Observable不接收angular2中的下一个值

import { Observable } from 'rxjs';

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

myObservable.subscribe(value => {
  console.log(value);
});

import { Observable, fromEvent } from 'rxjs';

const button = document.querySelector('button');
const clickObservable = fromEvent(button, 'click');

clickObservable.subscribe(event => {
  console.log('Button clicked');
});

import { Observable, interval } from 'rxjs';
import { take } from 'rxjs/operators';

const myObservable = interval(1000).pipe(take(5));

myObservable.subscribe(value => {
  console.log(value);
});