RxJS可观察concat不工作

concat 呼叫我知道如果我替换 康卡特 通过 merge 代码工作正常,输出为 foo bar qux quux cold ,所以我想情况并非如此。

const Rx = require('rxjs');

const observable1 = Rx.Observable.create((observer) => {
  observer.next('foo');
  observer.next('bar');
  return observer;
});
const observable2 = Rx.Observable.create((observer) => {
  observer.next('qux');
  observer.next('quux');
  return observer;
});
const result1 = observable1.concat(observable2);
result1.subscribe((x) => console.log(x));

// outputs
foo
bar

https://codepen.io/thiagoh/pen/WZyrRL