# Angular l10n

> An Angular library to translate texts, dates and numbers

This library is for localization of Angular apps. It allows, in addition to translation, to format dates and numbers through Internationalization API

## Documentation

Angular l10n Specification

## Architecture

## Table of Contents

- Installation
- Usage
- Types
- Intl API
- Server Side Rendering
- Previous versions
- Contributing
- License

## Installation

    npm install angular-l10n --save

## Usage

You can find a complete sample app here, and a live example on StackBlitz.

### Configuration

Create the configuration:

    export const l10nConfig: L10nConfig = {
        format: 'language-region',
        providers: [
            { name: 'app', asset: i18nAsset }
        ],
        cache: true,
        keySeparator: '.',
        defaultLocale: { language: 'en-US', currency: 'USD' },
        schema: [
            { locale: { language: 'en-US', currency: 'USD' }, dir: 'ltr', text: 'United States' },
            { locale: { language: 'it-IT', currency: 'EUR' }, dir: 'ltr', text: 'Italia' }
        ]
    };

    export function initL10n(l10nLoader: L10nLoader): () => Promise<void> {
        return () => l10nLoader.init();
    }

    const i18nAsset = {
        'en-US': {
            greeting: 'Hello world!',
            whoIAm: 'I am {{name}}'
        },
        'it-IT': {
            greeting: 'Ciao mondo!',
            whoIAm: 'Sono {{name}}'
        }
    };

Import the modules and the configuration:

    @NgModule({
        ...
        imports: [
            ...
            L10nTranslationModule.forRoot(l10nConfig),
            L10nIntlModule
        ],
        providers: [
            {
                provide: APP_INITIALIZER,
                useFactory: initL10n,
                deps: [L10nLoader],
                multi: true
            }
        ],
        bootstrap: [AppComponent]
    })
    export class AppModule { }

### Getting the translation

#### Pure Pipes

    <p title="{{ 'greeting' | translate:locale.language }}">{{ 'greeting' | translate:locale.language }}</p>
    <p>{{ 'whoIAm' | translate:locale.language:{ name: 'Angular l10n' } }}</p>

    <p>{{ today | l10nDate:locale.language:{ dateStyle: 'full', timeStyle: 'short' } }}</p>

    <p>{{ value | l10nNumber:locale.language:{ digits: '1.2-2', style: 'currency' } }}</p>

Pure pipes need to know when the locale changes. So import `L10nLocale` injection token in the component:

    export class AppComponent {

        constructor(@Inject(L10N_LOCALE) public locale: L10nLocale) { }

    }

##### OnPush Change Detection Strategy

To support this strategy, there is an async version of each pipe:

    <p>{{ 'greeting' | translateAsync }}</p>

#### Directives

    <p l10n-title title="greeting" l10nTranslate>greeting</p>
    <p [params]="{ name: 'Angular l10n' }" l10nTranslate>whoIAm</p>
    <!-- <p [l10nTranslate]="{ name: 'Angular l10n' }">whoIAm</p> -->

    <p [options]="{ dateStyle: 'full', timeStyle: 'short' }" l10nDate>{{ today }}</p>
    <p [options]="{ digits: '1.2-2', style: 'currency' }" l10nNumber>{{ value }}</p>

You can dynamically change parameters and expressions values as with pipes, but not in attributes.

#### APIs

    export class AppComponent implements OnInit {

        constructor(private translation: L10nTranslationService, private intl: L10nIntlService) { }

        ngOnInit() {
            this.translation.onChange().subscribe({
                next: () => {
                    this.greeting = this.translation.translate('greeting');
                    this.whoIAm = this.translation.translate('whoIAm', { name: 'Angular l10n' });

                    this.formattedToday = this.intl.formatDate(this.today, { dateStyle: 'full', timeStyle: 'short' });
                    this.formattedValue = this.intl.formatNumber(this.value, { digits: '1.2-2', style: 'currency' });
                }
            });
        }

    }

### Customize the library

The following features can be customized. You just have to implement the indicated class-interface and pass the token during configuration.

E.g.

