1장
1 https://typescriptlang.org/ko
2 https://typescriptlang.org/ko
3 https://www.typescriptlang.org/ko/docs/handbook/intro.html
4 https://typescriptlang.org/ko/play
5 https://www.typescriptlang.org/ko/docs/handbook/intro.html
6 https://rollbar.com/blog/top-10-javascript-errors-from-1000-projects-and-how-to-avoid-them