Question

为什么x的结果是

[object Object] 12

我不能在reduce函数中返回对象吗？我知道在map中，过滤器我可以返回对象，不知道下面的代码有什么问题。

const raw = [{
  "device_info": {
    "name": "nokia",
    "device_id": "123"
  },
  "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
    }

  }
}, {
  "device_info": {
    "name": "iphone",
    "device_id": "456"
  },
  "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
    }
  }
}]

const x = raw.map(obj => {
  return Object.values(obj.age_range).reduce((acc, obj2) => ({
    total_count: acc + obj2.total_count,
    device_id: obj.device_info.device_id
  }), 0)
})

console.log('x', x)

不知道什么是错的，需要帮助。

Answer 1

正如我已经explained给你的那样：在第一次迭代中，acc包含0，但是你返回一个对象。在下一次迭代中，acc将包含此对象，并尝试将此对象添加到新的total_count。我建议这个：

const x = raw.map(obj => {
  // calculate the total
  const total_count = Object.values(obj.age_range).reduce((acc, item) => acc + item.total_count, 0)
  // construct the object
  return { total_count, device_id: obj.device_info.device_id }
})

工作示例：

const raw = [{
  "device_info": {
    "name": "nokia",
    "device_id": "123"
  },
  "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
    }

  }
}, {
  "device_info": {
    "name": "iphone",
    "device_id": "456"
  },
  "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
    }
  }
}]

const x = raw.map(obj => {
  const total_count = Object.values(obj.age_range).reduce((acc, item) => acc + item.total_count, 0)
  return { total_count, device_id: obj.device_info.device_id }
})

console.log('x', x)

JSFiddle here。

Answer 2

您应该将acc初始化为对象，并且至少应该具有密钥total_count。

＆＃13;

const raw = [{
  "device_info": {
    "name": "nokia",
    "device_id": "123"
  },
  "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
    }

  }
}, {
  "device_info": {
    "name": "iphone",
    "device_id": "456"
  },
  "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
    }
  }
}]

const x = raw.map(obj => {
  return Object.values(obj.age_range)
    .reduce((acc, obj2) => {
      return {
        total_count: acc.total_count + obj2.total_count,
        device_id: obj.device_info.device_id
      }
    }, { total_count: 0 })
})

console.log('x', x)

＆＃13;

Answer 3

您可以切换构建对象的部分，并通过movint对象文字内部的计数来计算值。

const raw = [{ device_info: { name: "nokia", device_id: "123" }, 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 } } }, { device_info: { name: "iphone", device_id: "456" }, 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 } } }];
const x = raw.map(obj => ({
    total_count: Object.values(obj.age_range).reduce((acc, obj2) => acc +  obj2.total_count, 0),
    device_id: obj.device_info.device_id
}));

console.log(x);

在reduce函数中返回对象

3 个答案: