js树结构数组根据子项的id查询父项的pid

可以通过遍历树结构数组来查询子项的父项，具体代码实现如下：

/**
 * 根据子项的id查询父项的pid
 * @param {Array} treeData 树结构数组
 * @param {String} childId 子项的id
 * @return {String} 父项的pid
 */
function findParentPidById(treeData, childId) {
  for (let i = 0; i < treeData.length; i++) {
    const node = treeData[i]
    if (node.id === childId) {
      return node.pid
    } else if (node.children && node.children.length > 0) {
      const parentPid = findParentPidById(node.children, childId)
      if (parentPid !== null) {
        return parentPid
      }
    }
  }
  return null
}

调用方式如下：

const treeData = [
  {
    id: '1',
    pid: '0',
    label: '一级菜单1',
    children: [
      {
        id: '11',
        pid: '1',
        label: '二级菜单1-1',
      },
      {
        id: '12',
        pid: '1',
        label: '二级菜单1-2',
      },
    ],
  },
  {
    id: '2',
    pid: '0',
    label: '一级菜单2',
    children: [
      {
        id: '21',
        pid: '2',
        label: '二级菜单2-1',
      },
      {
        id: '22',
        pid: '2',
        label: '二级菜单2-2',
        children: [
          {
            id: '221',
            pid: '22',
            label: '三级菜单2-2-1',
          },
        ],
      },
    ],
  },
]

const parentPid = findParentPidById(treeData, '221')
console.log(parentPid) // 22