this.userService.getExpertisesListByIdUser(2).map((listExpertises: Array<any>) =>
      {
          let result:Array<Expertise> = [];
          let libs:Array<String> = [];
          if (listExpertises)
          {
              listExpertises.forEach((expert) =>
              {
                  libs.push(expert.name);
                  result.push(new Expertise(expert.id, expert.name, expert.username));
              });
          }

          localStorage.removeItem("libs");
          localStorage.setItem("libs", JSON.stringify(libs));

      })

      var storedNames = JSON.parse(localStorage.getItem("libs"));
      console.log(storedNames.length);   // That gives 0 as length : WRONG

getExpertisesListByIdUser(id: number): Observable<any>
{
    return this.http.get(`${this.baseUrl}/users/expertises/${id}`);
}