内容

Vue.jsのリストレンダリングのトランジションにjQueryのslideUp/slideDownのようなアニメーション効果をつける。

コード

HTML

<div id="app">
  <input v-on:keypress.enter="addItem" v-model="input" type="text">
  <button v-on:click="addItem">追加</button>
  <transition-group tag="ul" v-on:enter="enter" v-on:after-enter="afterEnter" v-on:leave="leave" v-on:after-leave="afterLeave">
    <li v-for="(item, index) in list" v-bind:key="item.id">{{ item.text }}<button v-on:click="removeItem(index)">削除</button></li>
  </transition-group>
</div>

CSS

ul {
  padding-left: 0;
  list-style-type: none;
}
li button {
  margin-left: 1em;
}
.v-enter-active,
.v-leave-active {
  overflow-y: hidden;
  transition: height 0.5s ease;
}

JavaScript

var counter = 0; // v-forのkey属性用
var app = new Vue({
  el: '#app',
  data: {
    input: '',
    list: []
  },
  methods: {
    addItem: function() {
      if (this.input.length !== 0) {
        this.list.push({
          id: counter,
          text: this.input
        });
        counter += 1;
        this.input = '';
      }
    },
    removeItem: function(index) {
      this.list.splice(index, 1);
    },
    enter: function(element) {
      var elementHeight = element.getBoundingClientRect().height;
      element.style.height = 0;
      element.offsetHeight; // reflow
      element.style.height = elementHeight + 'px';
    },
    afterEnter: function(element) {
      element.style.height = null;
    },
    leave: function(element) {
      var elementHeight = element.getBoundingClientRect().height;
      element.style.height = elementHeight + 'px';
      element.offsetHeight; // reflow
      element.style.height = 0;
    },
    afterLeave: function(element) {
      element.style.height = null;
    }
  }
});