    @Injectable() export class HttpTranslationLoader implements L10nTranslationLoader {

        private headers = new HttpHeaders({ 'Content-Type': 'application/json' });

        constructor(@Optional() private http: HttpClient) { }

        public get(language: string, provider: L10nProvider): Observable<{ [key: string]: any }> {
            const url = `${provider.asset}-${language}.json`;
            const options = {
                headers: this.headers,
                params: new HttpParams().set('v', provider.options.version)
            };
            return this.http.get(url, options);
        }

    }

    export const l10nConfig: L10nConfig = {
        ...
        providers: [
            { name: 'app', asset: './assets/i18n/app', options: { version: '1.0.0' } },
        ],
        ...
    };

    @NgModule({
        ...
        imports: [
            ...
            L10nTranslationModule.forRoot(
                l10nConfig,
                {
                    translationLoader: HttpTranslationLoader
                }
            )
        ],
        ...
    })
    export class AppModule { }

#### Storage

By default, the library does not store the locale. To store it implement the `L10nStorage` class-interface, so that the next time the user has the locale he selected.

#### User Language

By default, the library attempts to set the locale using the user's browser language, before falling back on the default locale. You can change this behavior by implementing the `L10nUserLanguage` class-interface, for example to get the language via server.

#### Translation Loader

By default, you can only pass JavaScript objects as translation data provider. To implement a different loader, you can implement the `L10nTranslationLoader` class-interface, as in the example above.

#### Translation Fallback

You can enable translation fallback during configuration:

    export const l10nConfig: L10nConfig = {
        ...
        fallback: true,
        ...
    };

By default, the translation data will be merged in the following order:

- `'language'`
- `'language[-script]'`
- `'language[-script][-region]'`

To change it, implement the `L10nTranslationFallback` class-interface.

#### Translation Handler

By default, the library only parse the params. `L10nTranslationHandler` is the class-interface to implement to modify the behavior.

#### Missing Translation Handler

If a key is not found, the same key is returned. To return a different value, you can implement the `L10nMissingTranslationHandler` class-interface.

### Validation

There are two directives, that you can use with Template driven or Reactive forms: `l10nValidateNumber` and `l10nValidateDate`. To use them, you have to implement the `L10nValidation` class-interface, and import it with the validation module:

    @Injectable() export class LocaleValidation implements L10nValidation {

        constructor(@Inject(L10N_LOCALE) private locale: L10nLocale) { }

        public parseNumber(value: string, options?: L10nNumberFormatOptions, language = this.locale.numberLanguage || this.locale.language): number | null {
            ...
        }

        public parseDate(value: string, options?: L10nDateTimeFormatOptions, language = this.locale.dateLanguage || this.locale.language): Date | null {
            ...
        }

    }

    @NgModule({
        ...
        imports: [
            ...
            L10nValidationModule.forRoot({ validation: LocaleValidation })
        ],
        ...
    })
    export class AppModule { }

### Routing

You can enable the localized routing importing the routing module after others:

    @NgModule({
        ...
        imports: [
            ...
            L10nRoutingModule.forRoot()
        ],
        ...
    })
    export class AppModule { }

A prefix containing the language is added to the path of each navigation, creating a semantic URL:

    baseHref/[language][-script][-region]/path

    https://example.com/en/home
    https://example.com/en-US/home

If the localized link is called, the locale is also set automatically.

To achieve this, the router configuration in your app is not rewritten: the URL is replaced, in order to provide the different localized contents both to the crawlers and to the users that can refer to the localized links.

If you don't want a localized routing for default locale, you can enable it during the configuration:

    export const l10nConfig: L10nConfig = {
        ...
        defaultRouting: true
    };

You can change the localized path, implementing the `L10nLocation` class-interface, and import it with the routing module:

    @Injectable() export class AppLocation implements L10nLocation {

        public path(): string {
            ...
        }

        public parsePath(path: string): string | null {
            ...
        }

        public getLocalizedSegment(path: string): string | null {
            ...
        }

        public toLocalizedPath(language: string, path: string): string {
            ...
        }

    }

    @NgModule({
        ...
        imports: [
            ...
            L10nRoutingModule.forRoot({ location: AppLocation })
        ],
        ...
    })
    export class AppModule { }

### Lazy loading

If you want to add new providers to a lazy loaded module, you can use `L10nResolver` in your routing module:

    const routes: Routes = [
        ...
        {
            path: 'lazy',
            loadChildren: () => import('./lazy/lazy.module').then(m => m.LazyModule),
            resolve: { l10n: L10nResolver },
            data: {
                l10nProviders: [{ name: 'lazy', asset: './assets/i18n/lazy', options: { version: '1.0.0' } }]
            }
        }
    ];

