比较对象数组中的日期和时间

Question

我正在尝试比较日期和时间来处理我的数据。我需要通过检查对象中的 updated_at 键来检查哪个是最新数据。

下面我给出了场景。

// below is my data to be manipulat
[{
  "is_latest": "",
  "created_at": "2021-09-21T21:24:05.000Z",
  "updated_at": "2021-09-21T17:53:29.000Z"
}, {
  "is_latest": "",
  "created_at": "2021-09-22T21:24:05.000Z",
  "updated_at": "2021-09-22T17:53:29.000Z"
}, {
  "is_latest": "",
  "created_at": "2021-09-29T21:24:05.000Z",
  "updated_at": "2021-09-29T17:53:29.000Z" // this is the latest data
}]

我正在尝试这样，但是如何在这里使用时刻来比较哪个是最新的。

for (var i = 0; i < data.length; i++) {
  if (data[i].updated_at > data[i + 1].updated_at) {
    data.is_latest = "true"
  }
}

但我没有得到如下预期的结果。

[{
  "is_latest": "false",
  "created_at": "2021-09-21T21:24:05.000Z",
  "updated_at": "2021-09-21T17:53:29.000Z"
}, {
  "is_latest": "false",
  "created_at": "2021-09-22T21:24:05.000Z",
  "updated_at": "2021-09-22T17:53:29.000Z"
}, {
  "is_latest": true,
  "created_at": "2021-09-29T21:24:05.000Z",
  "updated_at": "2021-09-29T17:53:29.000Z"
}]

我如何使用 map() 或 reduce() 来做到这一点？

Answer 1

您可以通过映射 updated_at 字段值并将它们分散在 Math.max 调用中来找到最新日期。将 Unix 纪元转换回日期后，您可以使用 Array.prototype.find 找到它并将 is_latest 设置为 true。

注意： 由于您的日期采用 ISO 8601 格式，将它们转换回来就像调用 Date.prototype.toISOString.

一样简单

const data = [{
  "is_latest": false,
  "created_at": "2021-09-21T21:24:05.000Z",
  "updated_at": "2021-09-21T17:53:29.000Z"
}, {
  "is_latest": false,
  "created_at": "2021-09-22T21:24:05.000Z",
  "updated_at": "2021-09-22T17:53:29.000Z"
}, {
  "is_latest": false,
  "created_at": "2021-09-29T21:24:05.000Z",
  "updated_at": "2021-09-29T17:53:29.000Z" // this is the latest data
}];

const latestDate = new Date(Math.max(...(data.map(({ updated_at }) =>
  new Date(updated_at))))).toISOString();

data.find(({ updated_at }) => updated_at === latestDate).is_latest = true;

console.log(data);

.as-console-wrapper { top: 0; max-height: 100% !important; }

Answer 2

您应该检查它的地图并获取最大日期索引。然后将其值设置为 true;

var data = [
{
  "is_latest": "",
  "created_at": "2021-09-21T21:24:05.000Z",
  "updated_at": "2021-09-21T17:53:29.000Z"
},
{
  "is_latest": "",
  "created_at": "2021-09-22T21:24:05.000Z",
  "updated_at": "2021-09-22T17:53:29.000Z"
},
{
  "is_latest": "",
  "created_at": "2021-09-29T21:24:05.000Z",
  "updated_at": "2021-09-29T17:53:29.000Z"
},
{
  "is_latest": "",
  "created_at": "2021-09-30T21:24:05.000Z",
  "updated_at": "2021-09-30T17:53:29.000Z"
}
]
var maxDateIndex = 0;

var newData = data.map((item, index) => {
  if(item.updated_at > data[maxDateIndex].updated_at) 
      maxDateIndex = index;
  item.is_latest = "false";
  return item;
});

newData[maxDateIndex].is_latest = "true";
console.log(newData);

Answer 3

无需转换为 Date 对象并返回；坚持使用字符串并使用 localeCompare。然后只需反向排序值并选择第一个。

let data = [{
    "is_latest": "",
    "created_at": "2021-09-21T21:24:05.000Z",
    "updated_at": "2021-09-21T17:53:29.000Z"
  },
  {
    "is_latest": "",
    "created_at": "2021-09-22T21:24:05.000Z",
    "updated_at": "2021-09-22T17:53:29.000Z"
  },
  {
    "is_latest": "",
    "created_at": "2021-09-29T21:24:05.000Z",
    "updated_at": "2021-09-29T17:53:29.000Z" // this is the latest data
  }
];
const trueVal = true; // change to "true" if you want a string
const falseVal = false; // change to "false" if you want a string
data.sort((a, b) => b.updated_at.localeCompare(a.updated_at));
data[0].is_latest = trueVal;
data.filter(datum => !datum.is_latest).forEach(datum => datum.is_latest = falseVal);
console.log(data);

比较对象数组中的日期和时间

Compare date and time in array of objects

javascript

nodes

node.js

reactjs