第 125 期(算法-递归)：统计子类目数量

[wingmeng]

已知数据如下：

const testData = [
  {
    name: '大中华区',
    type: 'area',
    children: [
      {
        name: '华北片区',
        type: 'region',
        children: [
          {
            name: '北京',
            type: 'city',
            children: [
              {
                name: '东城区',
                type: 'district',
                children: [
                  { name: '东华门街道专卖店', type: 'store' },
                  { name: '东四街门店', type: 'store' },
                  { name: '和平里专卖店', type: 'store' }
                ]
              }, {
                name: '朝阳区',
                type: 'district',
                children: [
                  { name: '亚运村旗舰店', type: 'store' },
                  { name: '朝外街道店', type: 'store' }
                ]
              }
            ]
          }
        ]
      }, {
        name: '华东片区',
        type: 'region',
        children: [
          {
            name: '上海',
            type: 'city',
            children: [
              {
                name: '黄浦区',
                type: 'district',
                children: [
                  { name: '佳佳旗舰店', type: 'store' }
                ]
              }
            ]
          }, {
            name: '青岛',
            type: 'city',
            children: [
              {
                name: '黄岛区',
                type: 'district',
                children: [
                  { name: '蜊叉泊商业街门店', type: 'store' }
                ]
              }
            ]
          }
        ]
      }
    ]
  }, {
    name: '海外大区',
    type: 'area',
    children: [
      {
        name: '欧洲',
        type: 'region',
        children: [
          {
            name: '巴黎',
            type: 'city',
            children: [
              {
                name: '第4区',
                type: 'district',
                children: [
                  { name: '圣安东尼大道旗舰店', type: 'store' }
                ]
              }
            ]
          }
        ]
      }
    ]
  }
];

请统计总的 area、region、city、district 和 store 的数量，并统计每个大区（area）下 region、city、district 和 store 的数量。效果如下：

参考代码：

主要用到了递归思想和 reduce 方法

const model = ['area', 'region', 'city', 'district', 'store'];

console.group('总计');
display(model, testData);
console.groupEnd();

testData.map(node => {
  console.group(node.name);
  display(model.slice(1), node.children);
  console.groupEnd();
});

function countNumber(type, data) {
  const _count = (arr) => {
    if (!(Array.isArray(arr) && arr.length)) {
      return 0;
    }

    if (arr[0].type === type) {
      return arr.length;
    }

    return arr.reduce((total, cur) => {
      return total + _count(cur.children);
    }, 0);
  };

  return _count(data);
}

function display(model, data) {
  model.map(s => {
    const title = s.substr(0, 1).toUpperCase() + s.substr(1);
    const number = countNumber(s, data);

    console.log(`${title}: ${number}`);
  });
}