rxjs 上游Observable重复被触发

Question

const { filter, tap } = require("rxjs/operators")
const { of } = require("rxjs")

const something = of(1).pipe(
 tap(() => console.log("emmm"))
)

something.pipe(filter(() => true)).subscribe()
something.pipe(filter(() => true)).subscribe()

运行结果

> rx-bug@ start D:\code\rx-bug
> node index.js

emmm
emmm

不应该只输出一次吗？

Answer 1

import { filter, tap } from 'rxjs/operators';
import { of, Subject } from 'rxjs';

const something = of(1).pipe(tap(() => console.log('emmm')));

const subject = new Subject();
something.subscribe(subject);

subject.pipe(filter((): boolean => true)).subscribe();
subject.pipe(filter((): boolean => true)).subscribe();

---

结果：

D:\source\js\rxjs>node index.js
emmm

D:\source\js\rxjs>