Validate two dates of this “dd-MMM-yyyy” format in javascript

Question

I have two dates 18-Aug-2010 and 19-Aug-2010 of this format. How to find whether which date is greater?

Answer 1

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.

Answer 2

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

Answer 3

Update: IE10, FX30 (and likely more) will understand "18 Aug 2010" without the dashes - Chrome handles either

so Date.parse("18-Aug-2010".replace("/-/g," ")) works in these browsers (and more)

Live Demo

Hence

function compareDates(str1,str2) {
  var d1 = Date.parse(str1.replace("/-/g," ")),
      d2 = Date.parse(str2.replace("/-/g," "));
  return d1<d2;
}

Answer 4

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

Answer 5

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)) ...