SOURCE

new Vue({
    el: '#app',
    data: {
        lists: ['1: apple', '2: banana', '3: orange', '4: melon']
    },
    methods: {
        //取消默认行为
        allowDrop(e){
            e.preventDefault();
        },
        //开始拖动
        dragStart(e, index){
            let tar = e.target;
            e.dataTransfer.setData('Text', index);
            if (tar.tagName.toLowerCase() == 'li') {
                // console.log('drag start')
                // console.log('drag Index: ' + index)
            }
        },
        //放置
        drop(e, index){
            this.allowDrop(e);
            // console.log('drop index: ' + index);
            //使用一个新数组重新排序后赋给原变量
            let arr = this.lists.concat([]),
                dragIndex = e.dataTransfer.getData('Text');
                temp = arr.splice(dragIndex, 1);

            arr.splice(index, 0, temp[0]);
            // console.log('sort');

            this.lists = arr;

        }
    }
})

<transition-group id='app' name="drog" tag="ul">
        <li draggable="true" v-for="(item, index) in lists" @dragstart="dragStart($event, index)" @dragover="allowDrop" @drop="drop($event, index)" v-bind:key="item">{{item}}</li>
</transition-group>

ul {
  min-height: 100px;
  width: 200px;
  margin: 20px auto;
  background: #eee;
}

li {
  min-height: 2em;
  margin-top: 10px;
  background: #abcded;
}


/*组件过渡类*/

.drog-move {
  transition: transform 1s;
}