execute array of observables in a sequence

observable-sequence.ts

const obsone = () =>
  new Observable((obs) => {
    setTimeout(() => {
      console.log('one');
      obs.next();
    }, 1000);
 });

const obstwo = () =>
  new Observable((obs) => {
    setTimeout(() => {
      console.log('two');
      obs.next();
    }, 1000);
});

function runSequence() {
  return [obsone, obstwo].reduce((accumulator, next) => {
    return new Observable(obs => {
      accumulator.subscribe(() => {
        next().subscribe(() => {
          obs.next();
        });
      });
    });
  }, of(1));
}

runSequence().subscribe(() => {
  console.log('done');
});