SOURCE

new Vue({
  el: '#list-demo',
  data: {
    items: [1, 2, 3, 4, 5, 6, 7, 8, 9],
    nextNum: 10
  },
  methods: {
    randomIndex: function() {
      return Math.floor(Math.random() * this.items.length)
    },
    add: function() {
      this.items.splice(this.randomIndex(), 0, this.nextNum++)
    },
    remove: function() {
      this.items.splice(this.randomIndex(), 1)
    },
  }
})

<div id="list-demo" class="demo">
  <button v-on:click="add">
    Add
  </button>
  <button v-on:click="remove">
    Remove
  </button>
  <transition-group name="list" tag="p">
    <span v-for="item in items" v-bind:key="item" class="list-item">
      {{ item }}
    </span>
  </transition-group>
</div>

.list-item {
  display: inline-block;
  margin-right: 10px;
}
.list-enter-active, .list-leave-active {
  transition: all 1s;
}
.list-enter, .list-leave-to
/* .list-leave-active for below version 2.1.8 */ {
  opacity: 0;
  transform: translateY(30px);
}