How to sort an array of objects by date?

Question

I am trying to sort an array of objects with each object containing:

var recent = [{id: "123",age :12,start: "10/17/13 13:07"} , {id: "13",age :62,start: "07/30/13 16:30"}];

Date format is: mm/dd/yy hh:mm.

I want to sort in order of date with the most recent first. If date is same it should be sorted by their time parts.

I tried out the below sort() function, but it is not working:

recent.sort(function(a,b))
{
    a = new Date(a.start);
    b = new Date(b.start);
    return a-b;
});

Also how should I iterate over the objects for sorting? Something like:

for (var i = 0; i < recent.length; i++)
    {
        recent[i].start.sort(function (a, b)
        {
            a = new Date(a.start);
            b = new Date(b.start);
            return a-b; 
        } );
    }

There can be any number of objects in the array.

Chris Charles · Accepted Answer · 2016-05-09 12:23:47Z

65

As has been pointed out in the comments, the definition of recent isn't correct javascript.

But assuming the dates are strings:

var recent = [
    {id: 123,age :12,start: "10/17/13 13:07"}, 
    {id: 13,age :62,start: "07/30/13 16:30"}
];

then sort like this:

recent.sort(function(a,b) { 
    return new Date(a.start).getTime() - new Date(b.start).getTime() 
});

More details on sort function from W3Schools

edited May 9, 2016 at 12:23

answered Oct 17, 2013 at 15:23

Chris Charles

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3 Comments

jherax Over a year ago

You can find some useful answers to this topic here: Sort Javascript Object Array By Date

pruett Over a year ago

note: don't forget the explicit return declaration

Emeka Elo Over a year ago

For most recent first, shouldn't it be new Date(b.start).getTime() - new Date(a.start).getTime()

Tom Bowers · Accepted Answer · 2013-10-17 15:24:19Z

7

recent.sort(function(a,b) { return new Date(a.start).getTime() - new Date(b.start).getTime() } );

edited Oct 17, 2013 at 15:24

answered Oct 17, 2013 at 15:16

Tom Bowers

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4 Comments

Barmar Over a year ago

Subtracting Date objects apparently returns the same thing as subtracting their getTime() values, although I can't find this requirement in any specification.

Tom Bowers Over a year ago

Yes, I've noticed that, although getTime() will always be consistent, and since the OP wants the time component to explicitly be used when sorting, it makes sense to be specific.

Barmar Over a year ago

A bigger compatibility problem may be that parsing mm/dd/yy format is not portable.

Tom Bowers Over a year ago

That's a good point. Generally, if you need to be portable, the ISO date should be used.

stayingcool · Accepted Answer · 2019-07-05 01:47:02Z

5

ES6:

recent.sort((a,b)=> new Date(b.start).getTime()-new Date(a.start).getTime());

answered Jul 5, 2019 at 1:47

stayingcool

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Comments

cchamberlain · Accepted Answer · 2016-12-06 19:44:24Z

1

This function allows you to create a comparator that will walk a path to the key you would like to compare on:

function createDateComparator ( path = [] , comparator = (a, b) => a.getTime() - b.getTime()) {
  return (a, b) => {
    let _a = a
    let _b = b
    for(let key of path) {
      _a = _a[key]
      _b = _b[key]
    }
    return comparator(_a, _b)
  }
}


const input = (
  [ { foo: new Date(2017, 0, 1) }
  , { foo: new Date(2018, 0, 1) }
  , { foo: new Date(2016, 0, 1) }
  ]
)

const result = input.sort(createDateComparator([ 'foo' ]))

console.info(result)

edited Dec 6, 2016 at 19:44

answered Dec 5, 2016 at 21:08

cchamberlain

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