npm install @ngx-translate/core --save
npm install @ngx-translate/http-loader --save // 針對Angular>=4.3
npm install @ngx-translate/http-loader@0.1.0 --save // 針對Angular<4.3

import {NgModule} from '@angular/core';
import {BrowserModule} from '@angular/platform-browser';
import {HttpClientModule, HttpClient} from '@angular/common/http';
import {TranslateModule, TranslateLoader} from '@ngx-translate/core';
import {TranslateHttpLoader} from '@ngx-translate/http-loader';
import {AppComponent} from './app';
export function createTranslateLoader(http: HttpClient) {
  return new TranslateHttpLoader(http, './assets/i18n/', '.json');
}
 
@NgModule({
  imports: [
    BrowserModule,
    HttpClientModule,
    TranslateModule.forRoot({
      loader: {
        provide: TranslateLoader,
        useFactory: (createTranslateLoader),
        deps: [HttpClient]
      }
    })
  ],
  bootstrap: [AppComponent]
})
export class AppModule { }

@NgModule({
  imports: [
    BrowserModule,
    HttpModule,
    TranslateModule.forRoot({
      provide: TranslateLoader,
      useFactory: (http: HttpClient) => new TranslateStaticLoader(http, '/assets/i18n', '.json'),
      deps: [HttpClient]
    })
  ],
  bootstrap: [AppComponent]
})
export class AppModule { }

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

constructor(private translate: TranslateService) {
 // this language will be used as a fallback when a translation isn't found in the current language
 translate.setDefaultLang('en');

 // use the brower's default lang, if the lang isn't available, it will use the 'en'
 let broswerLang = translate.getBrowserLang();
 translate.use(broswerLang.match(/en|cn/) ? broswerLang : 'en');
}

{
  "HELLO": "hello {{value}}"
}

translate.setTranslation('en', {
  HELLO: 'hello {{value}}'
});

{
  "HOME": {
    "HELLO": "hello {{value}}"
  }
}

translate.get('HELLO', {value: 'world'}).subscribe((res: string) => {
  console.log(res);
  //=> 'hello world'
});

{{ 'HELLO' | translate:param }}

param = {value: 'world'};

HELLO

{
  "HELLO": "Welcome to my Angular application!
This is an amazing app which uses the latest technologies!"
}

/**
 * The default lang to fallback when translations are missing on the current lang
 */
defaultLang: string;
/**
 * The lang currently used
 * @type {string}
 */
currentLang: string;
/**
 * an array of langs
 * @type {Array}
 */
langs: string[];
/**
 * a list of translations per lang
 * @type {{}}
 */
translations: any;

/**
 * Sets the default language to use as a fallback
 * @param lang
 */
setDefaultLang(lang: string): void;
/**
 * Gets the default language used
 * @returns string
 */
getDefaultLang(): string;
/**
 * Changes the lang currently used
 * @param lang
 * @returns {Observable<*>}
 */
use(lang: string): Observable;
/**
 * Gets an object of translations for a given language with the current loader
 * and passes it through the compiler
 * @param lang
 * @returns {Observable<*>}
 */
getTranslation(lang: string): Observable;
/**
 * Manually sets an object of translations for a given language
 * after passing it through the compiler
 * @param lang
 * @param translations
 * @param shouldMerge
 */
setTranslation(lang: string, translations: Object, shouldMerge?: boolean): void;
/**
 * Returns an array of currently available langs
 * @returns {any}
 */
getLangs(): Array;
/**
 * @param langs
 * Add available langs
 */
addLangs(langs: Array): void;
/**
 * Returns the parsed result of the translations
 * @param translations
 * @param key
 * @param interpolateParams
 * @returns {any}
 */
getParsedResult(translations: any, key: any, interpolateParams?: Object): any;
/**
 * Gets the translated value of a key (or an array of keys)
 * @param key
 * @param interpolateParams
 * @returns {any} the translated key, or an object of translated keys
 */
get(key: string | Array, interpolateParams?: Object): Observable;
/**
 * Returns a stream of translated values of a key (or an array of keys) which updates
 * whenever the language changes.
 * @param key
 * @param interpolateParams
 * @returns {any} A stream of the translated key, or an object of translated keys
 */
stream(key: string | Array, interpolateParams?: Object): Observable;
/**
 * Returns a translation instantly from the internal state of loaded translation.
 * All rules regarding the current language, the preferred language of even fallback languages will be used except any promise handling.
 * @param key
 * @param interpolateParams
 * @returns {string}
 */
instant(key: string | Array, interpolateParams?: Object): string | any;
/**
 * Sets the translated value of a key, after compiling it
 * @param key
 * @param value
 * @param lang
 */
set(key: string, value: string, lang?: string): void;
/**
 * Allows to reload the lang file from the file
 * @param lang
 * @returns {Observable}
 */
reloadLang(lang: string): Observable;
/**
 * Deletes inner translation
 * @param lang
 */
resetLang(lang: string): void;
/**
 * Returns the language code name from the browser, e.g. "de"
 *
 * @returns string
 */
getBrowserLang(): string;
/**
 * Returns the culture language code name from the browser, e.g. "de-DE"
 *
 * @returns string
 */
getBrowserCultureLang(): string;