모듈이 여러번 import 되면 어떻게 될까?

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//-----------------------------------------------------------
// Module의 내용이 아래와 같다면
export default Math.random() > 0.5 ? {} : [];

// 아래와 같이 import 했을때 다섯개는 모두 같은 인스턴스입니다
// 절반의 확률로 모두 {}이거나 []이고 (module1===module2 && module1===module3 && module1===module4 && module1===module5) === true 가 됩니다
import module1 from 'Module';
import module2 from 'Module';
import module3 from 'Module';
import module4 from 'Module';
import module5 from 'Module';

//-----------------------------------------------------------
// 또.. Module의 내용이 아래와 같다면
class Person { };
export default new Person();

// 아래의 세개도 마찬가지로 동일한 인스턴스입니다
import module1 from 'Module';
import module2 from 'Module';
import module3 from 'Module';

// 그런데 class를 export 한것이 아니라 instance를 export 한것이기는 하지만
// instance를 통해 class에 접근할 수 있기 때문에 module1을 만들때 사용했던 클래스를 이용해서 또 다른 객체를 추후에 만들고자 한다면 다음과 같이 만들 수 있습니다
let another = new module1.constructor();