输入：

const arrs = [
    {
        name: '广东',
        children: [
            {
                name: '深圳',
                children: [
                    {
                        name: '南山区',
                        children: []
                    }
                ]
            },
            {
                name: '广州',
                children: [
                    {
                        name: '白云区',
                        children: []
                    }
                ]
            }
        ]
    },
    {
        name: '上海',
        children: [
            {
                name: '浦东新区',
                children: []
            }
        ]
    },
    {
        name: '北京',
        children: [
            {
                name: '朝阳区',
                children: []
            }
        ]
    }
]

输出：

[
    {
        name: '广东',
        children: [
            {
                name: '深圳'，
                children: []
            },
            {
                name: '广州'，
                children: []
            }
        ]
    },
    {
        name: '上海',
        children: []
    },
    {
        name: '北京',
        children: []
    }
]

如上所示，删除了区的那一层，保留到市。

function removeLevel(arrs) {
    // todo
}

function removeLevel(arr) {
  function map(arr) {
        return isCity(arr) ? [] : arr.map(v => ({...v, children: map(v.children)}))
  }
  function isCity(arr) {
    return arr.length && arr[0].name.includes('区');
  }
  return map(arr)
}

function removeLevel(arrs, keep) {
     function innerRemove(arrs, level, depth = 0) {
        return depth >= level ? [] :
           arrs.map(item => ({...item, children: innerRemove(item.children, level, depth + 1) }));
     }
     return innerRemove(arrs, keep);
} 

// 保留 1 层
removeLevel(arrs, 1);

// 保留 2 层
removeLevel(arrs, 2);