Javascript date to locale string not correctly display

I didn't quite understand what exactly you need but based on the code you provided, and the reference to the respective library, my guess is that you don't need any third-party modules since JavaScript itself has provided us with the "Internationalization API" internally, accessing with Intl Class:

try this code:

console.log(
    Intl.DateTimeFormat('lo-LA', {
        hour: '2-digit',
        minute: 'numeric',
        second: '2-digit',
        year: 'numeric',
        month: 'numeric',
        day: 'numeric',
    }).format(new Date()));

Keep in mind, that you can also use timeZone: 'UTC', option in the options object (second argument) to change the time zone, try for yourself.

The output will be something like 4/6/2024, 20:36:26

According to MDN, not all localisations are supported. In your example, this might be a case of Lao not being included in the supported locales therefore, defaulting to the system's locale (which may not be what you want.)

You are able to provide a fallback when the requested locale is not supported.

console.log(new Date().toLocaleString(["lo", "id"]));

In the example above, I provided Indonesian as a fallback as it is similar to Lao's date format. You could also use British (en-GB) fallback.

Note, the time format might not be what you want if you go with the Indonesian fallback.

Technically, instead of using .toLocaleString() you should use .toLocaleDateString() for dates, which yields...

new Date().toLocaleDateString('lo-LA')

And my output now becomes...

2024-6-4

Which is the reverse of what you expected, but then again maybe the fact that my operating system's locale is different to yours may make a difference.

But anyway, I then use options to see if I can change it...

let Options = {
 day: 'numeric',
 month: 'numeric',
 year: 'numeric',
};


alert( new Date().toLocaleDateString('lo-LA',Options) ); //expect 4/6/2024

But it doesn't seem to put them in that order! :(

So I turn to the Wiki article... "List of date formats by country"

https://en.wikipedia.org/wiki/List_of_date_formats_by_country

But there's no info for Laos, so we're stuck! :(

Country Laos supports the default date format as Date Month and Year format. Hence the format is printed is correct. However you can change the format to display in differently with options as below

const options = { year: "numeric", month: "numeric", day: "numeric", }; console.log(new Date().toLocaleString('lo', options));

As others noted: Should the localisation for Laos not be supported, you may be able to use a fallback locale similar to Laos's instead.

Alternatively, you can format it yourself, e.g. with the ECMAScript Internationalization API (Intl namespace).

Example:

const date = Date.UTC(
  2024, 6, 4,
  23, 26, 55
);

console.log(formatAsLaos(date));

function formatAsLaos(date) {
  const formatter = Intl.DateTimeFormat("lo-LA", {
      // Use Laos' timezone; also try "UTC"
      timeZone: "Asia/Vientiane",

      // Ensure expected format
      calendar: "gregory",
      numberingSystem: "latn",
      hour12: false,
      dateStyle: "medium",
      timeStyle: "medium"
    });
    
  const formatParts = formatter.formatToParts(date);
  // (Convenience function)
  const getPart = (partType) => formatParts.find(({type}) => type === partType)?.value;

  const dateString = [getPart("day"), getPart("month"), getPart("year")].join(".");
  const timeString = [getPart("hour"), getPart("minute"), getPart("second")].join(":");

  return `${dateString}, ${timeString}`;
}