如何按日期對物件陣列進行排序，但首先是最新日期？

我有物件陣列：

const data = [{
  "id": "1",
  "effectiveDate": "2023-01-21"
}, {
  "id": "2",
  "effectiveDate": "2023-02-22"
}, {
  "id": "3",
  "effectiveDate": "2022-05-04"
}, {
  "id": "4",
  "effectiveDate": "2022-05-05"
}, {
  "id": "5",
  "effectiveDate": "2021-01-21"
}, {
  "id": "6",
  "effectiveDate": "2021-02-22"
}];

我所追求的是以具有最新日期的物件位于索引 0 上的方式對其進行排序的方式，其余物件從最舊的日期到未來的日期按升序排列，如下所示：

[{
  "id": "4",
  "effectiveDate": "2022-05-05"
}, {
  "id": "5",
  "effectiveDate": "2021-01-21"
}, {
  "id": "6",
  "effectiveDate": "2021-02-22"
}, {
  "id": "3",
  "effectiveDate": "2022-05-04"
}, {
  "id": "1",
  "effectiveDate": "2023-01-21"
}, {
  "id": "2",
  "effectiveDate": "2023-02-22"
}]

我排序的方式是：

const orderedDates = data.sort((a, b) => {
  const dateCompareResult = new Date(a.effectiveDate) - new Date(b.effectiveDate);
  return dateCompareResult;
});

這顯然給了我從過去日期到未來日期升序排列的日期，最新日期介于兩者之間。如何將最新的日期物件移動到索引 0？

uj5u.com熱心網友回復：

function getItemsInAscendingDateOrderAndClosestToNowFirst(arr) {
  const time = Date.now();

  const [closest, ...rest] = Array
    // create a shallow copy in order to
    // not mutate the original reference.
    .from(arr)
    // sort items by date closest to now.
    .sort((a, b) => {

      const aTime = new Date(a.effectiveDate).getTime();
      const bTime = new Date(b.effectiveDate).getTime();

      const aDelta = Math.abs(time - aTime);
      const bDelta = Math.abs(time - bTime);

      return (aDelta - bDelta);
    });

  return [
    closest,
    ...rest
      // sort all other items in ascending date order.
      .sort((a, b) =>
        new Date(a.effectiveDate).getTime()
        - new Date(b.effectiveDate).getTime()
      ),
  ];
}

const data = [{
  "id": "1",
  "effectiveDate": "2023-01-21"
}, {
  "id": "2",
  "effectiveDate": "2023-02-22"
}, {
  "id": "3",
  "effectiveDate": "2022-05-04"
}, {
  "id": "4",
  "effectiveDate": "2022-05-05"
}, {
  "id": "5",
  "effectiveDate": "2021-01-21"
}, {
  "id": "6",
  "effectiveDate": "2021-02-22"
}];
const sortedData =
  getItemsInAscendingDateOrderAndClosestToNowFirst(data);

console.log({ sortedData });

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

uj5u.com熱心網友回復：

我認為最簡單的方法是從最舊到最新排序，然后將最接近今天的元素移到開頭，例如

let data = [{"id": "1","effectiveDate": "2023-01-21"},
            {"id": "2","effectiveDate": "2023-02-22"},
            {"id": "3","effectiveDate": "2022-05-04"},
            {"id": "4","effectiveDate": "2022-05-05"},
            {"id": "5","effectiveDate": "2021-01-21"},
            {"id": "6","effectiveDate": "2021-02-22"}];

// Sort from oldest to youngest
data.sort((a, b) => b.effectiveDate.localeCompare(a.effectiveDate));

// Get today as milliseconds
let today = new Date().toLocaleDateString('en-CA');
let todayMS = Date.parse(today);

// Get index of closest element to today
let closestIndex = data.reduce((acc, obj, index) => {
  let diff = Math.abs(Date.parse(obj.effectiveDate) - todayMS);
  return acc.diff > diff? {diff, index} : acc;
}, {diff: Infinity, index:null}).index;

// Move closest element to start of array
data.unshift(data.splice(closestIndex, 1));

console.log(data);

ISO 8601 格式時間戳的好處之一是詞法比較給出了正確的結果。如果您不想使用字串比較，那么比較函式可以是：

data.sort((a, b) => Date.parse(b) - Date.parse(a))

但前提是時間戳是 ECMA-262 支持的 3 種格式之一（幸運的是，YYYY-MM-DD 是其中一種格式）。:-)

標籤：javascript 数组 日期 排序 目的

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