Detecting number format culture settings

Question

I have a webpage that needs to take numeric input, this part is easy enough with some combination of parseFloat, isNaN and (for displaying the values back to the user) toFixed. The problem is that Javascript seems to be completely ignorant of culture here. Some cultures use a decimal comma instead of a decimal point, but Javascript bulks at this.

Supporting the decimal comma isn't too much trouble, I can just replace a comma with a decimal point before parsing the users input and I can do the reverse before displaying the result to the user. My question is, is there a way for Javascript to know the users culture settings? I only care about the decimal separator, so for now I have no interest in other complications like thousands separators or currency.

Is there a reliable (client side) way to detect whether a visitor is using the decimal comma rather than the decimal point?

Update

In case anybody else wants it (or if anybody can see a flaw - other than not working in Chrome, as noted - or a better way), I ended up doing this:

var useComma = (0.1).toLocaleString().indexOf(",") > 0;

Now useComma will be true if the user has comma set as their decimal separator

JS has no native number formatting capabilities, and also has no native I18N capapilities either. — Marc B, Mar 16 '12 at 14:54
There might be a nice i18n ("internationalization") library out there you could use. The [Globalization](https://github.com/jquery/globalize) one looks like a good candidate, but I've never used it. — Cᴏʀʏ, Mar 16 '12 at 14:59
@Cory: Yeah, I was just looking through that library, but as far as I can tell, it doesn't detect the culture (unless I'm missing that part somewhere) and seems a little heavy for this one thing I need to do. — Matt Burland, Mar 16 '12 at 15:02

Clafou · Answer 1 · 2012-03-16T18:24:42.260

I think that trying to detect the user's locale may not actually help that much. If your Web Application is in English language, a user might actually use English-style formatting (e.g. 1.3) even though in their own culture it would be formatted differently (1,3 for fr-FR or es-ES)! And who would blame them?

You could try and be smart and use the solution proposed by Alex K, and/or take into account the accept-language header, the locales matching your localizations (if any) and even GeoIP for a best guess. But to reduce confusion you may want to give your user cues whenever you expect them to enter numerals or dates or other locale-sensitive data.... Display a default value or an example next to the fields, formatted using the same locale as you will be using to parse user input.

If you believe it gives you better user experience to be flexible, you could use a fallback technique and try the formats you expect the most.

score 2 · Accepted Answer · edited May 23 '17 at 11:56

2

How about

var decimalChar = (0.1).toLocaleString().charAt(1);

Edit, this appears not to work in chrome Internationalization(Number formatting "num.toLocaleString()") not working for chrome

edited May 23 '17 at 11:56

Community

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answered Mar 16 '12 at 15:01

Alex K.

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Seems to work for IE8 and FF 11, which covers most of my users. Thanks. I thought toLocaleString was only for dates! – Matt Burland Mar 16 '12 at 15:09
Some testers can use ## (more than one character) as a decimal separator ;o) – Viacheslav Ivanov Jan 09 '14 at 10:40

score 0 · Answer 3 · answered Feb 16 '21 at 09:07

function browser_i18n() {
    var o1 = new Intl.NumberFormat().resolvedOptions();
    var o2 = new Intl.DateTimeFormat().resolvedOptions();
    var o3 = new Intl.NumberFormat().formatToParts( 123456.789 );
    return {
        locale: o1.locale,
        sign: o1.signDisplay,
        group: o1.useGrouping,
        timeZone: o2.timeZone,
        calendar: o2.calendar,
        thousands: o3[ 1 ].value,
        decimals: o3[ 3 ].value,
    }
}
//

Detecting number format culture settings

3 Answers3