[javascript] toUpperCase() - 대소문자 바꿔서 출력하기(프로그래머스)

const readline = require('readline');
const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout
});

let input = [];

rl.on('line', function (line) {
    input = [line];
}).on('close',function(){
    str = input[0].split('');
    str.forEach((value, index) => {
        if (value === value.toUpperCase()) {
            str[index] = value.toLowerCase();
        } else {
            str[index] = value.toUpperCase();
        }
    });
    console.log(str.join(''));
});

const readline = require('readline');
const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout
});

let input = [];

rl.on('line', function (line) {
    input = [line];
}).on('close',function(){
    str = input[0];
    
   var small=['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'];
    var big = ['A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z']
   var answer =''; 
    for (var i =0;i<str.length;i++){
        if('A'<=str[i]&&str[i]<='Z'){
            for (var j=0;j<big.length;j++){
                if (big[j]>str[i]){
                    answer+=small[j-1];
                    break;
                }
            }
            
        }
        else{
            for (var j=0;j<big.length;j++){
                if (small[j]>str[i]){
                    answer+=big[j-1];
                    break;
                }       
            }
        }
    }
    console.log(answer);  
});