Sort date strings javascript

Question

I have datetimes and dates stored as strings in javscript that I need to compare.

Leaving them as strings seems to work:

const date1 = '2016-01-26 05:20:44'
const date2 = '2016-01-26 06:20:44'
const date3 = '2016-02-26'

date1 > date2 //false
date1 < date2 //true
date3 > date2 //true
date3 > date1 //true
date1 > date3 //false

The question: can I depend on this? Or is this a "it works, but it's not reliable" kind of deal?

Should I convert the date strings into date objects (using date or moment)

Yes, but strictly you should use localeCompare, e.g. date1 > date2 should be date1.localCompare(date2) > 0. — RobG
– RobG, Commented Feb 22, 2018 at 6:09

Scott Sauyet · Accepted Answer · 2018-02-22 01:16:50Z

2

If that is your format, it should continue to work. Think about it: one of the major advantages of that format is exactly that it's sortable.

Of course Date objects themselves are also sortable. The internal valueOf method used in comparing them returns milliseconds since a fixed time.

answered Feb 22, 2018 at 1:16

Scott Sauyet

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1 Comment

Trees4theForest Over a year ago

Thanks! I assumed that the date part was always sortable (been using it in filenames for years) but wasn't sure about the time part (and comparing mixed date and datetimes).

toto · Accepted Answer · 2018-02-22 01:49:38Z

0

Updated.....

function removeAllNoNumber(a) {
   return  a.toString().replace(/\D/g, '');
}

function padRight(source, padChar, padCount) {
  var dif = padCount - source.toString().length;
  if (dif <= 0) {
     return source;
  } else {
     var c = "";
     for (var i = 0; i < dif; i++) {
         c += padChar.toString();
     }
         return (source + c);
     }
}

function timeToInt(a){
     return parseInt(padRight(removeAllNoNumber(a),"0",14),10);
}


  var date1 = timeToInt("2016-01-26 05:20:44"); //20160126052044 
  var date2 = timeToInt("2016-01-26 06:20:44"); //20160126062044
  var date3 = timeToInt("2016-01-26"); //20160126000000

   if (date1 < date2) {

     alert("here");
   }

edited Feb 22, 2018 at 1:49

answered Feb 22, 2018 at 1:24

toto

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3 Comments

Trees4theForest Over a year ago

Ideally, I'd like to do this without converting to date objects.

toto Over a year ago

I update without date object using string... may help

RobG Over a year ago

Far simpler to compare using String.prototype.localeCompare.

Koustubh Kittur · Accepted Answer · 2018-03-07 12:00:30Z

0

Like this you can take extract the date from your given strings in the problem if the format never changes by using substring()

date1.substring(0,10)
date2.substring(0,10)
date3.substring(0,10)

output to substring

"2016-01-26"

"2016-01-26"

"2016-02-26"

and now you can compare the extracted substrings of dates by comparing them like

date1.substring(0,10) > date1.substring(0,10) //false

It is little messy but it will keep you main string unchanged.

answered Mar 7, 2018 at 12:00

Koustubh Kittur

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