JS: Sort by neareast timestamp

Question

I need to sort an array by the nearest timestamp to the current one, but the sorting is wrong. How can this be done?

console.log(new Date(1627569000000));
console.log(new Date(1627565400000));
console.log(new Date(1627561800000));
console.log(new Date(1627572600000));


const arr = [{
  from: 1627569000000
}, {
  from: 1627565400000
}, {
  from: 1627561800000
}, {
  from: 1627572600000
}];

const now = 1627557449263;


const [res] = arr.sort(item => item.from - now);


console.log(new Date(res.from))

Is your goal to sort the whole array, or only to get the nearest one? If you want to sort the full array, why only log the first entry? — A_A, Jul 29 '21 at 11:44
your question is not that clear what do you mean by sort nearest timestamp to the current one ? are you intended to get nearest one date? — Ravikumar, Jul 29 '21 at 11:44

omeanwell · Answer 1 · 2021-07-29T11:48:19.733

This might help you out

const arrayOfTimestampObjects = [
  { from: 1627569000000 },
  { from: 1627565400000 },
  { from: 1627561800000 },
  { from: 1627572600000 },
]
// The below gives [1627569000000, 1627565400000, ...]
const timestamps = arrayOfTimestampObjects.map((obj) => obj.from)

// [9733353, 6133353, 2533353, 13333353]
const differenceFromCurrentTime = timestamps.map((d) =>
  Math.abs(new Date() - new Date(d).getTime()),
)
// 2
const indexOfClosest = differenceFromCurrentTime.indexOf(
  Math.min(...differenceFromCurrentTime),
)
console.log(timestamps[indexOfClosest])
// 1627561800000 is the closest to the current time

score 0 · Answer 2 · answered Jul 29 '21 at 11:38

This sort function will return the values in the order of how close they are to now:

const res = arr.sort((a,b) => {
  if (Math.abs(now - a.from) > Math.abs(now - b.from)) {
    return 1
  }
  if (Math.abs(now - b.from) > Math.abs(now - a.from)) {
    return -1
  }
  return 0
} );

apple apple · Answer 3 · 2021-07-29T15:59:17.397

the function taken by Array.sort should be a compareFunction (it compare elements in the array), not keySelector.

You can first extract the key, sort by key, then get back the array.

const arr = [{from: 690}, {from: 654}, {from: 618}, {from:260}];

const now = 574.49263;

function OrderBy(arr,keySelector){
  return arr.map(x=>[x,keySelector(x)]) // pair of (element, key)
     .sort((x,y)=>x[1]-y[1]) // order by key
     .map(x=>x[0])  // select element
}
const res = OrderBy(arr,item => Math.abs(item.from - now)); // abs for distance

console.log(res)

JS: Sort by neareast timestamp

3 Answers3