如何按日期对对象数组进行排序，但首先是最新日期？

Question

I've got the array of objects:

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"
}];

What I'm after is the way to sort it in the way that the object with the most current date is on index 0 and the rest of the objects are ordered ascending from the oldest to future dates, like this:

[{
  "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"
}]

The way I'm sorting it is:

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

which obviously gives me dates sorted ascending from the past dates to the future dates with the most current date somewhere in between. How can I move the most current date object to index 0?

Answer 1

 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; }

Answer 2

I think the simplest way is to sort from oldest to newest, then move the element that's closest to today to the start, eg

 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);

One of the benefits of ISO 8601 formatted timestamps is that lexical comparisons give correct results. If you don't want to use string comparison then the comparison function can be:

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

but only if the timestamps are in one of the 3 formats supported by ECMA-262 (and fortunately, YYYY-MM-DD is one such format). :-)