caching-article-caching-value.ts

export class ProductService {
  
  private readonly URL = 'https://world.openfoodfacts.org/api/v0/product/';

  constructor(private http: HttpClient) {
  }

  cache = {};


  resolveProduct(code: string): Observable<any> {
    if (this.cache[code]) {
      console.log('Returning cached value!')
      return of(this.cache[code])
    }
    console.log('Do the request again')
    this.http.get(this.URL+code+'.json').pipe(
      tap(resolvedValue => {
          this.cache[code] = resolvedValue;
      }));
  }
}