javascript - 遍历大型数据集的最佳方式

Question

我有一个很大的 JSON 值数据集。以下是该 JSON 对象的一个​​小快照。

 {
     "response": [
     {
         "data": [
         {
             "value": 1,
             "minute": "2019-06-10 11:51",
             "action": "firstApp",
         },
         {
             "value": 10,
             "minute": "2019-06-10 11:51",
             "action": "secondApp",
         },
         {
             "value": 100,
             "minute": "2019-06-10 11:51",
             "action": "thirdApp",
         },
         {
             "value": 10,
             "minute": "2019-06-10 11:52",
             "action": "firstApp",
         },
         {
             "value": 20,
             "minute": "2019-06-10 11:52",
             "action": "secondApp",
         },
         {
             "value": 115,
             "minute": "2019-06-10 11:52",
             "action": "thirdApp",
         }, ]
     }]
 }

现在考虑数据数组中大约有 800 个这样的项目。我想做的是创建一个 JSON 对象，它对每个时间图都有值，就像下面的一样

[
   {
       "timestamp" : "2019-06-10 11:51",
       "firstApp" : {
           "value" : 1,
       }, 
       "secondApp": {
           "value":10,
       },
       "thirdApp": {
           "value" : 100,
       }
   },
   {
       "timestamp" : "2019-06-10 11:52",
       "firstApp" : {
           "value" : 10
       }, 
       "secondApp": {
           "value":20,
       },
       "thirdApp": {
           "value" : 115,
       }
   }
]

我已经编写了以下代码，但它花费了很多时间(大约 10-12 秒)(这是意料之中的) 请参阅此 CodeSandbox ( https://codesandbox.io/s/objective-bartik-0r30j?autoresize=1&expanddevtools=1&fontsize=14&hidenavigation=1&module=%2Fsrc%2Findex.js) 链接以查看代码的运行情况。

我面临的问题是需要花费大量时间(理所当然地)

1. 数据集很大
2. 我的代码很糟糕——因为到处都是循环

我无法控制 1 但我绝对可以控制 2 。你能给我一些关于如何解决这个问题的想法吗？

更新这是性能选项卡的屏幕截图[![在此处输入图片描述][1]][1]

谢谢

let data = {
  response: [
    {
      data: [
        {
          value: 1,
          minute: "2019-06-10 11:51",
          action: "firstApp"
        },
        {
          value: 10,
          minute: "2019-06-10 11:51",
          action: "secondApp"
        },
        {
          value: 100,
          minute: "2019-06-10 11:51",
          action: "thirdApp"
        },
        {
          value: 10,
          minute: "2019-06-10 11:52",
          action: "firstApp"
        },
        {
          value: 20,
          minute: "2019-06-10 11:52",
          action: "secondApp"
        },
        {
          value: 115,
          minute: "2019-06-10 11:52",
          action: "thirdApp"
        }
      ]
    }
  ]
};

function massageData(data) {
  let historyData = [];
  let uniqueTimeStamps = [];
  let event = {
    timestamp: "",
    firstApp: {
      value: 0
    },
    secondApp: {
      value: 0
    },
    thirdApp: {
      value: 0
    }
  };

  for (var i = 0; i < data.length; i++) {
    let item = data[i];

    if (item.minute) {
      if (!uniqueTimeStamps.includes(item.minute)) {
        let timestamp = item.minute;
        console.log("--------------------");
        console.log(timestamp);
        event.timestamp = timestamp;
        event.firstApp.value = getDataValue(data, timestamp, "firstApp");
        event.secondApp.value = getDataValue(data, timestamp, "secondApp");
        event.thirdApp.value = getDataValue(data, timestamp, "thirdApp");
        console.log(event);
        historyData.push(event);
        uniqueTimeStamps.push(item.minute);
      }
    }
  }

  return historyData;
}

function getDataValue(data, timestamp, action) {
  for (var i = 0, len = data.length; i < len; i++) {
    let item = data[i];
    console.log(item);
    if (item["minute"] === timestamp && item["action"] === action) {
      return parseInt(item["value"]);
    }
  }
}

let workData = data.response[0].data;
let formattedData = massageData(workData);
console.log(formattedData);

Answer 1

您可以为相同的时间戳采用经典哈希表，并使用哈希表更新值。

function massageData(data) {
    var historyData = [],
        hash = Object.create(null),
        i, item;

    for (i = 0; i < data.length; i++) {
        item = data[i];
        if (!hash[item.minute]) {
            historyData.push(hash[item.minute] = { timestamp: item.minute, firstApp: { value: 0 }, secondApp: { value: 0 }, thirdApp: { value: 0 } });
        }
        hash[item.minute][item.action].value = item.value;
    }
    return historyData;
}

var data = { response: [{ data: [{ value: 1, minute: "2019-06-10 11:51", action: "firstApp" }, { value: 10, minute: "2019-06-10 11:51", action: "secondApp" }, { value: 100, minute: "2019-06-10 11:51", action: "thirdApp" }, { value: 10, minute: "2019-06-10 11:52", action: "firstApp" }, { value: 20, minute: "2019-06-10 11:52", action: "secondApp" }, { value: 115, minute: "2019-06-10 11:52", action: "thirdApp" }] }] },
    workData = data.response[0].data,
    formattedData = massageData(workData);

console.log(formattedData);

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