Get array of distinct date(not time) from array of objects in javascript

Question

Hey I am working on a attendance project in reactjs , I am facing a problem that I received an array of attendances e.g (in range of last two weeks ) . All I need is filter an array of distinct date, not the time but only date . (Time can be different in one date)

let dates = [
  { id: 51, attendanceTime: "2022-12-26T06:07:02.000Z" },
  { id: 52, attendanceTime: "2022-11-26T06:07:36.000Z" },
  { id: 53, attendanceTime: "2022-10-12T06:28:43.000Z" },
  { id: 54, attendanceTime: "2023-01-01T06:48:53.000Z" },
  { id: 55, attendanceTime: "2022-12-26T06:56:23.000Z" },
];

I have tried methods but gettime() compare all not only date , getDate() compare only Day not month and year , So I need to filter such that it only differentiate on only date (day,month,year) and filter my array of distinct array. I need result like

const result = [
  { id: 51, attendanceTime: "2022-12-26T06:07:02.000Z" },
  { id: 52, attendanceTime: "2022-11-26T06:07:36.000Z" },
  { id: 53, attendanceTime: "2022-10-12T06:28:43.000Z" },
  { id: 54, attendanceTime: "2023-01-01T06:48:53.000Z" },
];

this is required result of distinct date array

`````` const uniqueAttendance = [ ...new Map(alld.map((v) => [new Date(v.attendanceTime).toDateString(), v])).values(), ]; ```````` — Muhammad Salman Ashraf, Jan 03 '23 at 06:24

score 0 · Answer 1 · answered Jan 03 '23 at 05:56

You can try something like that:

let dates = [
  {id: 51, attendanceTime: '2022-12-26T06:07:02.000Z'},
  {id: 52, attendanceTime: '2022-11-26T06:07:36.000Z' },
  {id: 53, attendanceTime: '2022-10-12T06:28:43.000Z'},
  {id: 54, attendanceTime: '2023-01-01T06:48:53.000Z'},
  {id: 55, attendanceTime: '2022-12-26T06:56:23.000Z'}
];

let distinct = [];

for(let i = 0; i < dates.length; i++){

  let dateFromDates = dates[i].attendanceTime.split("T");
  let duplicate = distinct.filter(dateFromDistinct => dateFromDistinct == dateFromDates[0]);
  if(duplicate.length == 0){
    distinct.push(dateFromDates[0]);
  }
}

console.log(distinct);

Time complexity: O(n^2)
Space complexity: O(n)

Also date format must be in that format that you share.

score 0 · Answer 2 · answered Jan 03 '23 at 05:57

You can use Array.filter() and Array.substring() to find unique values

 let dates = [
      {id: 51, attendanceTime: '2022-12-26T06:07:02.000Z'},
      {id: 52, attendanceTime: '2022-11-26T06:07:36.000Z' },
      {id: 53, attendanceTime: '2022-10-12T06:28:43.000Z'},
      {id: 54, attendanceTime: '2023-01-01T06:48:53.000Z'},
      {id: 55, attendanceTime: '2022-12-26T06:56:23.000Z'}
    ];
let uniqueDate=dates.filter((value,ind,arr)=>arr.findIndex(value2=>(value2.attendanceTime.substring(0, 10)===value.attendanceTime.substring(0, 10)))===ind)

console.log('Original',dates, '\nUnique',uniqueDate)

Working

filter() method creates new array with elements that pass test provided by a function.

syntax: dates.filter(function(currentValue, index, arr), thisValue)

substring() method extracts characters between two indices, from a string, and returns the substring.

Syntax: string.substring(start, end)

Get array of distinct date(not time) from array of objects in javascript

2 Answers2