javascript - 自动解析json属性为新对象

Question

我有 json 格式的传入数据，如下所示:

原始数据:

{
  "data": [{
      "id": "Device_6",
      "type": "SensingDevice",
      "Battery": {
        "type": "Number",
        "value": "4.08",
        "metadata": {
          "timestamp": {
            "type": "DateTime",
            "value": "2017-11-09T14:49:02.00Z"
          },
          "unit": {
            "type": "Text",
            "value": "voltage"
          }
        }
      },
      "DO": {
        "type": "Number",
        "value": "5.71",
        "metadata": {
          "timestamp": {
            "type": "DateTime",
            "value": "2017-11-09T14:49:02.00Z"
          },
          "unit": {
            "type": "Text",
            "value": "mg/l"
          }
        }
      },
      "Humidity": {
        "type": "Number",
        "value": "57.30",
        "metadata": {
          "timestamp": {
            "type": "DateTime",
            "value": "2017-11-09T14:49:02.00Z"
          },
          "unit": {
            "type": "Text",
            "value": "percent"
          }
        }
      },
      "PH": {
        "type": "Number",
        "value": "14.00",
        "metadata": {
          "timestamp": {
            "type": "DateTime",
            "value": "2017-11-09T14:49:02.00Z"
          }
        }
      },
      "temperature": {
        "type": "Number",
        "value": "41.00",
        "metadata": {
          "timestamp": {
            "type": "DateTime",
            "value": "2017-11-09T14:49:02.00Z"
          },
          "unit": {
            "type": "Text",
            "value": "celsius"
          }
        }
      },
      "waterTemperature": {
        "type": "Number",
        "value": "29.69",
        "metadata": {
          "timestamp": {
            "type": "DateTime",
            "value": "2017-11-09T14:49:02.00Z"
          },
          "unit": {
            "type": "Text",
            "value": "celsius"
          }
        }
      }
    }
  ],
  "subscriptionId": "59d5eeec4f3db340052d618c"
}

为了特定的应用目的，我需要将这个复杂的 JSON 转换为简单的 key:value 格式。

所以我在带有 node-json-transform 包的 Node js 中使用这段代码:

 var map_data = {
           list:'data',
            item :  { Battery: 'Battery.value',
                        DO: 'DO.value',
                        Humidity: 'Humidity.value',
                        PH: 'PH.value',
                        temperature: 'temperature.value',
                        waterTemperature: 'waterTemperature.value', },
    };
   console.log (map_data)

         var dataTransform = DataTransform(data, map_data);
         var data_result = dataTransform.transform();

输出看起来像我想要的:

[ { Battery: '4.08',
    DO: '5.71',
    Humidity: '57.30',
    PH: '14.00',
    temperature: '41.00',
    waterTemperature: '29.69' } ]

但是现在，如果我不知道属性的名称怎么办？所以我试图让它自动发现 key :

var keys = Object.keys(data.data[0]); 
var keysvalues = '';
    for (i=2; i < keys.length; i++) {
        keysvalues += keys[i]+':"'+ keys[i] + '.value",';
    }
var item = '{'+keysvalues+'}'; 
var map_data = {
            list:"data", 
            item,
    };
 var dataTransform = DataTransform(data, map_data);
 var data_result = dataTransform.transform();

这不起作用，因为对象 map_data.item 是一个“假”对象，我在其中手动添加了 {}，因此它被识别为字符串:

console.log(map_data)
{ list: 'data',
  item: '{Battery:"Battery.value",DO:"DO.value",Humidity:"Humidity.value",PH:"PH.value",temperature:"temperature.value",waterTemperature:"waterTemperature.value",}' } 

你能帮我看看如何让 item 对象成为一个真实的对象，这样我就可以按照我想要的格式自动解析 JSON 吗？

Answer 1

所以基本上你想创建一个给定所有嵌套对象的“值”属性的 map 。这意味着您必须过滤掉不是对象或没有 'value' Prop 的原始对象的键。以下是我的做法(我使用 ES6 来避免冗长)。

const isObject = (o) =>
  o instanceof Object && o.constructor === Object;

const getSingleMap = (datum, prop) => {
  const mapKeys = Object.keys(datum).filter(key => isObject(datum[key]) && datum[key][prop]);
  const obj = {};
  mapKeys.forEach(key => {
    obj[key] = datum[key][prop];
  });

  return obj;
}

const getMap = (rawData, prop) =>
  rawData.data.map(datum => getSingleMap(datum, prop));

要使用它，只需调用 const res = getMap(rawData, 'value');。

/*
res == [
  {
    "Battery": "4.08",
    "DO": "5.71",
    "Humidity": "57.30",
    "PH": "14.00",
    "temperature": "41.00",
    "waterTemperature": "29.69"
  }
];
*/

下面提供了一个更优雅的getSingleMap实现。

getSingleMap = (datum, prop) => {
  const mapKeys = Object.keys(datum).filter(key => isObject(datum[key]) && datum[key][prop]);
  return mapKeys.reduce((acc, key) => {
    acc[key] = datum[key][prop];
    return acc;
  }, {});
}

更新:我还用它创建了一个 npm 包，它叫做 json2kv，你可以找到它的来源 here