映射中的返回Object.keys未定義

Question

我下面的循環出了什么問題？ 我想計算total_count並在映射內進行一些操作后返回[total，total]，但是我不確定。

我的raw數據

const raw = [{
  "device_info": {
    "name": "cam1",
  },
  "age_range": {
    "0-10": {
      "age_range": "0-10",
      "total_count": 15,
      "male_count": 6,
      "female_count": 9
    },
    "11-20": {
      "age_range": "11-20",
      "total_count": 11,
      "male_count": 7,
      "female_count": 4
    },
    "21-30": {
      "age_range": "21-30",
      "total_count": 922,
      "male_count": 452,
      "female_count": 470
    }
  }
}, {
  "device_info": {
    "name": "cam2",
  },
  "age_range": {
    "0-10": {
      "age_range": "0-10",
      "total_count": 1,
      "male_count": 1,
      "female_count": 0
    },
    "11-20": {
      "age_range": "11-20",
      "total_count": 2,
      "male_count": 0,
      "female_count": 2
    },
    "21-30": {
      "age_range": "21-30",
      "total_count": 90,
      "male_count": 58,
      "female_count": 32
    }
  }
}]

環

const x = raw.map(obj => {
  return Object.keys(obj).forEach(key => {
    let total = 0
    if (key === 'age_range') {
      total = Object.keys(obj.age_range).reduce((acum, innerKey) => {
        return acum + obj.age_range[innerKey].total_count
      }, 0)
      console.log(total)
    }
  });
})

console.log('x', x)

https://jsfiddle.net/19m3f7fs/1

Answer 1

Array#forEach不返回任何內容，而是使用Array#map和Object.values ：

const x = raw.map(obj => {
  return Object.values(obj.age_range).reduce((acc, item) => acc + item.total_count, 0)
})

工作示例：

 const raw = [{ "device_info": { "name": "cam1", }, "age_range": { "0-10": { "age_range": "0-10", "total_count": 15, "male_count": 6, "female_count": 9 }, "11-20": { "age_range": "11-20", "total_count": 11, "male_count": 7, "female_count": 4 }, "21-30": { "age_range": "21-30", "total_count": 922, "male_count": 452, "female_count": 470 } } }, { "device_info": { "name": "cam2", }, "age_range": { "0-10": { "age_range": "0-10", "total_count": 1, "male_count": 1, "female_count": 0 }, "11-20": { "age_range": "11-20", "total_count": 2, "male_count": 0, "female_count": 2 }, "21-30": { "age_range": "21-30", "total_count": 90, "male_count": 58, "female_count": 32 } } }] const x = raw.map(obj => Object.values(obj.age_range).reduce((acc, item) => acc + item.total_count, 0)) console.log(x) 

Answer 2

您的問題是，raw.map返回來自Object.key（obj）.forEach（...）的任何內容

但是對於每個僅僅是“迭代器”功能。 它實際上不返回任何東西。

請參閱： https ： //developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach

Answer 3

像這樣更改。在第一個map變量中定義總數，並從forEach刪除收益。ForEach不返回任何東西。僅在第一個地圖內添加收益。

 const raw = [{ "device_info": { "name": "cam1", }, "age_range": { "0-10": { "age_range": "0-10", "total_count": 15, "male_count": 6, "female_count": 9 }, "11-20": { "age_range": "11-20", "total_count": 11, "male_count": 7, "female_count": 4 }, "21-30": { "age_range": "21-30", "total_count": 922, "male_count": 452, "female_count": 470 } } }, { "device_info": { "name": "cam2", }, "age_range": { "0-10": { "age_range": "0-10", "total_count": 1, "male_count": 1, "female_count": 0 }, "11-20": { "age_range": "11-20", "total_count": 2, "male_count": 0, "female_count": 2 }, "21-30": { "age_range": "21-30", "total_count": 90, "male_count": 58, "female_count": 32 } } }] const x = raw.map(obj => { let total = 0 Object.keys(obj).forEach(key => { if (key === 'age_range') { total = Object.keys(obj.age_range).reduce((acum, innerKey) => { return acum + obj.age_range[innerKey].total_count }, 0) } }); return total }) console.log('x', x)