How to sort an array of objects by multiple date fields?

Question

I have the following data structure:

var dates = [
  {
    id: '1',
    date1: '2022-03-21T18:59:36.641Z',
    date2: '2022-03-17T18:59:36.641Z',
  },
  {
    id: '2',
    date1: '2022-03-20T18:59:36.641Z',
    date2: '2022-03-17T18:59:36.641Z',
  },
  {
    id: '3',
    date2: '2022-03-17T18:59:36.641Z',
  },
  {
    id: '4',
    date2: '2022-03-15T18:59:36.641Z',
  }
];

var sorted = dates.sort(function(a,b) {
      return (a.date1 > b.date1) ? 1 : -1
   });

console.log({sorted});

Notice that date1 is not always available, but date2 is required. I'd like to sort by date1 first, then date2. I've created this fiddle to test, but still haven't figured it out: https://jsfiddle.net/y9sgpob8/4/

Please help me figure out how to get the results in the following order:

[{
  date1: "2022-03-20T18:59:36.641Z",
  date2: "2022-03-17T18:59:36.641Z",
  id: "2"
}, {
  date1: "2022-03-21T18:59:36.641Z",
  date2: "2022-03-17T18:59:36.641Z",
  id: "1"
}, {
  date2: "2022-03-15T18:59:36.641Z",
  id: "4"
}, {
  date2: "2022-03-17T18:59:36.641Z",
  id: "3"
}]

[How do I create a runnable stack snippet?](https://meta.stackoverflow.com/questions/358992) — adiga, Mar 18 '22 at 06:24

adiga · Accepted Answer · 2022-03-18T06:27:57.520

0

You need to sort based on

whether date1 exists
then based on date1 value
then based on date2 value

Since the dates are in ISO format, you can do string comparison to sort

const input=[{id:"1",date1:"2022-03-21T18:59:36.641Z",date2:"2022-03-17T18:59:36.641Z",},{id:"2",date1:"2022-03-20T18:59:36.641Z",date2:"2022-03-17T18:59:36.641Z",},{id:"3",date2:"2022-03-17T18:59:36.641Z",},{id:"4",date2:"2022-03-15T18:59:36.641Z",}];

input.sort((a,b) => 
  ( ('date1' in b) - ('date1' in a) )
  || (a.date1 ?? '').localeCompare(b.date1 ?? '')
  || a.date2.localeCompare(b.date2)
)

console.log(input)

edited Mar 18 '22 at 06:27

answered Mar 18 '22 at 06:20

adiga

34,372
9
61
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This is the simplest solution I've seen. Checking for the existence of `date1` and comparing that value was what I was missing. Thank you! – Brian Anderson Mar 18 '22 at 15:26

Marc Anthony B · Answer 2 · 2022-03-18T06:32:56.440

You could also separate the objects that only have date2 then sort and lastly merge it. See snippet below:

const dates = [
  {
    id: '1',
    date1: '2022-03-21T18:59:36.641Z',
    date2: '2022-03-17T18:59:36.641Z',
  },
  {
    id: '2',
    date1: '2022-03-20T18:59:36.641Z',
    date2: '2022-03-17T18:59:36.641Z',
  },
  {
    id: '3',
    date2: '2022-03-17T18:59:36.641Z',
  },
  {
    id: '4',
    date2: '2022-03-15T18:59:36.641Z',
  }
];

var array1 = [];
var array2 = [];

for (const date in dates) {
  if (dates[date].date1) {
    array1.push(dates[date]);
  } else {
   array2.push(dates[date]);
  }
}

var sorted1 = array1.sort(function(a,b) {
      return (a.date1 > b.date1) ? 1 : -1
   }); 
   
var sorted2 = array2.sort(function(a,b) {
      return (a.date2 > b.date2) ? 1 : -1
   }); 
   
const sorted = sorted1.concat(sorted2);  
console.log({sorted});

This solution works, and is easy to follow. There's more computation than @adiga's solution, but it would probably be easier for me to debug! Thank you for the solution! — Brian Anderson, Mar 18 '22 at 15:27

score 0 · Answer 3 · edited Mar 18 '22 at 07:48

All records not have date1 will be found in the end of the result, right? If so, You can separate to 2 arrays and merge them.

const dates=[{id:"1",date1:"2022-03-21T18:59:36.641Z",date2:"2022-03-17T18:59:36.641Z",},{id:"2",date1:"2022-03-20T18:59:36.641Z",date2:"2022-03-17T18:59:36.641Z",},{id:"3",date2:"2022-03-17T18:59:36.641Z",},{id:"4",date2:"2022-03-15T18:59:36.641Z",}];

const timeStamp = value => new Date(value).valueOf()

const arrWithDate1 = dates
                      .filter(elem => elem.date1)
                      .sort((a, b) => (timeStamp(a.date1) - timeStamp(b.date1)))

const arrWithDate2 = dates
                      .filter(elem => !elem.date1)
                      .sort((a, b) => (timeStamp(a.date2) - timeStamp(b.date2)))

console.log([...arrWithDate1, ...arrWithDate2]);

No, the ordering of the dates is not guaranteed. Thank you for this solution though! — Brian Anderson, Mar 18 '22 at 15:26

How to sort an array of objects by multiple date fields?

3 Answers3

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