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Validate two dates of this "dd-MMM-yyyy" format in javascript.

Answer 1

+2 A:

You will need to create a custom parsing function to handle the format you want, and get date objects to compare, for example:

function customParse(str) {
  var months = ['Jan','Feb','Mar','Apr','May','Jun',
                'Jul','Aug','Sep','Oct','Nov','Dec'],
      n = months.length, re = /(\d{2})-([a-z]{3})-(\d{4})/i, matches;

  while(n--) { months[months[n]]=n; } // map month names to their index :)

  matches = str.match(re); // extract date parts from string

  return new Date(matches[3], months[matches[2]], matches[1]);
}

customParse("18-Aug-2010");
// "Wed Aug 18 2010 00:00:00"

customParse("19-Aug-2010") > customParse("18-Aug-2010");
// true

CMS 2010-08-18 07:15:01

Answer 2

+1 A:

Firstly, the 'dd-MMM-yyyy' format isn't an accepted input format of the Date constructor (it returns an "invalid date" object) so we need to parse this ourselves. Let's write a function to return a Date object from a string in this format.

function parseMyDate(s) {
    var m = ['jan','feb','mar','apr','may','jun','jul','aug','sep','oct','nov','dec'];
    var match = s.match(/(\d+)-([^.]+)-(\d+)/);
    var date = match[1];
    var monthText = match[2];
    var year = match[3];
    var month = m.indexOf(monthText.toLowerCase());
    return new Date(year, month, date);
}

Date objects implicitly typecast to a number (milliseconds since 1970; epoch time) so you can compare using normal comparison operators:

if (parseMyDate(date1) > parseMyDate(date2)) ...

Delan Azabani 2010-08-18 07:17:21

Instead of using hackish `* 1` hacks to cast the result to an integer, you should rather use `parseInt(s.match(/(\d+)/g)[1], 10)` to get the Integer object.

Denis 'Alpheus' Čahuk 2010-08-18 07:25:24

With the OP's format `s.match(/(\d+)/g);` will return you a two element array, e.g. `"12-Aug-2010".match(/(\d+)/g); // ["12", "2010"]`, you are accessing the `1` and `2` indexes. Also you need some way to map the three letter month name with the month number...

CMS 2010-08-18 07:27:04

@Denis in this case we don't even need to convert the strings to numbers, the [`Date` constructor](http://bclary.com/2004/11/07/#a-15.9.3) will convert each argument internally `ToNumber` ;)

CMS 2010-08-18 07:28:34

@CMS, I've fixed both problems. Fixed the first one by removing 'global search' tag. Fixed the second one by using `indexOf` to search.

Delan Azabani 2010-08-18 07:34:11

@Delan, nice, you just have to adjust your indexes again for the `date` and `year` matches (and you can remove those ugly `* 1` without problems) :)

CMS 2010-08-18 07:37:31

No, they are correct now when the `g` modifier is off because `0` is the entire matched string, while `1` and on are the captured matches. I'll remove the multiplication :D

Delan Azabani 2010-08-18 07:40:37

@Delan, I see, but then, the two `match` method calls (for the `date` and `year` variables) will give you exactly the same result. You will be able to capture only the `date` part, not the year.

CMS 2010-08-18 07:46:50

Aaaah, I see. I've fixed it to run one match call that captures all three 'fields' of the date. Thanks ;)

Delan Azabani 2010-08-18 07:54:01

Answer 3

+2 A:

You can do the parsing manually, for your given format, but I'd suggest you use the date.js library to parse the dates to Date objects and then compare. Check it out, its awesome!

And moreover, its a great addition to your js utility toolbox.

naikus 2010-08-18 07:20:29

Answer 4

+1 A:

The native Date can parse "MMM+ dd yyyy", which gives:

function parseDMY(s){
  return new Date(s.replace(/^(\d+)\W+(\w+)\W+/, '$2 $1 '));
}
+parseDMY('19-August-2010') == +new Date(2010, 7, 19) // true
parseDMY('18-Aug-2010') < parseDMY('19-Aug-2010')     // true

matyr 2010-08-19 04:14:16

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Validate two dates of this "dd-MMM-yyyy" format in javascript.

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