async와 await // 1
https://velog.io/@khyup0629/javascript-async%EC%99%80-await%EC%9D%98-%EA%B0%9C%EB%85%90%EA%B3%BC-%EC%82%AC%EC%9A%A9%EB%B2%95
promise // 2
https://joshua1988.github.io/web-development/javascript/promise-for-beginners/
Class 사용하기-constructor, extends 등등
https://ordinary-code.tistory.com/22
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