Rxjs: super Multiple nested call

console.clear();

import {
  combineLatest,
  forkJoin,
  from,
  fromEvent,
  iif,
  interval,
  merge,
  of,
  timer
} from "rxjs";
import { ajax } from "rxjs/ajax";
import {
  buffer,
  catchError,
  debounceTime,
  delay,
  distinct,
  distinctUntilChanged,
  distinctUntilKeyChanged,
  filter,
  first,
  last,
  map,
  mergeAll,
  mergeMap,
  reduce,
  retry,
  scan,
  skip,
  skipWhile,
  take,
  takeUntil,
  takeWhile,
  tap,
  toArray,
  withLatestFrom
} from "rxjs/operators";

const input$ = fromEvent(document.getElementById("myInput"), "input").pipe(
  map(ev => (ev.currentTarget as HTMLInputElement).value)
);

const role$ = of("admin");
const theme$ = of("dark");

fromEvent(document, "click")
  .pipe(
    mergeMap(val => ajax.get("https://jsonplaceholder.typicode.com/posts")),
    map(res => res.response),
    mergeMap(posts =>
      combineLatest(role$, theme$).pipe(
        map(val => ({ role: val[0], theme: val[1], result: posts }))
      )
    ),
    mergeMap(obj => {
      return iif(
        () => obj.role === "admin",
        ajax.get(
          "https://jsonplaceholder.typicode.com/comments?postId=" +
            obj.result[0].id
        ),
        ajax.post("https://jsonplaceholder.typicode.com/comments", {})
      );
      /*
      if (obj.role === "admin") {
        return ajax.get("https://jsonplaceholder.typicode.com/comments?postId=" +
            obj.result[0].id)
      } else {
        return ajax.post("https://jsonplaceholder.typicode.com/comments", {})
      }
      */
    }),
    map(res => res.response)
  )
  .subscribe(
    res => console.log(res),
    err => console.log("err", err),
    () => console.log("completed")
  );

const users = [1, 2, 3];
const total = users.reduce((acc, curr) => acc + curr, 0);