前提是让后端给返回一个当前选择的树
例：

//已选择的树deptsTree，

const deptsTree: any = 
      {
        id: 1,
        parentId: 0,
        children: [
          {
            id: 94,
            parentId: 1,
            children: [
              {
                id: 95,
                parentId: 94,
                children: [],
                sort: 1,
                parentDeptId: 94,
                deptName: '门-叶子',
                level: 3,
                status: 'DISABLE',
                remark: 'ee'
              }
            ]
          }
        ]
      }
    //获取到的列表
    const depList: any= [
      {
        id: 1,
        parentId: 0,
        children: [
          {
            id: 46,
            parentId: 1,
            children: [
              {
                id: 47,
                parentId: 46,
                children: [],
                sort: 3,
                parentDeptId: 46,
                deptName: '板烧鸡腿堡',
                level: 3,
                status: 'ENABLE',
                remark: null
              }
            ],
            sort: 2,
            parentDeptId: 1,
            deptName: '汉堡包',
            level: 2,
            status: 'ENABLE',
            remark: null
          },
          {
            id: 48,
            parentId: 1,
            children: [],
            sort: 2,
            parentDeptId: 1,
            deptName: '披萨',
            level: 2,
            status: 'ENABLE',
            remark: null
          }
        ],
        sort: 1,
        parentDeptId: 0,
        deptName: '大树的根根1',
        level: 1,
        status: 'ENABLE',
        remark: null
      },
      {
        id: 57,
        parentId: 56,
        children: [],
        sort: 11,
        parentDeptId: 56,
        deptName: '二级部门',
        level: 2,
        status: 'ENABLE',
        remark: '11'
      },
      {
        id: 101,
        parentId: 0,
        children: [],
        sort: 99,
        parentDeptId: 0,
        deptName: '称',
        level: 1,
        status: 'ENABLE',
        remark: ''
      },
      {
        id: 70,
        parentId: 69,
        children: [],
        sort: 2343,
        parentDeptId: 69,
        deptName: '测的部',
        level: 3,
        status: 'ENABLE',
        remark: ''
      }
    ]
interface TreeNode {
  id: number
  parentId: number
  children: TreeNode[]
  sort?: number
  parentDeptId?: number
  deptName?: string
  level?: number
  status?: string
  remark?: string
}
//合并方法
export function mergeTrees(deptsTree: TreeNode[], mm: TreeNode): TreeNode[] {
  // 合并节点
  function mergeNodes(nodes: TreeNode[], item: TreeNode) {
    for (const node of nodes) {
      const outIds = nodes.map((el: any) => el.id)
      if (outIds.indexOf(item.id) == -1) {
        nodes.push(item)
        return
      }
      if (node.id == item.id) {
        const childrenIds = node.children.map((el: any) => el.id)
        if (item.children.length > 0 && childrenIds.indexOf(item.children[0].id) == -1) {
          const childItem: any = item.children[0]
          node.children.push(childItem)
          return
        } else {
          if (node.children && node.children.length > 0 && item.children && item.children.length > 0) {
            mergeNodes(node.children, item.children[0])
            break
          }
        }
      }
    }
  }

  mergeNodes(deptsTree, mm)

  return deptsTree
}
let newTree = mergeTrees(res1, deptTree)
console.log()