我有一个很大的JSON值数据集。以下是该JSON对象的小快照。
{
"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个这些项。我想做的是创建一个JSON对象，该对象具有每个timestmap的值，就像下面的
[
{
"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,
}
}
]
我已经这样编写了以下代码，但是它花费了很多时间（大约10-12秒）（这是很正常的） 请参考此CodeSandbox（https://codesandbox.io/s/objective-bartik-0r30j?autoresize=1&expanddevtools=1&fontsize=14&hidenavigation=1&module=%2Fsrc%2Findex.js）链接以查看实际代码。
我面临的问题是花很多时间（理应如此）
我无法控制1，但是我绝对可以控制2。您能否给我一些有关如何解决此问题的想法？
更新 这是“效果”标签中的屏幕截图 [！[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);
答案 0 :(得分：2)
您可以将经典哈希表用于相同的时间戳，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);.as-console-wrapper { max-height: 100% !important; top: 0; }
答案 1 :(得分：0)
下面涉及将对象用作哈希表的另一种类似方法。它应该更容易理解：
function massageData (data) {
const events = [];
const timestamps = {};
for (let i = 0; i < data.length; i++) {
const { action, minute, ...item } = data[i];
if (!(minute in timestamps)) {
const event = { timestamp: minute };
events.push(event);
timestamps[minute] = event;
}
timestamps[minute][action] = item;
}
return events;
}
const 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" }];
console.log(massageData(data));
这会将除minute和action之外的每个项目中的所有属性复制到每个event中的对象中，作为计算后的属性[action]。如果value确实是每个item上唯一存在的其他属性，则可以简化代码：
function massageData (data) {
const events = [];
const timestamps = {};
for (let i = 0; i < data.length; i++) {
const { action, minute, value } = data[i];
if (!(minute in timestamps)) {
const event = { timestamp: minute };
events.push(event);
timestamps[minute] = event;
}
timestamps[minute][action] = { value };
}
return events;
}
const 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" }];
console.log(massageData(data));