How to see what locales a given Node.js version supports and how to enable missing locales?

Question

My Node.js version on Windows 8.1 is:

$ node -v
v5.3.0

But it seems it doesn't support locale identification and negotiation. I mean the support of ECMAScript Internationalization API. Only en locale is supported. Here is an example in a browser and in Node.js. In a browser a locale is identified just fine:

// en
> Intl.NumberFormat('en', {currency: 'USD', style:"currency"}).format(300)
> "$300.00"

// ru
> Intl.NumberFormat('ru', {currency: 'USD', style:"currency"}).format(300)
> "300,00 $"

But in Node.js it doesn't work. Node.js returns the same en format for both en and ru:

// en
> Intl.NumberFormat('en', {currency: 'USD', style:"currency"}).format(300)
'$300.00'

// ru
> Intl.NumberFormat('ru', {currency: 'USD', style:"currency"}).format(300)
'$300.00'

Is there a way to see what locales does a given Node.js support and how can I enable desired locales?

Answer 1

Hy,

According to https://github.com/andyearnshaw/Intl.js/ there is a nodejs module, called

intl-locales-supported

which shows if a locale is supported.

var areIntlLocalesSupported = require('intl-locales-supported');

var localesMyAppSupports = [
    /* list locales here */
];

if (global.Intl) {
    // Determine if the built-in `Intl` has the locale data we need.
    if (!areIntlLocalesSupported(localesMyAppSupports)) {
        // `Intl` exists, but it doesn't have the data we need, so load the
        // polyfill and patch the constructors we need with the polyfill's.
        var IntlPolyfill    = require('intl');
        Intl.NumberFormat   = IntlPolyfill.NumberFormat;
        Intl.DateTimeFormat = IntlPolyfill.DateTimeFormat;
    }
} else {
    // No `Intl`, so use and load the polyfill.
    global.Intl = require('intl');
}

Answer 2

It's possible to support different locales for different subsets of the Intl API, so ECMA-402 doesn't expose APIs that answer whether a locale is "supported". Rather, it exposes APIs for each particular form of behavior, to indicate whether a locale is supported for that form. So if you want to ask whether a locale is supported, you'll have to separately query for each Intl subset you're going to use.

To query Intl.NumberFormat for support of a locale, use the Intl.NumberFormat.supportedLocalesOf function:

function isSupportedForNumberFormatting(locale)
{
  return Intl.NumberFormat.supportedLocalesOf([locale]).length > 0;
}

Assuming Node properly supports this, isSupportedForNumberFormatting("ru") would return false, while isSupportedForNumberFormatting("en") would return true.

Similar code should work for Intl.Collator and Intl.DateTimeFormat if you swap in the appropriate constructor name. And if you're using existing ECMA-262 functions that are locale-sensitive, like NumberFormat.prototype.toLocaleString, that ECMA-402 reformulates in terms of Intl primitives, check for support on the relevant Intl constructor (in that case, Intl.NumberFormat).