JavaScript 代码优化：将区县添加到只有一个城市代码的城市中

要将区县添加到只有一个城市代码的城市中，您可以在适当的位置添加以下代码：

const countyCode = '110228';
const cityCode = countyCode.slice(0, 4);
const city = cityMap.get(cityCode);
if (city) {
  city.children.push(makeOption(county[countyCode], countyCode));
}

完整的代码如下：

function useCascaderAreaData() {
  const { city_list: city, county_list: county, province_list: province } = areaList;
  const provinceMap = /* @__PURE__ */ new Map();
  Object.keys(province).forEach((code) => {
    provinceMap.set(code.slice(0, 2), makeOption(province[code], code, []));
  });
  const cityMap = /* @__PURE__ */ new Map();
  Object.keys(city).forEach((code) => {
    const option = makeOption(city[code], code, []);
    cityMap.set(code.slice(0, 4), option);
    const province2 = provinceMap.get(code.slice(0, 2));
    if (province2) {
      province2.children.push(option);
    }
  });
  Object.keys(county).forEach((code) => {
    const city2 = cityMap.get(code.slice(0, 4));
    if (city2) {
      city2.children.push(makeOption(county[code], code));
    }
  });

  // 添加区县到城市中
  const countyCode = '110228';
  const cityCode = countyCode.slice(0, 4);
  const city = cityMap.get(cityCode);
  if (city) {
    city.children.push(makeOption(county[countyCode], countyCode));
  }
  
  return Array.from(provinceMap.values());
}

请确保将区县代码和城市代码替换为您实际的代码。