我正在研究 rxjs Observables，但我不明白為什么 Observable.create 中的 setInterval 仍在運(yùn)行，即使我已經(jīng)取消訂閱該 observable 對(duì)象。Observable 是異步的嗎？應(yīng)該什么時(shí)候停？我有這個(gè)代碼供參考：var cancellableObserver = Observable.create((observer:any)=>{try {    observer.next("anyeong")    observer.next("ande")    console.log("logged once")    setInterval(()=>{        //this code block will keep running for every 2secs        observer.next("eotteokke") //but this line will stop after unsubscribe        console.log("will log every 2secs")    },2000)} catch (err) {    observer.error(err);}});var cancellableSubscription = cancellableObserver.subscribe((x:any) =>addItem(x),(err:any) =>addItem(err),() => addItem("cancellable completed"));setTimeout(() => {cancellableSubscription.unsubscribe();console.log("mary");}, 6001);