>

css

.header {
  width: 100%;
  background: #fff;
  height: 60px;
}
.header_menu {
  width: 60px;
  height: 60px;
  position: fixed;
  top: 0;
  right: 0;
}
.header_menu_line {
  width: 36px;
  height: 30px;
  margin-top: 15px;
  margin-left: auto;
  margin-right: auto;
  position: relative;
  cursor: pointer;
}
.header_menu_line span {
  width: 100%;
  height: 2px;
  background: #000;
  display: block;
  transition: .6s;
  position: absolute;
}
.header_menu_line span:first-child {
  top: 0;
}
.header_menu_line span:nth-child(2) {
  top: 14px;
}
.header_menu_line span:last-child {
  bottom: 0;
}
.header_menu_line.is-active span {
  transition: .6s;
}
.header_menu_line.is-active span:first-child {
  transform: rotate(45deg);
  top: 50%;
}
.header_menu_line.is-active span:nth-child(2) {
  opacity: 0;
}
.header_menu_line.is-active span:last-child {
  transform: rotate(-45deg);
  top: 50%;
}

.navi {
  width: 100%;
/*  height: 100vh;*/
  display: flex;
  justify-content: center;
  align-items: center;
  color: #fff;
}
.navi_wrap {
  list-style-type: none;
  text-align: center;
  padding-left: 0;
  background: #4b4b4b;
  padding: 40px 0;
}
.navi_wrap li a {
  text-decoration: none;
  color: #fff;
  display: block;
  padding: 20px;
}
.navi-enter, .navi-leave-to {
  opacity: 0;
}
.navi-enter-to, .navi-leave {
  opacity: 1;
}
.navi-enter-active, .navi-leave-active {
  transition: .6s;
}