从for循环到forEach，再到for...of，再到loda

1.for循环与forEach，比较简单的操作就不贴代码了，唯一不同的在于for循环内部相应break等中断操作，forEach不支持，
2.for...of，基于es6的新方法，完美支持break等中断循环操作，

for (let item of CityDataJson) {
        if (nameId == item.id) {
            for (let cityList of item.city) {
                if (cityId == cityList.id) {
                    for (let areaList of cityList.area) {
                        if (areaId == areaList.id) {
                            this.setState({
                                provinceId: CityDataJson[preventIndex].id,
                                provinceDesc: CityDataJson[preventIndex].name,
                                cityId: cityList[cityIndex].id,
                                cityDesc: cityList[cityIndex].name,
                                areaId: areaList[areaIndex].id,
                                areaDesc: areaList[areaIndex].name
                            });
                            break;
                        }
                    }
                    break;
                }
            }
            break;
        }
    }

3.基于lodash的findIndex方法，快速找到对应数据下标，代码如下；

   let preventIndex = findIndex(CityDataJson, ['id', nameId]),
        cityList = CityDataJson[preventIndex].city,
        cityIndex = findIndex(cityList, ['id', cityId]),
        areaList = cityList[cityIndex].area,
        areaIndex = findIndex(areaList, ['id', areaId]);
    console.log(cityIndex, cityId);
    this.setState({
        provinceId: CityDataJson[preventIndex].id,
        provinceDesc: CityDataJson[preventIndex].name,
        cityId: cityList[cityIndex].id,
        cityDesc: cityList[cityIndex].name,
        areaId: areaList[areaIndex].id,
        areaDesc: areaList[areaIndex].name
    });