title: Assigning json array to interface when string[] does not work
body: <p>I have the following json file which holds a list of blacklist terms.</p>
  
  <pre><code>{
    "blacklist": [
      "term1",
      "term2",
      "term3",
      "term4",
      "term5"
     ]
  }
  </code></pre>
  
  <p>It is used in blacklist service:</p>
  
  <pre><code>@Injectable()
  export class BlacklistService {
    private readonly BLACKLIST_TERMS_FOLDER = './assets/data/web-blacklist-terms';
    private readonly blacklistTerms1: any;
    private readonly blacklistTerms2: any;
  }
  
  constructor(
    public httpClient: HttpClient
  ) {
    this.blacklistTerms1 = this.httpClient.get(`${this.BLACKLIST_TERMS_FOLDER}/terms.json`);
  }
  
  
  public getAllBlackListTerms(): Observable&lt;any&gt; {
    return combineLatest([this.blacklistTerms1, this.blacklistTerms2])
  }
  </code></pre>
  
  <p>How would I add a type to <code>blacklistTerms</code>? I have tried string[] but it gives me the message <code>Type 'Observable ' is missing the following properties from type 'string[]': length, pop, push, concat, and 27 more.</code></p>