takeuntil-last.ts

import { combineLatest, Observable } from "rxjs";
import { takeUntil } from "rxjs/operators";

declare const a: Observable<number>;
declare const b: Observable<number>;
declare const notifier: Observable<any>;

const c = a.pipe(
  o => combineLatest(o, b),
  takeUntil(notifier)
).subscribe(value => console.log(value));