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Angular I18N

Angular | Working with I18N

by Ralph Angular, Javascript, Web Framework

In this post, you will learn how to get started with Angular I18n using ngx-translate, the internationalization (i18n) library for Angular. We will cover the following topics:

  • setup new angular app
  • install required dependencies
  • add bootstrap as ui framework
  • create app with demo page and translation services

This will be the final result (click to show video). Source code for this post is on GitHub.

Setup new Angular app

➜ ng new app
➜ cd app

Add required modules

➜ npm install @ngx-translate/core @ngx-translate/http-loader rxjs --save

Add Bootstrap as UI framework

We need the libraries for Bootstrap and flag icons. Download the required files into your asset/vendor/bootstrap/5.3.1 folder:

Flags Icons need a CSS file with the corresponding images for the flags, so we use the archive from GitHub.

Download and extract the archive into the folder assets/vendor/flag-icons

Current folder structure

This is our current folder structure:

Setup Application

We choose the following structure for the HTML architecture.

  • index.html contains the required css and js files.
    Also, the <app-root> component, which loads our app
  • app.component.html contains the main structure of every page.
    This includes header, navigation, place for main content and footer
  • The main content is inserted via the <router-outlet>

index.html

We will add the corresponding file in the main index.html in our project.

<!doctype html>
<html lang="en" class="h-100">

<head>
  <meta charset="utf-8">
  <title>I18N</title>
  <base href="/">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="icon" type="image/x-icon" href="favicon.ico">

  <link rel="stylesheet" href="/assets/vendor/bootstrap.min.css">
  <link rel="stylesheet" href="/assets/vendor/flag-icons.min.css">

  <link rel="stylesheet" href="/assets/vendor/bootstrap/5.1.3/css/bootstrap.min.css">
  <link rel="stylesheet" href="/assets/vendor/flag-icons/css/flag-icons.min.css">

  <link rel="stylesheet" href="/assets/css/default.css">

</head>

<body class="d-flex flex-column h-100">
  <app-root class="h-100"></app-root>

  <script src="assets/vendor/bootstrap/5.1.3/js/bootstrap.bundle.min.js"></script>
</body>

</html>

app.component.html

We borrow the main structure from the bootstrap example ‘Sticky Footer with Navbar‘ with some changes in the navigation bar.

<header>
    <nav class="navbar navbar-expand-md navbar-dark fixed-top bg-primary">
        <div class="container-fluid">
            <a class="navbar-brand" href="#">
                <img src="assets/img/logo-angular.png" height="40px" width="auto">
            </a>
            <button class="navbar-toggler" type="button" data-bs-toggle="collapse" 
                data-bs-target="#navbarCollapse"
                aria-controls="navbarCollapse" 
                aria-expanded="false"     
                aria-label="Toggle navigation">
                <span class="navbar-toggler-icon"></span>
            </button>
            <div class="collapse navbar-collapse" id="navbarCollapse">
                <ul class="navbar-nav me-auto mb-2 mb-md-0">
                    <li class="nav-item">
                        <a class="nav-link active" aria-current="page" href="#">Home</a>
                    </li>
                </ul>

                <div class="btn-group dropstart">
                    <button class="btn btn-primary dropdown-toggle" type="button" 
                        id="dropdownFlags"
                        data-bs-toggle="dropdown" aria-expanded="false">
                        <span class="flag-icon flag-icon-{{currentlang}}"></span>
                    </button>
                    <ul class="dropdown-menu">
                        <li *ngFor="let lang of languages" [value]="lang" 
                            (click)="useLanguage(lang)">
                            <a class="dropdown-item"
                                [ngClass]="{'active': currentlang == lang}">
                                <span class="flag-icon flag-icon-{{lang}}"></span>
                                &nbsp;
                                {{lang | uppercase}}
                            </a>
                        </li>
                    </ul>
                </div>
            </div>
        </div>
    </nav>
</header>
<main class="flex-shrink-0">
    <div class="container">
        <router-outlet></router-outlet>
    </div>
</main>
<footer class="footer mt-auto py-3 bg-dark">
    <div class="container">
        <span class="text-muted">(C) Ralph Göstenmeier</span>
    </div>
</footer>

app.component.ts

import { Component } from '@angular/core';
import { TranslateService } from '@ngx-translate/core';

import defaultLanguage from '../assets/i18n/de.json';

