vue2中 elementUI tree树一键展开/关闭_element的tree设置展开和关闭

代码实现如下：

<template>
<div>
   <el-button @click="handleCheckedTreeExpand">展开/折叠</el-button>
   <el-tree
     class="tree-border"
     :data="data"
     show-checkbox
     default-expand-all
     ref="tree"
     node-key="id"
     empty-text="加载中，请稍候"
     :props="defaultProps"
   ></el-tree>
</div>
</template>
<script>
export default {
  data() {
    return {
      // 展开状态
      isExpandAll: false,
      defaultProps: {
        children: "children",
        label: "label"
      },
      data: [{
        label: '一级 1',
        id: 1,
        children: [{
          id: 11,
          label: '二级 1-1',
          children: [{
            id: 111,
            label: '三级 1-1-1'
          }]
        }]
      }, {
        id: 2,
        label: '一级 2',
        children: [{
          id: 21,
          label: '二级 2-1',
          children: [{
            id: 211,
            label: '三级 2-1-1'
          }]
        }, {
          id: 22,
          label: '二级 2-2',
          children: [{
            id: 221,
            label: '三级 2-2-1'
          }]
        }]
      }, {
        id: 3,
        label: '一级 3',
        children: [{
          id: 31,
          label: '二级 3-1',
          children: [{
            id: 311,
            label: '三级 3-1-1'
          }]
        }, {
          id: 32,
          label: '二级 3-2',
          children: [{
            id: 321,
            label: '三级 3-2-1'
          }]
        }]
      }],
    }
  },
  methods: {
    // 展开/折叠事件
    handleCheckedTreeExpand(){
      this.isExpandAll = !this.isExpandAll
      let treeRef = this.$refs.tree
      let treeList = this.data
      this.TreeExpandOrFold(treeList, treeRef)
    },
    // 递归展开/折叠 树
    TreeExpandOrFold(treeList, treeRef){
      treeList.forEach((item,index)=>{
        treeRef.store.nodesMap[treeList[index].id].expanded = this.isExpandAll;
        if(item.children && item.children.length>0){
          let newTreeRef = treeRef.store.nodesMap[treeList[index].id]
          this.TreeExpandOrFold(item.children, newTreeRef)
        }
      })
    }
  }
}
</script>