Always import the modules you need:

    @NgModule({
        declarations: [LazyComponent],
        imports: [
            ...
            L10nTranslationModule
        ]
    })
    export class LazyModule { }

### Caching

Enable caching during configuration if you want to prevent reloading of the already loaded translation data:

    export const l10nConfig: L10nConfig = {
        ...
        cache: true
    };

### Preloading data

If you need to preload some translation data, for example to use for missing values, `L10nTranslationService` exposes the translation data in the `data` attribute. You can merge data by calling the `addData` method:

    export function l10nPreload(translation: L10nTranslationService, translationLoader: L10nTranslationLoader): () => Promise<void> {
        return () => new Promise((resolve) => {
            translationLoader.get('en-US', { name: 'app', asset: './assets/i18n/app', options: { version: '1.0.0' } })
                .subscribe({
                    next: (data) => translation.addData(data, 'en-US'),
                    complete: () => resolve()
                });
        });
    }

Then add the function to providers, before `initL10n`:

    providers: [
        {
            provide: APP_INITIALIZER,
            useFactory: l10nPreload,
            deps: [L10nTranslationService, L10nTranslationLoader],
            multi: true
        },
        ...
    ],

## Types

Angular l10n types that it is useful to know:

- `L10nLocale`: contains a language, in the format `language[-script][-region][-extension]`, where:

  - language: ISO 639 two-letter or three-letter code

  - script: ISO 15924 four-letter script code

  - region: ISO 3166 two-letter, uppercase code

  - extension: 'u' (Unicode) extensions

    Optionally:

  - dateLanguage: alternative language to translate dates

  - numberLanguage: alternative language to translate numbers

  - currency: ISO 4217 three-letter code

  - timezone: from the IANA time zone database

- `L10nFormat`: shows the format of the language to be used for translations. The supported formats are: `'language' | 'language-script' | 'language-region' | 'language-script-region'`. So, for example, you can have a language like `en-US-u-ca-gregory-nu-latn` to format dates and numbers, but only use the `en-US` for translations setting `'language-region'`

- `L10nDateTimeFormatOptions`: the type of options used to format dates. Extends the Intl `DateTimeFormatOptions` interface, adding the dateStyle and timeStyle attributes

- `L10nNumberFormatOptions`: the type of options used to format numbers. Extends the Intl `NumberFormatOptions` interface, adding the digits attribute

## Intl API

To format dates and numbers, this library uses the Intl API

Check the current browser support:

- ECMAScript compatibility tables
- Can I use

All modern browsers have implemented this API. You can use a polyfill like Polyfill.io to extend support to old browsers.

Just add one script tag in your `index.html`:

    <script crossorigin="anonymous"
        src="https://polyfill.io/v3/polyfill.min.js?flags=gated&features=Intl.~locale.en-US"></script>

When specifying the `features`, you have to specify what languages to load.

Other polyfills:

- Format.JS

The `L10nIntlService` also provides methods for other APIs, such as Collator, PluralRules and ListFormat.

### Intl API in Node.js

To use Intl in Node.js, check the support according to the version in the official documentation: Internationalization Support

## Server Side Rendering

You can find a complete sample app with @nguniversal/express-engine here.

SSR doesn't work out of the box, so it is important to know:

- `src\app\universal-interceptor.ts`: used to handle absolute URLs for HTTP requests on the server
- `src\app\l10n-config.ts`:
  - `AppStorage (implements L10nStorage)`: uses a cookie to store the locale client & server side
  - `AppUserLanguage (implements L10nUserLanguage)`: server side, negotiates the language through `acceptsLanguages` to get the user language when the app starts
- prerender & serve:ssr commands set `NODE_ICU_DATA` to full-icu to support Intl in Node.js

## Previous versions

- Angular v9 (Angular l10n v9.3.0)

  - Branch

- Angular v8 (Angular l10n v8.1.2)

  - Branch

- Angular v7 (Angular l10n v7.2.0)

  - Branch

- Angular v6 (Angular l10n v5.2.0)

  - Branch

- Angular v5 (Angular l10n v4.2.0)

  - Branch

- Angular v4 (Angular l10n v3.5.2)

  - Branch

- Angular v2 (Angular l10n v2.0.11)

  - Branch

## Contributing

- Building the library:

        npm install
        npm run build

- Testing:

        npm test

- Serving the sample app:

        npm start

## License

MIT

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