외계행성의 나이

https://school.programmers.co.kr/learn/courses/30/lessons/120834

프로그래머스

 

정답 코드

1. 

function solution(age){
    const arr = age.toString().split("");
    const alphabet = "abcdefghij";
    return arr.map((v)=> alphabet[v]).join("");
}

 

2. 

function solution(age){
    let chr = 'abcdefghij';
    return Array.from(age.toString()).map(v => chr[v]).join('');
}

 

 

메소드 설명

1.  toString(), String()

const num = 5;

const str1 = num.toString();
const str2 = (100).toString();
const str3 = (-10.11).toString();

console.log(typeof str1); //string
console.log(typeof str2); //string
console.log(typeof str3); //string

 

2.  join()

const elements = ["Fire", "Air", "Water"];

console.log(elements.join()); // Fire,Air,Water
console.log(elements.join("")); // FireAirWater
console.log(elements.join("-")); // Fire-Air-Water

 

3. Array.from()

const arr = [1, 2, 3, 4, 5];

function plusTwo(number) {
  return number + 2;
}

const newArr = Array.from(arr, plusTwo);

console.log(arr); // [ 1, 2, 3, 4, 5 ]
console.log(newArr); // [ 3, 4, 5, 6, 7 ]

 

3. 

let age = 23
undefined
age.toString()
'23'
Array.from(age.toString())
(2) ['2', '3']
let chr = 'abcdefghij'
Array.from(age.toString()).map(v => chr[v])
(2) ['c', 'd']
let chr = 'abcdefghij'
Array.from(age.toString()).map(v => chr[v]).join()
'c,d'
let chr = 'abcdefghij'
Array.from(age.toString()).map(v => chr[v]).join('')
'cd'