Parse UK format date string in JS

Issue

I'm trying to parse "13/12/2023" or "13/12/2023 10:00:00 AM" date strings to Date objects in JavaScript. As I understand it can not be done via new Date('13/12/2023') as it's expecting a US locale.

I'm trying to use the luxon library to do this work in the following way:

import { DateTime } from 'luxon';
var luxonDate = DateTime.fromFormat("13/12/2023", 'dd/MM/yyyy');

However the above only works for a Date without time. I need to parse time as well. I need to tweak format string to the following:

import { DateTime } from 'luxon';
var luxonDate = DateTime.fromFormat("13/12/2023", 'dd/MM/yyyy h:mm:ss a');

This works for Date with time BUT the problem is that time is optional for me in the string, so the only way I can think of to somehow identify if time passed and use correct format.

Does anyone know if there any other option of not doing it all manually?

Solution

You can always check validity after parsing, then try parsing again.

import { DateTime } from 'luxon';

function parseUKDateWithOptionalTime(s: string) : DateTime {
  let dt = DateTime.fromFormat(s, 'dd/MM/yyyy h:mm:ss a');
  if (!dt.isValid) {
    dt = DateTime.fromFormat(s, 'dd/MM/yyyy');
  }

  return dt;
}

Though - do keep in mind that when you parse a date without a time into a Luxon DateTime object, you're implying that you want the time to be 00:00 (midnight). Fundamentally, that's a different concept than a date (which would include all times within the day, not just midnight). The JavaScript Date object has the same issue (it's really a timestamp, not a date).

Thus, you might consider not using this function, but instead breaking apart your business logic into different paths. Ask yourself what it actually means when someone provides a whole date and how that differs than providing a date and time. For example, a whole date might indicate a birth day to acknowledge any time within the day, or a business day in which a discount is valid through the end of the day. Whereas a date and time usually indicates an exact point at which something occurred or will occur.

Answered By - Matt Johnson-Pint