@Component({
    selector: 'app-root',
    templateUrl: './app.component.html',
    styleUrls: ['./app.component.scss'],
})
export class AppComponent {
    title = 'I18N';

    languages = ['us', 'de', 'fr', 'sp'];
    currentlang = 'us';

    constructor(private translate: TranslateService) {
        this.currentlang = 'de';
        translate.setTranslation(this.currentlang, defaultLanguage);
        translate.setDefaultLang(this.currentlang);
    }

    ngOnInit(): void {}

    useLanguage(language: string): void {
        this.currentlang = language;
        this.translate.use(language.toLowerCase());
    }
}

app.module.ts

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { HttpClient, HttpClientModule } from '@angular/common/http';

import { AppRoutingModule } from './app-routing.module';
import { AppComponent } from './app.component';

import { TranslateLoader, TranslateModule } from '@ngx-translate/core';
import { TranslateHttpLoader } from '@ngx-translate/http-loader';

import { HomePageComponent } from './pages/home/component';
import { DemoPageComponent } from './pages/demo/component';

@NgModule({
    declarations: [AppComponent, HomePageComponent, DemoPageComponent],
    imports: [
        BrowserModule,
        AppRoutingModule,
        HttpClientModule,
        TranslateModule.forRoot({
            loader: {
                provide: TranslateLoader,
                useFactory: HttpLoaderFactory,
                deps: [HttpClient],
            },
        }),
    ],
    providers: [],
    bootstrap: [AppComponent],
})
export class AppModule {}

// required for AOT compilation
export function HttpLoaderFactory(http: HttpClient): TranslateHttpLoader {
    return new TranslateHttpLoader(http);
}

How the app works

The translation is done with the ngx-translate component.

Translation works with different JSON files (for each language a separate file), containing the required translation for each text to be displayed. Each text is addressed with a name within the JSON file.

So, the base structure of each JSON file is the following:

Translation files

assets/i18n/de.json

{
  "i18n-demo-header": "I18N Demo",
  "header": "I18N Funktionalität in Angular"
}

assets/i18n/us.json

{
  "i18n-demo-header": "I18N Example",
  "header": "I18N Functionality in Angular"
}

These translations could be used in a html file by using the translate pipe:

<h1>{{'header' | translate }}</h1>

More information and examples are here.

Changing the language is done with the help of the TranslateService

Inject your app with the TranslateService (in app.component.ts)

constructor(private translate: TranslateService) {
    translate.setDefaultLang('de');
}

Change Language

useLanguage(language: string): void {
    this.translate.use(language.toLowerCase());
}

Integrate in our UI

To easy switching the language, we have to do a few steps

Add a dropdown menu to our navigation bar.

And switching the language is done by calling useLanguage within each menu item:

<div class="btn-group dropstart">
    <button class="btn btn-primary dropdown-toggle" type="button"
        id="dropdownFlags"
        data-bs-toggle="dropdown" aria-expanded="false"><span
        class="flag-icon flag-icon-{{currentlang}}"></span>
    </button>
    <ul class="dropdown-menu">
        <li *ngFor="let lang of languages" [value]="lang"
            (click)="useLanguage(lang)">
            <a class="dropdown-item" 
                [ngClass]="{'active': currentlang == lang}">
                <span class="flag-icon flag-icon-{{lang}}"></span>
                &nbsp;
                {{lang | uppercase}}
            </a>
        </li>
    </ul>
</div>

Setup a list for all menu items:

<ul class="dropdown-menu">
<li *ngFor="let lang of languages" [value]="lang" (click)="useLanguage(lang)">