How to fix typing?

Question

Angular

On the stackblitz service, I wrote the simplest service that receives an array of users.
LIVE DEMO
Everything is ok, everything works. But after I export the project from this service and run it on my laptop, the following errors appear in the console:

ERROR in src/app/app.component.ts(22,9): error TS2322: Type 'Placeholder' is not assignable to type 'Placeholder[]'.
  Property 'length' is missing in type 'Placeholder'.
src/app/data.service.ts(16,5): error TS2322: Type 'Observable<Object>' is not assignable to type 'Observable<Placeholder>'.
  Type 'Object' is not assignable to type 'Placeholder'.
    The 'Object' type is assignable to very few other types. Did you mean to use the 'any' type instead?
      Property 'id' is missing in type 'Object'.

Please tell me what needs to be corrected so that they do not exist

Answer 1

getHttpData(): Observable<Placeholder[]> {
  return this.httpClient.get<Placeholder[]>(this.httpDataUrl);
}