Angular 5 i18n with JIT - Lazy Loading Language files

In Angular 5 with Just-in-Time (JIT) compilation, you can implement internationalization (i18n) for lazy-loaded modules by using a custom TranslateLoader and leveraging Angular's built-in TranslateModule from @ngx-translate/core. This approach allows you to load language files for each lazy-loaded module dynamically. Here's how you can achieve it:

1. Install Required Dependencies:

   Install the necessary packages for translation:

   bashCopy code
   npm install @ngx-translate/core @ngx-translate/http-loader --save
   

2. Create Language Files:

   Create language files for each supported language in the src/assets/i18n directory. For example, you can create files like en.json, fr.json, etc., each containing translation key-value pairs for the respective language.

   Example en.json:

   jsonCopy code
   {
     "greeting": "Hello, welcome!"
   }
   

   Example fr.json:

   jsonCopy code
   {
     "greeting": "Bonjour, bienvenue !"
   }
   

3. Create a Custom TranslateLoader:

   Create a custom TranslateLoader that will be used to load the translation files dynamically. This loader should fetch the translation files from the src/assets/i18n directory based on the selected language.

   Create a new file custom-http-loader.ts:

   typescriptCopy code
   import { TranslateHttpLoader } from '@ngx-translate/http-loader';
   import { HttpClient } from '@angular/common/http';
   
   export function createTranslateLoader(http: HttpClient) {
     return new TranslateHttpLoader(http, './assets/i18n/', '.json');
   }
   

4. Configure AppModule:

   In your app.module.ts, import and configure the TranslateModule to use the custom loader.

   typescriptCopy code
   import { BrowserModule } from '@angular/platform-browser';
   import { NgModule } from '@angular/core';
   import { HttpClientModule, HttpClient } from '@angular/common/http';
   import { TranslateModule, TranslateLoader } from '@ngx-translate/core';
   import { createTranslateLoader } from './custom-http-loader';
   
   @NgModule({
     imports: [
       BrowserModule,
       HttpClientModule,
       TranslateModule.forRoot({
         loader: {
           provide: TranslateLoader,
           useFactory: createTranslateLoader,
           deps: [HttpClient],
         },
       }),
     ],
     declarations: [/* Your components and other declarations */],
     bootstrap: [/* Your root component */],
   })
   export class AppModule {}
   

5. Lazy-Load Translations for Each Module:

   In your lazy-loaded modules, import and configure the TranslateModule as well. This step is essential to enable translation for lazy-loaded modules.

   For example, create a lazy-loaded module named LazyModule:

   typescriptCopy code
   import { NgModule } from '@angular/core';
   import { CommonModule } from '@angular/common';
   import { TranslateModule } from '@ngx-translate/core';
   import { LazyComponent } from './lazy.component';
   
   @NgModule({
     imports: [
       CommonModule,
       TranslateModule.forChild(), // Use forChild() here
     ],
     declarations: [LazyComponent],
   })
   export class LazyModule {}
   

6. Lazy-Load Language Files:

   In each lazy-loaded module, load the required language file dynamically. You can achieve this by importing the TranslateService and calling its use() method with the desired language code.

   For example, in your LazyComponent:

   typescriptCopy code
   import { Component } from '@angular/core';
   import { TranslateService } from '@ngx-translate/core';
   
   @Component({
     selector: 'app-lazy',
     template: `
       <div>{{ 'greeting' | translate }}</div>
     `,
   })
   export class LazyComponent {
     constructor(private translateService: TranslateService) {
       this.translateService.use('en'); // Set the desired language code here
     }
   }
   

   You can load different language files based on user preferences or other conditions.

By following these steps, you can implement i18n with lazy loading in Angular 5 using Just-in-Time (JIT) compilation. When a lazy-loaded module is accessed, its translation files will be fetched dynamically, allowing your application to support multiple languages efficiently.