Vue uses drag and drop to create a structure tree

<template>
  <div class="container">
    <div class="node-container">
      <div v-for="(item, index) in nodeList"
           :key="index"
           class="source-node"
           draggable="true"
           @dragstart="dragStart(item)">
        {{ item }}
      </div>
    </div>
    <div class="tree-container"
         @dragover="allowDrop"
         @drop="handleDrop">
      <tree-node v-if="nodeData"
                 ref="node"
                 :nodeData="nodeData"
                 @delete-node="deleteTree" />
    </div>
  </div>
</template>
<script>
import TreeNode from './treeNode.vue'
import { Node } from './config.js'
export default {
  name: 'vue-tree',
  components:
    TreeNode
  },
  // Descendant nodes cannot obtain node data, that is, they cannot create nodes independently, so the node creation method of the ancestor node is exposed to the descendant nodes provide () {
    return {
      createNode: this.createNode
    }
  },
  data () {
    return {
      nodeList: ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'],
      currNode: null,
      nodeData: null
    }
  },
  methods: {
    // Start dragging and get node data dragStart (item) {
      this.currNode = item
    },
    // If the root node is not generated, dragging is allowedallowDrop (event) {
      if (!this.nodeData) {
        event.preventDefault()
      }
    },
    //Drag ends, generate node handleDrop () {
      if (!this.nodeData) {
        this.nodeData = this.createNode()
      }
    },
    createNode () {
      let node = new Node(this.currNode)
      return node
    },
    // Delete the root node and delete the entire tree deleteTree () {
      this.nodeData = null
    }
  }
}
</script>
<style lang="scss" scoped>
.container {
  padding: 20px;
  width: calc(100% - 40px);
  height: calc(100% - 40px);
  .node-container {
    height: 100px;
    border: 1px dashed red;
    display: flex;
    .source-node {
      width: 50px;
      height: 30px;
      background: #fff;
      border: 1px solid blue;
      text-align: center;
      line-height: 30px;
      margin: 10px;
      cursor: pointer;
    }
  }
  .tree-container {
    height: calc(100% - 122px);
    margin-top: 20px;
  }
}
</style>

export class Node{
  constructor(name){
    this.name = name,
    this.children = []
  }
}

<template>
  <!-- 
    Structure: The outermost layer is node-inner. Each node-inner contains a node and a node-box. The node stores the current node, and the node-box stores all the child nodes of the current node. If the current node has several child nodes, there will be several node-ins in the node-box, and so on.
        <node></node>
        <node-box>
          <node-inner>
            <node></node>
            <node-box>...</node-box>
          </node-inner>
          <node-inner>
            <node></node>
            <node-box>...</node-box>
          </node-inner>
          ...
        </node-box>
      </node-inner>
   -->
  <div class="node-inner">
    <div class="node"
         :class="{ 'drag-over-node': isDragover }"
         @dragover="dragOver"
         @dragleave="dragLeave"
         @drop="nodeDrop">
      <span class="name">{{nodeData.name}}</span>
      <span class="del"
            @click="deleteNode">Delete</span>
    </div>
    <div v-show="nodeData.children.length > 0"
         class="node-box">
      <tree-node v-for="(item,index) in nodeData.children"
                 :key="index"
                 :nodeData="item"
                 @delete-node="deleteChild(index)" />
    </div>
  </div>
</template>
<script>
export default {
  name: 'tree-node',
  props: {
    nodeData: {
      type: Object,
      default: () => { }
    }
  },
  // Get the data passed by the ancestor node inject: ['createNode'],
  data () {
    return {
      isDragover: false
    }
  },
  methods: {
    // The node allows dragging to add child nodes dragOver (event) {
      event.preventDefault()
      if (!this.isDragover) {
        this.isDragover = true
      }
    },
    dragLeave() {
      if (this.isDragover) {
        this.isDragover = false
      }
    },
    // Add child nodes to the node nodeDrop () {
      let node = this.createNode()
      this.nodeData.children.push(node)
      this.isDragover = false
    },
    // Delete the current node, which essentially means handing it over to the parent to delete the child node deleteNode () {
      this.$emit("delete-node")
    },
    // Receive the instruction to delete the child node and execute the delete function deleteChild (index) {
      this.nodeData.children.splice(index, 1)
    }
  }
}
</script>
<style lang="scss" scoped>
.node {
  border: 1px solid orange;
  border-radius: 4px;
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: space-between;
  background-color: #fff;
  height: 36px;
  padding: 0 12px 0 16px;
  line-height: 36px;
  margin-bottom: 10px;
  .name {
    font-size: 16px;
    margin-right: 12px;
  }
  .del {
    color: red;
    font-size: 12px;
    cursor: pointer;
  }
  &.drag-over-node {
    box-shadow: 6px 6px 12px rgba(106, 20, 134, 0.15);
  }
}
.node-box {
  display: inline-flex;
  flex-direction: column;
  .node-inner {
    margin-left: 80px;
    // Connect the vertical bars&:not(:last-child):before {
      position: absolute;
      left: -70px;
      top: 22px;
      border: 1px solid orange;
      content: "";
      width: 8px;
      background-color: #fff;
      border-bottom-color: #fff;
      height: 100%;
      border-top-color: #fff;
      z-index: 3;
    }
    // Connect horizontal bar&:after {
      left: -61px;
      width: 60px;
      content: "";
      position: absolute;
      top: 14px;
      height: 8px;
      border: 1px solid orange;
      content: "";
      background-color: #fff;
      border-right-color: #fff;
      border-left-color: #fff;
      z-index: 3;
    }
    // The last vertical bar has a rounded corner &:nth-last-child(2):before {
      border-bottom-left-radius: 6px;
      border-bottom-color: orange;
    }
    // The first horizontal bar is extended &:first-child:after {
      left: -81px;
      width: 80px;
      z-index: 2;
    }
  }
}
.node-inner {
  position: relative;
}
</style>