鼠标任意拖动元素排列顺序（vue）

参考地址：https://codesandbox.io/s/condescending-butterfly-enjqpr?file=/src/App.vue

<template>
  <div>
    <transition-group name="drag" class="list" tag="ul">
      <li
        @dragstart="dragStart(item, index)"
        @dragover.prevent="dragOver(index)"
        @dragend="dragEnd()"
        draggable
        v-for="(item, index) in todolist"
        :key="item.label"
        :class="['list-item', { 'is-dragover': index === newIndex }]"
      >
        {{ item.label }}
      </li>
    </transition-group>
  </div>
</template>

<script>
export default {
  data() {
    return {
      todolist: [
        { label: "列表1" },
        { label: "列表2" },
        { label: "列表3" },
        { label: "列表4" },
        { label: "列表5" },
        { label: "列表6" },
      ],
      oldIndex: "",
      oldData: "",
      newIndex: "",
    };
  },
  methods: {
    dragStart(val, i) {
      this.oldIndex = i;
      this.oldData = val;
    },
    dragOver(i) {
      this.newIndex = i;
    },
    dragEnd() {
      let newItems = [...this.todolist];
      // 删除老的节点
      newItems.splice(this.oldIndex, 1);
      // 在列表中目标位置增加新的节点
      newItems.splice(this.newIndex, 0, this.oldData);
      this.todolist = [...newItems];
      this.newIndex = "";
    },
  },
};
</script>

<style lang="scss" scoped>
.list {
  list-style: none;
  .drag-move {
    transition: transform 0.3s;
  }
  .list-item {
    position: relative;
    cursor: move;
    width: 300px;
    background: #2997f4;
    border-radius: 4px;
    color: #FFF;
    margin: 10px 0;
    height: 50px;
    line-height: 50px;
    text-align: center;
  }
}

.list-item.is-dragover::before {
  content: "";
  position: absolute;
  bottom: -8px;
  left: 0;
  width: 100%;
  height: 4px;
  background-color: #0c6bc9;
}
.list-item.is-dragover::after {
  content: "";
  position: absolute;
  bottom: -12px;
  left: -6px;
  border: 3px solid #0c6bc9;
  border-radius: 50%;
  width: 6px;
  height: 6px;
  background-color: #fff;
}
</style>