div拖拽互换位置（vue）

template模板

<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：

<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
	}