Ordering Array of dates javascript

Question

I have an array of dates $myArray

(2012-09-31,1999-01-23,2018-08-29,1808-04-20,2017-11-05,1001-10-01,)

I want to list these dates in most current to oldest, i am using a function

function myFunction() {
myArray.sort(function(a, b){return b-a});
}

The above function does not seem to order the array in any particular way.

b/c javasciprt don't understand your string as date, see sort-javascript-object-array-by-date — aahhaa
– aahhaa, Commented Aug 29, 2017 at 14:20
We can't help you based on what's in the question, as we have no idea what's in your array. Date instances? Strings? If it were Date instances, b-a would work, so... — T.J. Crowder
– T.J. Crowder, Commented Aug 29, 2017 at 14:21
@Rory, your deleted answer was correct. I think the commenter was omitting new from the Date calls, which would cause a different result. — spanky
– spanky, Commented Aug 29, 2017 at 14:28
@spanky you could be correct, although I think your approach of using localeCompare() is better :) — Rory McCrossan
– Rory McCrossan, Commented Aug 29, 2017 at 14:31

spanky · Accepted Answer · 2017-08-29 14:24:22Z

4

In this particular case, you can actually use .localeCompare() to do the comparison.

The reason is that your date strings are formatted to be most general to most specific, and are all the same length.

var myArray = ['2012-09-31', '1999-01-23', '2018-08-29', '1808-04-20', '2017-11-05', '1001-10-01'];

function myFunction() {
  myArray.sort(function(a, b) {
    return b.localeCompare(a);
  });
}

myFunction();

console.log(myArray);

This would not work if the leading 0 on a month or day could be removed, or if the format was for example yyyy-dd-mm or mm-dd-yyyy.

answered Aug 29, 2017 at 14:24

spanky

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Comments

Serge K. · Accepted Answer · 2017-08-29 14:22:53Z

3

You can use sort() without any parameters as it will order it alphabetically which work with this time format and then reverse it :

var list = ['2012-09-31', '1999-01-23', '2018-08-29' , '1808-04-20', '2017-11-05', '1001-10-01'];

console.log(list.sort().reverse());

answered Aug 29, 2017 at 14:22

Serge K.

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1 Comment

spanky Over a year ago

I'm so accustomed to using .localeCompare() that I forget the default .sort() is alphabetical. Using .sort() alone here is nicer.

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