div拖拽互换位置（vue）

<transition-group tag="div" class="container">
<div class="item" v-for="(item,index) in items" :key="item.key" :style="{background:item.color,width:'80px',height:'80px'}"
draggable="true"
@dragstart="handleDragStart($event, item)"
@dragover.prevent="handleDragOver($event, item)"
@dragenter="handleDragEnter($event, item)"
@dragend="handleDragEnd($event, item)" >
</div>
</transition-group>

<script>
export default {
name: 'Toolbar',
data () {
return {
items: [
{ key: 1, color: '#ffebcc'},
{ key: 2, color: '#ffb86c'},
{ key: 3, color: '#f01b2d'}
], dragging: null
}
},
methods:{
handleDragStart(e,item){
this.dragging = item;
},
handleDragEnd(e,item){
this.dragging = null
},
//首先把div变成可以放置的元素，即重写dragenter/dragover
handleDragOver(e) {
e.dataTransfer.dropEffect = 'move'// e.dataTransfer.dropEffect="move";//在dragenter中针对放置目标来设置!
},
handleDragEnter(e,item){
e.dataTransfer.effectAllowed = "move"//为需要移动的元素设置dragstart事件
if(item === this.dragging){
return
}
const newItems = [...this.items]
console.log(newItems)
const src = newItems.indexOf(this.dragging)
const dst = newItems.indexOf(item) newItems.splice(dst, 0, ...newItems.splice(src, 1)) this.items = newItems
}
}
}
</script><style scoped>
.container{
width: 80px;
height: 300px;
position: absolute;
left: 0;
display:flex;
flex-direction: column;
padding: 0;
}
.item {
margin-top: 10px;
transition: all linear .3s
}