js map()


### map return new array
> [Array.prototype.map()](https://developer.mozilla.org/ko/docs/Web/JavaScript/Reference/Global_Objects/Array/map)

> [[Javascript] 15가지 유용한 map, reduce, filter](https://medium.com/@Dongmin_Jang/javascript-15%EA%B0%80%EC%A7%80-%EC%9C%A0%EC%9A%A9%ED%95%9C-map-reduce-filter-bfbc74f0debd)






