Set angular LOCALE_ID according to browser language

Question

I'm trying to use Kendo components in my multilanguage application. To format the dates properly, Kendo required the LOCALE_ID from Angular to be set. I'm not sure how to accomplish that in a clean way.

Currently, I'm using the HTTP_ACCEPT_LANGUAGE to find in which language I should serve my app. I do it like this in my nginx.conf:

# Parse AcceptLanguage header
  # en,es,pl,fr
  # en,es;q=0.8,pl;q=0.7,fr;q=0.6
  set $first_language $http_accept_language;
  if ($http_accept_language ~* '^(.+?),') {
    set $first_language $1;
  }

  set $language_suffix 'en';
  if ($first_language ~* 'fr') {
    set $language_suffix 'fr';
  }

  root /usr/share/nginx/html/$language_suffix;

This works. The correct .xlf files are used and messages appear translated.

Now, I need to set the LOCALE_ID to get my Kendo components to render the dates in a correct format. I tried to set it by getting the browser current language. Here's how I tried to accomplish that:

app.module.ts

...
import { LOCALE_ID, NgModule } from '@angular/core';
import { LocaleService } from './shared/service/locale.service';
...

@NgModule({
  declarations: [
    ...
  ],
  imports: [
    ...
  ],
  providers: [
    ...
    {
      provide: LOCALE_ID,
      deps: [LocaleService],
      useValue: (localeService) => localeService.getLanguage()
    }
  ],
})

locale.service.ts

import { Injectable } from '@angular/core';

@Injectable({
  providedIn: 'root'
})
export class LocaleService {

  constructor() { }

  getLanguage() {
    // return navigator.language || navigator.userLanguage
    return 'fr-FR';
  }
}

I get this error message from the Kendo component.

ERROR TypeError: value.replace is not a function
    at CldrIntlService.set [as localeId] (cldr-intl.service.js:38)
    at new CldrIntlService (cldr-intl.service.js:24)
    at _createClass (core.js:19829)
    at _createProviderInstance (core.js:19801)
    at resolveNgModuleDep (core.js:19765)
    at NgModuleRef_.push../node_modules/@angular/core/fesm5/core.js.NgModuleRef_.get (core.js:20473)
    at resolveDep (core.js:20844)
    at createClass (core.js:20724)
    at createDirectiveInstance (core.js:20595)
    at createViewNodes (core.js:21821)

If I set it this way, it works:

{ provide: LOCALE_ID, useValue: 'fr-FR' }

I'm a beginner, still trying to find my way around Angular. What did I miss? Is that the proper way to achieve that?

I inspired myself from:
- How to set locale in DatePipe in Angular 2?
- Browser language detection

Answer 1

Maybe you should use FactoryProvider to instanciate your injectable and return the locale value, for example :

providers: [
    {
      provide: LOCALE_ID,
      useFactory: (localeService: LocaleService) => {
        console.log('locale ID', localeService.language);
        return localeService.language;
      },
      deps: [LocaleService]
    }
  ],

See this related question

Answer 2

The following is working for me (code added on the providers list of the app.module):

    {
        provide: LOCALE_ID,
        useValue: navigator.language,
    },

I'm also importing and registering supported locales, not sure that's necessary:

import { registerLocaleData } from '@angular/common'    
import localeEnAu from '@angular/common/locales/en-AU'
...
registerLocaleData(localeEnAu)
...