개발야옹

https://school.programmers.co.kr/learn/courses/30/lessons/70129

function solution(s) {
    var answer = [0,0];
    
    while(s !== '1') {
        s = s.split("").filter((item) => {
            if(item === '1') return '1'
            else answer[1] += 1;
        }).join("");
        
        s = s.length.toString(2).toString();
        answer[0] += 1;
    }
    
    return answer;
}

https://school.programmers.co.kr/learn/courses/30/lessons/42862?language=javascript 

function solution(n, lost, reserve) {
    var answer = 0;
    
    lost = lost.map((l) => {
       if(reserve.includes(l)) {
           reserve = new Set(reserve);
           reserve.delete(l);
           reserve = Array.from(reserve);
       } else return l;
    });
    
    let borrow = new Array(n).fill().map(n => 0);
    borrow = borrow.map((n, index) => {
        if(reserve.includes(index+1)) {
            return 1;
        } else return 0;
    });
    
    let student = new Array(n).fill().map(n => true);
    student = student.map((n, index) => {
        if(lost.includes(index+1)) {
            return false;
        } else return true;
    });
    
    student.forEach((s, index) => {
        if(!s) { // 체육복 없는 학생
            let left = index -1 < 0 ? null : index -1;
            let right = index +1 >= student.length ? null : index +1;
            
            if(left !== null && borrow[left] === 1) {
                student[index] = true;
                borrow[left] = 0;
            } else if(borrow[right] !== null && borrow[right] === 1) {
                student[index] = true;
                borrow[right] = 0;            
            }
        }
    })

    return student.filter(s => s === true).length;
}

https://school.programmers.co.kr/learn/courses/30/lessons/120808

const GCD = (num1, num2) => {
    let result = -1;
    for(let i = 2; i <= Math.min(num1, num2) ; i++ ) {
        if(num1 % i === 0 && num2 % i === 0) {
            result = i;
        }
    }
    return result;
}

function solution(numer1, denom1, numer2, denom2) {
    numer1 = numer1 * denom2;
    numer2 = numer2 * denom1;
    denom1 = denom1 * denom2;
    denom2 = denom2 * denom1;
    
    let numer = numer1 + numer2;
    let denom = denom1;
    
    return GCD(numer, denom) === -1 ? [numer, denom] : [numer/GCD(numer, denom) , denom/GCD(numer, denom) ]
}

https://school.programmers.co.kr/learn/courses/30/lessons/120878

const gcd = (num1, num2) => {
    let result = -1;
    for(let i = 2; i <= Math.min(num1, num2) ; i++) {
        if(num1 % i === 0 && num2 % i === 0 ) {
            result = i;
        }
    }
    return result;
}

const solve = (num) => {
    const arr = [];
    let i = 2;
    while(i <= num) {
        if(num % i !== 0) {
            i++;
        } else {
            arr.push(i);
            num = num / i;
            i = 2;
        }
    }
    return arr;
}

function solution(a, b) {
    var answer = 0;
    while(gcd(a,b) > 0) {
        const Gcd = gcd(a,b);
        a = a/Gcd;
        b = b/Gcd;
    }
    
    const result = solve(b).filter(a => a !== 2 && a !== 5);
    
    return result.length === 0 ? 1 : 2;
}