I am trying to return an array with objects that have the nearest date.

I have something like this:

let arr = [
 {
   "name": "test1",
   "date": "2022-05-01T00:00:00.000 00:00"
 },
 {
   "name": "test2",
   "date": "2022-05-01T00:00:00.000 00:00"
 },
 {
   "name": "test3",
   "date": "2022-04-01T00:00:00.000 00:00"
 },
 {
   "name": "test4",
   "date": "2022-03-01T00:00:00.000 00:00"
 },
]

I need to return an array with the objects with the nearest date, something like this:

let arrNewDates = [
 {
   "name": "test1",
   "date": "2022-05-01T00:00:00.000 00:00"
 },
 {
   "name": "test2",
   "date": "2022-05-01T00:00:00.000 00:00"
 },
]

Because they are the objectst with the nearest date to the current date.

I've been thinking in ways to solve this problem, but no success. Does anyone know a function that can solve that?

Thanks,

CodePudding user response：

You can use a filter go through the entire array and only keep elements that are at span distance. Something similar to this:

const closestDates = (input: Record<string, string>[], span: number) => { 
 return input.filter(item => Math.abs(new Date(item.date) - new Date()) <= span) ) 
}

And then you can use it like this:

closestDate(arr, 1000)

Note:

1. I'm using Record<string, string>, but you should use a narrower type
2. span is measured in milliseconds

CodePudding user response：

First we need a helper function getDateDifference to get the actual date difference of two items, similarly to @Radu Diță.

The next step would be to iterate in a double for loop over the whole array to compare each dateDifference and each time we get a smaller one we save that result in an array.

The complexity would be O(n²) since we have to compare each item with each other.

const arr = [{
    name: "test1",
    date: "2022-05-01T00:00:00.000 00:00",
  },
  {
    name: "test2",
    date: "2022-05-01T00:00:00.000 00:00",
  },
  {
    name: "test3",
    date: "2022-04-01T00:00:00.000 00:00",
  },
  {
    name: "test4",
    date: "2022-03-01T00:00:00.000 00:00",
  },
];

const getDateDifference = (item1, item2) => {
  return Math.abs(new Date(item1.date) - new Date(item2.date));
};


let closestDistance = undefined;
let arrNewDates = [];
arr.forEach((item1) => {
  arr.forEach((item2) => {
    if (item1 !== item2) {
      const dateDifference = getDateDifference(item1, item2);
      if (closestDistance === undefined || dateDifference < closestDistance) {
        closestDistance = dateDifference;
        arrNewDates = [item1, item2];
      }
    }
  });
});

console.log(arrNewDates);