In rxjs 6.5+

import { combineLatest } from 'rxjs';

combineLatest([a$, b$, c$]);

And for most applications it’s helpful to map the array of observables to a new value as well:

combineLatest([a$, b$, c$]).pipe(
  map(([a$, b$, c$]) => ({
    a: a$, 
    b: b$, 
    c: c$
  }))
);

Also see: https://www.learnrxjs.io/learn-rxjs/operators/combination/combinelatest