element-ui tree 手动展开功能实现(异步树也可以)

<el-tree
        :props="mulprops"
        :load="loadNode"
        lazy
        node-key="id"
        show-checkbox
        accordion
        @current-change="currentChange"
        :filter-node-method="filterNode"
        @check="handleCheck"
        ref="tree"
        :default-checked-keys="defaultCheckedNodes"
        :default-expanded-keys="defaultExpandedNodes">
    </el-tree>

handleCheck(nodeData,  treeChecked) {
      let node = this.$refs.tree.getNode(nodeData.id)
      //将选中的未展开的节点进行展开
      if(node.checked && !node.expanded){
        node.expand(function(){
          for(let i=0; i< node.childNodes.length; i++){
            node.childNodes[i].expand()
          }
        })
      }
    }

<el-tree
        :props="mulprops"
        :load="loadNode"
        lazy
        node-key="id"
        show-checkbox
        accordion
        @check-change="handleCheckChange"
        :filter-node-method="filterNode"
        ref="tree"
        :default-checked-keys="defaultCheckedNodes"
        :default-expanded-keys="defaultExpandedNodes"
    >
    </el-tree>

handleCheckChange(nodeData, nodeSelected) {
      //展开选中的未展开的节点
      let tree = this.$refs.tree;
      let node = tree.getNode(nodeData.id)
      //展开选中的未展开的节点
      this.expandNotExpandNodes(node);

      //具体业务实现
      console.log(nodeData, nodeSelected)
    },
    //展开选中的未展开的节点
    expandNotExpandNodes(node) {
      let tree = this.$refs.tree;
      if (node.checked && !node.expanded && !node.isLeaf) {
        node.expand(function () {
          let childNodes = node.childNodes;
          for (let i = 0; i < childNodes.length; i++) {
            let childNode = childNodes[i];
            //手动触发check-change事件，事件处理函数中回继续调用此函数，形成递归展开
            tree.$emit('check-change', childNode.data, childNode.checked, childNode.indeterminate);
          }
        })
      }
    },