does anyone have used toPromise and Promise.all from rxjs in http

Has anyone used toPromise and Promise.all from rxjs in http? Please give me an example.
How can I check both of the request is success in component with promise.all return some message like API is success?

getPostAsync() {
    return this.http.get('https://jsonplaceholder.typicode.com/posts')
                    .pipe(map((res:Response) => { return res.json();}))
                    .pipe(catchError((error) => { return throwError(error);}))
}

getPostAsync1() {
    return this.http.get('https://jsonplaceholder.typicode.com/posts/1')
                    .pipe(map((res:Response) => { return res.json();}))
                    .pipe(catchError((error) => { return throwError(error);}))
}