输入：

扁平化输出：

{
   code: int,
   text: str,
   parentCode: int,
   parentText: str,
   grandParentCode: int,
   grandParentText: str
}[]

/**
 * @desc 将三级数组扁平化为带有父级及以上节点
 * @param {array} source
 * @return {object} 伪数组
 */
export function deepTraversalCity (source, list = { length: 0 }, grand = {}, par = {}, depth = 0) {
  depth++
  for (var key in source) {
    const item = source[key]
    if (!item.children || item.children.length === 0) {
      item.parentCode = par.code
      item.parentText = par.text
      item.grandParentCode = grand.code
      item.grandParentText = grand.text
      delete item.children
      const temp = list.length
      list[temp] = item
      list.length++
    } else {
      depth === 1 && (grand = item)
      deepTraversalCity(item.children, list, grand, item, depth)
    }
  }
  return list
}