什么样的方法可以使可观察对象同时以同步和异步的方式工作?

const { Observable } = rxjs;

const helloWorld$ = new Observable(observer => {
  observer.next('Hello World');
  observer.complete();
});

console.log('Before subscribing helloWorld$');

helloWorld$.subscribe({
  next: console.log,
  complete: () => console.log('helloWorld$ on complete')
});

console.log('After subscribing helloWorld$');

<script src="//cdnjs.cloudflare.com/ajax/libs/rxjs/6.6.3/rxjs.umd.min.js">
</script>

const { Observable } = rxjs;

const helloEarth$ = new Observable(observer => {
  // mocking an ajax call
  setTimeout(() => {
    observer.next('Hello Earth from a galaxy far, far away...');
    observer.complete();
  }, 1000);
});

console.log('Before subscribing helloEarth$');

helloEarth$.subscribe({
  next: console.log,
  complete: () => console.log('helloEarth$ on complete')
});

console.log('After subscribing helloEarth$');

<script src=“//cdnjs.cloudflare.com/ajax/libs/rxjs/6.6.3/rxjs.umd.min.js”>
</脚本>