When user click charge button, Observable subscribe event endlessly.

[llighter]

https://github.com/llighter/ionic-studycard4/blob/b70e3067f4b3c33dd87e6e8e496a339ad12d0144/src/app/decks/deck-detail/deck-detail.component.ts#L103-L115

//emit value every 1s
const interval$ = interval(1000);
//take the first 5 emitted values
const example = interval$.pipe(take(5));
//output: 0,1,2,3,4
const subscribe = example.subscribe(val => console.log(val));

Set take(number) as many as Stage need.

[llighter]

https://www.learnrxjs.io/operators/filtering/take.html

[llighter]

https://www.learnrxjs.io/operators/filtering/takewhile.html

takeuntil_ => isStageFull(1)
위 코드를 pipe에 추가하고 구독하는 부분에서 조건문을 제거한다.