两级普通list转树形结构

toCascader (ary) {
      const array = []
      ary.map(item => {
        const obj = {}
        obj.value = item.className
        obj.label = item.className
        obj.children = []
        item.fieldNamelist.map(field => {
          const f = {}
          f.value = field
          f.label = field
          obj.children.push(f)
        })
        array.push(obj)
      })
      return array
    }