Sorting date in string format using JavaScript

Question

I got this list of date array that I am trying to sort:

var arr = ['2017/12/16', 
'2017/05/01',
'2017/04/20',
'2017/03/10',
'2017/08/12',
'2017/03/06',
'2017/02/04',
'2017/01/07',
'2016/02/08',
'2015'09/08'];

They are in yyyy/mm/dd format. I tried to use this function to sort:

arr.sort(function(a,b) {
 a = a.split('/').reverse().join('');
  b = b.split('/').reverse().join('');
  return a > b ? 1 : a < b ? -1 : 0;
});

However, it tells me that a.split is not a function.

You realize you have a typo in the last date, it's '2015/09/08', while it should be '2015/09/08' after replacing the inner quotation with a slash. — Djaouad
– Djaouad, Commented Aug 26, 2017 at 11:21
Why do you try convert the date? Just use var sorted = arr.sort(); — alexmac
– alexmac, Commented Aug 26, 2017 at 11:24

Patrick Hund · Accepted Answer · 2017-08-26 12:08:57Z

3

There is no need to convert the strings in your array, you can simply compare strings by using the default behavior of Array#sort:

var arr = [
    '2017/12/16',
    '2017/05/01',
    '2017/04/20',
    '2017/03/10',
    '2017/08/12',
    '2017/03/06',
    '2017/02/04',
    '2017/01/07',
    '2016/02/08',
    '2015/09/08'
];

arr.sort();

console.log(arr);

edited Aug 26, 2017 at 12:08

answered Aug 26, 2017 at 11:24

Patrick Hund

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5 Comments

alexmac Over a year ago

Why do you use callback for sort function? arr.sort() is enough.

QWERTY Over a year ago

@PatrickHund Nope it does not work, it is still printing the unsorted array

Patrick Hund Over a year ago

Did you fix the syntax error in your code? The last date string in the input array has a single quote char in it that doesn't belong there. You can see that my code example works simply by hitting the “Run code snippet” button

Nina Scholz Over a year ago

btw, sort sorts the given array in situ.

Dekel Over a year ago

@PatrickHund note that sort works inplace, you don't need to create a new variable for that.

Dekel · Accepted Answer · 2017-08-26 12:02:20Z

1

Instead of split/reverse/join just convert the string to Date object and let javascript do the sorting for you:

var arr = ['2017/12/16', 
'2017/05/01',
'2017/04/20',
'2017/03/10',
'2017/08/12',
'2017/03/06',
'2017/02/04',
'2017/01/07',
'2016/02/08',
'2015/09/08'
];

arr.sort(function(a, b) {
  da = new Date(a);
  db = new Date(b);
  if (da == db) {
    return 0;
  }
  return da > db ? 1 : -1;
});

console.log(arr);

edited Aug 26, 2017 at 12:02

answered Aug 26, 2017 at 11:22

Dekel

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6 Comments

QWERTY Over a year ago

But strangely my result sorted in descending order

QWERTY Over a year ago

Nope it does not work. No matter I changed the < or > sign, it is still printing the original unsorted array

Dekel Over a year ago

Without looking at your code that you use it will be a bit hard to help :)

QWERTY Over a year ago

Ah I figured out why is it so already. Because my array was an object array so I needed to do a.date and b.date. Thanks!!!

georg Over a year ago

A few issues with this snipptet, 1) "parsing of date strings with the Date constructor... is strongly discouraged" (developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…), 2)da > db is not correct in a sort callback and 3) conversions are simply not needed in this case (see below)

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